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A-level Biology Longridge Towers School > Chapter 6 Exchange > Flashcards

Chapter 6 Exchange Flashcards

1
Q

What is surface area with respect to organisms?

A

The total area of the organism that is exposed to the external environment.

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2
Q

Explain one advantage of red blood cells being concave compared to being spherical.

A

There is a greater surface area for oxygen diffusion.

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3
Q

Describe 4 features of specialised exchange surfaces.

A

A large surface area to volume ratio.

Very thin, so shorter diffusion distance.

Movement of the environmental medium to maintain concentration gradient.

Effective internal transport system to ensure diffusion gradient is maintained.

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4
Q

How do you calculate the surface area of a cube?

A

Area of one side (length x length) x 6 sides

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5
Q

How do you calculate the volume of a cube?

A

Length x width x height

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6
Q

How do you calculate the ratio of surface area to volume?

A

Surface area / volume

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7
Q

How do you calculate the surface area of a sphere?

A

4 π r2

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8
Q

How do you calculate the volume of a sphere?

A

4/3 π r3

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9
Q

What is the basal metabolic rate?

A

The metabolic rate of an organism when at rest.

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10
Q

What activities require energy when an animal is at rest?

A

The functioning of vital organs such as the lungs, heart and brain.

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11
Q

Give 3 ways that the metabolic rate of an organism can be measured.

A

Rate of oxygen consumption

Rate of carbon dioxide production

Rate of heat production.

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12
Q

Describe 4 methods for determining metabolic rate.

A

Respirometers - the overall volume of gas is measured as carbon dioxide is removed from a closed system.

Oxygen probes - oxygen concentration is measured in a closed system.

Carbon dioxide probes - carbon dioxide concentration is measured in a closed system.

Calorimeters - energy produced is measured in a closed system.

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13
Q

What is the relationship between the mass of an organism and metabolic rate?

A

The greater the mass of the organism the higher the metabolic rate.

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14
Q

Why is the BMR per unit of body mass higher in smaller animals than larger animals?

A

Smaller animals have a greater surface area to volume ratio. This means they lose more heat. They therefore use up more energy to maintain their body temperature.

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15
Q

What is the equation for diffusion?

A

diffusion = (surface area x difference in concentration) / length of diffusion path

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16
Q

What method does Chlamydomonas use to exchange materials?

A

Chlamydomonas is a small single-celled organism so exchange of materials is efficient by diffusion.

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17
Q

How does mass transport of oxygen occur in insects?

A

Contraction of muscles through abdominal pumping enabling mass movements of air in and out.

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18
Q

How does oxygen reach the working muscles in an insect?

A

Through the tracheoles.

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19
Q

How do active, flying insects increase the air flow into the tracheal system?

A
  1. They close the spiracles
  2. They use muscles to create a pumping movement for ventilation.
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20
Q

What is the advantage of having water at the end of tracheoles?

A

In periods of high activity, anaerobic respiration will create lactate which will reduce the water potential of respiring cells causing them to take up water by osmosis. This loss of water from the tracheoles means gas is further inside them.

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21
Q

What are spiracles?

A

Openings in the exoskeleton of an insect with valves to allow air to enter the insect and flow into the tracheae.

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22
Q

What are the three ways gases move in and out of the tracheal system?

A

Along the diffusion gradient.

Mass transport.

Movement of the water at the end of the tracheoles.

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23
Q

Why are the insect’s spiracles generally closed?

A

To prevent water loss.

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24
Q

What are gills mainly made of?

A

Gill filaments.

