Chapter 7 – Membrane Structure and Function

The flexible boundary that separates a living cell from its surroundings composed of lipids and proteins

Plasma Membrane

forms a bilayer with hydrophobic tails inside the membrane, and hydrophilic heads exposed to water on either side

Phospholipids

regions of the protein are oriented toward the cytosol and extracellular fluid inside and outside the membrane

hydrophilic region

regions of the protein embedded in the bilayer

Hydrophobic regions

Double layer of phospholipids with hydrophobic tails inward and hydrophilic heads facing water on both sides.

Phospholipid Bilayer

Non-polar fatty-acid portion of a phospholipid that avoids water and points toward the interior of the membrane.

Hydrophobic Tail

Polar phosphate-containing region of a phospholipid that interacts with aqueous environments.

Hydrophilic Head

a protein that penetrates the hydrophobic core of the lipid bilayer

Integral Protein

• (goes through the membrane)

Integral Protein

a protein loosely bound to the membrane surface

Peripheral Protein - (on the hyrodphillic heads - on the top)

does not penetrate the bilayer.

Peripheral Protein

Integral protein that spans the entire membrane (lipid bilayer)

Transmembrane Protein - (enters and exits on both sides of the membrane - completely through)

what moves laterally across the membrane (side by side) within the bilayer

Phospholipids

what affects membrane fluidity based on temperature

Cholesterol

what increases fluidity ?

Unsaturated fats (not saturated)

has doubloe bonds

unsaturated fats

allows tight packing that decreases membrane fluidity

Saturated Fats

no double bonds

saturated fats

a type of fat located in animal cells

cholesterol

restrains (stop) the movement of phospholipids

warm temp (stays fluid) - unsaturated fat

maintains fluidity by preventing tight packing

cool temp - (when the phospholipids move it gets more solid) - making it more structured/less fluid

a buffer for temperature, has 4 fused carbon rings, and is a steroid 

Cholesterol

what affects both permeability and movement of transport proteins

fluidity

There’s more of this in cool environments

unsaturated fats - don’t want to freeze in the cold (keep things fluid)

There’s more of this in warmer environments 

saturated fats - don’t want to sweat your balls off (makes things less fluid aka more solid)

getting too cold or hot)

• lipid composition

has to do with transporting, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and ECM

cell surface membrane proteins

channel and carrier proteins

Transport Proteins

Transport protein that has a hydrophilic channel that certain molecules or ions can use as a tunnel

Channel Protein

bind to molecules and change shape to shuttle them across the membrane

Carrier Protein - (receive the molecule and changes its shape)

another name for channel proteins

Aquaporins

a channel protein that increases the rate of passage of water molecules (transports water)

aquaporins

what are Glycolipids and glycoproteins

carbohydrates

- important in immune response, development in phospholipids, mono, poly, or disaccharide  

• Carbohydrates

used for cell-cell recognition and signaling

Glycolipids and glycoproteins

a protein that attaches to fibers of the extracellular matrix

Integrins

molecules that dissolve in the lipid bilayer and pass through the membrane rapidly (easily)

Hydrophobic (nonpoloar) Molecule - don’t like water and they are hydrophobic like the membrane

faces difficulty crossing the hydrophobic membrane core without a transport protein

Hydrophilic Molecule

need transport proteins to cross membranes 

hydrophillic polar ions or molecules

movement from high to low concentration 

Diffusion

substances diffuse down what

Concentration Gradient

Movement of substances across a membrane with no energy input, following concentration gradients.

Passive Transport

includes osmosis and diffusion

passive transport

• (low to high concentration)

osmosis

• (to equal out the sides/equation- solute that moves through the water

difussion

Diffusion of free water across a selectively permeable membrane

Osmosis

Ability of a surrounding solution to cause a cell to gain or lose water.

Tonicity

Solution with the same solute concentration as the inside of the cell

Isotonic Solution

has no net water movement, is stable, and equal

Isotonic Solution

Solution with higher solute concentration on the outside of a cell

Hypertonic Solution

what will happen to the cell if it has a higher concentration of solute on the outside than the inside of the cell

will lose water, shrivel, and likely die

Solution with lower solute concentration on the outside (more water in the inside)

Hypotonic Solution

what will happen to the cell ifthe higher concentration of solute on the inside than the outside of the cell (likes water so it moves inside)

• will gain water, swell and lyse (burst) 

healthy state of a plant in hypotonic surroundings that stops swelling

Turgid Cell (very firm)

Plant cell become this in isotonic solutions and the plant wilts (no net movement of water)

Flaccid Cell

happens in a hypertonic environment because there’s not enough water the plant will wilt and may die (flaccid)

Plasmolysis

best enviorment for p[plants

hypotonic

Passive transport of ions or molecules via transport proteins down their concentration gradients.

Facilitated Diffusion

binding of a specific substance to the protein

• chemical stimulus—

movement of substances against their concentration gradients

Active Transport

requires (ATP) to move and uses carrier proteins only

active transpo9rt

energizes the transport of K⁺ into the cell and Na⁺ out of the cell 

Sodium-Potassium Pump - You want sodium to be higher on the outside than the inside of the cell (think too much salt is bad for you)

Voltage across a membrane, typically negative inside the cell relative to outside.

Membrane Potential

drive the diffusion of ions across a membrane

• electrochemical gradient,

potassium and proton pumps do what?

maintains the electrochemical gradient

Electrogenic pump in plants, fungi, and bacteria that actively transports H⁺ out of the cell.

Proton Pump

is a transport protein that generates voltage across a membrane, storing energy that can be used for cellular work

• electrogenic pump (proton pump)

bulk transport

endo and exo

process that releases materials from the cell when vesicles fuse or attach to the plasma membrane.

Exocytosis

takes in macromolecules by forming vesicles from the plasma membrane.

Endocytosis

“Cellular eating”; engulfs large particles or other cells into a food vacuole.

Phagocytosis

“Cellular drinking”; takes in extracellular fluid and brings it inside

Pinocytosis (PP like pee)

• specific solutes bind to the receptors on the membrane that are clustered in coated pits that form coated vesicles

Receptor-Mediated Endocytosis

Protein pore that allows specific ions to diffuse down electrochemical gradients.

Ion Channel

the plasma membrane

Made of phospholipid bilayer