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Transcript of Biology 12
THE MOLECULES OF CELLS
DNA STRUCTURE AND REPLICATION
CHEMISTRY OF WATER
CELL STRUCTURE AND FUNCTION
MOLECULES AND COMPOUNDS
All organisms are made of cells, and all cells come from already existing cells.
Prokaryotes are unicellular and are exemplified by bacteria. They also don't have membrane enclosed structures that eukarotes do. Eukaryotes are multicellular.
Prokaryotes have a cell wall, a capsule (slime layer surrounding the cell wall), a plasma membrane, flagellum (long appendages that rotate and allow the bacteria to move) and fimbriae (pili - short appendages which allow the bacteria to attach to other surfaces), cytoplasm which contains a single chromosome called a nucleiod, plasmids, ribosomes, and thykaloids.
MEMBRANE STRUCTURE AND FUNCTION
DNA STRUCTURE AND CONTROL OF GENE EXPRESSION
METABOLISM: ENERGY AND ENZYMES
Prokaryotic Vs Eukaryotic
Everything (nonliving and living) is made of matter.
Elements - atoms
- atoms with differing numbers of neutrons
Atoms react through their electrons
Ions - when atoms gain or lose electrons for a full outer orbital
- nonmetal and metal
- metal and metal
Polar Covalent Bonds occur when there is unequal sharing of electrons.
Hydrogen Bonds are weak bonds that keep the structure and function of cellular molecules.
Water is a polar molecule with is bonded to other water molecules through hydrogen bonding.
[This allows for water's special properties]
(H) pH lower than 7
(OH) pH higher than 7
Carbohydrates, lipids, proteins, and nucleic acids are macromolecules with specific cell functions.
Polymers are monomers that are joined together.
Dehydration Reaction :
Hydrolysis Reaction :
water is removed
water is added
Sugar monomers join to make a polysaccharide
Plants store glucose as starch
Animals store glucose as glycogen
Humans can't digest cellulose (makes up plant cell walls)
Lipids have differing structures and functions
Fats and Oils :
long-term energy storage; contain glycerol and three fatty acids
Fatty acids - saturated or unsaturated
in the plasma membrane; have polarized ends facing outward and non-polarized tails facing inward
Hormones come from cholesterol
Numerous functions within cells
Made up of polypeptides - amino acids joined together
Primary Structure :
Secondary Structure :
Tertiary Structure :
Quaternary Structure :
sequence of amino acids
alpha helix or beta pleated sheet
bend/twist into 3D shape
when a protein has several polypeptides
Nucleic acids are polymers of nucleotides
3 parts of a nucleotide :
Contains sugar deoxyribose, and is the genetic material that stores information for replication
DNA and RNA specify protein synthesis
ATP - energy of cells
ATP turns to ADP + phosphate so that the cell can do metabolic work
Plasma Membrane Structure and Function
Fluid-Mosaic Model :
lipid bilayer is fluid and proteins are embedded within the membrane
Peripheral Proteins :
Integral Proteins :
structural proteins that stabilize the shape of the plasma membrane
(move substances across the membrane)
carbohydrate chains attached to proteins and lipids
The Permeability of The Plasma Membrane
Ions, charged molecules, and macromolecules can't freely cross the plasma membrane (have to be transported across) whereas gases and water can.
Osmosis : diffusion of water across a differentially permeable membrane. * High-Low concentration *
Isotonic Solution :
Hypertonic Solution :
Hypotonic Solution :
water not gained or lost
water is gained; cell swells/bursts
water is lost; cell shrivels
No energy is required for facilitated transport because carrier proteins move molecules down their concentration gradient (high-low concentration). Diffusion also doesn't require energy.
Active transport is when a carrier protein acts as a pump to move molecules up their concentration gradient (low-high concentration). Energy (ATP) required
Larger substances exit the cell through exocytosis, where the substance is transported by a vesicle.
Large substances can enter the cell through endocytosis:
Receptor-mediated endocytosis (type of pinocytosis) which uses receptor molecules in the plasma membrane and a coated pit (which forms a vesicle).
rna STRUCTURE AND FUNCTION
cONTROL OF GENE EXPRESSION
2 sugar-phosphate backbones
paired nitrogen bases
A (adenine) - T (thymine)
G (guanine) - C (cytosine)
In replication, DNA unzips and a new, complementary stands bind to an old strand.
