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Biology 12

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kate beacham

on 25 January 2013

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Transcript of Biology 12

By: Kate Beacham Biology 12 Chapter 2:
The Molecules of Cells 2.1 2.2 Molecules
and Compounds 2.3 Chemistry
of Water 2.7 Proteins 2.5 2.6 Lipids 2.8 Nucleic Acids 2.4 Organic
Molecules Basic
Chemistry Carbohydrates The 6-carbon sugar used by the cell for a “quick” energy source is called glucose. Polysaccharides are formed when sugar monomers are joined together. Animals store glucose as glycogen, while plants store it as starch. Cellulose that forms plant cell walls is something that humans can’t digest. When atoms gain or loose one or more electrons, to complete their outer orbitals, they become ions. The attraction of positively and negatively charged ions is called an ionic bond. When there is one or more shared pairs of electrons it is called a covalent bond.
A molecule’s shape is important to its biological role. A tetrahedral shape can be formed by Carbon combining with 4 other atoms.
When electrons are not shared equally it is a polar covalent bond. One of the atoms has a greater attraction for the shared electrons and this gives off a slight charge on both atoms. A weak bond, called a hydrogen bond, is between a hydrogen atom that is a slightly positive and a slight negative charge of an oxygen or nitrogen atom within the same or different molecule. This weak bond helps keep the function of a cellular molecule and its structure. The polarity of a water molecule lets hydrogen bonding between water molecules occur. The uniqueness of its properties is because of the polarity of water and hydrogen bonding. These properties give living things the ability to exist and carry on cellular activities.
Small portions of water molecules are dissociated to make an equal amount of hydrogen ions and hydroxide ions. The term neutral is applied to solutions with equal amounts of H+ and OH-. When solutions have a pH of less then 7 they are said to be acidic. When solutions are acidic they have more hydrogen ions than hydroxide ions. Basic solutions are the opposite of this. They have a pH of more then 7 and their solutions have more hydroxide ions than hydrogen ions. Something cells are sensitive to are pH changes. To help keep the pH in a normal range biological systems normally have buffers.
H – O – H H + + OH- Water hydrogen ion + hydroxide ion The chemistry of organic compounds is accounted by the chemistry of carbon. Macromolecules that have specific functions in cells are carbohydrates, lipids, proteins, and nucleic acids.
When monomers join together they form polymers. Polymers: long-chain carbohydrates, proteins, and nucleic acids. A water molecule is taken away for every bond formed during dehydration. On the other hand a water molecule is added for every bond broken during a hydrolysis reaction. The functions of protein in the cell are numerous. Some speed up chemical reactions because they are enzymes. There are 4 structures of proteins. The first one is called the primary structure. The primary structure of a polypeptide has its own certain order and there is a possibility of 20 different amino acids. The second one is called the secondary structure it is normally a beta-pleated sheet or an alpha helix. A polypeptide bends and twists into a three-dimensional shape when it becomes a tertiary structure. There is only a possible quaternary structure and this is when proteins can have several polypeptides. Polymers of nucleotides are nucleic acids. There are three components to every nucleotide: a base, a sugar, and a phosphate (phosphoric acid). The generic material that stores information, is called DNA, and it does this for its own replication and for the sequence of amino acids in proteins. DNA has the sugar deoxyribose. RNA helps DNA to specifies protein synthesis.
The energy currency of cells is called ATP and it has unstable phosphate bonds. The energy that cells use to do metabolic work is released during the hydrolysis of ATP to ADP + P CHNOPS - an acronym that helps us to remember the 6 most important living elements: neutrons protons electrons Carbon Atom C atomic mass- 12 atomic number-6 Matter is made of elements and is what living and nonliving things are composed of.
Elements have atoms and atoms are made of subatomic particles (protons, neutrons, and electrons) protons and neutrons make up the atomic mass. The number of protons and electrons is shown by the atomic number in neutrally charged atoms. Protons have a positive charge, an electron’s charge is negative, and neutrons are uncharged. When atoms of one element have different numbers of neutrons they are called isotopes. There are many uses for radioactive isotopes (EX: working as tracers in biological experiments and medical procedures).
The reactivity of an atom is determined by the amount of electrons in the outer orbital. The first orbital is filled with 2 electrons and the ones outside of that are filled with 8 electrons. It is stated in the octet rule that atoms react with other atoms to complete their outer orbital. Chapter 3:
Cell structure and function Chapter 4 Structure and Function Cardiovascular System Chapter 12 DNA Structure and Control of Gene Expression Chapter 25: Enzymes Respiratory System Chapter 15 Chapter 21 The Reproductive System Nervous System Chapter 17 The Cellular Level of Organization 3.1 Prokaryotic Cells 3.2 Origin and Evolution of the Eukaryotic cell 3.4 Eukaryotic Cells 3.3 Animal cell Plant cell Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfer Plasma Membrane Structure and Function 4.1 The Pereabillity of the Plasma Membrane 4.2 A lipid bilayer is fluid and it has the consistency of light oil, according to the fluid-mosaic model of the plasma membrane. The phospholipids (hydrophilic heads) make up the inner and outer surfaces. The hydrophobic tails make the inside.
