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AS-Level Biology (AQA) > 3.1 (6) - Exchange > Flashcards

3.1 (6) - Exchange Flashcards

Exchange between organisms and their environment Gas exchange in single-celled organisms and insects Gas exchange in fish Gas exchange in the leaf of a plant Limiting water loss Structure of the human gas-exchange system The mechanism of breathing Exchange of gases in the lungs Enzymes and digestion Absorption of the products of digestion

1
Q

What is the environment around cells of multicellular organisms called?

A

Tissue fluid

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2
Q

What are some examples of things that need to be interchanged between an organism and its environment?

A
  • Respiratory gases (oxygen and carbon dioxide)
  • Nutrients (glucose, fatty acids, amino acids, vitamins and minerals)
  • Excretory products (urea and carbon dioxide)
  • Heat
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3
Q

Except for heat, in what ways can exchanges take place?

A
  • Passively (diffusion and osmosis)

- Actively (active transport)

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4
Q

What does ‘surface area to volume ratio’ mean?

A

It’s the ratio of how big the surface area of something is compared to its volume

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5
Q

How do you calculate the ‘surface area to volume’ ratio?

A

1) Calculate the total surface area of the shape
2) Calculate the volume of the shape
3) Put these numbers into a ratio (SA:V)
4) Simplify if necessary

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6
Q

In what ways could organisms have evolved to speed up the rate of diffusion?

A

They could have:

  • a flattened shape so that no cell is ever far from the surface (eg. a flatworm or leaf)
  • specialised exchange surfaces with large areas > increases the SA:V ratio even further (eg. lungs in mammals or gills in fish)
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7
Q

What are the characteristics of exchange surfaces to allow effective transfer of materials across them?

A
  • Large SA, relative to its volume > increases exchange rate
  • Very thin > diffusion distance is short, allowing quicker diffusion
  • Selectively permeable
  • Movement of the environmental medium maintains a diffusion gradient
  • A transport system to move the internal medium maintains a diffusion gradient
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8
Q

What levels of concentration of oxygen and carbon dioxide do tracheole ends have? Why?

A

Low concentration of oxygen
High concentration of carbon dioxide
(Because of nearby respiration)

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9
Q

Why do insects flex their bodies by muscle contraction?

A
  • Doing this expands and compresses their system (including air sacs)
  • Fluctuating air pressure moves air in and out of the body > ventilates the system
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10
Q

Why is there water in tracheole ends?

A
  • During intense activity, lactic acid builds up around muscles
  • Because lactic acid is soluble, it reduces the water potential of the cells around the tracheoles > the water moves into them
  • This reduces the water in the tracheole ends > extends the reach of air into the tissues
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11
Q

What is the correct order of the structure of fish gills?

A

1) Gill arch
2) Gill filaments
3) Lamellae
4) Capillaries

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12
Q

Explain how countercurrent flow works

A
  • Blood is pumped through the lamellae in the opposite direction to the water flowing across the gills
  • Low oxygenated blood is in contact with low oxygenated water, but O2 diffusion from water to blood still occurs
  • High oxygenated blood meets high oxygenated water so diffusion can still occur, even when the blood is highly oxygenated
  • Means that there is a diffusion gradient across the ENTIRE length of the lamellae
  • CC flow happens so that a low equilibrium is NOT reached, but a much higher one is reached instead
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13
Q

Why do exchange surfaces need a large SA:V ratio?

A

Speeds up the rate of exchange

Provides more surface across which substance can diffuse per unit volume

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14
Q

Why are exchange surfaces very thin?

A

Keeps the diffusion pathway short

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15
Q

Why are exchange surfaces partially permeable?

A

To allow selected materials to diffuse easily

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16
Q

Why do exchange surfaces move the external medium (eg. air)?

A

To maintain a diffusion gradient

conc grad

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17
Q

Why do exchange surfaces move the internal medium (eg. blood)?

A

To maintain a diffusion gradient

conc grad

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18
Q

What 2 gases are essential for plants to live?