single-stranded nucleic acid
complementary to DNA (U (uracil) instead of T)
Types of RNA
Messenger RNA - mRNA
Transfer RNA - tRNA
Ribosomal RNA - rRNA
*RNA is used when creating proteins*
Two processes of Gene Expression
produces an RNA sequence complementary to a DNA strand
a guanine cap and adenine tail is added to mRNA (primary mRNA to mature mRNA) as well as introns are removed
moved to the cytoplasm for translation
triplet code/codon (3 bases of an mRNA) codes for one amino acid (order is specified by DNA)
tRNA molecules carry amino acids to a ribosome and their anticodons pair up with complementary codons
P site moves a peptide chain to a new tRNA, which is in A site
translocation occurs when the ribosome moves and the tRNA shuffle down to the next site
E site is the exit for used tRNA
the chain is complete when a stop codon is reached, resulting in a polypeptide
In cells which have specialized functions, only certain genes are active (housekeeping genes control the common functions of a cell).
contain a group of genes, a promoter, a DNA sequence where RNA polymerase binds to being transcription, and an operator where a repressor protein binds to
Five levels of control in Eukaryotes
pretranscriptional , transcriptional, posttranscriptional, translational, posttranslational
hererochromatin - highly condensed genes (inactive)
euchromatin - loosely packed genes (active)
the speed of transcription
differences in mRNA affect gene expression
in the cytoplasm the length of time the mRNA is functional
length of time the protein is functional
Gene mutation is the permanent change in the sequence of bases in DNA
Can be caused by:
errors in replication
A series of mutations can lead to the development of cancer
carcinogenesis - the loss of tumor suppressor gene active and/or the gain of oncogene activity
malignant - when tumor cells are able to invade other tissues
Cancer cells are genetically unstable, do not correctly regulate the cell cycle, escape signals for cell death, and can survive and continue growing in other parts of the body (metastasis)
Enzymes and metabolic Pathways
A metabolic pathway is a series of reactions
Each reaction in a metabolic pathway requires a specific enzyme
Enzymes speed up the reaction when substrates bind to them
maximum rate: when all the active sites for substrates to bind to enzymes are filled
Temperature and pH levels affect enzymes, either by increasing the speed or by denaturing the enzyme so that it cannot function correctly any more
enzymes have cofactors or coenzymes that help them carry out a reaction, and the quantity/activity of an enzyme is regulated by cellular mechanisms
feedback inhibition regulates enzyme activity
THE BLOOD VESSELS
THE VASCULAR PATHWAYS
THE HUMAN HEART
Absorption & Elimination
Ingestion & Digestion
Pancreas, Liver, Gallbladder
The respiratory system
Mechanism of Breathing
the limbic system and higher mental functios
The central nervous system
The peripheral nervous system
Blood is taken
from the heart by
Substance exchange with the tissues happens at
Blood is taken
the heart by
Left & Right side + 4 Chambers
Oxygen-poor blood is taked to the tight atrium by venae cavae, then it is pumped to the pulmonary circuit through the pulmonary trunk by the right ventricle.
Oxygen-rich blood is taked to the left atrium from the lungs by pulmonary veins, then it is pumped into the systemic circuit through the aorta by the left ventricle.
Atrioventricular valves :
valves that blood coming from the atria pass through into the ventricles
Semilunar Valves :
valves that blood leaving the ventricles passes through
SA node causes atria to contract (pacemaker)
AV node causes ventricles to contract (stimulus received from the SA node)
Oxygen-poor blood is taken to the lungs by the two pulmonary arteries from the right ventricle. Oxygen-rich blood is taken to the left atrium by the four pulmonary veins.
Oxygen-rich blood is pumped to the body by the left ventricle. Blood travels through the aorta which branches off into arteries and continues to branch into arterioles and capillaries. Venules come off of the capillaries and become veins, carrying oxygen-poor blood to the vena cava.
Portal systems start and end in capillaries
Systolic pressure : ventricles contract
Diastolic pressure : ventricles relax
Arteries have higher blood pressure than veins; veins use muscles and valves to return blood to the heart.
2 Main Parts of Blood :
water, proteins, nutrients, and wastes
red blood cells (transport oxygen and have hemoglobin), white blood cells (defend against diseases), and platelets (blood clotting)
At a Capillary :
Blood pressure causes water to move out of blood at the arterial end. Osmotic pressure causes water to move into blood at the venule end. Wastes diffuse into blood and nutrients diffuse out of blood into tissues.
Strokes, heart attacks, and aneurysms can occur because of hypertension or atherosclerosis
Cardiovascular diseases can be managed with medical/surgical procedures (healthy living is best obviously)
Food is taken in by the mouth
Salivary glands produce saliva (contains salivary amylase) to start breaking down starch. Teeth chew food, and the tongue forms a bolus for swallowing
The epiglottis blocks off the glottis, and peristalsis begins when the food enters the esophagus (muscular tube that takes food from the pharynx to the stomach).
The stomach mixes food with acidic gastric juice (contains pepsin - digests proteins).