The proteins make the mosaic part. The peripheral proteins help stabilize the plasma membrane, and shape it. They also are signaling pathways. Other proteins, the integral ones, make channels, move substances across the membranes (carriers), work in cell recognition, are receptors, and they carry on enzymatic reactions.
Some lipids and proteins that are found in the membrane have carbohydrate chains attached to them. Membrane Messenger RNA: A RNA
polymerase enzyme binds tightly with a promoter (a special sequence of nucleotides contained in a region of DNA) and then transcription begins.
The RNA polymerase opens the DNA helix up right in front of it. Then complementary base pairing is able to occur the same way as with DNA replication. The enzyme then joins the RNA nucleotides resulting in a mRNA molecule. After, the formation of
mRNA, it has a order of bases similar to that of DNA (where A,T,G, or C are in the DNA template U,A,C, or G are incorporated into the
mRNA molecule.) The bases
sequence of DNA has a
faithful copy found in
the mRNA. Transcription:
This process is required by gene expression.
In eukaryotes transcription takes place in the nucleus.
During this a gene, which is a segment of DNA, acts as a template for RNA molecules production.
There are 3 types of these useful RNA products that are transcribed from DNA.
Certain regions that don't code for proteins can interrupt protein-coding regions. Processing of mRNA: After the transcription of mRNA into eukaryotic cells they need to be processed before they enter the cytoplasm. After processing the newly synthesized primary mRNA molecule becomes mature. In humans most genes have parts of DNA that aren't a part of the gene that interrupt the genes. These interrupted genes are called introns (intragene segments.) The other pieces of the gene are called exons (ultimately expressed.) Exons, not introns, result in a protein product. Complementary bases for both introns and exons are contained in primary mRNA. However, during processing one end is changed by adding a cap made of altered guanine nucleotide, while the other end has a series of adenosine nucleotides (a poly-A tail) added. Also exons are join and form mRNA molecules that are mature and have
continuous exons meanwhile the introns are removed. Normally all the exons of a gene are brought
together through processing, but sometimes cells
only use certain exons to form a mature RNA
transcript. Different protein products in
each cell can be the result. Ribosomes and Ribosomal RNA: Translation occurs in the cytoplasm and on the endoplasmic reticulum where the ribosomes small structural bodies are found. Ribosomes are made of lots of proteins and several rRNA's. rRNA's are produced in the nucleolus within the nucleus in eukaryotic cells. rRNA is then joined with proteins made in and sent out from the cytoplasm and this forms 2 ribosomal subunits (1big, 1 small). These subunits leave the nucleus and go to the cytoplasm where they join together, forming a ribosome right when protein synthesis starts. Ribosomes have binding sites for mRNA and for the 3 tRNA molecules. The sites organize complementary base pairing between anticodons of tRNA and codons of mRNA's. New tRNA's arrive and polypeptides form and get longer as ribosomes move down the mRNA. After the polypeptides are fully formed and a mRNA stop codon is reached translation is ended. After this the ribosome dissociates into the 2 subunits and falls off the mRNA molecule. After the first portion of mRNA is translated by a ribosome and it has started to move down the mRNA another ribosome attaches to the same one. This means several copies of polypeptides are made simultaneously. The whole thing is called a polyribosome. Translation: Definition--> translation is a
process through which the sequence of codons
located in mRNA directs the sequence of amino acids in polypeptides. It is the second way that gene expression leads to protein synthesis. This process needs mRNA, tRNA, and rRNA enzymes. The Genetic Code: a pattern of bases in DNA is transcribed into mRNA and this in the end codes for a certain pattern of amino acids to form a polypeptide. It is a triplet code that has a redundant code. Triplet's are called codons too. More than 1 codon codes most amino acids. Protection against mutations that are possibly harmful and change the pattern of bases is given by its redundancy. 61 out of 64 codons code for amino acids and the other 3 (UAA, UGA, UAG) are stop codons that signal polypeptide termination instead of coding for amino acids. The genetic code, in living things, is almost universal. This suggests that all living things there ever has been are related. Transfer RNA: these molecules transfer amino acids to the site of protein synthesis at the ribosomes. Every tRNA molecule is a doubled back single-stranded polynucleotide. This allows complementary base pairing to make a boot like shape. One end has an amino acid and the other has an anicodon (a triplet of 3 complementary bases of a certain codon of mRNA. For each of the 20 amino acids found in proteins there's at least 1 tRNA molecule. When the complex of tRNA-amino acid gets to the ribosomes the anticodon pairs with a mRNA codon. The mRNA's codons order determines the order that tRNA-amino acids go to a ribosome and the final order of amino acids in a protein. The order that tRNA's bring amino acids to the ribosomes during