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Structural Basis of Life
Transcript of Structural Basis of Life
The Structural Basis of Life
Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion.
The English scientist Robert Hooke first observed plant cells with a crude microscope in the late 1600s. Then, in the 1830s two German scientists, Matthias Schleiden and Theodor Schwann, proposed that all living things are composed of cells. German pathologist Rudolf Virchow extended this idea by contending that cells arise only from other cells. Since the late 1800s, cell research has been exceptionally fruitful and provided us with four concepts collectively known as the cell theory
A cell is the basic structural and functional unit of living organisms. When you define cell properties, you define the properties of life.
■ The activity of an organism depends on both the individual and the collective activities of its cells.
■ According to the principle of complementarity of structure and function, the biochemical activities of cells are dictated by their shapes or forms, and by the relative number of their specific subcellular structures.
■ Continuity of life from one generation to another has a cellular basis.
One or more per cell
Denser than surrounding cytoplasm
Usually in the form of chromatin
Contains genetic information
Composed of DNA
Thicken for cellular division
Set number per species (i.e. 23 pairs for human)
Composed of two layers
Numerous openings for nuclear traffic
Visible when cell is not dividing
Contains RNA for protein manufacture
• Collective term for cytosol and organelles contained within
• Colloidal suspension
• Cytosol mainly composed of water with free-floating molecules
• Viscosity constantly changes
Paired cylindrical organelles near nucleus
Composed of nine tubes, each with three tubules
Involved in cellular division
Lie at right angles to each other
Tubular network fused to nuclear membrane
Goes through cytoplasm onto cell membrane
Stores, separates, and serves as cell's transport system
Smooth type: lacks ribosomes
Rough type (pictured): ribosomes embedded in surface
Protein 'packaging plant'
A membrane structure found near nucleus
Composed of numerous layers forming a sac
Digestive 'plant' for proteins, lipids, and carbohydrates
Transports undigested material to cell membrane for removal
Vary in shape depending on process being carried out
Cell breaks down if lysosome explodes
Second largest organelle with unique genetic structure
Double-layered outer membrane with inner folds called cristae
Energy-producing chemical reactions take place on cristae
Controls level of water and other materials in cell
Recycles and decomposes proteins, fats, and carbohydrates, and forms urea
Each cell contains thousands
Miniature 'protein factories'
Composes 25% of cell's mass
Stationary type: embedded in rough endoplasmic reticulum
Mobile type: injects proteins directly into cytoplasm
Biological Level of Organization
At this level, atoms, tiny building blocks of matter, combine to form molecules such as water and proteins. Molecules, in turn, associate in specific ways to form organelles, basic components of the microscopic cells.
The cell is smallest unit of life that is able to carry out all the functions of living things. Cells have some common functions, but individual cells vary widely in size and shape, reflecting their unique functions in the body.
Tissues are groups of similar cells that have a common function. The four basic tissue types in the human body are epithelium, muscle, connective tissue, and nervous tissue.
The organ consists of different tissues that function together to do a certain job.
The organ system consists of different organs that work together for a specific function. These are the following organ systems with their major organs and functions
Within a population there are organisms, just one of those organisms is called an organism.
Population is a group of organisms of the same species in any given area.
A community consists of various populations of organisms living together in a given area.
Membrane-bound sacs for storage, digestion, and waste removal
Contains water solution
Contractile vacuoles for water removal (in unicellular organisms)
A plastid usually found in plant cells
Contain green chlorophyll where photosynthesis takes place
Most commonly found in plant cells
Extracellular structure surrounding plasma membrane
Primary cell wall: extremely elastic
Secondary cell wall: forms around primary cell wall after growth is complete
Two Primary Types of Cells
Prokaryotes are unicellular organisms, found in all environments. Prokaryotes are the largest group of organisms, mostly due to the vast array of bacteria which comprise the bulk of the prokaryote classification.
• No nuclear membrane (genetic material dispersed throughout cytoplasm)
• No membrane-bound organelles
• Simple internal structure
• Most primitive type of cell (appeared about four billion years ago)
Eukaryotes are generally more advanced than prokaryotes. There are many unicellular organisms which are eukaryotic, but all cells in multicellular organisms are eukaryotic.
