I. Cell--Basic Unit of living things
1. Contain genetic material to govern development, metabolism, and specializations
2. Specialized Properties of cells:
A. Contractility B. Conductivity C. Metabolism D. Irritability E. Reproduction
II. Cell Components
1. Nucleus A. Contains Genetic Material a. Chromatin=DNA + Protein B. RNA Synthesis a. Transcription b. Splicing c. Transport to cytoplasm C. Modulates cell division a. Mitosis b. Meiosis D. Modulates programmed cell death (Apoptosis)
2. Cytoplasm Organelles A. Ribosomes a. Protein Synthesis (Translation) B. Endoplasmic Reticulum a. Intracellular transport b. Synthesis of fatty acids and steroids c. Construction of cellular membranes C. Golgi Apparatus a. Protein processing b. Intracellular transport D. Lysosomes a. Intracellular digestion E. Mitochondria a. Generation of metabolic energy b. Steroid Biosynthesis F. Microtubules and microfilaments a. Intracellular skeleton b. Intracellular movement G. Centrioles a. Cell division H. Inclusions and Vacuoles a. Storage of Chemical Substances b. Vacuoles have liquid center surrounded by membrane
3. Plasma Membrane
A. Functions a. Transport of substances in and out of the cell b. Protection of Cell c. Contains receptors for chemicals to elicit various cell responses i. Hormones, antibodies, etc.
B. Membrane Structure a. Size=7.5 to 10 nm b. Composition i. Lipid (42%) --Phospholipids (25%) --Cholesterol (13%) --Misc. lipids (4%) ii. Protein (55%) iii. Carbohydrate (3%) C. Membrane Lipid Bilayer a. Hydrophilic, Lipophobic, Polar Head i. Glycerol ii. Phosphate iii. Choline, Serine, Ethanolamine b. Hydrophobic, Lipophilic, Non-polar Tails i. Saturated fatty acids ii. Unsaturated fatty acids --Increase Fluidity and Transport Ability c. Thermodynamically form bilayer --Heads outside,Tails inside d. Cholesterol i. Also has polar and nonpolar ends ii. Adds rigidity to membrane iii. Decreases transport D. Membrane Protein a. Functions i. Channels ii. Carrier Molecules iii. Receptors iv. Enzymes v. Filamentous Meshwork vi. Cell Adhesion E. Membrane Carbohydrates a. Extracellular b. Attach to Lipids or Proteins c. Form Cell Coat or Glycocalyx i. 5-20 nm thick normally ii. 200 nm in intestinal microvilli d. Functions i. Protection ii. Facilitates absorption iii. Facilitates recognition (specificity) iv. Contributes to cell adhesion 4. Cilia and Flagella A. Extensions of Plasma Membrane B. Movement a. Cilia--Short and numerous b. Flagella--Long and fewer C. Have 9+2 microtubule arrangement
III. Cellular Environment
1. Body Fluids (Water)
A. All living things need water to survive B. Water is the most abundant constituent of the body fluids a. 60% of the total body mass (normal) b. 70% of body mass in lean animal c. 45% of body mass in fat animals C. Functions a. Chemical Solvent i. Water-soluble ii. Opposite of Fat-soluble b. Transporter i. Both solutes and non-solutes c. Absorbs Heat i. High specific heat ii. Acts like a heat buffer d. Lubricant --Lowers Friction associated with: i. Fluid Flow ii. Cell Movement iii. Movement of body parts
D. Distribution of Body Water a. Intracellular (2/3 of total body water)
i. Cytosol--Fluid component of Cell b. Extracellular (1/3 of total body water) i. Interstitial (3/4 of extracellular) 1. Surrounds cells 2. Gel (Ground Substance of C.T.) --keep water around cells --disallows flow and accumulation to lower body parts or flow from cuts ii. Plasma (1/4 of extracellular) 1. 92% of Plasma is water 2. 8% is mostly protein iii. Transcellular 1. Water in body cavities 2. Usually minimal compared to other volumes 3. Examples --Cerebral Spinal Fluid --Intraocular Fluid --Digestive System (Ruminants have higher transcellular water) --Synovial Fluid (Joints)
2. Ions, Electrolytes and pH.
A. Body Fluids are filled with many different kinds of charged particles called Ions.
a. Cations--Postively Charged Particles
i. H+, Na+, K+, H+, Ca2+, Mg2+, etc.
b. Anions--Negatively Charged Particles
i. 0H-, HCO3-, Cl-, SO4-, etc.
