3.4 Eukaryotic Cell structure

Question 1

3 Nucleus functions

Answer 1

1. act as control centre of the cell through production of mRNA and tRNA and then protein synthesis
2. retain genetic material of cell in the form of DNA and chromosomes
3. manufacture ribosomal RNA and ribosomes

Question 2

Nuclear envelope

Answer 2

double membrane that surrounds nucleus
outer membrane is continuous with ER and has ribosomes on surface

Question 3

2 Nuclear envelope functions

Answer 3

1. Controls exit and entry of materials in and out of nucleus
2. Contains reactions taking place within it

Question 4

Nuclear pores

Answer 4

allow passage of large molecules(e.g. RNA) out of nucleus
3000 pores in each nucleus
40-100nm in diameter

Question 5

nucleoplasm

Answer 5

granular jelly-like material that makes up most of nucleus

Question 6

Nucleolus

Answer 6

small spherical region within nucleoplasm
manufactures ribosomal RNA and assembles ribosomes

Question 7

Function of mitochondria

Answer 7

1. site of aerobic respiration(krebs cycle and oxidative phosphorylation pathway)
2. production of ATP from glucose

Question 8

Cristae

Answer 8

extensions formed from folded part of mitochondria’s inner part of double membrane
provide larger SA for attachment of enzymes and other proteins

Question 9

Matrix

Answer 9

makes up remainder of mitochondria
contains protein, lipids, ribosomes and DNA that allows mitochondria to control production of some of their own proteins

Question 9

chloroplast envelope

Answer 9

double plasma membrane that surrounds organelle
highly selective in what it allows to enter and exit

Question 10

Grana

Answer 10

Where light absorption take place
stacks of up too 100 disc- like structures- thylakoids
Thylakoids contain chlorophyll
Thylakoids have tubular extensions that join up with thylakoids in adjacent grana

Question 11

Stroma

Answer 11

fluid-like matrix
where second stage of photosynthesis(synthesis of sugars) takes place
number of other structures(e.g. starch grains) are present

Question 12

4 Chloroplast adaptations

Answer 12

1. 2-10μm long and 1μm in diameter
2. granal membrane provide large SA for attachment(in highly ordered fashion) of chlorophyll, electron carriers and enzymes that carry out first stage of photosynthesis
3. fluid of stroma process all enzymes needed to make sugars in 2nd stage photosynthesis
4. chloroplasts contain DNA and ribosomes so can quickly and easily manufacture some proteins needed for photosynthesis

Question 13

endoplasmic reticulum

Answer 13

sheet-like membranes that spread through cytoplasm of cells
continuous with outer nuclear membrane
RER has ribosomes present on outer surface whilst SER doesn’t
SER is more tubular

Question 14

2 functions of rough endoplasmic reticulum

Answer 14

1. provide large SA for synthesis of proteins and glycoproteins
2. provide pathway for transport of materials(especially proteins) throughout cell

Question 14

2 functions of smooth endoplasmic reticulum

Answer 14

1. synthesis, store and transport lipids
2. synthesis, store and transport carbohydrates

Question 15

5 Golgi apparatus functions

Answer 15

1. add carbohydrates to proteins to form glycoproteins
2. produce secretory enzymes
3. secrete carbohydrates
4. transport, modify and store lipids
5. form lysosomes

Question 16

Golgi apparatus

Answer 16

consists of stack of membrane that make up flattened sacs(cisternae) with small hollow structures(vesicles)

proteins and lipids produced by ER pass through golgi apparatus in strict sequence
it modifies the proteins by adding non-protein components(e.g. carbs)
also labels the proteins, which allows them to be accurately sorted and sent to correct destination

Question 17

Golgi vesicles

Answer 17

transports modified proteins and lipids after pinching them off golgi cisternae
they move to cell surface, where they fuse with membrane and release the contents to outside

Question 18

lysosomes

Answer 18

formed when vesicles produced by golgi apparatus contains enzymes e.g. protease and lipase and lysozomes
lysosomes isolate these useless or dangerous enzymes from rest of the cell before releasing them to outside or phagocytic vesicle within cell

Question 19

lysozomes

Answer 19

enzymes that hydrolyse the cell walls of certain bacteria

Question 20

4 functions of lysosomes

Answer 20

1. hydrolyse material ingested by phagocytic cells(e.g. white blood cells and bacteria)
2. release enzymes to outside of cell(exocytosis) in order to destroy material around cell
3. digest worn out organelles so that the useful chemicals they are made of can be re-used
4. completely break down cells after they have died(autolysis)

Question 21

ribosome

Answer 21

small cytoplasmic granules in all cells
found in cytoplasm or associated with rough ER
have two subunits(small and large)
contain ribosomal RNA and protein
25% dry mass of cell
site of protein synthesis

Question 22

80S ribosomes

Answer 22

in eukaryotic cell
25nm in diameter

Question 23

70S ribosome

Answer 23

in prokaryotic cell, mitochondria and chloroplast smaller than 80S

Question 24

cell wall

Answer 24

consist of microfibrils of cellulose, embedded in a matrix - has high strength has thin layer(middle lamella) which marks boundary between adjacent cell walls and cements adjacent cells together

Question 25

3 functions of cell wall

Answer 25

1. provide mechanical strength in order to prevent cell wall from bursting under pressure created by osmotic entry of water 2. give mechanical strength to plant as a whole 3. to allow water to pass along it and so contribute to movement of water through plant

Question 26

fungi cell wall

Answer 26

don't contain cellulose has mixture of nitrogen-containing polysaccharide(chitin), glycan and glycoproteins

Question 27

algae cell wall

Answer 27

made up of either cellulose or glycoproteins, or a mixture of both

Question 28

3 functions of plant vacuoles

Answer 28

1. support herbaceous plant by making cells turgid 2. sugars and amino acids act as temporary food store 3. pigments may colour petals to attract pollinating insects

Question 29

Vacuoles

Answer 29

fluid filled sac bound by single membrane(tonoplast) one large central vacuole in mature plant contains solution of mineral salts, sugars, amino acids, wastes and sometimes pigments(anthocyanins)