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