Cell structure and transport

Question 1

What proportion of total body water is extracellular?

Answer 1

1/3

Question 2

What proportion of total body water is intracellular?

Answer 2

2/3

Question 3

Of the extracellular water, how much of it is interstitial?

Answer 3

3/4

Question 4

Of the extracellular water, how much of it is intravascular (in the plasma)?

Answer 4

1/4

Question 5

Describe the features of an isotonic solution

Answer 5

The concentration of solutes on both sides of the membrane are equal. Therefore, the net movement of water is zero

Question 6

Describe the features of a hypertonic solution

Answer 6

The concentration of solutes is greater outside the cell. Therefore, there is a net movement of water out of the cell, resulting in the cell shrinking

Question 7

Describe the features of a hypotonic solution

Answer 7

The concentration of solutes is greater inside the cell. Therefore, there is a net movement of water into the cell, resulting in the cell swelling

Question 8

List five broad functions of the circulatory system

Answer 8

1. Exchange of substances with the environment
2. Transport oxygen to cells
3. Remove metabolites and carbon dioxide from cells
4. Thermoregulation
5. Transport immune cells and mediators

Question 9

Where would you find continuous capillaries?

Answer 9

1. Muscle
2. Skin
3. Lungs
4. Fat
5. Connective tissue
6. Neural tissue

Question 10

Where would you find fenestrated capillaries?

Answer 10

1. Kidneys
2. Intestines
3. Endocrine glands
4. Joints

Question 11

Where would you find discontinuous capillaries?

Answer 11

1. Bone marrow
2. Liver
3. Spleen

Question 12

What are the three forces driving movement of substances across capillary walls?

Answer 12

1. Diffusion
2. Pinocytosis
3. Bulk flow (starlings forces)

Question 13

What is the main starlings force driving filtration of substances out of capillaries?

Answer 13

Hydrostatic pressure of the capillary

Question 14

What is the main starlings force driving filtration of substances into of capillaries?

Answer 14

Oncotic pressure of capillaries

Question 15

What propels lymph down initial lymphatics?

Answer 15

Extrinsic lymphatic pump, relying on external muscle contraction to propel lymph downstream. Other contributing factors are:

1. Respiration
2. External tissue compression
3. Vasomotion and pulse pressure changes in neighbouring arterioles

Question 16

What prevents back flow of lymph from the collecting lymphatics back into the initial lymphatics?

Answer 16

Bicuspid valves

Question 17

What propels lymph down collecting lymphatics?

Answer 17

Contractile smooth muscle

Question 18

What is the difference between oedema and lymphoedema?

Answer 18

The difference relates to the cause of the excess fluid. Oedema can be caused by decreased plasma protein, increased vascular permeability or increased venous pressure. However, lymphoedema relates specifically to excess fluid caused by a defective lymphatic system. General causes include obstruction, lack of skeletal muscle contraction (defective extrinsic lymphatic pump) or damaged lymphatic vessels.

Question 19

Define osmolarity

Answer 19

The concentration of particles in one litre of solution, independent of the size and weight of the particles

Question 20

Define osmolality

Answer 20

The concentration of particles in one kilogram of solution, independent of the size and weight of the particles

Question 21

Define tonicity

Answer 21

The state of a solution with respect to its osmotic pressure (isotonic, hypertonic, hypotonic)

Question 22

What are factors which decrease membrane fluidity?

Answer 22

1. Longer tails
2. Increasing saturation
3. Decreasing temperature
4. Increasing cholesterol

Question 23

What are factors which increase membrane fluidity?

Answer 23

1. Shorter tails
2. Increasing unsaturation
3. Increasing temperature
4. Decreasing cholesterol

Question 24

What are the components of Fick’s law?

Answer 24

Flux = concentration difference x surface area x diffusion coefficient / membrane thickness

Question 25

Are hydrophobic or hydrophilic molecules better at diffusing through membranes?

Answer 25

Hydrophobic, because they are lipid soluble. Therefore, they diffuse through phospholipid membranes faster.

Question 26

What type of molecules pass through membranes most readily?

Answer 26

Non-polar molecules

Question 27

Briefly describe simple diffusion

Answer 27

Movement of molecules down their concentration or electrical gradient. Directly though the membrane, through pores or through protein channels.

