Cells Ultrastructure (not a lecture)

Question 1

What features does a nucleus have:
State functions.

Answer 1

Nuclear DNA: euchromatin is actively transcribing chromatin,
heterochromatin in less active cell
Nucleolus - forms rRNA
Nuclear membrane - double membrane, perforated with pores

Question 2

What features does a mitochondria have:
State functions.

Answer 2

Site of oxidative phosphorylation
Double membrane: Outer is smooth for lipid synthesis + fatty acid metabolism, Inner is folded and has cristae for respiratory chain, ATP production
Matrix - Site of Krebs cycle
Intramembranous space - Nucleotide phosphorylation APD to ATP

Question 3

What features does a RER have:
State functions.

Answer 3

Site of protein synthesis.
Highly folded flattened membrane sheets

Question 4

What features does a SER have:
State functions.

Answer 4

Site of lipid synthesis
Processes and stores synthesised proteins
Highly folded flattened membrane sheets

Question 5

What features does a Golgi apparatus have:
State functions.

Answer 5

Processing and modification of proteins
Parallel stacks of membrane - processes and modifies macromolecules
Cis face - receives vesicles from SER, for protein phosphorylation
Medial face - form complex oligosaccharides by adding sugars to lipids and peptides
Trans face - proteolysis of peptides into active forms

Close to the nucleus of the cell
Can’t be seen in most cells but in a plasma cell, perinuclear hoff

Question 6

What features does a vesicles have:
State functions.

Answer 6

Very small, spherical membrane-bound organelles - transport & store material + exchange cell membrane between compartments
Types: Cell-surface derived pinocytotic and phagocytotic vesicles
Golgi- derived transport vesicles + ER - derived transport vesicles
Lysosomes
Peroxisomes

Question 7

Explain the function of lysosomes:

Answer 7

Contains digestive enzymes, site of breakdown for most molecules.
They also breakdown debris from dead cells & bacteria and damaged cell organelles.

Question 8

Explain function of peroxisomes:

Answer 8

Small, membrane-bound organelles containing enzymes which oxidase long-chain fatty acids - beta oxidation ?
Also produce hydrogen peroxide that can destroy pathogens.

Question 9

What is the cytoskeleton?

Answer 9

Filamentous proteins which brace the internal structure of the cell
Helps cells maintain their shape and internal organisation

Question 10

What are the three parts of the cytoskeleton? In size order from smallest to biggest

Answer 10

Microfilaments, Intermediate filaments, microtubules

Question 11

What are microfilaments?

Answer 11

Smallest 5nm.
Actin protein forms a bracing mesh on the inner surface of cell membrane

Question 12

What are intermediate filaments?

Answer 12

10nm.
Anchored transmembrane proteins which can spread tensile force through tissues.
6 types:
- Cytokeratins - epithelial cells
- Desmin - myocytes
- Glial fibrillary acidic protein - astrocytic glial cells
- Neurofilament protein - neurons
- Nuclear laminin - nuclei of all cells
- Vimentin - mesodermal cells

Question 13

What are microtubules?

Answer 13

25nm. Tubulin protein
In all cells except erythrocytes due to lack on nucleus

Question 14

What storage products and inclusion found in cells?

Answer 14

• Lipofuscin - Membrane-bound orange-brown pigment, degradation of lipids common in heart and liver
• Lipid - Non-membrane-bound vacuoles, appears as empty space in histology since dissolved in processing, stored in adipocytes and liver
• Glycogen - CHO polymer in cytoplasm, normally seen on electron microscopy