c. Salt--A combination of a Cation and an Anion except for H+ and 0H-
d. Electrolyte--A substance that conducts an electric current in solution
i. Often Dissociated Anions + Cations in solution --Salts, Acids, and Bases
e. Acids and Bases
i. Acids 1. Release H+ ions 2. Proton donors 3. Decrease pH ii. Bases 1. Release 0H- ions 2. Proton receivers 3. Increase pH iii. pH 1. pH 7 is neutral 2. pH 0 is most acidic 3. pH 14 is most alkaline (basic) 4. Body pH is approx. 7.4 5. Sick animals will have abnormally high or low pH. --Treat with electrolytes
IV. Movement of Materials Across Membranes 1. Concentration Gradient--Molecules, ions, and colloidal particles tend to move from an area of higher concentration to an area of lower concentration
2. Bidirectional Transfer
A. Membranes are selectively permeable 3. Ionic Transfer
A. Membranes maintain an Electrical Potential between inner and outer surface of cell
B. Electrochemical Gradient is formed
4. Membrane Transport involves both passive and active movement process
A. Passive--Movement with Concentration or Electrochemical Gradient
a. Diffusion, Facilitated Diffusion, Osmosis, Filtration
B. Active--Movement against Concentration or Electrochemical Gradient
a. Requires Energy--Usually in form of ATP b. Active Transport, Endocytosis, Exocytosis
5. Passive membrane transport processes
A. Diffusion a. Moves Nonpolar substances soluble in lipids --Oxygen, Carbon Dioxide, Nitrogen, Steroids, Fat-soluble vitamins
b. Small uncharged polar molecules move more slowly --Water, Urea, Glycerol
c. Membrane Channels and Pores
i. Assist diffusion process ii. Usually are proteins (Hydrophilic) iii. Move Small Polar Molecules and Ions (<0.8 nm diameter) 1. Water, Urea, Glycerol 2. H+, Na+, HCO3-, K+, Ca2+, Cl-, Mg2+ --Specific channels for certain ions iv. Channels can be opened or closed 1. Chemical signals 2. Electrical signals 3. Mechanical signals B. Facilitated Diffusion a. Carrier Proteins move material across the membrane --Mediated Transport i. Uniport--one substrate, one direction ii. Symport--two substrates, one direction iii. Antiport--two substrates, opposite directions b. Moves with concentration or electrical gradient --Electrochemical gradient
c. Does not require Cellular Energy d. Examples--Sugars, Amino Acids, Ions
C. Osmosis a. The passage of solvent through a semipermeable membrane separating solutions of different concentrations i. Water is usually the solvent ii. Net diffusion from side having higher water concentration to lower concentration iii. Solution with highest water concentration has lowest solute concentration b. Osmotic Pressure i. Measure of the tendency of water to osmose --The pressure needed to stop diffusion through a semipermeable membrane ii. Osmosis is in opposite direction of diffusion iii. Osmosis requires selective membrane, diffusion does not. c. Tonicity i. The tone of a solution is the effective osmotic pressure ii. Only particles (molecules & ions) that are impermeable contribute to tone iii. Blood Cell Example 1. Blood cells are in osmotic equilibrium with plasma 2. The tone of solutions that can be infused into the blood is compared to the solution inside red blood cells a. Hypotonic --Lower osmotic pressure than cell --Blood cell swells --May even burst-Hemolysis b. Isotonic --Same osmotic pressure of cell --Equilibrium c. Hypertonic --Higher osmotic pressure --Cell Shrinks d. Oncotic Pressure i. The difference between the osmotic pressure of blood and the osmotic pressure of interstitial fluid or lymph ii. Important force in maintaining fluid balance between blood and lymph in vessels and the fluid in surrounding tissues iii. Balance most often disrupted by decrease in plasma proteins 1. Starvation, Liver Failure, Intestinal disorders 2. Causes edema or ascites formation D. Filtration 1. Pressure gradient causes movement of molecules rather than concentration gradient 2. Hydrostatic pressure causes gradient a. Blood pressure 3. Most evident in kidney renal corpuscle 6. Active Membrane Processes A. Active Transport a. Carrier Proteins move material across the membrane--Also mediated transport --Uniport, Symport, Antiport b. Moves against a Electrochemical gradient c. Requires energy--ATP d. Examples i. Na+/K+ ATPase Pump --Nerve Cells --All cells --Antiporter ii. Ca++ ATPase Pump --Muscle Cells --Uniporter iii. Na+/Glucose Pump --Kidney Cells --Symporter e. Needed to maintain cellular homeostasis B. Cytosis a. Endocytosis i. Cell takes in substance that encloses small portions of external environment 1. Phagocytosis --Large particles --Solids 2. Pinocytosis --Small particles & solutions ii. Receptor-mediated endocytosis 1. Protein receptors in plasma membrane recognize hormones, iron, and cholesterol 2. Ligand causes endocytosis forming vesicle called coated pit. b. Exocytosis i. Membrane-bound vesicles fuse with plasma membrane ii. Release contents into external environment --Secretion/Excretion mechanism iii. Stimulated by Ca2+ c. Both Endo- and Exocytosis require energy
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Membrane Structure
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V. Cell Division 1. Steps (Cell Cycle) A. Interphase a. G1 phase--Growth one phase i. Cell doubles in size ii. High metabolism iii. Preparation for S phase b. S phase i. DNA synthesis and replication c. G2 phase--Growth two phase i. Preparation for Mitosis B. Mitosis--Nuclear division a. Prophase b. Metaphase c. Anaphase d. Telophase C. Cytokinesis--Cytoplasmic division D. Cells produced are Diploid 2. Meiosis A. Cell division responsible for the production of haploid reproductive cells. a. Sperm b. Egg B. Cells produced are Haploid VI. Cell Death 1. Necrosis A. Indiscriminate Cell Death and Decay B. "Cell Homicide" C. Causes a. Insufficient Blood Supply b. Physical agents --Trauma, UV Light, Radiation c. Chemical agents --Toxins 2. Apoptosis A. Programmed Cell Death B. "Cell Suicide" C. Normal process in living animals for tissue remodeling and differentiation D. As important as cell division E. Steps a. Chromatin Condensation b. DNA Fragmentation c. Cytoplasmic baling (cell shrinkage) d. Macrophage digestion F. Examples a. Hair loss (Balding) b. Fetal differentiation c. Mammary gland involution (Drying off) d. Bone remodeling e. Ovarian Follicular Atresia f. Luteolysis g. Many more