• Nuclear membrane surrounding genetic material
• Numerous membrane-bound organelles
• Complex internal structure
• Appeared approximately one billion years ago
Tissues composed of layers of cells that cover organ surfaces such as surface of the skin and inner lining of digestive tract: the tissues that serve for protection, secretion, and absorption.
the most abundant and widely distributed of the primary tissues, but its amount in particular organs varies. For example, skin consists primarily of connective tissue, while the brain contains very little.
Muscle cells are the contractile tissue of the body. Its function is to produce force and cause motion, either locomotion or movement within internal organs. Muscle tissue is separated into three distinct categories: visceral or smooth muscle, which is found in the inner linings of organs; skeletal muscle, which is found attached to bone in order for mobility to take place; and cardiac muscle which is found in the heart.
Nervous tissue is the main component of the nervous system—the brain, spinal cord, and nerves—which regulates and controls body functions. It contains two major cell types: neurons and supporting cells. Neurons are highly specialized nerve cells that generate and conduct nerve impulses. Typically, they are branching cells with cytoplasmic extensions or processes that enable them to respond to stimuli (via processes called dendrites) and transmit electrical impulses over substantial distances within the body (via processes called axons).
Functions of the Skin
The integumentary system consists of the largest organ in the body, the skin. This extraordinary organ system protects the internal structures of the body from damage, prevents dehydration, stores fat and produces vitamins and hormones.
Components of the skin include hair, nails, sweat glands, oil glands, blood, lymph vessels, nerves and muscles. Concerning integumentary system anatomy, the skin is composed of a layer of epithelial tissue (epidermis) that is supported by a layer of connective tissue (dermis) and an underlying subcutaneous layer (hypodermis or subcutis).
The epidermis is characterized into two distinct types: thick skin and thin skin. Thick skin is about 1.5 mm thick and is found only on the palms of the hands and soles of the feet. The rest of the body is covered by thin skin, the thinnest of which covers the eyelids.
The layer beneath the epidermis is the dermis. This is the thickest layer of skin composing almost 90 percent of its thickness. This layer contains specialized cells that help regulate temperature, fight infection, store water and supply blood and nutrients to the skin. The specialized cells of the dermis also help in the detection of sensations and give strength and flexibility to the skin. Components of the dermis include blood vessels, lymph vessels, sweat glands, sebaceous gland, hair follicles, sensory receptors, collagen, elastin.
• The skin's most important function is to protect
• It acts as the main barrier between the environment ard the internal organs of the body, shielding them from injury, the harmful rays of sunlight, and invasion by infective agents, such as bacteria
• The skin is a sensory organ containing many cells that are sensitive to touch, temperature, pain, pressure, and itching
• It also plays a role in keeping the body temperature constant
• The epidermis contains a unique fatty substance that makes the skin waterproof — thus making it possible to sit in a bath without soaking up the water like a sponge
• The outer epidermis also has an effective water-holding capacity. which contributes to its elasticity and serves to maintain the body balance of fluid and electrolytes. If the water content drops below a certain level, the skin becomes cracked, reducing its efficiency as a barrier.
The three types of muscle (skeletal, cardiac and smooth) have significant differences. However, all three use the movement of actin against myosin to create contraction. In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the nerves, the motoneurons (motor nerves) in particular. Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with. All skeletal muscle and many smooth muscle contractions are facilitated by the neurotransmitter acetylcholine.
of Muscle Tissue
Properties of Muscle Tissue
The shortening of muscle.
Muscles contract in two ways. During an isotonic contraction, muscles exert a steady pull and get much shorter. During an isometric contraction, muscles exert a strong pulling force, or tension, but become only slightly shorter. You would use an isotonic contraction to pick up this book, and an isometric contraction to hold it steady. Regardless of how relaxed you feel, your muscles are always slightly contracted to maintain your body’s posture. This partial contraction produces firmness, or muscle tone, without which your body would collapse under the influence of gravity.
• Producing body movement
• Stabilizing body positions
• Storing and moving substances within the body
• Generating heat
1. Electrical excitability, a property of both muscle and nerve cells, is the ability to respond to certain stimuli by producing electrical signals such as action potentials.
2. Contractility is the ability of the muscle tissue to contract forcefully when stimulated by an action potential.
3. Extensibility is the ability of the muscle to stretch without being damaged. Extensibility allows a muscle to contract forcefully even if it is already stretched. Normally, smooth muscle is subject to the greatest amount of stretching.
4. Elasticity is the ability of the muscle tissue to return to its original length and shape after contraction or extension.
perimentally using work loop analysis.
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support and protect the various organs of the body, produce red and white blood cells and store minerals. Together, they make up the skeletal system.
