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Biology exam practise > Organisms exchange substances with their environment > Flashcards

Organisms exchange substances with their environment Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

3 marks

Describe how gas exchange occurs in single-celled organisms and explain why this method cannot be used by large, multicellular organisms.

A
  1. Diffusion (across the cell surface membrane);
  2. Large organisms have small(er) sa : vol ratio
  3. Diffusion pathway would be too long
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2
Q

4 marks

Decsribe fish ventillation

A
  1. Mouth opens, opercular valve shuts
  2. Floor of mouth lowered
  3. Water enters due to decreased pressure, increased volume
  4. Mouth closed, opercular valave opens
  5. Floor of mouth raised= increased pressure, decreased volume
  6. Increased pressure pushes water over gills
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3
Q

3 marks

Describe and explain the importance of three adaptation of the gas exchange surface in the tracheal system of an insect

A
  1. Tracheole (wall) thin/one cell thick;
  2. (So) rapid diffusion (into cells)
  3. Tracheoles enter/supply tissues/muscle fibres;
  4. (So) diffusion direct into cells
  5. Tracheoles are highly branched;
  6. (So) large surface area for (rapid) diffusion;
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4
Q

6 marks

Describe how the structure of the insect gas exchange system:
*   provides cells with sufficient oxygen
*   limits water loss.

A
  1. Spiracles, tracheae, tracheoles;
  2. Spiracles allow diffusion of oxygen
  3. Tracheoles are highly branched so large surface area for exchange
  4. Tracheole walls thin so short diffusion distance to cells
  5. Tracheole walls are permeable to oxygen/air
  6. Exoskeleton impermeable- covered with waterproof waxy cuticle so reduce water loss
  7. Spiracles can close so less water loss
  8. Hairs around spiracles reduce water loss
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5
Q

How does asthma affect the mean volume of air breathed out

A
  1. Muscle walls of bronchi/bronchioles contract;
  2. Walls of bronchi/bronchioles secrete more mucus;
  3. Diameter of airways reduced;
  4. (Therefore) flow of air reduced;
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6
Q

5 marks

Describe how humans breathe in and out

A

Breathing in
1. Diaphragm muscles contract and diaphragm flattens
2. External intercostal muscles contract and ribcage pulled up
3. Increase in volume of thoraic cavity and pressure decreases
Breathing out
4. Diaphragm muscles relaxes and diaphragm becomes curved
5. External intercostal muscles relax and ribcage moves down
6. Decrease in volume of thoraic cavity and increase in pressure –> air pushed down pressure gradient

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7
Q

4 marks

Describe expiration

A
  1. Contraction of internal intercostal muscles
  2. Relaxation of diaphragm muscles and external intercostal muscles
  3. Causes decrease in thoracic cavity
  4. Air pushed down pressure gradient
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8
Q

5 marks

Describe the processes involved in the absorption of the products of starch digestion

A
  1. Glucose moves in with sodium into epithelial cell via co -transport
  2. Via channel/ carrier protein
  3. Sodium removed from epithelial cell by active transport/ sodium-potassium pump
  4. Into blood
  5. Maintaining low concentration of sodium in epithelial cell
  6. Glucose moves into blood
  7. Via facilitated diffusion
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9
Q

2 marks

The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum.
Explain how.

A
  1. Maintains a sodium concentration gradient
  2. Na+ moving in by facilitated diffusion, brings glucose with it/ Na+ moving in by co-transport, brings glucose with it
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10
Q

4 marks

Describe and explain features you would expect to find in a cell specialised for absorption.

