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Bio PPQs > Exchange of substances > Flashcards

Exchange of substances Flashcards

1
Q

Describe the role of enzymes in the digestion of proteins in a mammal

(4 marks)

A
  • Hydrolysis of peptide bonds
  • Endopeptidase act in the middle of a polypeptide
  • Exopeptidases act at end of polypeptide
  • Dipeptidase acts on a dipeptide/ between 2 amino acids
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2
Q

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

(5 marks)

A
  • Micelles contain bile salts and fatty acids/ monoglycerides
  • Makes fatty acids soluble in water
  • Fatty acids absorbed by diffusion
  • Triglycerides reformed in cells
  • Vesicles move to cell membrane
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3
Q

Describe the relationship between size and SA:V ratio of organisms

(1 marks)

A

As size increase SA:V ratio decreases

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4
Q

Explain why oxygen uptake is a measure of metabolic rate in organisms

(1 mark)

A

Oxygen used in respiration which provides energy/ ATP

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5
Q

Explain how the countercurrent mechanism in fish gills ensures the maximum amount of oxygen passes into the blood flowing through the gills

(3 marks)

A
  • Water and blood flow in opposite directions
  • Blood always passing water in a higher concentration gradient
  • Diffusion gradient maintained throughout length
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6
Q

Explain 2 ways in which the strutcure of fish gills is adapted for efficient gas exhange

(2 marks)

A
  • Many lamallae/ filaments so large surface area
  • Thin surface so short diffusion pathway

When talking about making gas exhange more efficient, remember Fick’s Law:
Rate of diffusion = surface area x concentration gradient / diffusion pathway

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7
Q

Amoebic fish gill disease is caused by a parasite that lives on the gills of some species of fish. The disease causes the lamellae to become thicker and to fuse together. AGD reduces the efficiency of gas exchange in fish.
Give two reasons why.

A
  • Thicker lamellae so greater diffusion distance
  • Lamellae fuse so reduced surface area
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8
Q

The volume of water passing over fish gills increase if the temperature of the water increases. Suggest why

(1 mark)

A
  • Increased metabolism/ respiration/ enzyme activity
  • Less oxygen (dissolved in water)
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9
Q

Explain the movement of oxygen into the gas exhange system of an insect when it is at rest.

(3 marks)

A
  • Oxygen used in respiration
  • Oxygen concentration gradient
  • So oxygen diffuses in
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10
Q

Explain 3 ways in which an insect’s tracheal system is adapted for efficient gas exhange

(3 marks)

A
  • Tracheoles have thin walls so short diffusion distance
  • Highly branched so short diffusion distance
  • Highly branched so large SA
  • Tracheae provide tubes full of air so fast diffusion
  • Fluid in the end of the tracheoles that move out during excercise
  • Body can be moved by muscles to move air so maintains concentration gradient
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11
Q

The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain oxygen from water.
Explain how the presence of gills adapts the damselfly to its way of life.

(2 marks)

A
  • Damselfly larvae has higher metabolic rate
  • Uses more oxygen
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12
Q

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs

(4 marks)

A
  • Trachea and bronchi and bronchioles
  • Down pressure gradient
  • Down diffusion gradient
  • Across alveolar epithelium (squamous epithelium)
  • Across capillary endothelium
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13
Q

Explain how a plant’s cutcile reduces water loss

(1 mark)

A

Impermeable to water/ stops water passing through

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14
Q

Some babies are born with a hole between the right and left ventricles. These babies are unable to get enough oxygen to their tissues. Suggest why

(2 marks)

A
  • Blood flows from left ventricle to right ventricle/ mixing of oxygenated and deoxygenated blood
  • Lower volume of oxygenated blood leaves left ventricle
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15
Q

Explain the role of the heart in the formation of tissue fluid

(2 marks)

A
  • Contraction of ventricles produces high hydrostatic pressure
  • Forces water out of capillaries
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16
Q

High absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead to a build up of tissue fluid. Explain how.

(2 marks)

A
  • Higher salt results in lower water potential of tissue fluid
  • Less water returns to capillary by osmosis
    OR
  • Higher salt results in higher hydrostatic pressure
  • More fluid forced out of capillary
17
Q

Describe how tissue fluid is formed and how it is returned to the circulatory system

(6 marks)

A

Formation:
- High hydrostatic pressure
- Forces water out
- Large proteins remain in capillary
Return:
- Lower water potential in capillary
- Due to plasma proteins
- Water enters capillary
- By osmosis
- Excess water drained by lymph vessels

18
Q

Describe, using the oxygen dissociation curve for human haemoglobin, how haemoglobin loads and unloads oxygen in the body.

