Cell Ultrastructure

Question 0

Explain why electron microscopes produce images of higher resolution than light microscopes.

Answer 0

Electrons have a shorter wavelength than visible light, therefore the limit of resolution is lower and more can be resolved.

Limit of resolution is directly proportional to wavelength.

Question 1

What does limit of resolution mean?

Answer 1

The minimum distance at which two objects can be distinguished.

Question 2

What is the structure and function of the phospholipid bilayer?

Answer 2

Phosphate heads = hydrophilic Fatty acid tails = hydrophobic
Impermeable barrier to water-soluble molecules (selective permeability).
Transport of materials along cell surface (+ endocytosis/exocytosis)
Intercellular adhesion
Intracellular recognition
Signal transduction (glycocalyx).

Question 3

What is the structure and function of polyribosomes?

Answer 3

RER = proteins destined for exocytosis/plasma membrane.
Free ribosomes = most proteins produced remain in cell.
Eukaryotic = 40S + 60S = 80S

Question 4

What is the structure and function of the Golgi complex?

Answer 4

Flattened cisternae.
Modifies proteins e.g. glycosylation; then cleaves, sorts, concentrates, packages, and secretes (lysosomes, vesicles, plasma membrane).
Signal mediated diversion of proteins.

Question 5

What is the structure and function of lysosomes?

Answer 5

Acidic sac containing hydrolytic enzymes (active transport of H+).
Merges with phagocytosed material -> phagolysosome.
Protective glycocalyx on inside of membrane -> prevents autolysis.

Question 6

What is the structure and function of the peroxisome?

Answer 6

Liver & kidney.
Detoxifies alcohol, phenols, formic acid, formaldehyde, etc. by oxidation.
Contains crystallised enzymes.

Question 7

What is the structure and function of the mitochondria?

Answer 7

Site of ATP production (oxidative phosphorylation).
mtDNA separate from DNA -> inherited via mother.
MATRIX = enzymes + mtDNA
INNER & OUTER MEMBRANE = varied permeability + enzymes.

Question 8

What is the structure and function of the cytoskeleton?

Answer 8

Network of protein filaments & microtubules in cytoplasm control cell morphology, intracellular organisation, and cell movement.
ACTIN FILAMENTS = skeletal muscle contraction.
INTERMEDIATE FILAMENTS = e.g. keratin.
MICROTUBULES = cell movement e.g. cilia/flagellum (9 + 2).