A
  1. microvilli so large surface area for absorption
  2. Large number of co-transport/carrier proteins for active transport and FD
  3. Large number of mitochondria so make more ATP by respiration fot AT
  4. Membrane-bound digestive enzymes so maintains concentration gradient for fast absorption
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11
Q

5 marks

Explain how the epithelial cells are adapted for the absorption of glucose

A
  1. Microvilli to increase surface area
  2. Many mitochondria to produce ATP for active transport
  3. Carrier proteins for active trasnport
  4. Channel and carrier protiens for facilitated diffusion
  5. Co- transport of sodium ions and glucose
  6. Membrane- bound enzymes digest disaccharides / produce glucose
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12
Q

2 marks

Desribe functions of bile salts

A
  1. Emulsify lipids/fats;
  2. Increases surface area (of lipid/fat) for (increased) lipase activity;
  3. Form micelles;
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13
Q

5 marks

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels

A
  1. Micelles contain bile salts, fatty acids and monoglycerides
    2.Micelles release fatty acids to the lining of the iluem
  2. Fatty acids absorbed by diffusion
  3. Triglycerides reformed in cells
  4. Vesicles move to cell membrane
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14
Q

4 marks

Describe digestion of proteins

A
  1. Hydrolyisis of peptide bonds
  2. Endopeptidases break bonds in the middle of the AA chain
  3. Exopeptiades remove terminal amino acids
  4. Dipeptidases breaks bonds between dipeptides into single AA
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15
Q

Mechanism for absorption of amino acids into the ileum

A
  • Glucose moves in with sodium into epithelial cell
  • Via carrier/channel protein
  • Sodium removed from epthelial cell by active transport using sodium- potassium pump
  • Maintaining low concentration of sodium in epithelial cell
  • Glucose moves into blood
  • By facilitated diffusion
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16
Q

4 marks

Toxins cause lining of ileum to lose microvilli
Explain why damage to the cells lining the ileum reduces the absorption of the products of digestion and why this reduces absorption of water.

A
  1. Surface area reduced
  2. and so less digestion products enter cell (sodium ions and glucose)
  3. and so water potential does not decrease
  4. and so less water enters cell by osmosis
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17
Q

3 marks

How does exposure to CO affect loading and unloading of oxygen by haemologlobin

A
  1. A low Po2 Hb exposed to CO has a higher affinity for oxygen than normal Hb
  2. In respiring tissue its unloading less oxygen than it should
  3. At high Po2 (lungs) it has a lower affinity for oxygen than normal Hb- only 50% saturation of the no CO Hb (less oxygen loaded at lungs)
18
Q

3 marks

Explain why the thickness of the aorta wall changes all the time during each cardiac cycle

A
  1. Aorta wall stretches because ventricle contracts (pressure increases)
  2. Aorta wall recoils because ventricle relaxes (pressure falls)
  3. Maintain smooth flow / pressure
19
Q

What factor limits the minimum internal diameter of the lumen of a capillary

A

Diameter of red blood cell

20
Q

6 marks

Explain how the structures of the walls of arteries, veins and capillaries are related to their functions.

A

Artery
1. thickest wall, enabling it to carry blood at high pressure / withstand pressure surges
2. most elastic tissue, which evens out pressure
3. most muscle which maintains pressure
4. muscle in wall to control blood flow
Vein
5. thin wall does not have to withstand high pressure
Capillary
6. thin wall, allowing diffusion
7. only endothelium present, allowing short diffusion pathway
All vessels
8. have endothelium that reduces friction

21
Q

2 marks

How is the pressure in the ventricle related to the thickness of ventricle wall

A
  • Thickness of wall increases because ventricle wall contracts
  • Contraction caused by increase in pressure
22
Q

Name the type of blood vessel that controls blood flow to muscles and explain how these blood vessels change blood flow during exercise.

A
  1. Arteriole;
  2. (Circular/smooth) muscle relaxes;
  3. Widens/dilates (lumen of) blood vessel so increases blood flow;
23
Q

3 marks

The oxygen dissociation curve for heamoglobin shifts right during vigorous exercise. Explain the advanatge of this shift

A
  1. Low pH due to increased CO2/ increased respiration
  2. Increased dissociation of haemoglobin
  3. Oygen diffuses from r.b.c to tissues
24
Q

Why does carbonmonoxide kill people. Use loading and unloading of O2.