translation are dictated by the base sequence of mRNA. A complete protein or a polypeptide chain is formed by the order of amino acids. Initiation: brings all translation components together. Initiation factors (protein) are needed to assemble mRNA, initiator tRNA, and big and small ribosomal subunits for the beginning of protein synthesis. In prokaryotes a mRNA is attached by a small ribosomal subunit around a start codon (AUG). Initiator tRNA pairs with this one because its UAC is its anticodon. Now a large ribosomal subunit joins to the small subunit. There are 3 binding sites for tRNA's on a ribosome. There's a P/ peptide site, A/ amino acid site, and a E/ exit site (where tRNA exits). Initiator tRNA is able to bind to P site even though it only carries methionine (an amino acid). A site is for tRNA carrying the next amino acid. Translation Requires Three Steps: This process
must be very orderly to make the amino acids of a polypeptide sequenced properly. There are 3 steps in protein synthesis: initiation, elongation, and termination. All 3 need enzymes to work properly. Termination: during this the polypeptide and other assembled parts that carry out protein synthesis are separated from one another. It happens at a stop codon. This process needs a release factor (protein) that severs the polypeptide from the last tRNA. The polypeptide is set free and it takes on its 3-D shape. The ribosomes break down into the 2 subunits. Proteins that function properly hold the most importance to the cell and the organism. Genotype and phenotype are linked by protein. The DNA pattern that underlies the proteins is what distinguishes different types of organisms. Proteins account for the difference between cell types and organisms. Elongation: is where polypeptides get bigger 1 amino acid at a time. It needs tRNA's participation and elongation factors, that start the binding of tRNA anticodons to mRNA codons at a ribosome. There are 4 steps:
tRNA with peptide is at the P site and a tRNA with the next amino acid it at A site.
When the next tRNA is in place at A site, the peptide chain is transferred to it.
Energy is needed for the formation of the peptide bond. This adds 1 amino acid by adding the peptide formA site. (a ribosomal subunit is needed for this).
Translocation: mRNA moves forward 1 codon length. tRNA bearing the peptide is at the P site now. 1 tRNA exits and the new codon (at A site) is ready for the next complementary tRNA. Chapter 6: Enzymes and Metabolic Pathways 6.3 In the chromatin there is a region called the NUCLEOLUS and this is where rRNA is made and where protein gathers, making ribosomal subunits after coming from the cytoplasm. The plasma membrane, that all cells have, has a phospholipid bilayer with proteins embedded in it. This membrane lets certain molecules in and out of the cell, but some are not allowed. Cytoplasm is a fluid that fills the cells insides.
Prokaryotic cells have a nucleoid, not bound in a nuclear envelope, but not a nucleus. Along with the nucleus prokaryotic cells also do not have most of the organelles that are in eukaryotic cells.
Prokaryotic cells are more diverse metabolically, but they are less structurally complex than eukaryotic cells. This is shown by prokaryotic cell such as bacteria and archaea.
Cells are the smallest units of living matter and all organisms are composed of them.
The only way to get new cells is from pre-existing cells. Self-reproduction is something that cells are capable of.
In order for there to be a good ratio of surface-area-to-volume cells need to stay small. They need to keep this ratio for the exchanged of molecules with the environment. Chapter 14 Digestive System and Nutrition 12.1 The Blood Vessels 12.2 The Human Heart 12.3 The Vascular Pathways 12.4 12.5 ◦There is a right and left side to the heart, as well as 4 chambers.
There is a right and left atrium and a right and left ventricle. O2 poor blood is delivered to the right atrium via the venae cavae. The right ventricle then pumps it to the pulmonary circuit via the pulmonary trunk. O2 rich blood is taken to the left atrium from the lungs via the pulmonary veins. Then the left ventricle pumps the blood into the systemic circuit through the aorta.
Blood needs to go through the atrioventricular valves when it goes from the atria to the ventricles. Blood also passes through semilunar valves when it leaves the ventricles.
Cardiac cycle: the SA node is our cardiac pacemaker and it starts our heartbeat. It does this by making the atria contract. Then the AV node makes the ventricles contract by conveying the stimulus to the ventricles.
The closing of the atrioventricular valves that is followed by the closing of the semilunar valves is what causes the “lub-dup” sound of our heart. Cardiovascular Disorders Blood 14.2 25.3 25.2 RNA structure and Function 25.1 DNA Structure and Replication 25.4 Control of Gene Expression 25.5 Gene Mutations Gene Expression 14.3 Digestive Enzymes Accessory Organs of Digestion Male Reproductive System 21.1 21.2 Female Reproductive System 21.3 Female Hormone Levels The Respiratory System 15.1 Mechanism of Breathing 15.2 Gas Exchange in the Body 15.3 Nervous Tissue 17.1 The Peripheral Nervous System 17.4 The Central Nervous System 17.2 The Limbic System and Higher Mental Functions 17.3 The genital tract of males is made of organs that produce seminal fluid and sperm. It also includes the external genitalia.