The skeletal system supports and protects the body while giving it shape and form. This system is composed of connective tissues including bone, cartilage, tendons, and ligaments. Nutrients are provided to this system through blood vessels that are contained within canals in bone. The skeletal system stores minerals, fats, and produces blood cells. Another major role of the skeletal system is to provide mobility. Tendons, bones, joints, ligaments and muscles work in concert to produce various movements. The skeleton is composed of fibrous and mineralized connective tissues that give it firmness and flexibility. It consists of bone, cartilage, tendons, joints, and ligaments.
Bone - a type of mineralized connective tissue that contains collagen and calcium phosphate, a mineral crystal. Calcium phosphate gives bone its firmness. Bone tissue may be compact or spongy. Bones provide support and protection for body organs.
Cartilage - a form of fibrous connective tissue that is composed of closely packed collagenous fibers in a rubbery gelatinous substance called chondrin. Cartilage provides flexible support for certain structures in adult humans including the nose, trachea, and ears.
Tendon - a fibrous band of connective tissue that is bonded to bone and connects bone to bone.
Ligament - a fibrous band of connective tissue that joins bones and other connective tissues together at joints.
Joint - a site where two or more bones or other skeletal components are joined together.
Types of Epithelium
1. Simple Squamous epithelium – consists of a single layer of flat cells. It is found in parts of the body where filtration or diffusion is priority processes. One type, endothelium, lines the heart and blood vessels. Another type, mesothelium, forms the serous membranes that line the thoracic and abdominopelvic cavities and cover the organs within them.
2. Simple Cuboidal epithelium — consists of a single layer of cube-shaped cells; functions in secretion and absorption. It is found covering the ovaries, kidneys and eyes, and lining some glandular ducts.
3. Noncialated simple columnar — consists of a single layer of nonciliated rectangular cells. It lines most of the gastrointestinal tract. Specialized cells, containing microvilli perform absorption. Goblet cells secrete mucus.
4. Ciliated simple columnar- consists of a single layer of ciliated rectangular cells. It is found in found in few portions of the upper respiratory tract, where it moves foreign particles trapped in mucus out of the respiratory tract.
5. Stratified Squamous Epithelium- consists of a several layer of ciliated rectangular cells. It is found in portions of the upper respiratory tract, where it moves foreign particles trapped in mucus out of the respiratory tract.
6. Stratified cuboidal epithelium – consists of several layers of cells. It is found in adult sweat glands and a portion of the male urethra
7. Transitional epithelium - consists of several layers of cells whose appearance varies with the degree of stretching
8. Pseudostratified columnar epithelium – has only one layer but gives the appearance of many; contains goblet cells and lines most of the upper respiratory tract
Different layers of the epidermis
• Stratum germinativum (also called "stratum basale" — this contains a single row of cells that continuously divide, with the new cells being pushed outwards.
• Stratum spinosum — which consists of 8-10 rows Of cells covered in spine-like projections. As the cells continue to push outwards, they enter the granular layer
• Stratum granulosum — here, their nuclei start to break down, and they become filled with keratin.
• Stratum lucidum — is a thin, clear layer of dead skin cells and is named for its translucent appearance. It contains a clear substance called eleidin, which eventually becomes keratin. This layer is only found on the palms of the hands and the soles of the feet.
• Stratum comeum — the outermost layer that is flat and completely dead. The outermost cells are constantly worn away, and are replaced by new cells growing up from below.
• Sebaceous glands — are usually connected to hair follicles. Trey produce an oily liquid called sebum, which keeps skin and hair son and flexible
• Sweat glands — lie in the dermis. Each one is connected to a smal depression in the surface, called sweat pore, by a short sweat duct When the body overheats, the glands produce a salty fluid called sweat
Theory of Muscular Contraction: As muscle contracts, the actin filaments slide towards the centre of the sarcomere and further overlap with the myosin filaments, and sometimes with each other.
is the bone's shaft or body-the long cylindrical, main portion of the bone.
are the distal and proximal ends of the bone.
a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length.
a thin layer of hyaling cartilage covering the epiphysis where the bone forms an articulation (joint) with another bone
is a tough sheath of dense irregular connective tissue that surrounds the bone surface where it's not covered by the articular cartilage
is the space within the diaphysis that contains fatty yellow bone marrow
thin membrane that lines the medullary cavity
Christia Erika Respicio
Divine Joy Ricarte