3.2.1 Cell Structure

Question 1

what are the distinguishing features of eukaryotic cells?

Answer 1

• cytoplasm containing membrane-bound organelles
• so DNA enclosed in a nucleus

Question 2

animal cell organelles (8)

Answer 2

cell-surface membrane
mitochondrion
nucleus
ribosomes
rough endoplasmic reticulum
smooth endoplasmic reticulum
golgi apparatus + vesicles
lysosome

Question 3

plant cell organelles (11)

Answer 3

cell-surface membrane
mitochondrion
nucleus
ribosomes
rough endoplasmic reticulum
smooth endoplasmic reticulum
golgi apparatus + vesicles
lysosome
chloroplast
cell wall
cell vacuole

Question 4

describe the structure of the cell-surface membrane

Answer 4

• hydrophilic phosphate heads - attracted to water
• hydrophobic fatty acid tails - repelled from water
• made of phospholipids in a phospholipid bilayer

Question 5

describe the function of the cell-surface membrane

Answer 5

• selectively permeable - enables control of passage of substances in/out of cell
• molecules/receptors/antigens on surface - allow cells recognition/signalling

Question 6

describe the structure of the nucleus

Answer 6

• nuclear envelope, has a double membrane and nuclear pores
• nucleoplasm
• nucleolus (dense region)
• protein/histone-bound, linear DNA - chromatin = condensed, chromosome = highly condensed

Question 7

describe the function of the nucleus

Answer 7

• holds/stores genetic information which codes for polypeptides (proteins)
• site of DNA replication
• site of transcription (part of protein synthesis) producing mRNA
• nucleolus makes ribosomes/rRNA

Question 8

describe the structure of a ribosome

Answer 8

• made of ribosomal RNA nad a protein (2 subunits - large and small)
• not a membrane-bound organelle

Question 9

function of a ribosome

Answer 9

• site of protein synthesis (translation

Question 10

structure of rough endoplasmic reticulum

Answer 10

• contains network of membranes,enclosing a fluid-filled space - cisternae
• surface of cisternae is covered with ribosomes
• attatched to outer nucleus membrane

Question 11

structure of smooth endoplasmic reticulum

Answer 11

• contains network of membranes,enclosing a fluid-filled space - cisternae
• attatched to outer nucleus membrane

Question 12

function of rough endoplasmic reticulum

Answer 12

• ribosomes on surface synthesise proteins
• proteins processed/folded/transported inside rER
• proteins packaged into vesicles for transport e.g. to golgi apparatus

Question 13

function of smooth endoplasmic reticulum

Answer 13

• synthesises and processes lipids e.g. cholesterol and steroid hormones

Question 14

structure of golgi apparatus + golgi vesicles

Answer 14

• flattened membrane sacs
• golgi vesicle - small membrane sac

Question 15

function of golgi apparatus + vesicles

Answer 15

golgi apparatus:
- modifies protein e.g. adds carbohydrates to produce glycoproteins
- modifies lipids e.g. adds carbohydrates to make glycolipids
- packages proteins/lipids into golgi vesicles
- produces lysosomes
golgi vesicles:
- transports proteins/lipids to their required destination e.g. moves to and fuses with cell-surface membrane

Question 16

structure of lysosomes

Answer 16

• membrane
• hydrolytic enzymes

Question 17

function of lysosomes

Answer 17

• release hydrolytic enxymes (lysozymes)
• to break down/hydrolyse pathogens or worn-out cell components

Question 18

structure of mitochondria

Answer 18

• outer membrane
• cristae - inner membrane fold
• matrix - containing small (70S) ribosomes + circular DNA

Question 19

function of mitochondria

Answer 19

• site of aerobic respiration
• to produce ATP for energy release e.g. for protein synthesis, vesicle movement, active transport

Question 20

describe the structure of chloroplasts in plants and algae

Answer 20

• double membrane
• stroma including: thylakoid membrane, small/70s ribosomes, circular DNA, starch granules/lipid droplets
• lamella - thylakoid linking grata
• grana - stacks of thylakoid

Question 21

function of chloroplasts in plants and algae

Answer 21

• absorbs light energy for photosynthesis
• to produce organic substances e.g. carbohydrates/lipids

Question 22

structure of cell wall in plants, algae and fungi

Answer 22

• composed mainly of cellulose in plants/algae
• composed of chitin (nitrogen-containing polysaccharide) in fungi

Question 23

function of cell wall in plants, algae and fungi

Answer 23

• provides mechanical strength to cell
• so prevents cell changing shape of bursting under pressure due to osmosis

Question 24

structure of cell vacuole in plants

Answer 24

• tonoplast membrane
• cell sap

Question 25

function of cell vacuole in plants

Answer 25

• maintains turgor pressure in cell (stopping plant wilting)
• contains cell sap - stores sugars, amino acids, pigments and any waste chemicals

Question 26

tissue

Answer 26

group of specialised cells with a similar structure working together to perform a specific function, often with the same origin

Question 27

organ

Answer 27

aggregations of tissues performing in specific functions

Question 28

organ systems

Answer 28

group of organs working together to perform specific functions

Question 29

how can you apply your knowledge of organelles to explain adaptations of eukaryotic cells (general answer format)

Answer 29

(named cell) has man (named organelle e.g. ribosomes)
to (link organelle to function e.g. increase rate of protein synthesis, making many antibodies)