Biology Unit 2b cell membrane and transport

key functions of the cell membrane

protects and supports the cell and controls what goes in and out of the cell

fluid mosaic model

Shows that the cell membrane is not a fixed structure. The molecules can move around (fluid) and have a variety of components (mosaic).

Phospholipids

Form the lipid bilayer and only allow lipid-soluble molecules to pass through. Made up of heads and tails

Phospholipid heads

Polar and hydrophilic (water loving). Face the watery solutions inside and outside the cell

Phospholipid tails

Nonpolar and hydrophobic (water fearing). Face each other away from the water

Proteins

Allows molecules to go from one side of the membrane to the other. Tube like structure

Carbohydrates

Act like communication flags to other molecules/cells.

Triglycerides

Made of a glycerol head and 3 fatty acid tails. Two types are fats and oils

Fats

Solid at room temperature and made up of a glycerol and 3 saturated fatty acids (butter)

Oils

Liquid at room temperature and made up of a glycerol and 3 fatty acid tails ( at least one unsaturated)

fats and oils

lipids that store energy

Saturated

Fats with the maximum number of hydrogens, straight chains, pack on top of eachother, and solid at room temperature

Unsaturated

Fat with less than the maximum number of hydrogens, double bonds, can't pack together, kinky tails, liquid at room temperature

Solution

A mixture of evenly distributed parts

Solvent

The substance that does the dissolving (water)

Solute

The substance that is being dissolved

Materials that enter the cell

Water, glucose, oxygen, amino acids, ions, etc.

Materials that exit the cell

Water, wastes, carbon dioxide, ions, etc.

Passive Transport

Movement of materials across the cell membrane without the use of additional energy (ATP)

Diffusion

Molecules move from an area of higher concentration to an area with lower concentration through the phospholipids; small non-water molecules

dynamic equilibrium

Particles move in both directions at equal rates

concentration gradient

two different concentrations on the outside of the cell vs the inside of the cell

Facilitated diffusion

When molecules are too big or soluble in lipids, a carrier protein moves them from high concentration to low concentration

Carrier protein

A protein that transports a specific molecule across the membrane

Osmosis

Movement of water across the cell membrane from high concentration to lower concentration

Aquaporin

A channel protein that allows water to pass through the cell membrane

hypertonic solution

Concentration in greater than in the cell; causes cell to shrink

isotonic solution

Concentration in the environment is the same as in the cell; cell stays the same

Hypotonic solutions

Concentration in the environment is lower than in the cell; causes cell to swell

active transport

Movement of materials across the cell membrane that requires energy (ATP)

molecular active transport

A molecule moves across the cell membrane through the protein pump using energy

protein pump

a membrane protein that pushes molecules across the cell membrane to a higher concentration

bulk transport

Large molecules or clumps of material move across the cell membrane

Endocytosis

process of using the cell membrane to bring in large particles or molecules

Exocytosis

process of using the cell membrane vesicles release large particles/molecules out of the cell

Steroids/cholesterol

A type of lipid that adds flexibility