A

At low pO2, Hb exposed to CO has higher affinity for O2 than normal Hb
In respiring tissues it is unloading less O2 than it should
At high PO2, it has lower affinity for O2 than normal Hb- less O2 loaded to lungs

25
Q

3 marks

Explain how oxygen in a RBC is made available for respiration in active tissues

A
  • Low pH due to increased CO2 due to increased respiration;
  • Increased dissociation of haemoglobin
  • Oxygen diffuses from r.b.c. to tissues
26
Q

What does atheroma lead to

A

Atheroma leads to blockage of coronary artery

27
Q

3 marks

Explain why high blood pressure leads to the accumulation of tissue fluid

A
  • High blood pressure (as ventricle contracts)= high hydrostatic pressure
  • Increase in outward pressure from arteriole end of capillary
  • So more tissue fluid formed
28
Q

3 marks

Why does venule end of capillary have lower blood plasma water potential

A
  1. Water has left capillary
  2. Proteins in blood too large to leave
  3. Higher concentration of blood plasma proteins
29
Q

6 marks

Explain how tissue fluid is formed and how it may be returned to the circulartory system

A
  1. High hydrostatic pressure at arterial end
  2. Soluble molecules pass out
  3. Proteins remain - too large
  4. This lower water potential at venule end
  5. Water moves back into venule end via osmosis
  6. Lymphatic system collects any excess tissue fluid which returns to blood
30
Q

2 marks

A decrease in the pH of blood plasma reduces the affinity of haemoglobin for oxygen.
Explain how aerobic respiration in cells leads to a change in the pH of blood plasma.

A
  1. CO2 is produced
  2. Forms carbonic acid
  3. Hydrogen ions released
31
Q

2 marks

What is the advantage to tissue cells of a reduction in the affinity of haemoglobin for oxygen when the plasma pH decreases?

A
  1. Low pH due to high rates of respiration
  2. Cells need more oxygen
  3. More oxygen released
32
Q

3 marks

Explain the importance of the xylem being kept open as a continuous tube

A
  1. There are no barriers to the movement of water
  2. Due to cohesion between the H bonds
  3. As water molecules evaporate, tension is created (cohesion-tension theory)
33
Q

5 marks

Why is the diameter of the trunksmallest at midday

A
  1. Midday= more sunlight
  2. Stomata open in light= more water loss
  3. Water evaporates more when warm (fall in WP- water is drawn out of xylem)
  4. Hydrogen bonds between water molecules= cohesive= creates a column of water within xylem
  5. Adhesion (water molecules stick to wall of xylem) = helps to pull the water column upwards
  6. Xylem pulled inwards by tension/ faster flow of water
34
Q

2 marks

Explain one way sieve tube cells are adapted for mass transport

A
  • Cytoplasm only at edges of the cell/ fewer organelles
  • Easy flow of the sugars
35
Q

1 mark

Explain why values for the pressure in the xylem are negative

A

(Inside xylem) lower than atmospheric pressure / (water is under) tension;

36
Q

2 marks

One way in which seive cells are adapted for mass transport of sugars

A
  1. Cytoplasm only at edge of the cell
  2. Easy flow of the sugars
37
Q

2 marks

One way in which companion cells are adapted for mass transport of sugars

A
  1. Lots of mitochondria
  2. Release energy for active transport of sucrose into the phloem
38
Q

5 marks

Describe mass flow hypothesis

A
  1. Sucrose actively transported into phloem using companion cells
  2. This lower water potential of phloem
  3. Water enters phloem via osmosis from xylem
  4. Increase in water volume = increase in hydrostatic pressure= more liquid forced to sink cell
  5. Sucrose actively transported to sink cell–> used in respiration as insoluble starch
39
Q

2 marks

Advantage of sunken stomata on xerophytic plants

A
  • Reduces transpiration/ evaporation
  • Fall in water potential gradient
40
Q

2 marks

Use knowledge of structure of leaf to explain why less water is loss through the upper surface of leaves than is lost through the lower surface

A
  1. More stomata on the lower surface
  2. Waxy cuticle on upper surface
41
Q

4 marks

Explain how xylem tissue is adapted for its function

A
  1. Tubes with no end walls- continuous water columns
  2. No cytoplasm / no organelles - allows easier water flow
  3. Lignin- Withstand tension
  4. Pits in walls- allow lateral movement / get round blocked vessels

Biology exam practise (9 decks)

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