3.2.1 | CELL STRUCTURE

Question 1

what are the distinguishing feature of eukaryotes

Answer 1

cytoplasm containing membrane-bound organelles and DNA enclosed in nucleus

Question 2

describe the structure of the phospholipid bilayer

Answer 2

hydrophilic phosphate heads attracted to water pointing outwards and hydrophilic fatty acid tails repelled from water facing inwards

Question 3

describe the function of the cell-surface membrane

Answer 3

selectively permeable which enables control of substance entering and leaving cell
receptors (glycoproteins/glycolipids) on surface allow cell recognition/signalling

Question 4

describe the structure of the nucleus

Answer 4

surrounded by a nuclear envelope (double membrane) containing nuclear pores
contains nucleolus
contains linear DNA/chromatins

Question 5

describe the function of the nucleus

Answer 5

holds/stores genetic information which codes for polypeptides
site of DNA replication
site of transcription, producing mRNA
nucleolus makes ribosomes/rRNA

Question 6

what is a ribosome made of

Answer 6

ribosomal RNA and protein

Question 7

describe the function of a ribosome

Answer 7

site of protein synthesis

Question 8

describe the structure of rough and smooth endoplasmic reticulum

Answer 8

rER and sER are both a network of cisternae (fluid-filled membrane-bound sacs)
rER has ribosomes on surface

Question 9

describe the function of rough endoplasmic reticulum

Answer 9

ribosomes on surface synthesise proteins
proteins processed/transported inside rER
proteins packed into vesicles for transport to golgi apparatus

Question 10

describe the function of smooth endoplasmic reticulum

Answer 10

synthesises and processes lipids

Question 11

describe the structure of golgi apparatus

Answer 11

flattened fluid-filled membrane-bound sacs called cisternae and golgi vesicles

Question 12

describe the function of golgi apparatus

Answer 12

modifies proteins and lipids
packages proteins/lipids into golgi vesicles
produces lysosomes

Question 13

describe the function of golgi vesicles

Answer 13

transports proteins/lipids to their required destination

Question 14

describe the function of lysosomes

Answer 14

digest pathogens using enzymes (lysozymes) and break down waste material

Question 15

what size are ribosomes in eukaryotes

Answer 15

80S

Question 16

describe the structure of lysosomes

Answer 16

membrane bound organelle containing hydrolytic enzymes

Question 17

describe the structure of mitochondria

Answer 17

surrounded by a double membrane with cristae (inner membrane fold)
matrix containing 70S ribosomes and circular DNA

Question 18

describe the function of mitochondria

Answer 18

site of aerobic respiration to produce ATP for energy release

Question 19

describe the structure of chloroplasts (in plant and algae)

Answer 19

double membrane enclosing stroma (fluid)
stroma contains thylakoids, starch granules, 70S ribosomes and circular DNA
contain lamella (thylakoid linking grana)
contain grana (stacks of thylakoid)

Question 20

describe the function of chloroplasts (in plants and algae)

Answer 20

absorb light energy for photosynthesis

Question 21

what is the cell wall in plants and algae composed of

Answer 21

cellulose

Question 22

what is the cell wall in fungi composed of

Answer 22

chitin

Question 23

describe the function of the cell wall in plants, algae and fungi

Answer 23

provides strength to cell to prevent bursting or cell changing shape under pressure

Question 24

describe the structure of the cell vacuole in plants

Answer 24

tonoplast membrane surrounding cell sap

Question 25

describe the function of the cell vacuole in plants

Answer 25

maintains turgor pressure in cell, preventing plant from wilting contains cell sap which stores sugars, amino acids, pigments and any waste chemicals

Question 26

what is a tissue

Answer 26

group of specialised cells with a similar structure working together to perform a specific function

Question 27

what is an organ

Answer 27

group of tissues performing specific functions

Question 28

what is an organ system

Answer 28

group of organs working together to perform specific functions

Question 29

what size of ribosomes in prokaryotes

Answer 29

70S

Question 30

what are the distinguishing features of prokaryotes

Answer 30

cytoplasm lacks membrane-bound organelles and DNA not enclosed in a nucleus

Question 31

what is the cell wall in prokaryotes composed of

Answer 31

murein

Question 32

explain why viruses are described as acellular

Answer 32

not made of cells, no cell membrane/cytoplasm/organelles

Question 33

explain why viruses are described as non-living

Answer 33

have no metabolism, cannot independently move/respire/replicate

Question 34

describe the general structure of a virus particle

Answer 34

nucleic acids surrounded by a capsid attachment proteins allow attachment to host cells no cytoplasm, ribosomes, cell wall, cell-surface membrane etc. some also surrounded by a lipid envelope (HIV)

Question 35

define resolution

Answer 35

the minimum distance apart two objects can be distinguished as separate objects

Question 36

define magnification

Answer 36

number of times greater an image is than the size of the real object

Question 37

give the equation for magnification

Answer 37

magnification = image size / actual size

Question 38

describe and explain the principles of cell fractionation and ultracentrifugation as used to separate cell components

Answer 38

homogenise tissue/ use a blender - breaks open cell releasing organelles place in a cold, isotonic, buffered solution - cold to reduce enzyme activity so organelles are not damaged - isotonic to prevent water moving in or out of organelles causing them to burst - buffered to keep pH constant so enzymes don't denature filter to remove large debris ultracentrifugation: separates organelles in order of density - centrifuge at a high speed - remove pellet of heaviest organelle and respin supernatant at a higher speed - repeat at increasing speeds until desired organelle

Question 39

why do light microscopes have low resolution

Answer 39

long wavelength of light

Question 40

why do SEM and TEM have high resolution

Answer 40

short wavelength of electrons

Question 41

how does a TEM produce an image

Answer 41

electrons pass through specimen denser parts absorb more and appear darker

Question 42

how does a SEM produce an image

Answer 42

electrons deflected/bounce off specimen surface

Question 43

what image does a SEM produce

Answer 43

2D image of cross section black and white

Question 44

how does an optical microscope produce an image

Answer 44

light passes though specimen different structures absorb different amounts and wavelengths

Question 45

what image does a TEM produce

Answer 45

3D image of surface black and white

Question 46

what image does an optical microscope produce

Answer 46

2D image of cross section coloured (with stain)

Question 47

what microscope(s) are internal structures of a specimen visible with

Answer 47

TEM