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25
What increases the surface area of the gills?
They have many gill filaments with many gill lamellae on them.
26
Describe how countercurrent flow allows for effective gaseous exchange.
Blood flows in the opposite direction to water. Ensures there is always a diffusion gradient between water and the gills allowing maximum uptake of oxygen.
27
Explain how parallel flow decreases gaseous exchange.
Oxygen can only be absorbed by diffusion at the start where oxygen concentration in the water is higher than in the blood. Equilibrium is quickly reached.
28
What are the two processes which require gases in a plant?
Photosynthesis and respiration.
29
How is a leaf adapted for gas exchange?
Many small pores (stomata) for a short diffusion pathway. The spongy mesophyll layer has a network of air spaces.
30
During daytime, what is the exchange of gases in and out of the plant? Why?
Carbon dioxide in and oxygen out. Due to photosynthesis. Respiration doesn't create enough carbon dioxide or use enough oxygen.
31
During night time, what is the exchange of gases in a plant? Why?
Carbon dioxide out and oxygen in. Respiration is still occuring, photosynthesis is not. This is why they used to take plants out of patient’s rooms at night!
32
How are the gas exchange systems of plants similar to insects?
The cells using the gases are close to the external air. Diffusion occurs in the gas phase, not water. Pores for air to enter and leave.
33
Where are stomata mainly found?
Bottom side of the leaf to limit evaporation and transpiration.
34
What cells control the opening and closing of stomata?
Guard cells.
35
What causes guard cells to open?
Guard cells are open when they are turgid.
36
What is a disadvantage to having open stomata?
Excessive water loss.
37
What is the name of the plants that are well adapted to dry environments?
Xerophytes
38
How do insects reduce water loss? Explain one example.
Waterproof coverings, spiracles that can be opened and closed
39
What is the process known as when a plant loses water?
Transpiration
40
How does a thick cuticle reduce transpiration?
It is a waterproof barrier which increases diffusion distance.
41
How does rolled up leaves reduce transpiration?
The stomata end up on the inside part of the leaf. This means water vapour becomes trapped and the air is saturated with water. It has a high water potential removing the water potential gradient between inside and outside the leaf.
42
How does having hairy leaves reduce transpiration?
These trap moisture near to the leaf, increasing water potential in the air, and reducing the water potential gradient. Less water is therefore evaporated.
43
How does having stomata in pits or grooves reduce transpiration?
Water vapour is trapped in the pit/groove. This increases the water potential in the air, and reduces the water potential gradient. Less water is therefore evaporated.
44
How does having a reduced surface area to volume ratio in the leaves of the plant reduce transpiration? What is a drawback of this adaptation?
The smaller the surface area to volume ratio, the slower the rate of diffusion. This slows evaporation. But has to be balanced against surface area for photosynthesis.
45
What adaptations do cacti have to help them survive in the desert?
Their leaves have become spines to reduce water loss. Photosynthesis happens in the stem. The stem has a thick cuticle. The stem has a large diameter and accordion shape so it can store water. Deep tap roots. Shallow roots
46
What are the adaptations that marram grass has to survive in a dry sandy environment?
Rolled leaves. Deep grooves to protect the stomata. Thick cuticle. No stomata on exposed surfaces. Inner surfaces have a large number of hairs.
47
Suggest why must humans have a high rate of gaseous exchange?
Because they have a large volume of cells and have to maintain a high body temperature (related to high metabolic rate).
48
What are the lungs made up of?
Bronchioles and alveoli
49
What is the airway from the mouth/nose to the lungs?
The trachea.
50
Why is the trachea supported by a ring of cartilage?
To prevent it collapsing when air pressure inside is low.
51
What are the bronchi?
The two divisions of the trachea, each leads to a lung.
52
What are bronchioles?
Branching divisions of the bronchi, getting smaller, leading to alveoli.
53
What are bronchioles made of? Why?
Muscle, lined with epithelial cells. This controls the flow of air.
54
What is the role of goblet cells and ciliated cells in the bronchi?
Goblet cells produce mucus to trap dirt/dust/pathogens. Ciliated cells waft the mucus back up the throat to be swallowed.
55
What allows the alveoli to stretch and recoil?
Elastic fibres.
56
During inspiration which muscles contract and which relax?
External intercostal muscles and diaphragm contract. Internal intercostal muscles relax.
57
During expiration which muscles contract and which relax?
Internal intercostal muscles contract. External intercostal muscles and diaphragm relax.
58
What happens to the rib cage during inhalation?
The ribcage moves upwards and outward increasing the volume of the thorax.
59
What happens to the rib cage during exhalation?
The ribcage moves downwards and inwards, decreasing the volume of the thorax.
60
What happens to the pulmonary pressure during inhalation?
The pressure in the lungs decreases as thoracic volume increases. Atmospheric pressure is greater, so air is forced into the lungs.
61
What happens to the pulmonary (of the lungs) pressure during exhalation?
The pressure in the lungs (pulmonary) increases as thoracic volume decreases. Atmospheric pressure is lower, so air is forced out of the lungs.
62
During normal breathing, how is air expelled from the lungs?
The elastic recoil of the lungs is generally enough, alongside the relaxation of the external intercostal muscles and diaphragm.
63
How do you calculate pulmonary ventilation?
pulmonary ventilation = tidal volume x breathing rate
64
What is tidal volume?
The volume of air normally taken into the lungs each breath during rest.
65
Where are gases exchanged in mammals?
The epithelium of the alveoli.
66
Why is there a short diffusion distance in the lungs?
