Bio Midterm Learning Outcomes (cell membranes and membrane transport).

describe the structure and common concepts of the eukaryotic membranes.

composed of a phospholipid bilayer embedded with proteins, cholesterol and carbohydrates.

hydrophobic tail hydrophilic head

cholesterol stabilizes movement

carbohydrates helps with signals

describe the general functions of the plasma membrane

• signaling

• transport

• protection

• enzymatic activities

• act as a barrier

relate fluid mosaic model to membrane structure and function

describes the nature of how molecules move in, out and around various structures in our cells. Its easy to repair and alter because of its fluid nature and has diverse types of proteins, carbohydrates, lipids.

explain how the plasma membrane provides selective permeability

it blocks out large, charged and polar molecules from entering the cell because of the hydrophobic core that repels water and polar substances. It lets in small and polar molecules inside.

explain how each membrane component contributes to the function of the eukaryotic membrane

proteins act as help in transport (eg carrier and channel proteins), the lipid bilayer acts as a barrier/protection, cholesterol helps with fluidity, carbohydrates help with cell recognition.

describe factors affecting membrane fluidity and predict the impact of certain changes on membrane fluidity and membrane function.

• temperature: a higher temperature leads to the lipid bilayer to be more fluid as kinetic energy increases. When the bilayer is more fluid it is more permeable because there is more gaps which could lead to foreign substances to enter.

• cholesterol: cholesterol ingrates itself into the bi layer. In higher temperature it restricts the movement to prevent it from becoming too fluid. at lower temperatures, it prevents packing too tightly.

• fats: unsaturated fats solidify slower at lower temperature so an increase of it can help maintain fluidity at low temperature (desaturase).

predict how the cell will respond to changes in temperature to maintain proper membrane fluidity

unsaturated fatty acids.

key roles/functions of membrane proteins

integral: inside the bilayer, act as channel proteins to transport substances across membrane, interact with hydrophobic core.

peripheral: on the surface of bilayer, act as receptors for cell signaling, do not interact with hydrophobic core.

passive vs active membrane transport

passive: doesn’t use conformational change or energy to move molecules along their concentration gradient (eg. simple and facilitates diffusion, osmosis)

active: uses energy and carrier proteins to move molecules against their concentration gradient (eg. sodium potassium pump)

describe exocytosis and endocytosis. Where would these occur?

exocytosis: cell moves molecules out of the cell into a vesicle that fuses with the cell membrane, releasing its contents out of the cell. This would occur in the cell membrane duhh

endocytosis: cellular process where substances are brought into the cell and is surrounded by the cell membrane. this would occur in the plasma membrane.

predict the effects on cellular processes if a particular membrane component is defective/damaged

using lipid bilayer as an example: if the bilayer was defective or damaged it would cause great harm for the cells. Since the bilayer is selectively permeable, it only lets in things that need to be let in and blocks out stuff it doesn’t. however, if it stopped working, foreign substances could get in and water + oxygen cant get in the cell. Everything inside the cell would leave causing the cell to denature

describe osmosis and how tonicity influences this process.

osmosis is the diffusion/movement of water along the concentration gradient. Water moves to areas with high solute concentration. there are 3 types of tonicity: hypertonic, hypotonic and isotonic. A hypertonic solution would cause the cell to shrink as solute moves in and water moves out of the cell rapidly, a hypotonic solution would cause the cell to swell as solute moves out and water moves into the cell and isotonic is equal.

importance of osmoregulation in organisms

it maintains the level of water and solute which is crucial for homeostasis. (basically maintains isotonic conditions)

predict and explain movement of a particular substance given info about relative solute concentrations on either side of the membrane in plant and animal cells

a substance will move from high concentration to low concentration using passive transport until equilibrium is reached. To move something against the concentration gradient you would need active transport and atp. if concentration outside of membrane is higher it will move inside via passive transport to low concentration and vice versa.