Biology - cells and movement across membranes Flashcards
what are cells
Basic units of all living things
Unicellular are made up of one cell
Multicellular are made up of multiple cells
Eukaryotic cell structure
contain cell membrane and cytoplasm
most eukaryotic cells contain a nucleus (except mature red blood cells)
plant cells have a cell wall and a sap vacuole, and certain plant cells contain chloroplasts
Cell membrane function
partially permeable layer
contains cell contents
controls movement of substances in and out of the cell
cytoplasm function
site of chemical reactions
holds the cell organelles
contains enzymes and food reserves
contains dissolved salt ions and sugar
nucleus function
contains DNA in the form of chromosomes
found inside the cytoplasm
regulates cell functions
mitochondria function
controls production of energy from aerobic respiration
contains an inner and outer membrane
chloroplast
contains chlorophyll to trap light energy and convert to chemical energy through photosynthesis
found inside of plant cells
vacuole function
stores water-soluble chemicals
helps to keep plant cell firm
found inside the cytoplasm
fluid-filled (sap) containing sugars and salts
Cell wall function
outer layer made of cellulose
prokaryotic cells
smaller than eukaryotic and DNA is not found in a nucleus
chromosomal dna function
circular coiled molecule of double-stranded dna
not found in a nucleus, but freely suspended in the cytoplasm
carries genetic information and regulates cell processes
plasmid dna function
small molecule of double-stranded dna
carries genetic information for particular specialist functions e.g. antibiotic resistance
can replicate separately from the chromosomal dna
can be moved between bacteria cells
this is the section that is used when bacteria is a vector for genetic engineering
cell wall function
provides protection and structural support to bacteria
freely permeable to small molecules so does not control movement of substances
made of proteins, lipids and sugars - different from plant cell walls
some bacteria cells also have a slime capsule around the cell wall
what is a tissue
group of similar cells with a similar structure and function, working together to do a particular job
what is an organ
made from a group of different tissues that work together to do a particular job
what is an organ system
is made of a group of different organs that work together to do a particular job
what is differentiation
process of eukaryotic cells becoming specialised to a particular function
red blood cells function and adaptations
function: oxygen transport
adaptations: concave shape to increase the surface area to volume ratio; contains haemoglobin, which allows them to carry oxygen; no nucleus to increase available volume for haemoglobin; and mature RBC have no mitochondria
egg cells function and adaptation
function: reproduction
adaptations: large food store in order to build molecules for the developing embryo
sperm cells function and adaptations
function: reproduction
adaptations: long tail and streamlines head; many mitochondria in order to provide the energy for swimming
root hair cell function and adaptations
function: absorption of water and mineral ions from soil
adaptations: long hair-like structure to provide large surface area
diffusion definition
net movement of particles from an area of high concentration to an area of low concentration
it is a passive process and doesn’t require energy
factors affecting the rate of diffusion
- concentration gradient
- temperature
- distance
- size of particles (smaller diffuse faster)
- surface area (large surface area increase rate of diffusion)
osmosis definition
net movement of water molecules across a partially permeable membrane from a region of higher water concentration to an area of a lower water concentration
what happens to plant cells in water
(higher water potential outside cell than within, causing water to enter the cell)
plant cell: flow of water will exert pressure on the cytoplasm which will press against cell wall (called TURGOR)
what happens to animal cells in water
(higher water potential outside cell than within, causing water to enter the cell)
animal cells: does not contain a cell wall and therefore the membrane will burst from pressure
what happens in plant cells in more concentrated solution
(lower water potential outside cell rather than cytoplasm therefore cell will lose water)
plant cell: becomes FLACCID as pressure reduces and cell membrane and cytoplasm shrink away from cell wall
what happens in animal cells in more concentrated solution
(lower water potential outside cell rather than cytoplasm therefore cell will lose water)
animal cell: become CRENATED as cytoplasm decreases
active transport
allows molecules to move against a concentration gradient, using energy released by respiration
cells using active transport tend to have lots of mitochondria for energy
thought to be achieved by carrier proteins that are found in the membrane