In the seminiferous tubules of the testes is where spermatogenesis happens and this is where the production of sperm that mature occurs and are mainly stored in the epididymides. Before sperm enters the urethra with the seminal fluid they enter the vasa deferentia. The bulbourethral glands, prostate gland, and the seminal vesicles produce seminal fluid. The secretions and sperm is called semen.
The penis and the scrotum are the external genitals of males. The penis is the organ of sexual intercourse. The scrotum contains the testes. When the expandable tissue in the penis fills with blood erection has occurred. Orgasm in males, a physical and emotional climax, results in an ejaculation, from the penis, of semen.
Through the secretion of hormones the hypothalamus controls the male reproductive system.
The secretion of FSH and LH from the anterior pituitary gland is by GnRH from the hypothalamus. The promotion of spermatogenesis in the seminiferous tubules of the testes is caused by FSH. Testosterone’s production by the interstitial cells is promotes by LH (ICSH). The development of sale secondary sex characteristics and the proper functioning of the sex organs of males need testosterone. The internal organs that produce the oocyte
and let fertilization happen and the external
organs are included in the female genital tract.
When an ovary produces an egg or oocyte it is called oogenesis. After the oocyte is released (ovulation) it is transported through an oviduct or fallopian tube to the uterus. There a zygote, the fertilized oocyte, an begin to develop after is become implanted in the endometrium.
The vaginal opening, clitoris, labia minora, labia majora are all a part of the external genitals of the female. The organ for the exit for menstrual fluids, birth canal, and sexual intercourse is the vagina. An active role in orgasm is played by the external genitals, especially the clitoris. The clitoris culminates in vaginal oviduct contraction, and uterine. Neurons – nerve cell that characteristically has three parts: cell body, dendrites, and an axon.. A myelin Sheath covers long axons.
- Sensory neuron: a neuron that takes impulses, carrying information from sensory receptors to the CNS
Interneuron: a neuron found in the CNS and conveys messages between parts of the ventral nervous system.
Motor neuron: take nerve impulses from the central nervous system to the effectors (muscles and glands).
Action potential is needed to transmit impulses across a synapse
-the leakage of K+ to the axons outside creates resting potential
Neurotransmitters are chemicals that work in the transfer of messages between 2 neurons or a neuron and a muscle cell
-the neurotransmitter, released by the presynaptic neuron, binds with a receptor in the postsynaptic membrane and this causes excitation or inhibitory signals.
- the excitatory and inhibitory signals summed up is called integration. The CNS takes in signals and integrates the sensory input and makes a motor output. Both the spinal cord and the brain are protected by bone; the spinal cord and the brain are what make up the CNS.
Sensory information is sent to the brain by the spinal cord. The spinal cord also receives motor output from the brain and also carries out the reflex action. Neuron cell bodies are contained in the gray matter of the spinal cord. Meanwhile, myelinated axons occur in bundles called tracts and they are found in the white matter.
There are several functional and anatomical regions that the brain can be divided into. In the cerebrum is where sensation, reasoning, learning, memory, language, and speech take place. There are 2 cerebral hemispheres in the cerebrum and they are connected by the corpus callosum. A thin layer of gray matter covers the cerebrum and makes up the cerebral cortex. The frontal, parietal, occipital, and temporal lobes are the 4 lobes that the cerebral cortex of each cerebral hemisphere. In the frontal lobe the primary motor area sends out motor commands to lower brain centers that pass the information on to motor neurons. In the parietal lobe the primary somatosensory area takes in sensory information from lower brain centers in communication with sensory neurons. Processing centers for reasoning and speech are also in the cortex.
The hypothalamus (controls homeostasis) and the thalamus (specializes in sending sensory input on to the cerebrum) are included in other regions of the brain. The coordination of skeletal muscle contraction are mainly from the cerebellum. There are centers for vital function like breathing and the heartbeat in the medulla oblongata and pons. The Urinary System Chapter 16 Anatomy of the Kidney and Excretion 16.3 Regulatory Functions of the Kidneys 16.2 16.1 Urinary System Emotions and higher brain functions are associated with the limbic systems.
The hippocampus (acts as a conduit for sending messages to long-term memory and retrieving them again) and the amygdala (adds emotional overtones to memories) are contained in the limbic system. The thalamus and the basal nuclei, as well as the cerebral cortex and the hypothalamus have various connections.
Memory, learning, language, and speech are included in higher brain functions.
Short and long-term memory are the two basic types of memory. The formation of long term memories needs the hippocampus. Glutamate is involved in this process and it is known as long term potentiation, at this chemical level.
Many areas of the brain are involved in language and speech, however, the Broca and Wernicke’s area are indispensable. There are different, yet overlapping roles played by the right and left hemispheres. Nerves and ganglia are the only thing contained in the PNS. The somatic and autonomic systems are the 2 subdivisions.