The last of the digestion occurs in the duodenum
Bile from the liver and pancreatic juice (contains sodium-bicarbonate, trypsin, lipase, and pancreatic amylase) from the pancreas enter the duodenum, turning the acid chyme from the stomach basic.
The hepatic portal vein supplies the liver with blood. Blood is detoxified and glucose levels are monitored here. Excess nitrogen is removed. The liver also produces plasma proteins and bile.
The gallbladder stores liver-produced bile until it needs to be secreted into the duodenum through the common bile duct). Bile is an EMULSIFIER.
Villi line the walls of the small intestine. Villi absorb small nutrient molecules. Amino acids and glucose are absorbed through blood vessels in the villi. Lipoproteins (glycerol and fatty acids) enter lacteals.
The large intestine is made of the cecum, the colon, and the rectum. Water, salts, and some vitamins are absorbed in the large intestine. Defecation occurs at the anus.
4 sphincters throughout the digestive tract:
Digestive enzymes break food down into smaller molecules that can be absorbed.
salivary amylase starts breaking down starch in the mouth
pepsin starts breaking protein into peptides in the stomach
pancreatic amylase, trypsin, and lipase break down starch, protein, and fat
the small intestine produces enzymes that finish breaking down starch and protein
Gas Exchanges in the body
Oxygen enters the blood stream to be supplied throughout the body and carbon dioxide (cellular waste) exits the blood stream.
Nasal cavities, the nasopharynx, the pharynx, and the larynx make up the upper respiratory tract
The trachea, the bronchi & bronchioles, ad the lungs (made up of many alveoli - air sacs surrounded by capillaries) make up the lower respiratory tract
Breathing requires inspiration (inhaling) and expiration (exhaling)
The diaphragm and intercostal muscles receive nerve impulses from the medulla oblongata to contract (diaphragm lowers/rib cage moves up and out). Negative pressure is created, causing air to flow in.
The diaphragm and intercostal muscles stop contracting when the respiratory center stops sending signals, causing the uscles to relax (diaphragm moves back up/rib cage moves down and in). This cause air to be pushed out of the lungs.
Oxygen diffuses into the capillaries at the lungs because of low concentration. Carbon dioxide diffuses out of the capillaries into the alveoli where it is exhaled.
At the body tissues, oxygen diffuses out of the blood stream into the body tissues, and carbon dioxide diffuses into the blood stream from the body tissues.
Hemoglobin, which is sensitive to temperature and pH changes allows for carbon dioxide and oxygen to be transported throughout the body.
Common bronchial/pulmonary diseases
Acute Bronchitis: inflamed airways because of infection (acute) or because of an irritant (chronic). Mucus and pus coughed up.
Asthma: inflamed airways because of an irritant. Muscles spasms cause bronchioles to constrict.
Pneumonia: gas exchange is made difficult because of pus and fluid in alveoli.
Pulmonary Tuberculosis: elasticity of lungs is reduced because of tubercles forming around bacteria.
Emphysema: gas exchange surface area is reduced because of bursting/fusing alveoli.
Pulmonary Fibrosis: lung elasticity is reduced because of a build up of fibrous connective tissue.
made of dendrites, a cell body, and an axon (long axons are covered in a myelin sheath.
Sensory neurons (take info from sensory receptors to the CNS)
Interneurons (inside the CNS)
Motor neurons (take info from the CNS to effectors)
Action potential needed to transmit nerve impulses
Resting potential at -65mV
Depolarizes to +40mV when sodium gates open
Repolarizes to -65mV when potassium gates open
Sodium-potassium pumps return axon to resting potential
Neurotransmitters carry sensory info across chemical synapses. Excitatory and inhibitory signals are summed up by synaptic integration.
The CNS: spinal cord & brain
Sensory input it sent to the brain through the spinal cord and reflex actions are carried out because of motor output sent to the spinal cord from the brain.
Spinal cord: gray matter inside matter (which is made of myelinated axons that run in tracts).
Brain: white matter inside gray matter (which is made of nonmyelinated axons and cell bodies)
Spinal cord & brain are protected by bone and meninges.
Cerebrum: responsible for sensation, reasoning, learning, memory, language and speech. The corpus callosum connects the two cerebral hemispheres. A thin layer of gray matter called the cerebral cortex covers the cerebrum. Four lobes: frontal, parietal, occipital, temporal. Primary motor area sends motor commands. Primary somatosensory are receives sensory information.
Diencephalon contains the hypothalamus (maintains homeostasis) and the thalamus (sends sensory input to the cerebrum).
Cerebellum coordinates muscle contractions.
Brain stem contains the medulla oblongata & pons (control reflexive actions).
