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Cells to Systems > Cell structure and transport > Flashcards

Cell structure and transport Flashcards

1
Q

What proportion of total body water is extracellular?

A

1/3

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2
Q

What proportion of total body water is intracellular?

A

2/3

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3
Q

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

A

3/4

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4
Q

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

A

1/4

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5
Q

Describe the features of an isotonic solution

A

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

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6
Q

Describe the features of a hypertonic solution

A

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

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7
Q

Describe the features of a hypotonic solution

A

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

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8
Q

List five broad functions of the circulatory system

A
  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
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9
Q

Where would you find continuous capillaries?

A
  1. Muscle
  2. Skin
  3. Lungs
  4. Fat
  5. Connective tissue
  6. Neural tissue
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10
Q

Where would you find fenestrated capillaries?

A
  1. Kidneys
  2. Intestines
  3. Endocrine glands
  4. Joints
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11
Q

Where would you find discontinuous capillaries?

A
  1. Bone marrow
  2. Liver
  3. Spleen
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12
Q

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

A
  1. Diffusion
  2. Pinocytosis
  3. Bulk flow (starlings forces)
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13
Q

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

A

Hydrostatic pressure of the capillary

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14
Q

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

A

Oncotic pressure of capillaries

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15
Q

What propels lymph down initial lymphatics?

A

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
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16
Q

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

A

Bicuspid valves

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17
Q

What propels lymph down collecting lymphatics?

A

Contractile smooth muscle

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18
Q

What is the difference between oedema and lymphoedema?

A

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.

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19
Q

Define osmolarity

A

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

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20
Q

Define osmolality

A

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

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21
Q

Define tonicity

A

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

22
Q

What are factors which decrease membrane fluidity?

A
  1. Longer tails
  2. Increasing saturation
  3. Decreasing temperature
  4. Increasing cholesterol
23
Q

What are factors which increase membrane fluidity?

A
  1. Shorter tails
  2. Increasing unsaturation
  3. Increasing temperature
  4. Decreasing cholesterol
24
Q

What are the components of Fick’s law?

A

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

25
Q

Are hydrophobic or hydrophilic molecules better at diffusing through membranes?

A

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

26
Q

What type of molecules pass through membranes most readily?

A

Non-polar molecules

27
Q

Briefly describe simple diffusion

A

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

28
Q

Briefly describe Facilitated diffusion

A

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

29
Q

Briefly describe active transport

A

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

30
Q

What is an example of a ligand gated ion channel?

A
  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
31
Q

What is an example of a voltage gated ion channel?

A

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

32
Q

What is an example of primary active transport?

A

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)

33
Q

What is an example of secondary active transport?

A
  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.
34
Q

What are reticulocytes?

A

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

35
Q

What species has nucleated reticulocytes?

A

Chickens. Mammalian reticulocytes don’t have nuclei

36
Q

What is the oxygen bearing molecule in RBC?

A

Haemoglobin

37
Q

How many ahem subunits does each haemoglobin have?

A

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

38
Q

How is the majority of carbon dioxide carried by RBC

A

As bicarbonate ions

39
Q

Briefly describe haemolytic anemia

A

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

40
Q

What are platelets?

A

Also known as thrombocytes, they are involved in clotting

41
Q

What is meant by aggregation?

A

Formation of a platelet plug in response to small endothelial injuries

42
Q

What is meant by coagulation?

A

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

43
Q

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

A

Thrombin

44
Q

Where are the sites of haemopoiesis during foetal development?

A
  1. Liver
  2. Spleen
  3. Bone marrow
45
Q

Where are the sites of haemopoiesis during embryogenesis?

A
  1. Liver
  2. Spleen
  3. Yolk sac
46
Q

What are haemopoietic stem cells?

A

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

47
Q

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

A

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

48
Q

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

A

Fall in effective circulating volume resulting in tissue hypoxia

49
Q

What are the thee specific effects of EPO?

A
  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
50
Q

What would you expect to find in a plasma sample?

A
  1. Water
  2. Proteins (albumin, globulins, fibrinogen)
  3. Salts
  4. Hormones
51
Q

What would you expect to find in a serum sample

A

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

Cells to Systems (10 decks)

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