Physiology of Cells Chapter 4

Cell Cycle The events that occur during the life cycle of a cell. 3 stages: The events that occur during the life cycle of a cell. 3 stages: –Interphase –Mitosis –cytokinesis

Interphase Period of time from cell formation to cell division Period of time from cell formation to cell division –G1 – active cell metabolism –S – DNA replication –G2 – enzymes and proteins needed for division are produced; organelles are duplicated

Mitosis Prophase – Prophase – –chromatin shortens, thickens, becomes visible as chromosomes –nuclear membrane disappears –centrioles and spindle fibers appear

Metaphase – Metaphase – –chromosomes line up along equator of the cell –attach to spindle fibers

Anaphase – Anaphase – –spindle fibers contract –pull the chromatids of the chromosomes apart.

Telophase – Telophase – –spindle fibers and centrioles disappear –chromosomes continue to move to opposite poles

Cytokinesis Chromosomes lengthen and become chromatin again Chromosomes lengthen and become chromatin again nuclear membrane reforms nuclear membrane reforms Cytoplasm divides Cytoplasm divides

Interphase

Signals For Cell Division Surface to volume ratio Surface to volume ratio Frequency of division is dependent of the type of cell Frequency of division is dependent of the type of cell Availability of space Availability of space Release of inhibitory or stimulatory chemicals by surrounding cells Release of inhibitory or stimulatory chemicals by surrounding cells

Plasma Membrane Flexible, selectively permeable Flexible, selectively permeable composed chiefly of phospho- lipid and protein bilayer composed chiefly of phospho- lipid and protein bilayer

Phospholipids Phospholipids Phospholipids –impermeable to water soluble materials –Polar, phosphorus containing heads (hydrophilic) are exposed to water both inside and outside the cell (2 layers) –Nonpolar tails (hydrophobic) are sandwiched between 2- layered heads

Passive Processes – requires no energy Simple diffusion Simple diffusion Simple diffusion Simple diffusion –movement of lipid soluble materials across the plasma membrane –molecules move down a “concentration gradient” using kinetic energy as the driving force.

Dialysis Dialysis Dialysis –Process in which solutes of differing sizes are separated from each other as they may (or may not) diffuse across a selectively permeable membrane

Osmosis Osmosis –diffusion of water through the plasma membrane –occurs when there is a difference in water concentration on either side of the membrane.

Net movement (unequal) of water occurs until a balance is reached between the hydrostatic pressure (pressure of water inside the cell trying to push out) is equal to the osmotic pressure (tendency of a cell to pull water in). Net movement (unequal) of water occurs until a balance is reached between the hydrostatic pressure (pressure of water inside the cell trying to push out) is equal to the osmotic pressure (tendency of a cell to pull water in).

Hydrostatic Pressure Osmotic Pressure

The net movement is determined by the “tonicity” (concentration of solutes) of the solution The net movement is determined by the “tonicity” (concentration of solutes) of the solution

–Hypertonic solutions – solutions that contain greater amounts of solutes than comparable solutions. If a cell is placed in a hypertonic solution… Hypertonic solutions Hypertonic solutions

–Hypotonic solutions- solutions that contain smaller amounts of solutes than comparable solutions. If a cell is placed in a hypotonic solution… Hypotonic solutions- Hypotonic solutions-

–Isotonic solutions – solutions that contain equal amounts of solutes with comparable solutions. If a cell is placed in an isotonic solution… Isotonic solutionsIsotonic solutions

A cell containing 75% water and 25% solutes is placed in a solution of 100% water. What will the cell do? A. Shrivel B. Swell C. Nothing D. Step out for a cup of Starbuck’s coffee

A cell containing 75% water and 25% solutes is placed in a solution of 100% water. What type of solution is the cell in? A. Hypotonic B. Hypertonic C. Isotonic D. Cannot tell for the information given

A cell containing 75% water and 25% solutes is placed in a solution of 65% water and 35% solutes. What type of solution is the cell in? A. Hypotonic B. Hypertonic C. Isotonic D. Cannot tell from the information given.

A cell containing 75% water and 25% solutes is placed in a solution of 65% water and 35% solutes. What will happen to the cell? A. Swell B. Shrivel C. Nothing D. Go to the Klein Collins/Tomball football game.

Facilitated diffusion Facilitated diffusion Facilitated diffusion Facilitated diffusion –lipid insoluble substances (usually glucose): “hitch a ride” with a lipid soluble carrier molecule “hitch a ride” with a lipid soluble carrier molecule OR Travel through a channel protein –process is highly selective, but requires no cell energy.

Small molecules forced out of tissues due to hydrostatic pressure Ex. Fluids, but not larger particles, leave the capillaries and enter tissues Ex. Fluids, but not larger particles, leave the capillaries and enter tissuesFiltration

Active Processes – Requires cell energy in the form of ATP Active transport – (ex: solute pump) the movement of ions and/or amino acids “uphill” against the concentration gradient Active transport – (ex: solute pump) the movement of ions and/or amino acids “uphill” against the concentration gradient

Cotransport – insoluble or large molecule is allowed through a protein pore only when another entering molecule causes a change in the shape of the protein pore. Cotransport – insoluble or large molecule is allowed through a protein pore only when another entering molecule causes a change in the shape of the protein pore.

(hint: think about entering a gated apartment complex in your car by driving in behind someone who knows the code to the gate… same idea…) (hint: think about entering a gated apartment complex in your car by driving in behind someone who knows the code to the gate… same idea…)

Bulk transport Bulk transport –Exocytosis – movement of macromolecules out of the cell (hormones, neurotransmitters, mucus, wastes); this is accomplished by fusing a sac, containing the material, with the plasma membrane. Exocytosis

Endocytosis Endocytosis Endocytosis –movement of macromolecules into the cell Phagocytosis – solids Phagocytosis – solids Pinocytosis – liquids Pinocytosis – liquids

Receptor mediated – (ex: cholesterol) Receptor mediated – (ex: cholesterol) Receptor mediated Receptor mediated –taken into the liver by first binding to a cholesterol receptor on the surface of liver cells –“hypercholesterolemia” results when there is a lack of these receptors

Disorders Cell Transport Cell Transport –Cystic Fibrosis; Cl - ion pumps in cell membranes are missing –Duschene’s Muscular Dystrophy – leaky Ca + channels

Cell Membrane Receptors Cell Membrane Receptors –Type 2 Diabetes – obesity triggers a reduction in the number of insulin receptors on cell surface Cell Reproduction Cell Reproduction –Cancers

DNA and Protein Synthesis DNA and Protein Synthesis –Mutations –Sickle cell anemia – produces abnormal hemoglobin from an error in DNA strand –Inborn metabolic disorders - due to improper protein synthesis ex: PKU, albinism, etc.

Review of transport of small substances nonpolar passive dialysis polar/ionic facilitated diffusion active transport active water osmosis passive hypotonic hypertonic