Cells and Organelles

Question 1

what is the role of the plasma membrane?

Answer 1

It encloses cell content and provides an effective barrier between the extracellular environment and inside of the cell

Question 2

What property of the phospholipid layer creates an effective barrier?

Answer 2

Its amphipathic nature

Question 3

What is glycocalyx?

Answer 3

Coating of carbohydrates on cell surface

Question 4

what is the role of carbohydrates on surface of cell membrane?

Answer 4

They allow for recognition of the cell

Question 5

What roles can have proteins have on the cell membrane?

Answer 5

Integral: allow transfer of molecules across the cell membrane
Receptor: ligands bind to it

Question 6

What are lipid rafts?

Answer 6

Regions enriched with particular phospholipids and cholesterol

Question 7

What is the role of lipid rafts in cell membranes?

Answer 7

They act as signalling platforms to direct proteins to their receptors

Question 8

What is the role of cholesterol on the cell membrane?

Answer 8

regulates fluidity of the membrane

Question 9

What is the nucleus bound by?

Answer 9

A double membrane

Question 10

How is DNA packaged in the nucleus?

Answer 10

As chromatin

Question 11

What is nuclear lamina made up of and what is its function?

Answer 11

Made of intermediate filaments. They provide mechanical support to the membrane and position the nuclear pores.

Question 12

What doe the nuclear pore complex allow?

Answer 12

Molecules to pass through

Question 13

What are the four compartments of the mitochondria and what is each one involved in?

Answer 13

Outer membrane: selectively permeable to allow pyruvate to enter for CaC cycle

Inner membrane: Folded into multiple cristae and is involved in ETC

Matrix: contains enzymes involved in CaC cycle

Intermembrane space: creates gradient for ETC

Question 14

What are the two functions of mitochondria?

Answer 14

Site of energy production
Involved in triggering apoptosis: When irreparable DNA damage occurs, cytochrome C which is involved in ETC leaves the cytoplasm to trigger proteolytic caspase cascade to achieve apoptosis.

Question 15

What cells are mitochondria found abundantly in?

Answer 15

Ovum and sperm cells

Question 16

What is endoplasmic reticulum continuous with?

Answer 16

Nuclear membrane

Question 17

What are the two types of ER and what is their role and give examples?

Answer 17

Rough: protein synthesis (covered in ribosomes)
e.g. found in fibroblasts which produce collagen, plasma cells which produce antibodies

Smooth: Calciums storage, lipid synthesis
e.g. hepatocytes to produce lipids, leydig cell for biosynthesis fo steroid hormone

Question 18

What is the role of Golgi apparatus?

Answer 18

Sorts proteins

Question 19

Describe what happens to proteins as they pass through eh Golgi stack

Answer 19

Proteins are packaged into vesicles and sent from the ER to the Golgi. They pass through the Golgi stack and undergo enzymatic modification which labels them for their specific cell destination.

Question 20

what is the role of lysosomes?

Answer 20

Lysosomes are vesicle which contain hydrolytic enzymes which break down/degrade unwanted particles.

Question 21

what is the role of endosomes?

Answer 21

They are vesicles that transport molecules from the plasma membrane to lysosomes

Question 22

What is the role of peroxisomes? give examples

Answer 22

They are vesicles which contain enzymes involved in oxidative reactions e.g. detoxification, fatty acid metabolism, biosynthesis of bile acids.

Question 23

What are 4 functions of the cytoskeleton?

Answer 23

Provide mechanical linkages to let tissues bear stress
To provide structure and support to cell
To allow movement of cell components
To allow the cell to adopt specific behaviours (e.g. growth, division, migration)

Question 24

NAme 3 types of cytoskeletal filaments

Answer 24

Microtubules
Intermediate filaments
Microfilaments

Question 25

Describe microtubules, give examples and their roles

Answer 25

Microtubules are cylindrical tubes of tubulin.
e.g. motor proteins kinesin and dynein

Motility of cilia and flagella
Mitotic chromosomal movement
Vesicle/organelle movement

Question 26

Give examples of intermediate filaments

Answer 26

e.g. keratin in skin
lamin in nuclear lamina (provides nuclear membrane support)
desmin in cardiac muscle
Vimentin in fibroblasts of the dermis

Question 27

What are microfilaments involved in and give examples of their roles

Answer 27

Involved in structure and movement
e.g. actin

Cell projections e.g microvilli, stereo cilia
Cytoplasm e.g. cell contraction, shape change
Membrane extension e.g. lamellipodia, filopodia
Contractile ring e.g. cytokinesis

Question 28

Where is axoneme found and what does it do?

Answer 28

Axoneme is the cytoskeletal component found in cilia and flagella.

It allows for bending and is mostly composed of microtubules.

Question 29

Describe Tay Sachs disease

Answer 29

Lysosomal storage disorder where lysosomes don’t break down lipids. Lipid build up destroys neurons and causes progressive damage to the nervous system.

Question 30

what is kartagener’s syndrome?

Answer 30

Mutation in the dynein microtubule resulting if cilia and flagella defects. This results in recurrent respiratory infection and infertility due to immotile sperm

Question 31

What is Vohvinel syndrome?

Answer 31

recessive mutation in the connexin protein results in defects in GAP junctions. These cause thick, honeycomb-like calluses.

Question 32

What is epidermolysis bullosa simplex?

Answer 32

A rare skin disease causing blistering. It occurs due to defects in IFs/hemidesmosomes which lack integrity at the demo-epidermal junction.

Question 33

What occurs when E-cadherins from the Adherns junction is partially/completely lost in tumour cells?

Answer 33

Epithelial cancer

Question 34

what are cell junctions?

Answer 34

Transmembrane protein complexes which connect cell membranes with cytoskeleton, adjacent cells and the basement membrane.

Question 35

What are three types of cell junctions?

Answer 35

Tight/occluding
GAP/communication
Anchoring

Question 36

What are anchoring junctions?

Answer 36

Connection between adjacent cells

Question 37

WHICH anchoring junctions connect cell to cell and what are their roles?

Answer 37

Adherens: connect actin filaments. Hold epithelial cells together.

Desmosomes: connect intermediate filaments. They strongly bind keratinocytes in the epidermis

Question 38

WHICH anchoring junctions connect cell to ECM and what are their roles?

Answer 38

Focal Adhesion: connects actin filaments. Involved in cell anchorage and mechanical and biochemical signalling.

Hemidesmosomes: connect intermediate filaments. Bind epidermis to dermis at demo-epidermal junction

Question 39

What do tight junctions connect, where are they found and what is their role?

Answer 39

They connect actin filaments and provide cell to cell contact.
They are found close to the surface of epithelial cells

They seal adjacent cells in an epithelial sheet to form a watertight seal (blood-brain barrier) and also align cells to maintain polarity.

Question 40

Describe the two ways in which tight/occluding jucntions can work>

Answer 40

As gates: regulate the permeability of the paracellular space to prevented unwanted particles going in or out.

As fences: Forms an apical and basolateral intramembrane diffusion barrier so that molecules on each side of the membrane do not mix and are different, making them polar.

Question 41

WHAT kind of contact is found in GAP junctions, which proteins are they made up of, and what is their role?

Answer 41

Cell to cell contact

Made up of Hexamer and connexin proteins

Allow passage of small molecules and ions into the cell