Information from external sensory receptors is taken to the CNS by the somatic system. Voluntary motor commands are also taken by this to the skeletal muscles, and from the cerebrum. Lots of reflex arcs are contained here and in this interneurons, in the spine, quickly send messages, without CNS input, to motor neurons.
The involuntary system called the autonomic system has control of the smooth muscles of the glands and internal organs. Our responses that occur during stressful times is associated with the sympathetic division. Meanwhile, the parasympathetic system is associated with our responses that happen while we are relaxed. Lipids have varying structures and functions. Fats and oils contain glycerol and three fatty acids and there function is for long-term energy storage. Fatty acids can be unsaturated or saturated. Phospholipids have a polarized head and they make up the plasma membrane in our cells. Some specific hormones are derived from a complex ring compound called cholesterol.  Gas and water are some of the substances that can cross a plasma membrane freely, meanwhile, particularly ions, charged molecules, and macromolecules need to be assisted to cross it.
 Diffusion and facilitated transport are passive ways of crossing a plasma membrane they do not need to use chemical energy (ATP). On the other hand active ways of crossing, like active transport or facilitated transport do.
 Some are able to diffuse across the membrane from an area of high concentration to low concentration, like water, gases, and lipid-soluble compounds.
 Osmosis is the diffusion of water across a differentially permeable membrane. Water moves to an area of lower water concentration across a membrane. In an isotonic solution cells don’t gain or loose water, in a hypertonic solution they gain water, and in a hypertonic solution the lose water.
 Carrier proteins transport some molecules across the membrane. Facilitated transport: carrier protein helps move the molecule across its concentration gradient and no energy is needed.
 Active transport: carrier protein works as a pump and makes the substance go against its concentration gradient and energy (ATP molecules) are needed.
 Through exocytosis and endocytosis larger substances and exit or enter a membrane. Secretion is involved in exocytosis. Phagocytosis and pinocytosis are included in endocytosis. A type of pinocytosis called receptor-mediated endocytosis uses a coated pit and receptor molecules in the plasma membrane that pinches of, forming a vesicle.  Digestive enzymes are like all enzymes, they are specific to their substrate and they speed up certain reactions and they operate at optimum body temperature and pH. They break food into smaller molecules like amino acids, glucose, fatty acids, and glycerol so they can be absorbed. Food passes through the digestive tract and as it does:
 Salivary amylase starts digestion of starch in the mouth.
 Pepsin starts the digestion of proteins into peptides in the stomach.
 Starch, protein, and fat is digested by pancreatic amylase, trypsin, and lipase in the intestines. These enzymes produced in the small intestines finish starch and protein digestion. The allowance of O2 from the air and into the blood and the exit of CO2 from the blood to the outside of the body is the main function of the respiratory system. There are two major parts of the respiratory system.
The upper respiratory tract, one of two major components, is made of the nose (your navel cavities, the nasopharynx, the pharynx, and the larynx. Your larynx contains the vocal cords.
The second of the two components is the lower respiratory tract. It is made up of the trachea, the bronchi, the bronchioles, and the lungs. Lots of alveoli are contained in the lungs. Alveoli are small air sacs that are surrounded by a capillary network. Inspiration and expiration are included in ventilation.
Excitatory nerve impulses are sent to the diaphragm and muscles of the rib cage from the respiratory center in the medulla oblongata. This is when inspiration begins. The diaphragm lowers as they contract and the rib cage moves out and up. A partial vacuum is created when the lungs expand and this makes air rush in and this is called inspiration.
Expiration takes place when impulses to the diaphragm and the muscles of the rib cage stop having signals sent to them by the respiratory center. The diaphragm resumes its dome shape as it relaxes and air is pushed out of the lungs as the rib cage retracts. Air being pushed out of the lungs is called expiration. Through diffusion oxygen and carbon dioxide are exchanged during internal and external respiration.
When CO2 leaves the blood through the alveoli and O2 takes its place going into the blood via the alveoli external respiration is taking place. CO2 diffuses into the alveoli from the blood because the PCO2 is higher in the pulmonary blood than in the alveoli, in the lungs. CO2 present in the blood mostly as HCO3- and because of this carbonic acid is formed at first and then broken down into carbon dioxide and water. In the alveoli the PO2 is higher than in the blood so O2 diffuses into the blood and then is transported in to the tissues as oxyhemoglobin (HbO2 a combination of O2 and hemoglobin).
In the tissues is where internal respiration happens and it happens when O2 leaves and CO2 enters the blood. The reason why this occurs is because the level of PO2 is higher in the arterial blood than in the tissues, and the PCO2 is lower. Carbonic acid forms and is broken down to form the bicarbonate ion (HCO3-) and hydrogen ions when carbon dioxide enters the blood. Within the plasma as the bicarbonate ion is how carbon dioxide mainly gets taken to the lungs. Reduced hemoglobin (HHb) is formed as hemoglobin and hydrogen ions are combined. The urine conducted by the ureters to the bladder is produced by the kidneys. Urine is stored in the bladder before it is released through the urethra. Through this the kidneys serve three function:
The excretion of metabolic wastes most specifically that of nitrogenous waste.