A
  • Carbon dioxide (for photosynthesis)

- Oxygen (respiration)

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19
Q

What is the definition of ‘transpiration’?

A

The process of water loss through leaves

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20
Q

What happens to the stomata when there is a lack of water?

A

Ions are pumped into the stomatal cells to increase its solute potential, moving water into the cell and closing the gap

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21
Q

What happens to the stomata when there is an abundance of water?

A

Ions are pumped out of the stomatal cells to reduce its solute potential, pumping water out and opening the gap

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22
Q

From the top to the bottom, what are the components of the structure of a leaf cell?

A

Upper epidermis

  • Waxy cuticle
  • Epithelial cell
  • Palisade mesophyll

Spongy mesophyll

  • Spongy mesophyll cells
  • Air space

Lower epidermis

  • Stomata
  • Guard cells
  • Epidermal cells
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23
Q

What are some features that insects have adapted to reduce water loss?

A
  • Small SA:V ratio (minimises the area that water is lost over)
  • Waterproof coverings over their body surfaces (this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle)
  • Spiracles (the openings of tracheae at the body surface. They can be closed to reduce water loss)
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24
Q

How do plants limit water loss?

A
  • Waterproof covering over parts of their leaves

- Stomatal closure (when necessary)

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25
Q

What is a xerophyte?

A

A plant that is adapted to live in an environment with little/no water available

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26
Q

What are some of adaptations of xerophytes that help to reduce water loss?

A
  • Thicker cuticle (less water can escape)
  • Rolling up of leaves:
    1) protects the stomata
    2) traps air within the leaf so that it becomes saturated
    with water vapour (high water potential)
    3) there’s no water potential gradient between inside
    and outside of leaf, so no water is lost
  • Hairy leaves (traps moist air)
  • Stomata in pits/grooves of leaf (trap moist air)
  • Leaves have a reduced SA:V ratio (rate of water loss is reduced in smaller leaves)
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27
Q

What are the 5 major parts of mammalian gas-exchange system?

A
  • Lungs
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
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28
Q

What are the lungs?

A

Lobed structures made up of bronchioles and alveoli

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29
Q

What is the trachea?

A

An airway that’s supported by rings of cartilage, which prevents it from collapsing when air pressure falls from breathing in

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30
Q

What are the bronchi?

What is their function?

A

2 divisions of the trachea, leading to 1 lung each

They produce mucus to trap dirt. They have cilia to move the dirty mucus to the throat

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31
Q

What are the bronchioles?

What are their function?

A

Subdivisions of the bronchi

Their walls are made of muscle, which allows them to constrict so that they can control air flow from alveoli

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32
Q

What are the alveoli?

A

Mini air sacs at the end of bronchioles

Between the alveoli there are some collagen and elastic fibres (allow the alveoli to stretch when filling with air)

They are lined with epithelium (kind of tissue)

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33
Q

What happens to air when the air pressure of the atmosphere is greater than the air pressure in the lungs?

A

Air is forced into the lungs (inspiration)

34
Q

What happens to air when air pressure in the lungs is greater than the air pressure of the atmosphere?

A

Air is forced out of the lungs (expiration)

35
Q

The movement of what 3 muscles bring about pressure changes in the lungs?

A
  • Diaphragm
  • Internal intercostal muscles (their contraction leads to expiration)
  • External intercostal muscles (their contraction leads to inspiration)
36
Q

Describe the process of inspiration in 5 steps

A

1) External intercostal muscles contract and internal intercostal muscles relax
2) Ribs are pulled upwards and outwards, increasing the volume of the thorax
3) The diaphragm muscles contract (flattens), also increasing the volume of the thorax
4) The increased volume of the thorax results in reduced pressure in the lungs
5) The pressure of the atmosphere is now greater than pulmonary pressure, so air is forced out of the lungs

37
Q

Describe the process of expiration in 5 steps

A

1) Internal intercostal muscles contract and external intercostal muscles relax
2) Ribs move downwards and inwards, decreasing the volume of the thorax
3) The diaphragm muscles relax, so it’s pushed up again by the contents of the abdomen that were compressed during inspiration. Volume of thorax decreases
4) The decreased volume of the thorax increase pressure in the lungs
5) The pulmonary pressure is now greater than that of the atmosphere, so air is forced out of the lungs

38
Q

Why is the diffusion of gases between alveoli and blood so rapid?