Question 28

Briefly describe Facilitated diffusion

Answer 28

Movement of molecules down their concentration or electrical gradient. Facilitated by a carrier molecule, transporter, or binding of another molecule inducing a conformational change.

Question 29

Briefly describe active transport

Answer 29

Movement of molecules up their concentration or electrical gradient. Movement is carrier mediated and energy dependent.

Question 30

What is an example of a ligand gated ion channel?

Answer 30

1. Acetylcholine binding to nicotinic ACh receptors on the post-synaptic neuron, opening sodium channels and promoting action potential generation 2. GABA binding to receptors in the CNS, opening Cl- channels and inhibiting action potential generation

Question 31

What is an example of a voltage gated ion channel?

Answer 31

Voltage gated calcium channels on the sarcoplasmic reticulum in skeletal muscle fibres, channels open when there is sufficient depolarisation

Question 32

What is an example of primary active transport?

Answer 32

The sodium potassium pump, using ATP to pump both sodium and potassium against their concentration gradients. 3 sodium molecules leave for every 2 potassium molecules which enter, this sets up a chemical gradient for both ions and also an electrical gradient across the cell membrane (inside more negative than outside)

Question 33

What is an example of secondary active transport?

Answer 33

1. Sodium calcium antiporters, allowing sodium to re-enter the cell based on the electrochemical gradient set up by the sodium potassium pump. 2. Sodium glucose symporters, allowing sodium to re-enter the cell based on the electrochemical gradient set up by the sodium potassium pump. In the gut and renal tubules the coupled glucose is moving up its concentration gradient.

Question 34

What are reticulocytes?

Answer 34

Immature red blood cells. They compose about 1% of RBC and circulate for a day before maturing

Question 35

What species has nucleated reticulocytes?

Answer 35

Chickens. Mammalian reticulocytes don't have nuclei

Question 36

What is the oxygen bearing molecule in RBC?

Answer 36

Haemoglobin

Question 37

How many ahem subunits does each haemoglobin have?

Answer 37

4, hence each RBC can carry 4 Oxygen molecules (O2)

Question 38

How is the majority of carbon dioxide carried by RBC

Answer 38

As bicarbonate ions

Question 39

Briefly describe haemolytic anemia

Answer 39

The body destroys RBC at a faster rate than they are being produced

Question 40

What are platelets?

Answer 40

Also known as thrombocytes, they are involved in clotting

Question 41

What is meant by aggregation?

Answer 41

Formation of a platelet plug in response to small endothelial injuries

Question 42

What is meant by coagulation?

Answer 42

Formation of a fibrin clot (thrombus) in response to larger injuries

Question 43

What causes fibrinogen to polymerize into fibrin during the coagulation pathway?

Answer 43

Thrombin

Question 44

Where are the sites of haemopoiesis during foetal development?

Answer 44

1. Liver 2. Spleen 3. Bone marrow

Question 45

Where are the sites of haemopoiesis during embryogenesis?

Answer 45

1. Liver 2. Spleen 3. Yolk sac

Question 46

What are haemopoietic stem cells?

Answer 46

Multipotent cells which can form cells of any blood line (Myloid, Lymphoid and Erythroid)

Question 47

What hormone controls erythropoiesis in mammals? Where is it produced?

Answer 47

Erythropoietin (EPO), produced by fibroblast-like cells in the cortex and outer medulla of the kidney

Question 48

What is a typical stimulus for EPO production by renal peritubular cells?

Answer 48

Fall in effective circulating volume resulting in tissue hypoxia

Question 49

What are the thee specific effects of EPO?

Answer 49

1. Shortens cell cycle time by increasing mitotic division rate of stem cells and erythroblasts 2. Increased rate of maturation of erythroblasts into reticulocytes within the bone marrow 3. Increased rate of reticulocyte release from the bone marrow

Question 50

What would you expect to find in a plasma sample?

Answer 50

1. Water 2. Proteins (albumin, globulins, fibrinogen) 3. Salts 4. Hormones

Question 51

What would you expect to find in a serum sample

Answer 51

Same as plasma sample except without the proteins involved in clotting (fibrinogen)