2.1 - Cell structure

Question 1

Draw a diagram of the cell-surface membrane and describe its function

Answer 1

Phospholipid bilayer
Proteins - receptors
Cholesterol - controls membrane fluidity
Function: to control what enters and leaves the cell

Question 2

Draw the structure of the nucleus and describe its function

Answer 2

Nuclear envelope - controls passage of ions, molecules, RNA between nucleoplasm and cytoplasm
Nucleolus - assembling ribosomal subunits
Chromatin
Nucleoplasm
Function: code for protein synthesis

Question 3

Draw the structure of the mitochondria and describe its function

Answer 3

Cristae
Mitochondrial matrix - contains respiratory enzymes
Double membrane
Function: producing ATP via aerobic respiration

Question 4

Draw the structure of a chloroplast and describe its function

Answer 4

Thylakoids
Grana
Lamellae
Stroma
Double membrane
Function: site of photosynthesis

Question 5

Draw the structure of the Golgi apparatus and vesicles and describe their functions

Answer 5

Apparatus - modifies proteins and lipids
Vesicles - transport these to target cells

Question 6

Draw the structure of the rough endoplasmic reticulum and describe its function

Answer 6

Has ribosomes on its surface
Function: protein synthesis

Question 6

Draw the structure of a ribosome and describe its function

Answer 6

Function: site of protein synthesis

Question 6

Draw the structure of the smooth endoplasmic reticulum and describe its function

Answer 6

Function: making and processing lipids

Question 7

Draw the structure of the cell wall and describe its function

Answer 7

Function: provide structural support to cell

Question 8

Draw the structure of a lysosome and describe its function

Answer 8

Function: breakdown of proteins, polysaccharides, lipids, nucleic acids, old organelles

Question 9

Draw the structure of a vacuole and describe its function

Answer 9

Tonoplast
Function: keep cell rigid and isolate unwanted chemicals

Question 10

Describe the function of the cytoplasm

Answer 10

Site of many metabolic reactions in the cell

Question 11

List the key differences between a eukaryotic and prokaryotic cell

Answer 11

Prokaryotes are smaller
Prokaryotes have no membrane-bound organelles in cytoplasm
Prokaryotes have smaller 70S ribosomes whereas eukaryotes have larger 80S
Prokaryotes have no nucleus
Prokaryotes have a cell wall made of murein

Question 12

List features that SOME prokaryotes have, but not all

Answer 12

One or more plasmids
A capsule surrounding cell
One or more flagella

Question 13

Describe the general structure of a virus and draw a diagram

Answer 13

Generic material, capsid, attachment protein

Question 14

Describe how an optical microscope works, as well as its advantages and disadvantages

Answer 14

Uses light and focuses using lenses
Live specimens can be used
Sample is shown in colour

Question 15

Describe how a transmission electron microscope works, as well as its advantages and disadvantages

Answer 15

Uses electrons and focuses using magnets
High resolution due to shorter wavelength of electrons so smaller organelles can be observed
Only dead specimens can be used
Sample is shown in black and white
Requires thinner specimens
Requires complex preparation
Produces 2D images

Question 16

Describe how a scanning electron microscope works, as well as its advantages and disadvantages

Answer 16

Uses electrons
Produces 3D images

Question 17

Define magnification

Question 18

Define resolution

Question 19

What is the formula to calculate magnification?

Answer 19

Image size/actual size

Question 20

Describe the process of cell fractionation and ultracentrifugation

Answer 20

Blend sample in homogeniser to form homogenate
Filter homogenate to remove cell debris
Spin in centrifuge at low speed
Densest organelle forms pellet first
Decant supernatant and re-spin in another test tube at a higher speed
Next densest organelle forms pellet and so on

Question 21

What are some examples of artefacts?

Answer 21

Dust, air bubbles, fingerprints

Question 22

Explain why the solution used in cell fractionation should be ice-cold, buffered and isotonic

Answer 22

Ice-cold - prevent enzymes damaging organelles
Buffered - keep pH constant so enzymes don’t denature
Isotonic - so no water enters or leaves the cell by osmosis

Question 23

Order that organelles form a pellet in ultracentrifugation

Answer 23

Nuclei
Chloroplasts (if carrying out cell fractionation of plant tissue)
Mitochondria
Lysosomes
Endoplasmic reticulum
Ribosomes