Keeping a normal water-salt balance.
Keeping a healthy acid-base balance in the blood.
The kidneys also serve a function not related to urine production. The 4th major function is the production of hormones.
Red blood cell production is stimulated by erythropoietin.
The adrenal cortex releases aldosterone because renin leads to its secretion.
Another thing that the kidneys do is convert vitamin D to its active biological form. The kidneys are divided into the renal cortex, medulla, and pelvis macroscopically. Microscopically they can also contain nephron.
There is a blood supply for each single nephron. The glomerular capsule is approached by the afferent arteriole, which then splits to become the glomerulus (capillary tuft). After the efferent arteriole leaves to glomerulus capsule it branches off into the peritubular capillary network.
The glomerular capsule, proximal convoluted tubule, loop of nephron, and the distal convoluted tubule are all parts of the nephron. Small molecules enter the capsule from the glomerulus via the spaces between the podocytes. There are lots of mitochondrion and microvilli in the cuboidal epithelial cells of the proximal convoluted tubule that carry out active transport from the tubule to the blood. The same cells of the distal convoluted tubule have tons of mitochondria, but not the microvilli. Active transport from the blood to the tubule is carried out by them.
Salts in water and nitrogenous waste products are what urine is made of. The three steps of urine formation are:
Glomerular filtration: water and small molecules of nutrients and wastes move to the inside of the glomerular capsule from the blood.
Tubular reabsorption: takes place mostly at the proximal convoluted tubule. Its where water and nutrients return to the blood.
Tubular secretion: specific substances, like H+, are transported into the distal convoluted tubule from the blood. There are three steps to the reabsorption of water and the production of hypertonic urine.
Salts reabsorption increases blood volume and pressure as well because more water is reabsorbed too. The kidneys reabsorption is controlled by aldosterone and ANH.
A solute gradient that increases toward the inner medulla is established when sodium is actively transported out of the ascending limb of the loop of nephron.
The gradient now established draws water from the descending limb of the loop of nephron and the collecting duct. The hormone ADH controls the permeability of the collecting duct.
The pH of blood is kept in normal limits by the kidneys.
The kidneys excrete H+ and absorb HCO3 – when needed to keep the pH around 7.4. in the urine ammonia also buffers H+. The hypothalamus and anterior pituitary have control of the ovarian cycle. It is normally divided into the follicular and luteal phase.
FSH causes the follicle to mature. The follicle secretes estrogen as well as some progesterone. This is the follicular phase.
After ovulation and during the latter half of the ovarian cycle the follicle is converted into the corpus luteum, that secretes progesterone as well, by the LH.
The uterine cycle: varies because it depends on whether fertilization does or doesn’t occur. The endometrium is thickened by the estrogen produced by the new ovarian cycle and this happens in all cases. Ovulation occurs because it is caused by a surge of LH. On day 14 of a 28-day cycle is normally when ovulation occurs. The corpus luteum produces progesterone, which makes the endometrium thicken and get secretory.
When no pregnancy occurs the low level of hormones results in menstruation because the low levels caused the endometrium to breakdown.
If pregnancy occurs the thickened endometrium has the embryo implanted in it. The hCG production by the placenta keeps the corpus luteum in the ovary maintained. The placenta later produces estrogen and progesterone. During a pregnancy menstruation usually doesn’t occur. Investigators did 2 separate experiments. With 35 S and the DNA of 32 P investigators labeled a bacterial virus’s protein coat. Then they showed that the bacterial host only largely took up the radioactive P. This was followed by the reproduction of viruses. This was the data that convinced them that DNA is the genetic material.
DNA is made up of two sugar-phosphate backbone and paired nitrogen containing bases. DNA is a double helix. The nitrogen-containing bases are Adenine (A) which is paired with Thymine (T) and Guanine (G) is paired with Cytosine (C).
DNA “unzips” during replication then opposite to the original strand a complementary strand is formed. Because of this replication is semiconservative (there is one new strand and one conserved old strand in the new double helixes). RNA is complementary to DNA segment, but it is a single stranded nucleic acid. Instead of having T, RNA has U (uracil).
Messenger RNA, ribosomal RNA, and transfer RNA are included in functional RNA. All three have certain function in protein synthesis. Every cell type has its own mixture of proteins and this makes it different from all other cells. Cells that act our specialized functions only have certain genes active. Housekeeping genes are the other active genes and they are called this they are the governors of the common functions of many cells.
Genes are clustered into operons in bacteria. A group of genes that are normally coding for proteins related to a certain metabolic pathway are contained in an operon, as well as a DNA pattern where transcription is started after a RNA polymerase binds to it. The structural genes code for enzymes that metabolize lactose happens in the case of a lac operon. The repressor binds to the operator and shuts off the operon when lactose is absent. The RNA polymerase is allowed to transcribe the structural genes after lactose, when present, binds to the repressor so that it can’t bind with the operator. Instead of being inducible some bacterial operons are repressible.