The hippocampus converts short-term memory into long-term memory.
The amydgala is responsible for adding emotions to our memories.
The limbic system allows us to have emotions and higher mental functions:
3 Types of Memory:
Broca's area and Wernicke's area (in the left hemispere) are responsible for humans to understand written and spoken words as well as speaking themselves.
The PNS (peripheral nervous system) contains nerves and ganglia:
Somatic system: takes sensory information to the CNS and takes motor commands to the muscles from the CNS. It also has reflex arcs where quick responses to homeostasis-disrupting stimuli occur.
Autonomic system: controls smooth muscles and glands (involuntary). It has 2 divisions:
- Sympathetic Division: "Fight or Flight"
- Parasympathetic Division: "Rest and Digest"
Urine is produced by the kidneys, taken through ureters to the bladder, and excreted through the ureter.
Kidneys have 4 functions:
Metabolic waste excretion
Water-salt balance maintenance
Acid-base balance maintenance (in the blood)
Hormone production (erythropoietin stimulates red blood cell production, renin stimulates aldosterone secretion)
ANATOMY of the kidney and excretion
Kidneys contain a renal cortex, renal medulla, and renal pelvis. They also contain millions of nephrons.
An afferent arteriole takes blood to the glomerular capsule, which becomes the glomerulus (capillary tuft), inside the nephron. An efferent arteriole takes the blood away from the glomerulus to the peritubular capillary network.
Parts of a nephron: glomerular capsule, proximal convoluted tubule, loop of Henle, and the distal convuluted tubule which connects to a collecting duct.
Glomerular filtration is when blood pressure causes water and other small molecules (nutrients and wastes) to leave the blood in capillaries in the glomerulus. This fluid becomes FILTRATE.
Tubular reabsorption happens in the proximal convoluted tubule (as well as the loop of the nephron), which contains microvilli. Lots of water and nutrients move back into the blood.
Tubular secretion is when excess substances in the blood are transported into the filtrate in the distal convoluted tubule.
Regulatory functions of the kidneys
Salt reabsorption increases blood volume and pressure. Aldosterone and ANH (controls the permeability of the collecting duct) hormones affect how mch sodium is being reabsorbed.
A solute gradient in the inner medulla results due to salt being actively transported out of the ascending limb of the loop of Henle - this causes water in the descending limb (and hte collecting duct) to diffuse out of the filtrate.
Blood pH is maintained by the kidneys because they reabsorb bicarbonate ions and excrete hydrogen ions to keep the pH at 7.4.
Male Reproductive System
Female reproductive system
implantation and pregnancy
Spermatogenesis is the production of sperm, which occurs in the seminiferous tubules in the testes. The sperm are stored in the epididymis. The vas deferens take the sperm, along with seminal fluid (produced from the seminal vesicles, prostate gland, and Cowper's gland) to the urethra.
2 external genetalia structures: the penis and the scrotum (contains the testes).
This system is controlled by the hypothalamus, which secretes GnRH to the anterior pituitary. This causes the secretion of FSH (promotes sperm maturation) and LH (promotes testosterone production).
Testosterone matures primary sex organs an develops secondary sex characteristics.
Oogenesis is the production of an ovum. Ova are contained in the ovaries. Ova are contained in follicles and as they mature, the follicle bulges out of the ovary. A mature follicle is called a Graafian follicle. The leftover follicle structure becomes a corpus luteum, which secretes hormones to prepare for possible pregnancy. Ovulation occurs when the ovum is released.
An ovum is directed into the oviduct from the ovaries by fimbrae. Inside the oviduct, cilia brush it towards the uterus, where it will embed itself if fertilized.
Hormones regulate this system: FSH matures ova and LH stimulates estrogen and progesterone secretion. Estrogen is responsible for primary sex organ maturation as well as the development of secondary sex characteristics. Estrogen thickens the endometrium (inner lining of the uterus) and progesterone matures ait and makes it secretory. If fertilization doesn't occur, these hormone levels drop and the endometrium is shed - menstruation.
2 cycles: ovarian and uterine
Fertilization of an ovum occurs in the oviduct. The zygote begins diving by mitosis, and it embeds itself in the endometrium wall in the uterus. A new hormone, HCG, is released to keep the corpus luteum from degenerating so that estrogen and progesterone continue to be secreted.
Placenta forms from embryonic and maternal tissues. This allows for plasma component exchange. As the placenta matures, it starts secreting estrogen and progesterone. When it is matured enough, it takes over, and HCG secretions stop and the corpus luteum degenerates.
The posterior pituitary releases the oxytocin hormone during labor. Pressure on the cervix (uterus contractions) stimulate this release - this is a positive feedback relationship.