2.1 Cell structure

Question 1

Function of nucleolus

Answer 1

where ribosomes are made, contains rRNA

Question 2

Function of cilia (made of microtubules) and flagella

Answer 2

cell mobility, contains receptors that detect signals about immediate environment

Question 3

Function of lysosomes

Answer 3

contains (hydrolysing) enzymes, break down organelles, apoptosis

Question 4

Function of cytoskeleton

Answer 4

provide cell stability, microtubules move organelles / proteins (in protein synthesis), change shape of cell, mechanical strength (not membrane bound)
- vesicles move along microfilaments, microtubules extend and uses ATP (3)

Question 5

Function of Golgi apparatus

Answer 5

modifies and repackages proteins into vesicles, receives proteins from the RER, makes lysosomes, replenishes plasma membrane (make glycolipids)

Question 6

Function of mitochondria, and structure

Answer 6

produces ATP, site of aerobic respiration, releases energy, contains mitochondrial (mt)DNA so can product own enzymes and reproduce
- inner membrane = cristae and fluid inside = matrix
- why may look different sizes: cut in different planes / angles, vary in shape, growing or artefact

Question 7

Function of endoplasmic reticulum

Answer 7

network of membranes enclosing flattened sacs = cisternae
- SER: where carbohydrates and lipids are synthesised
- RER: where proteins are synthesised

Question 8

Function of phospholipid bilayer

Answer 8

acts as a barrier

Question 9

Function of intracellular membranes

Answer 9

compartmentalisation, isolate reactions / substances, provide selective permeability – controls what substances enter organelles, create specific environments, form vesicles

Question 10

Function of nuclear pores

Answer 10

allow substances to enter and exit the nucleus (e.g. mRNA)

Question 11

Function of transmembrane proteins

Answer 11

form channels / carriers, for transport / facilitated diffusion

Question 12

Function of cholesterol molecules

Answer 12

between phospholipids to stabilise membrane / regulate fluidity

Question 13

Function of glycoproteins / glycolipids on cell surface

Answer 13

cell signalling, act as antigens, recognition of cells as foreign from non-self, receptor for hormone/signal, receptor on transport proteins, cell adhesion – attach to water molecules
- how acts as a receptor: specific shape complementary to trigger molecule, trigger binds to the receptor

Question 14

Advantages of staining

Answer 14

easier to see and identify organelles / cells, provide contrast, count __ cells

Question 15

Types of staining

Answer 15

• acetic orcein: dark red chromosomes
• eosin: cytoplasm
• iodine: cell membrane and nucleus
• haematoxylin/methylene blue (all purpose): nucleic acid,
• Sudan red: lipids

Question 16

How to improve a staining procedure

Answer 16

• place a stain at the edge of the sample
• lower the cover slip at an angle
• use blotting paper to remove excess stain
• use more than one stain

Question 17

Define artefact (microscopy)

Answer 17

bubbles trapped under the cover slip as you prepare a slide for light microscope

Question 18

Stages during the secretion of a protein that requires energy

Answer 18

transporting vesicles to the plasma membrane or fusing vesicle to the membrane/exocytosis

Question 19

Prokaryotic vs eukaryotic (e.g. fungi) cell

Answer 19

• plasmids, circular DNA, 70S ribosomes vs membrane-bound organelles, nucleus and 20 micrometers wide and 80S ribosomes
• genetic material: ‘naked’ DNA vs chromosomes, chromatin, histones

Question 20

Animal vs plant cell

Answer 20

cellulose cell wall, chloroplast, large/permanent vacuole, tonoplast, plasmodesmata – vs – centriole, lysosomes, cilia and flagella

Question 21

Adaptation of guard cell

Answer 21

• large vacuole to take up water / become turgid
• cell wall is thicker on one side causes cell bend / open stomata
• mitochondria generate ATP

Question 22

Protein synthesis, order

Answer 22

nucleus, nuclear pore, ribosome/RER, vesicle, Golgi apparatus, plasma membrane

Question 23

Define magnification and resolution

Answer 23

• Magnification: image size/actual size
• Resolution: ability to distinguish between 2 separate points, see detail

Question 24

How to improve a drawing of a cell

Answer 24

labelling, scale bar, no shading, add a title

Question 25

Magnification and resolution of light, SEM and TEM microscope

Answer 25

Magnification Resolution (nm)
Light 1 500 200
SEM 100 000 3-10
TEM 500 000 0.5

Question 26

Magnification and resolution of light, SEM and TEM microscope

Answer 26

——– Magnification Resolution (nm)
Light 1 500 200
SEM 100 000 3-10
TEM 500 000 0.5

Question 27

Light microscope features

Answer 27

colour visible, wide field of view, organelles not visible (low resolution as wavelength of light too long)

Question 28

Scanning electron microscope features

Answer 28

3D shape can be seen, can see surface features / detail

Question 29

Transmission electron microscope features

Answer 29

• Advantages – small objects can be seen, high resolution as wavelength of electrons is shorter
• Disadvantages – cannot look at living cells as cells must be in a vacuum, must cut thin section, preparation may create an artefact, doesn’t produce a colour image
• Electron microscope shows more detail because it has a greater resolving power / objects closer together can be distinguished and electron (beams) have a shorter wavelength

Question 30

Laser scanning confocal microscope features

Answer 30

lower resolution than EM, can have a fluorescent tag, can see movement as can be used on living cells, can see different layers / at diff depths of sample

Question 31

Chloroplast structure and role of vacuole

Answer 31

• large permanent vacuoles maintain turgor, membrane = tonoplast
• chloroplasts: double membrane structure and fluid enclosed = stroma, internal network of membranes which form flattened sacs = thylakoids – several stacked together = granum (pl. grana) – which are joined by membranes = lamellae