Cells, Plasma, and Cell Death

Question 1

What is the cytoskeleton made of?

Answer 1

Microtubules
Microfilaments
Intermediate Filaments

Question 2

What are microtubules made of and what is their specific function?

Answer 2

Hollow tubes of tubular dimers (alpha and beta) made by MTOCs (microtubule organising centres)
(Dimers usually dissolve in the cytoplasm)
Provide framework for the movement of Intracellular components and Extracellular cilia/flagella

Question 3

What are centrioles made of and what are their specific function?

Answer 3

Contain 9 groups of microtubule triplets

Forms cilia and flagella

Question 4

What are centrosomes made of and what are their specific function?

Answer 4

Contains two centrioles

Creates spindle fibres during cell division

Question 5

How do cilia/flagella work?

Answer 5

Centrioles anchor to the cell membrane forming basal bodies (extracellularly)
Basal bodies have ten pairs of microtubules (9 surrounding a single pair in the centre) and motor proteins which move the cilia/flagella

Question 6

How are vesicles moved within the cytoplasm?

Answer 6

Vesicles are moved via motor proteins along the cytoskeleton - requiring ATP hydrolysis

Question 7

What are microfilaments made of and what is their specific function?

Answer 7

Linear polymer of globular actin (G-actin) that is helically shaped
Provides specific structure and strength to a cell (filaments have flexibility and strength)

Question 8

What are intermediate filaments made of and what is their specific function?

Answer 8

Variety of proteins are grouped into dimers, tetramers, unit-length filaments (ULF), and rope-like Intermediate filaments
Provide the support for other filaments

Question 9

What is apoptosis?

Answer 9

Highly regulated (caspase activated) process of programmed cell death

Question 10

What are the steps in apoptosis?

Answer 10

1) Cell shrinks
2) Chromatin aggregates at the nuclear membrane
3) The cell membrane loses its integrity and forms apoptosis bundles
4) The DNA is fragmented among the bundles
5) No immune response (although phagocytes destroy vesicles formed) and ATP is used

Question 11

What is necrosis?

Answer 11

Response to cell injury that leads to premature cell death

Question 12

What are the steps in necrosis?

Answer 12

1) Na+ enters cell, causing swelling of the cytoplasm as water enters as well
2) Cell membrane loses its integrity and bursts (lyses)
3) Organelles and K+ are released into the Extracellular environment
4) DNA is fragmented randomly
5) Cytotoxic chemicals are also released leading to a immune response
6) No vesicles are formed, no ATP is used

Question 13

Define osmolality

Define osmolarity

Answer 13

Concentration of solute / kilogram of solvent

Concentration of solute / litre of solution

Question 14

Normal range of plasma osmolality

Answer 14

285-295 mmol/Kg

Question 15

Define osmotic pressure

Define oncotic pressure

Answer 15

Pressure due to ions

Pressure due to colloids in the blood

Question 16

Show the relationship between:
Tonicity
Osmolality
Osmotic pressure

Answer 16

Hypertonic - increased osmolality - increase in osmotic pressure
Isotonic - normal osmolality - normal osmotic pressure
Hypotonic - decreased osmolality - decrease in osmotic pressure

Question 17

Normal plasma pH

Answer 17

7.36 - 7.44

Question 18

Normal plasma lactate

Answer 18

0.5 - 1.6 mmol/L

Question 19

What is the complement pathway?

Answer 19

Cascade of proteins which when activated cause inflammation, and opsonisation and phagocytosis of pathogens

Question 20

What are the different pathways of the complement pathway?

Answer 20

Classical
Alternative
Mannose-binding Lectin

These 3 lead onto the lytic pathway

Question 21

What are the steps in the classical pathway?

Answer 21

1) C1 forms a complex with the antigen-antibody complex
2) C3 convertase (C4b2a) is activated (from C2a and C4b fragments)
3) C3 convertase will now cleave C3 into C3a and C3b

Question 22

What are the steps in the alternative pathway?

Answer 22

1) Factors B,D,H,I interact with C3b and the pathogen cell wall
2) Together they form the C3 convertase C3bBb
3) C3 convertase will now cleave C3 into C3a and C3b (amplification loop)

Question 23

What are the steps in the Mannose-binding Lectin pathway?

Answer 23

1) MBL binds to mannose residues on the pathogen surface activating MBL-Activated Serine Proteases (MASP) 1 and 2
2) MASP-1 and MASP-2 activate C2 and C4 to form the C3 convertase C4b2a
3) C3 convertase will now cleave C3 into C3a and C3b

Question 24

What are the roles of C3a and C3b proteins?

Answer 24

C3a (C4a, C5a): Anaphylatoxin - activate mast cells

C3b (C4b, C1q): Attache to pathogens covalently (opsonisation)

Question 25

What are the steps in the lytic pathway?

Answer 25

1) C3b activates C5 convertase which cleaves C5 into C5a and C5b
2) C5a is an anaphylatoxin (activates mast cells) and a chemotactic (attracts nuetrophils and macrophages)
3) C5b forms the MAC (membrane attack complex) with C6, 7, 8, 9
4) The MAC inserts itself into the membrane (transmembrane complex) causing cell lysis

Question 26

What is the specific function of the ER?

Answer 26

Post-translation modification of proteins (+ packages them into vesicles)
Converts fatty acids into Lipids