2.1 Cell structure

Question 1

Magnification and resolution of a light microscope

Answer 1

x1500
200 nm

Question 2

Magnification and resolution of a TEM

Answer 2

> x500,000
0.5 nm

Question 3

Magnification and resolution of a SEM

Answer 3

x500,000
3-10 nm

Question 4

What is the image from a TEM

Answer 4

2D
Black and White
Organelles visible

Question 5

What is the image from an SEM

Answer 5

3D
Black and White
Cell surface visible

Question 6

Advantages/Disadvantages of light microscope

Answer 6

Cheap
Easy to use
Can view live cultures / tissues

2D images only
cannot view most organelles

Question 7

Advantages/Disadvantages of TEM

Answer 7

More organelles can be seen
Very high magnification + resolution

Dead specimen
Very thin specimen
Lengthy treatment to produce thin specimens

Question 8

Advantages/Disadvantages of SEM

Answer 8

External 3D structure

Lower resolution than TEM
Dead specimens

Question 9

Why is staining used?

Answer 9

Increases the contrast between organelles so differnet organelles can be viewed

Increases the contrast so biological molecules can be seen

Question 10

Function of the nucleus

Answer 10

Contains DNA
Controls production of mRNA
Starts mitosis

Question 11

Function of nucleolus

Answer 11

Manufactures ribosomal RNA and assembles the ribosomes
Ribosomes pass through nuclear pores

Question 12

Function of the Nuclear envelope

Answer 12

Double membrane
Contains nuclear pores - mRNA and ribosomes pass out and nucleotides pass in

Question 13

Function of Rough Endoplasmic Reticulum

Answer 13

Transports proteins made on attached ribosomes

Question 14

Function of Smooth Endoplasmic Reticulum

Answer 14

Lipid, carbohydrate and steroid synthesis - stored in the SER and transported when needed

Question 15

Function of the Golgi apparatus

Answer 15

Modifies proteins and lipids before packaging them into Golgi vesicles

Question 16

Function of ribosomes

Answer 16

Site of protein synthesis
Made of two subunits
80s in larger ribosomes in eukaryotes
70s in prokaryotes

Question 17

Function of Mitochondria

Answer 17

Site of respiration
Inner membrane contains enzymes which catalyse aerobic reactions which produce ATP

Question 18

Function of lysosomes

Answer 18

Specialised vesicles formed by the Golgi surrounded by a single membrane
Contains digestive enzymes:
–> Breaks down material ingested by phagocytes
–> Release hydrolytic enzymes outside of cell
–> Digests worn out cells - autophagy
–> Role in apoptosis

Question 19

Function of Chloroplasts

Answer 19

Site of Photosynthesis

Question 20

Function of the Plasma membrane

Answer 20

Regulates the movement of substances in and out of the cell
Receptor molecules allows it to respond to chemicals e.g. hormones

Question 21

Function of centrioles

Answer 21

Self-replicating
Nine bundles of microtubules
Forms spindle fibres for mitosis /meiosis

Question 22

Function of Cell wall

Answer 22

Cellular support and structure
Made of polysaccharide cellulose

Question 23

Function of Flagella

Answer 23

Microtubule pairs slide over each other causing flagella to beat
Moves the cell
–> e.g. the sperm tail

Question 24

Function of Cilia

Answer 24

Projections of cell membrane made of microtubules
Move an entire organism or cell i.e. mucus

Question 25

Function of Microvilli

Answer 25

Increases SA of cell surface membrane - increased rate of exchange

Question 26

Function of permanent vacuole

Answer 26

Keeps cell pressurised

Question 27

What is the importance of the cytoskeleton?

Answer 27

Network of protein fibres Mechanical strength and shape Holds organelles in place Move organelles around the cell using ATP