A
  • RBCs are slowed as they pass through pulmonary capillaries, allowing more time for diffusion
  • The distance between the alveolar air and RBCs is reduced as the RBCs are flattened against the capillary walls
  • The walls of alveoli and capillaries are very thin, therefore the distance over which diffusion takes place is very short
  • Alveoli and pulmonary capillaries have a very large total SA
  • Breathing constantly ventilates the lungs, and the heart constantly circulates blood around the alveoli
  • Blood flow through the pulmonary capillaries maintains a concentration gradient
39
Q

What are some ways to measure someone’s lung health?

A
  • Tidal volume
  • Ventilation rate
  • Forced expiratory volume
  • Forced vital capacity
40
Q

What is tidal volume?

A

The volume of air breathed in each breath

41
Q

What is ventilation rate?

A

The number of breaths per minute

42
Q

What is forced expiratory volume?

A

The maximum volume of air that can be exhaled in 1 second

43
Q

What is forced vital capacity?

A

The maximum volume of air exhaled as possible

44
Q

What is spirometry?

A

A test that measures the volume of air a person’s lungs can inhale and exhale (also at what rate)

45
Q

How is spirometry done?

A
  • Place mouth on mouthpiece that is attached to spirometer
  • Inhale as deeply as possible
  • Exhale as hard, fast and completely as possible
46
Q

What is asthma?

A

Inflammation of the airways (it’s usually an immune response)

47
Q

What does asthma do to the airways?

A
  • Airways becomes inflamed and irritated
  • Smooth muscle in bronchioles contracts and lots of mucus is produced
  • Airway becomes constricted and airflow is severely reduced, reducing oxygen availability for gas exchange
48
Q

What are some symptoms of asthma?

A
  • Wheezing
  • Tight chest
  • Shortness of breath
49
Q

What causes emphysema?

A

Air particulates in pollution or from smoking

50
Q

What does emphysema do to the airways?

A
  • Pollutant particles get stuck in the alveoli
  • Inflammation attracts phagocytes which produces an enzyme that will break down the elastin in alveoli
  • This reduces alveoli’s ability to contract after inhaling (air cant be exhaled effectively)
  • Emphysema can also destroy alveoli walls, reducing SA for gas exchange
51
Q

What are some symptoms of emphysema?

A
  • Wheezing
  • Shortness of breath
  • Increased ventilation rate
52
Q

What is fibrosis?

A

Formation of scar tissue due to physical damage by dust/asbestos

53
Q

What does fibrosis do to the airways?

A
  • Scar tissue is formed in lungs (less elastic)
  • Reduces tidal volume and FEV
  • Reduction in the rate of gas exchange because of thicker tissue increasing diffusion pathway
54
Q

What are some symptoms of fibrosis?

A
  • Shortness of breath
  • Fatigue
  • Weakness
  • Dry cough
  • Chest pain
55
Q

What type of infection is pulmonary tuberculosis (PTB)?

A

Bacterial infection

56
Q

What happens to airways as a result of PTB?

A
  • Hard lumps (tubercles) form in the lungs as immune cells form walls around bacterial cells
  • Infected tissue in tubercles dies, exchange surface is damaged and tidal volume is decreased
  • Causes patient to breath faster (because of lower tidal volume)
57
Q

What are some symptoms of PTB?

A
  • Persistent coughing
  • Coughing blood and mucus
  • Chest pain
  • Shortness of breath
  • Fatigue
58
Q

What are the major parts of the digestive system?

A
  • Salivary glands
  • Oesophagus
  • Stomach
  • Pancreas
  • Ileum
  • Large intestine
  • Rectum
59
Q

What is the function of the salivary glands?

A

Secrete salivary amylase, which hydrolyses starch into maltose

60
Q

What is the function of the oesophagus?

