cells and transport

organelles

structures found inside cells that have specific functions e.g. RER

plasma membrane

controls the entry and exit of materials into/out of the cell

semi-permeable

property of membranes that allows some substances to pass but not others

phospholipid bi-layer

a double layer of phospholipids containing proteins that make up membranes

phospholipid

a molecule that has a polar, hydrophilic phosphate head and 2 non-polar hydrophobic tails

hydrophilic

molecules attracted to water

hydrophobic

molecules repelled by water

passive transport (diffusion)

movement of substances across a membrane, down the concentration gradient and without ATP e.g. osmosis

active transport (diffusion)

movement of small molecules from an area of high concentration to an area of low concentration

facilitated diffusion

passive movement of larger/charged particles across membranes via protein channels

osmosis

diffusion of water across a semi-permeable membrane from an area of high concentration to an area of low concentration (until equilibrium is reached)

ATP

main form of energy used in cells e.g. for active transport

active transport

movement of molecules across a membrane against a concentration gradient using ATP and protein pumps

solute

particles dissolved in a liquid e.g. oxygen

isotonic solution

solution that has the same concentration of solutes as inside the cell

hypertonic

a solution with a higher concentration of solutes than inside a cell. e.g. sugar solution. Cell will lose water and become flaccid

hypotonic

a solution that has a lower concentration of solutes than inside a cell. Cell will become turgid

turgid

cells that have fained water and are tight

flaccid

cells that have lost water and become floppy

plasmolysis

when cytoplasm pulls away from cell wall in plants due to loss of water

endocytosis

the uptake of large molecules into cell by surrounding them with plasma membrane to form vessicles

exocytosis

the export of large molecules from a cell by vesicles fusing with plasma membrane

surface area to volume ratio

ratio that decreases as cells get larger or rounder. Determines the efficiency of transport by diffusion

carrier proteins/protein chanel

proteins embedded in plasma membrane that allow larger/chraged molecules to pass through the membrane by facilitated diffusion

cell/plasma membrane

the membrane around the outside of a cell

cytolysis

bursting of an animal cell due to water intake in a hypotonic solution

ribosome

site of protein synthesis in cells

golgi apparatus

stack of flattened membrane sacks that modifies and packages proteins for export in vesicles

nucleus

organelle that contains the genetic material and controls the activity of cell

endoplasmic reticulum 1

network of membranes covered with ribosomes that makes proteins and transports them within the cell. Common in cells that make enzymes e.g. pancreas

endoplasmic reticulum 2

network of membranes that make lipids and hormones e.g. oestrogen

cell wall

barrier of cellulose that surrounds plasma membranes in plant cells and gives shape and support