chapter 5

Endomembrane System

A group of membranes and organelles that work together to synthesize, modify, package, and transport proteins and lipids.

Ribosomes

Organelles that synthesize proteins.

Endoplasmic Reticulum (ER)

An organelle that folds and modifies proteins.

Golgi Apparatus

An organelle that sorts and packages proteins.

Golgi Vesicle

A transport vesicle that carries proteins to their target destination.

Phospholipids

Major component of the plasma membrane, consisting of a hydrophobic tail and a hydrophilic head.

Integral Proteins

Proteins that span the entire bilayer and facilitate the movement of substances in and out of the cell.

Peripheral Proteins

Proteins located on the exterior or interior surface of the membrane, often serving as enzymes or structural attachments.

Glycoproteins (carbohydrates)

Proteins that have carbohydrates bound to them.

Glycolipids (carbohydrates)

Lipids that have carbohydrates bound to them.

Selective Permeability

The property of a membrane that allows some substances to cross more easily than others.

Small & Nonpolar Molecules

Molecules that pass easily and quickly through the lipid bilayer without requiring proteins for transport.

Small & Polar Molecules

Molecules that have more difficulty crossing the bilayer but can do so without protein assistance.

Large & Nonpolar Molecules

Molecules that can pass through the bilayer, but the process is slow.

Large & Polar Molecules

Molecules that find it too difficult to pass through the bilayer without assistance due to their size and charge.

Passive Transport

The movement of substances across a membrane without the use of energy.

Diffusion

The process of solute moving from areas of high concentration to areas of low concentration.

Osmosis

The movement of water from areas of low solute concentration to high solute concentration.

Tonicity

The ability of a solution to cause a cell to lose or gain water.

Isotonic Solution

A solution where the concentration of solutes is the same inside and outside of the cell.

Hypotonic Solution

A solution with a lower concentration of solutes than inside the cell, causing the cell to expand.

Hypertonic Solution

A solution with a higher concentration of solutes than inside the cell, causing the cell to shrink.

Facilitated Transport

A type of passive transport that requires transmembrane proteins to move substances down their concentration gradient.

Channel Proteins

Proteins that allow specific molecules to pass through the membrane; some are always open, while others open in response to signals.

Carrier Proteins

More specific proteins that bind to a single substance, change shape, and carry it to the other side of the membrane.

Active Transport

The movement of substances against their concentration gradient (from low to high concentration) that requires energy.

Exocytosis

The process by which transport vesicles fuse with the plasma membrane to release their contents outside the cell.

Endocytosis

The process by which vesicles are formed from the plasma membrane to bring molecules into the cell.

Phagocytosis

A type of endocytosis involving the engulfment of food or pathogens.

Pinocytosis

A type of endocytosis that involves the uptake of extracellular fluid.

Receptor Mediated Endocytosis

A highly specific form of endocytosis involving coated vesicles that bind to specific molecules.

fluidity (effects of temperature)

• colder= closer phospholipids → restricts small molecules 

• warmer= more separated phospholipids —> leaves larger gaps

fluidity (effects of cholesterol)

• randomly distributed across the bilayer, helping it stay fluid.

• increases fluidity at low temps and decreases fluidity at high temps

fluidity (effects of fats (unsat. vs. sat.)

• - saturated are straight, easy to pack tight,

• unsaturated fats have double bonds that create kinks in the chains, making it more fluid.