Biology - cells and movement across membranes

Question 1

what are cells

Answer 1

Basic units of all living things
Unicellular are made up of one cell
Multicellular are made up of multiple cells

Question 2

Eukaryotic cell structure

Answer 2

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

Question 3

Cell membrane function

Answer 3

partially permeable layer
contains cell contents
controls movement of substances in and out of the cell

Question 4

cytoplasm function

Answer 4

site of chemical reactions
holds the cell organelles
contains enzymes and food reserves
contains dissolved salt ions and sugar

Question 5

nucleus function

Answer 5

contains DNA in the form of chromosomes
found inside the cytoplasm
regulates cell functions

Question 6

mitochondria function

Answer 6

controls production of energy from aerobic respiration
contains an inner and outer membrane

Question 7

chloroplast

Answer 7

contains chlorophyll to trap light energy and convert to chemical energy through photosynthesis
found inside of plant cells

Question 8

vacuole function

Answer 8

stores water-soluble chemicals
helps to keep plant cell firm
found inside the cytoplasm
fluid-filled (sap) containing sugars and salts

Question 9

Cell wall function

Answer 9

outer layer made of cellulose

Question 10

prokaryotic cells

Answer 10

smaller than eukaryotic and DNA is not found in a nucleus

Question 11

chromosomal dna function

Answer 11

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

Question 12

plasmid dna function

Answer 12

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

Question 13

cell wall function

Answer 13

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

Question 14

what is a tissue

Answer 14

group of similar cells with a similar structure and function, working together to do a particular job

Question 15

what is an organ

Answer 15

made from a group of different tissues that work together to do a particular job

Question 16

what is an organ system

Answer 16

is made of a group of different organs that work together to do a particular job

Question 17

what is differentiation

Answer 17

process of eukaryotic cells becoming specialised to a particular function

Question 18

red blood cells function and adaptations

Answer 18

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

Question 19

egg cells function and adaptation

Answer 19

function: reproduction

adaptations: large food store in order to build molecules for the developing embryo

Question 20

sperm cells function and adaptations

Answer 20

function: reproduction

adaptations: long tail and streamlines head; many mitochondria in order to provide the energy for swimming

Question 21

root hair cell function and adaptations

Answer 21

function: absorption of water and mineral ions from soil

adaptations: long hair-like structure to provide large surface area

Question 22

diffusion definition

Answer 22

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

Question 23

factors affecting the rate of diffusion

Answer 23

1. concentration gradient
2. temperature
3. distance
4. size of particles (smaller diffuse faster)
5. surface area (large surface area increase rate of diffusion)

Question 24

osmosis definition

Answer 24

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

Question 25

what happens to plant cells in water

Answer 25

(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)

Question 26

what happens to animal cells in water

Answer 26

(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

Question 27

what happens in plant cells in more concentrated solution

Answer 27

(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

Question 28

what happens in animal cells in more concentrated solution

Answer 28

(lower water potential outside cell rather than cytoplasm therefore cell will lose water)
animal cell: become CRENATED as cytoplasm decreases

Question 29

active transport

Answer 29

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