Biology - Chapter 3

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Plasma membrane

The semipermeable membrane between the cell contents and either the cell wall or the cell's surroundings

Phospholipid

Made up of phosphate head and 2 fatty acid chains

Phospholipid bilayer

A double layer of phospholipids that makes up plasma and organelle membranes

Fluid mosaic model

explains that the plasma membrane is flexible and made up of many different molecules

Hydrophilic

Water loving, polar molecule

Hydrophobic

Water hating, nonpolar molecule

Simple diffusion

Movement of a solute from an area of high concentration to an area of low concentration

Solute

A substance that is dissolved in a solution

Solvent

A liquid substance capable of dissolving other substances

Concentration gradient

A difference of a substance’s concentration across a distance

Passive transport

The movement of substances across a cell membrane without the use of energy until equilibrium

Active transport

The movement of materials across a cell membrane using energy

Facilitated diffusion

passive movement of molecules across cell membranes through protein channels or with carrier proteins

Osmosis

movement of water across membrane from low solute to high solute concentrations

ATP (adenosine triphosphate)

Main energy source that cells use for most of their work

Functions of protein

Transport, catalysis, communication, adhesion, link to cytoskeleton

Functions of carbohydrates

Help cells recognise each other, signalling, cell adhesion, help immune system tell self vs non-self

Function of cholesterol

Controls membrane fluidity, high temperatures stops membrane being too fluid, low temperatures stop membrane being too rigid

Integral protein channels

Allows specific substances to pass through

Carrier transmembrane proteins

Bind to molecules, change shape, and transport them across the membrane before returning to their original shape

Hypotonic

Lower solute concentration, fluid outside cell has a lower solute concentration than inside, so water moves into the cell and it swells

Hypertonic

Higher solute concentration, fluid outside the cell has a higher solute concentration than inside, so water moves out of the cell and it shrinks

Isotonic

equal solute concentrations, no net movement of water

Tonicity

a measure of solute concentrations on either side of the membrane

Plasmolysis

Plant cell loses water and shrinks

Turgid

Plant cell gains large amount of water and becomes swollen or inflated

Protein mediated active transport

Move substances against their concentration gradient

Steps for protein mediated active transport

Binding, conformational change (atp energy causes pump to change shape), release

Bulk transport

Movement of large molecules across plasma membrane through exocytosis and endocytosis

Exocytosis

process where cells release large molecules, such as proteins, hormones, and neurotransmitters, using vesicles

Steps for exocytosis

Vesicular transport, fusion, release

Endocytosis

process where cells take in large molecules or groups of molecules too large to pass through protein channels

Steps for endocytosis

Fold (membrane folds inward), trap (membrane fuse ends to trap in vesicle), bud (vesicle pinches off membrane)