A

Carries food from the mouth to the stomach

61
Q

What is the function of the stomach?

A

Stores and digests food

62
Q

What is the function of the pancreas?

A

Produces pancreatic juice, which contains:

  • peptidases to hydrolyse proteins
  • lipase to hydrolyse lipids
  • pancreatic amylase to hydrolyse starch and maltose
63
Q

What is the function of the ileum?

A

Digests food using enzymes

64
Q

What is the function of the large intestine?

A

Absorbs water

65
Q

What is the function of the rectum?

A

Stores faeces

66
Q

What are the 2 stages of digestion?

A
  • Physical digestion

- Chemical digestion

67
Q

What is physical digestion?

A

Food is broken down into smaller pieces using the teeth, making it easier to ingest the food and provides a large SA for chemical digestion

68
Q

What is chemical digestion?

A

Uses enzymes to hydrolyse foods into smaller molecules for absorption

69
Q

What are 3 types of digestive enzymes?

A
  • Carbohydrases
  • Lipases
  • Peptidases
70
Q

What happens during carbohydrate digestion?

A

1) Begins in the mouth with salivary amylase (hydrolyses starch into maltose)
2) Pancreatic amylase is secreted (by the pancreas) into the ileum to break down maltose into alpha glucose
3) Alkaline salts are secreted in pancreatic juice and from the ileum wall to correct the pH for enzymes

71
Q

What happens during lipid digestion?

A

1) The ester bonds between the fatty acid and glycerol molecule are hydrolysed, which releases:
- Fatty acids
- Monoglycerides (glycerol bonded to a single fatty
acid)

2) Bile salts will emulsify the lipids (increasing their SA and speeding up ROR)
3) Emulsification breaks down lipids into micelles (tiny fat droplets) to increase the fat’s SA and accelerate rate of digestion

72
Q

What are 3 peptidases involved in protein digestion?

A
  • Endopeptidases
  • Exopeptidases
  • Dipeptidases
73
Q

What is the function of endopeptidases?

A

They hydrolyse peptide bonds between amino acids in the central region of a protein, forming lots of peptide molecules

74
Q

What is the function of exopeptidases?

A

They hydrolyse the peptide bonds on the terminals of the new amino acids (hydrolysed by endopeptidases), releasing dipeptidases

75
Q

What is the function of dipeptidases?

A

They hydrolyse the bond between the amino acids of a dipeptide, releasing the AAs

These AAs are soluble, so they can be absorbed

76
Q

What are the components of the villi found in the ileum?

A
  • Lacteal
  • Blood capillary
  • Thin epithelium
77
Q

What is the function of the lacteal (found in villi)?

A

Tiny lymphatic blood cell that absorbs fatty acids and glycerol

78
Q

What is the function of the blood capillary (found in villi)?

A

Absorbs glucose and amino acids

79
Q

What is the function of the thin epithelium (found in villi)?

A
  • One cell thick to increase diffusion rate

- They have microvilli to increase SA for absorption

80
Q

What are the properties of villi that increase the efficiency of absorption?

A
  • Increase SA for diffusion
  • Thin walls, reducing diffusion pathway
  • Contain muscles so they can move
  • Well supplied with blood vessels so that blood can carry absorbed molecules away, maintaining a diffusion gradient
  • Villi have microvilli, increase SA
81
Q

By what 2 processes of molecular movement are carbohydrates and proteins absobed?

A

Diffusion and co-transport

82
Q

How are lipids absorbed in the ileum?

A

1) Micelles come into contact with the ileum wall by peristalsis
2) Once the lipids are hydrolysed into their monoglycerides and fatty acids, the molecules can diffuse across the membrane of epithelial cells, because they are non-polar molecules
3) The molecules are taken to the ER and recombined into various triglycerides
4) Then, they move to the golgi apparatus
5) In the GA, they associate with cholesterol and lipoproteins to form chylomicrons (lipid transport particles)
6) Exocytosis moves the chylomicrons from the epithelial cells into lacteals

AS-Level Biology (AQA) (11 decks)

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