In eukaryotes control of gene expression is more complicated. They have 5 levels of control: pretranscriptional control, transcriptional control, posttranscriptional control, translational control, and posttranslational control.
Inactive genes are found in the highly condensed heterochromatin (ex: inactivated X-chromosomes called Barr bodies). Euchromatin, genes found in looser-packed DNA, need to have the nucleosomes shifted to be exposed.
The transcription factors that help the RNA polymerase and transcriptional activators that hugely help the rate of transcription are included in the transcriptional level of control.
The differences in mRNA processing affect gene expression in posttranscriptional control.
The length of time the mRNA is functional is involved in translational control, which occurs in the cytoplasm.
The length of time the protein is functional is involved in posttranslational control, which also occurs in the cytoplasm. There is a variety of ways that proteins can be activated. A permanent change in the pattern of bases in DNA is called a gene mutation. This changes affect on a proteins activity can go from no effect to a complete inactivity.
Errors in replication, mutagens, and transposons result in a change in the pattern of nucleotides in the DNA and they can cause a gene mutation.
The change of one DNA nucleotide can be a possible change into a certain amino acid, is called a point mutation. When one ore more nucleotides are inserted or deleted from DNA is the normal occurrence for a frameshift mutation.
Cancers development is involved in a series of accumulating mutations that differ for the different kinds of cancer. Carcinogenesis start with the loss of a tumor suppressor gene activity or the gain of oncogene activity. Mutations in lots of other genes also contribute. They normally follow a common multistep progression. The normal cells regulation is defied by cancer cells and they don’t exhibit contact inhibition and so they form tumors. These cells become malignant when they have the ability to invade their surrounding tissues.
The primary characteristics of cancer cells are don’t regulate the cell cycle correctly, are genetically unstable, and they escape the signals for cell death, and they can survive and multiply/ grow in other places in the body (metastasis). Chromosomal aberrations and multiple mutations are found in cancer cells. They are normally nonspecialized and continue to cycle through the cell cycle. to either internal and external signal for apoptosis they don’t respond; they also induce the expression of telomerase to fix their telomeres. Prokaryotic cells were probably the first cells; while eukaryotic cells probably came from them in stages.
It is suggested that eukaryotic cells are closer to archaea than bacteria by biochemical data.
Mitochondria and chloroplasts might have come from endosymbiotic events, meanwhile, the nuclear envelope probably evolved from the plasma membrane through invagination. The NUCLEAR ENVELOPE that binds the nucleus has pores, which work as passageways between the nucleoplasm and cytoplasm. Chromatin, within the nucleus, is a complex of protein and DNA. It is divided into chromosomes (separate structures of chromatin). The organelles that function in protein synthesis are called RIBOSOMES. They are found in the cytoplasm by themselves or in groups called polyribosomes or they can be bound to the endoplasmic reticulum (ER). The processing of proteins and their repackaging into LYSOSOMES or vesicles for transport to the plasma membrane or different organelles is done by the Golgi apparatus. Lysosomes carry out intracellular digestion. The ER, Golgi apparatus, the lysosomes, vacuoles, and vesicles are all a part of the ENDOMEMBRANE SYSTEM. This system compartmentalizes the cell. Ribosomes cover the rough endoplasmic reticulum (RER) which takes part in folding, modification, and the transport of proteins. The smooth endoplasmic reticulum (SER) forms vesicles to carry products to the Golgi apparatus; it also has other various metabolic functions depending on the kind of cell. Large storage sacs, called VACUOLES, meanwhile vesicles are smaller ones. Plant cells large vacuole stores substances and give support to the plant cell. Enzymes contained in PEROXISOMES oxidize molecules by making hydrogen peroxide, which is subsequently broken down. In order to keep their structure cells need a constant input of energy. Energy from the sun is captured by chloroplasts and then photosynthesised to produce carbohydrates. MITOCHONDRIA. the cells energy powerhouse, breakdown carbohydrates too produce ATP. Chloroplasts are only contained by plants, algae, and cyanobacteria. Actin filaments, intermediate filaments, and microtubules make up the CYTOCKELETON. The cytoskeleton keeps the cells shape while letting it and its organelles move. Motor molecules, like myosin in muscle cells, and actin filaments interact. There are microtubules in centrioles, cilia, and flagella. They work as tracts in the cytoplasm for vesicles and other organelles to move depending on the action of certain motor molecules. { A series of reactions, called metabolic pathways, that proceed in an orderly, step-by-step manner. There is a specific enzyme for each reaction.
When enzymes form a complex with their substances the reaction rate increases. As substrate concentration increases enzymes activity normally increases. The maximum rate is achieved when all of the active sites are filled.