The epithelial cells of the alveoli and the endothelial cells of the capillaries are very thin. The red blood cells are flattened against the capillary walls.
67
What happens to the red blood cells in the capillaries which increases gaseous exchange?
They flatten themselves against the side of the capillary resulting in a shorter diffusion distance. They move slowly to increase diffusion time.
68
How is a concentration gradient maintained in the lungs?
Breathing ventilates the lungs. The heart circulates the blood around the alveoli providing a constant supply of deoxygenated blood..
69
How is surface area increased in the lungs?
The high number of alveoli (300m per lung) and a network of pulmonary capillaries surrounding each alveoli.
70
What are the 5 main risk factors for lung disease?
Smoking Air pollution Genetic make-up Infections Occupation.
71
What is COPD?
Chronic obstructive pulmonary disease.
72
What is the difference between correlation and causation?
Correlation is when one variable changes, there is a change in another variable. Causation is when one variable changes, it causes a change in the second variable.
73
Why can we not say that correlation is the same as causation?
There may be other factors at play that have created the correlation between the two variables. They may not affect each other, but have both been affected by something else.
74
What are the main parts of the digestive system?
Oesophagus, stomach, ileum, large intestine, rectum, salivary glands, pancreas.
75
What are the two types of digestion?
Chemical and physical
76
What is the advantage of physical breakdown before chemical breakdown?
Increases surface area for chemical digestion
77
What reaction do digestive enzymes catalyse?
Hydrolysis
78
What is hydrolysis?
The splitting of molecules by adding water
79
What are the main types of hydrolytic enzymes?
Carbohydrases, lipases and proteases
80
What is a disaccharidase?
A hydrolytic enzyme which breaks up a disaccharide into a monosaccharide
81
What are the two enzymes involved in starch digestion?
Amylase (starch -> maltose) Maltase (Maltose -> alpha glucose)
82
Where is amylase found?
Salivary glands and pancreatic juice.
83
Where is maltase found?
It is part of the cell-surface membrane of the epithelial cells lining the ileum.
84
Besides maltase, what other disaccharidases are present in the ileum? What do they digest?
Sucrase (sucrose -> glucose and fructose), Lactase (lactose -> glucose and galactose).
85
What are lipids digested into?
Fatty acids and monoglycerides
86
What is a monoglyceride?
A glycerol and single fatty acid
87
What do the bile salts do?
Bile salts split lipids into droplets, increasing their surface area.
88
What process increases the surface area of lipids?
Emulsification
89
What is a peptidase?
Another term for a protease. A hydrolytic enzyme which breaks down proteins.
90
What are proteins broken down into?
Amino acids
91
What does an endopeptidase hydrolyse?
The peptide bond in the central region of a protein molecule. This results in shorter peptides.
92
What does exopeptidase hydrolyse?
The terminal amino acids from a peptide. Creating amino acids and dipeptides.
93
What does a dipeptidase hydrolyse?
The bond between the two amino acids of a dipeptide.
94
Which of the peptidases are membrane bound? What does this mean?
Dipeptidases are membrane bound. They are found on the cell-surface membrane of the epithelial cells of the ileum.
95
What are the folds called in the ileum and what's their purpose?
Villi, they increase absorption of nutrients.
96
What is the lumen of the ileum?
The cavity, or hole, on the inside of the ileum.
97
Give 4 adaptations of villi and the function of each.
They have a thin wall providing a short diffusion distance. They contain muscle to mix ileal contents and increase the concentration gradient. They have a high blood supply. This increases the concentration gradient. They have microvilli to increase the surface area.
98
By what process are amino acids and monosaccharides absorbed?
Co-transport.
99
What are the basic steps in the co-transport of glucose?
Na+ ions are actively transported out of the cell into the bloodstream. This causes diffusion of Na+ ions into the cell from the ileum lumen as a concentration gradient is created. Na+ diffuses through a carrier protein with a glucose molecule. Glucose moves into the bloodstream via facilitated diffusion.
100
What other product of digestion is transported by co-transport?
Amino acids.
101
What is the first stage in lipid digestion?
Emulsification into lipid droplets.
102
Why are lipid droplets formed?
To increase the surface area for enzyme action.
103
What is formed when the lipids are digested by lipases?
Monoglycerides and fatty acids.
104
What is formed from the monoglycerides, bile salts and fatty acids?
Micelles.
105
What is the role of a micelle?
They carry the monoglycerides and fatty acids to the cell surface membrane.
106
How do fatty acids cross the cell surface membrane?
They are non-polar molecules, so move through by simple diffusion.
107
When the fatty acids and monoglycerides have crossed the cell surface membrane into an epithelial cell, what happens to them?
They are transported to the endoplasmic reticulum where they are reformed into triglycerides.
108
When triglycerides have been formed in the epithelial cell, what is the next stage in absorption?
They move to the golgi apparatus, where they are modified and combined with proteins to form lipoproteins and packaged into vesicles for exocytosis.
109
What are the vesicles called which are formed from triglycerides, proteins and cholesterol for absorption into the blood?
Chylomicrons
110
How do chylomicrons take lipids out of the epithelial cells?
They leave through exocytosis. They move into lacteals, which are lymph vessels. These transport them to the bloodstream.
111
What is visking tubing?
Visking tubing is a non-living partially permeable membrane made from cellulose.
112
Why do we use visking tubing?
We use visking tubing to model the movement of substances through a cell membrane.
113
What substances can pass through visking tubing?
Glucose and water can pass through visking tubing.
114
What cannot pass through visking tubing?
Starch

A-level Biology Longridge Towers School (37 decks)

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