(3 marks)

A
  • Loading of oxyen at high partial pressure
  • In lungs, haemoglobin is almost fully saturated/ has a high affinity for oxygen
  • Unloads oxygen at low partial pressure
  • Unloading linked to higher carbon dioxide concentration
19
Q

Heat from respiration helps mammals to maintain a constant body temperature. Use this info to explain the ration between the SA:V ratio of mammals and the oxygen dissociation curves of their haemoglobins.

(4 marks)

A
  • Smaller mammal has greater SA:V ratio
  • Larger SA:V ratio= more heat lost
  • Larger SA:V ratio= greater rate of respiration
  • Oxygen required for respiration so Hb releases more oxygen more readily
20
Q

Explain how changes in the shape of haemoglobin result in the S-shape (sigmoidal) oxyhaemoglobin dissociation curve for HbA

(2 marks)

A
  • First oxygen binds to Hb causing change in shape
  • Change in shape allows O2 to bind more easily (cooperative binding)
21
Q

Describe and explain the ceffect of increasing CO2 concentration on the dissociation of oxyhaemoglobin

(2 marks)

A
  • More oxygen unloading
  • By decreasing PH/ increasing acidity
22
Q

Some proteases are secreted as extracellular enzymes by bacteria. Suggest one advantage to secreting an extracellular protease in its natural environment.

(2 marks)

A
  • To digest protein
  • So they can absorb amino acids for growth
23
Q

Describe the role of enzymes in the digestion of proteins in a mammal

(4 marks)

A
  • Hydrolysis of peptide bonds
  • Endopeptidases act in the middle of a polypeptide/ protein
  • Exopeptidases act at ends of protein
  • Dipeptidases act on dipeptides/ between 2 amino acids
24
Q

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

(5 marks)

A
  • Micelles contain bile salts and fatty acids/ monoglycerides
  • Make fatty acids soluble in water
  • Fatty acids absorbed by diffusion
  • Triglycerides reformed in cells
  • Vesicles move to cell membrane

Make sure to read exactly what the question is asking for- only wants absorption not digestion

25
Q

Explain the cohesion-tension theory

(5 marks)

A
  • Water evaporates/ is transpired from leaves
  • Water lost, lowers water potential in leaf cells
  • Water pulled up xylem
  • Water potential gradient creates tension/ pulls up water
  • Molecules cohere by hydrogen bonds and forms water columns
  • Adhesion of water to walls of xylem
  • Up transpiration stream
26
Q

Explain how water enters xylem from the endodermis in the root and is then transported to the leaves

(6 marks)

A

(In the root)
- Casparian strip blocks apoplast pathway
- Active transport by endodermis
- Of ions/ salts into xylem
- Lower water potential in xylem/ water enters xylem down gradient

(Xylem to leaf)
- Evaporation/ transpiration from leaves
- Cohesion/ tension between water molecules
- Adhesion of water molecules to xylem
- Creates continuous water column

27
Q

Root pressure moves water through the xylem. Describe what causes root pressure

(4 marks)

A
  • Active transport by endodermis
  • Of ions/ salts into xylem
  • Lowers water potential
  • Water enters by osmosis
28
Q

Describe how a high pressure is produces in the leaves

(3 marks)

A
  • Water potential becomes lower (as sucrose enters phloem)
  • Water enters phloem by osmosis
  • Increased volume of water increases pressure
29
Q

Give 2 precautions the students should have taken when seting up the potometer to obtain reliable measurements of water uptake by the plant shoot

(2 marks)

A
  • Seal joints/ ensure airtight
  • Cut shoot under water
  • Cut shoot at a slant
  • Dry off leaves
  • Insert into apparatus under water
  • Ensure no air bubbles are present
  • Shut tap
  • Note where bubble is at start
30
Q

Describe the mass flow hypothesis for the mechanism of transloaction in plants

(5 marks)

A
  • In source cell, sucrose actively transported into phloem
  • By companion cells
  • Lowers water potential of sieve tube and water enters by osmosis
  • Increase in pressure causes mass movement towards sink
  • Sucrose converted in root for respiration

Bio PPQs (7 decks)

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