The shape of a protein is affected by environmental changes, like the temperature and pH levels. When the shape of a protein is affected the ability of an enzyme to do its job is also affected.
Enzymes activity and quantity is regulated by cellular mechanisms. Feedback inhibition regulates the activity of most metabolic pathways. To help them carry out reactions many enzymes have cofactors or coenzymes. There are three types of blood vessels.
The blood vessels that take blood away from the heart are called arteries and arterioles.
There is an exchanges of substances with the tissues at the capillaries
The blood vessels that take blood back to the heart are called veins and venules. The two divisions of the cardiovascular system are called the pulmonary circuit and the systemic circuit.
Pulmonary circuit: involves the lung, heart, veins, arteries and the pulmonary capillaries. The pulmonary trunk takes blood from the right ventricle of the heart, and then O2 poor blood is taken to the lungs by the 2 pulmonary arteries. The O2 rich blood is taken back to the left atrium of the heart by the 4 pulmonary veins.
Systemic circuit: O2 rich blood is pumped into the aorta from the left ventricle. The aorta branches off making arteries that take the blood to different organs. The arteries are divided into arterioles and capillaries. The capillaries lead to venules which turn into veins. The O2 poor blood is taken to the vena cava by a vein that probably has the same name as the artery that took the blood to the organ.
The capillaries are where the portal systems start and end. The start of the hepatic portal vein is in the intestinal capillaries and it ends in the hepatic capillaries.
Under pressure blood is pushed into the aorta from the left ventricle. Because systolic pressure occurs during ventricular contraction it is higher in pressure. Meanwhile, diastolic pressure is less because it occurs during relaxation. There is a higher pressure in arteries than in veins. Veins have muscular movement and one-way valves to help them take the blood back to the heart. Two cardiovascular disorders that can lead to strokes, heart attacks, and aneurysms are hypertension and atherosclerosis. There are procedures, both medical and surgical, to manage these diseases. However, the best way to do this is prevention. To do this follow a heart-healthy diet, don’t smoke, stay exercises, and keep a proper weight. The plasma and the formed elements are the two main parts of blood.
Plasma: Have water, proteins, nutrients, and wastes. Prothrombin and fibrinogen are two proteins known to aid the clotting process.
Formed elements: Have red blood cells, white blood cells, and platelets. Oxygen transport is done by the hemoglobin containing red blood cells. The defence against disease is done by white blood cells. Monocytes are phagocytic; neutrophils are too. The development of adaptive immunity to disease is something lymphocytes are involved with. Platelets are also involved with blood clotting.
Water moves or at the arterial end when blood gets to a capillary because of blood pressure. Water moves in at the venule end because of osmotic pressure. In the middle wastes move in and nutrient go out by diffusion. The pancreas, liver, and the gallbladder are the three accessory organs of digestion, and they send secretions to the duodenum through ducts.
Pancreatic juice is made by the pancreas and this juice contains sodium bicarbonate and enzymes that chemically digest starch, protein, and fat. The enzyme that digests starch is pancreatic amylase, trypsin digests protein, and lipase digests fat.
There are many important functions of the liver. The liver gets blood from the small intestines via the hepatic portal vein. It helps to detoxify harmful substances present. It also helps to get rid of excess nitrogen from the body and monitor our bloods glucose concentrations. Plasma proteins and bile are produced here. Bile helps break apart (emulsify) fats in the intestine.
Bile is stored here and then secreted via the common bile duct into the duodenum. Bile readies fat for digestion by lipase. The digestion tract is involved with several things. It is involved with ingestion, digestion, and the elimination of indigestible material. The following parts are in the digestive tract:
Food is taken in the body via the mouth. Saliva is sent to the mouth by the salivary glands, once in the mouth the teeth chew the food, the tongue makes a bolus for swallowing, and saliva starts the digestion of starch (saliva is an enzyme that contains salivary amylase.
The food and air passage cross at the pharynx. The epiglottis normally covers the air passage when we swallow, allowing the food to enter the esophagus and this is where peristalsis starts.
The muscular tube that takes food from the pharynx to the stomach is called the esophagus.
The place where food is stored is the expandable stomach. The stomach churns, mixing the food with acidic gastric juice. An enzyme that digests protein is called pepsin and its found in gastric juice.
There are 3 parts of the small intestines: duodenum, jejunum, and ileum. Bile from the liver and pancreatic juice from the pancreas are received in the duodenum. There are finger like projections on the walls of the small intestines called villi and it is here that small nutrient molecules are absorbed. At the blood vessels of a villus amino acids and glucose enter. Before entering lymphatic vessels called lacteals in a villus glycerol and fatty acids are joined together and packaged as lipoproteins.
The large intestines includes the cecum, colon, and the rectum, which ends at the anus. The colon includes the ascending, transverse, descending, and sigmoid colon. Water, salts, and some nutrients are absorbed in the small intestines. The Digestive Tract 14.1 c. Action potential ends: repolarization occurs when K+ gates open and K+ moves outside the axon.
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