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A Level - Biology > 6: Exchange > Flashcards

6: Exchange Flashcards

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1
Q

Name some examples of exchange

A

Oxygen - aerobic respiration
Nutrients
Waste products - carbon dioxide and urea
Heat

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2
Q

What is SA:V?

A

Surface area to Volume ratio
SA : V
Volume value is always equals to 1

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3
Q

How do smaller to larger animals SA:V ratio compare?

A

Smaller animals have a higher SA:V

Larger animals have a smaller SA:V

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4
Q

How do unicellular cells exchange?

A

Large SA:V ratio
Adv. can happen more directly & easily
Simple diffusion can occur through one membrane
Loses more energy to heat

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5
Q

What are the features of an exchange surface?

A

High SA:V ratio - increases rate of collisions with exchange surface
Thin layer - short diffusion pathway length
Movement of external & internal environment - maintains a steep conc. gradient
Selectively permeable membrane

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6
Q

Why is diffusion too slow in multi-cellular organisms?

A

Some cells are deep within the body - long diffusion pathway

Low SA:V

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7
Q

What does heat loss depend on?

A

Surface area
High SA:V means high rate of heat loss
Causes high metabolic rate & exchange rate

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8
Q

What is the diffusion equation?

A

Diffusion α (SA x difference in concentration)/ length of diffusion path
α = related to

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9
Q

How does gas get to the body cells in insects?

A

Spiracles -> Trachea -> Tracheoles -> Muscle fibre

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10
Q

What is the trachea?

A

Internal network of air-filled pipes in insects

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11
Q

What are tracheoles?

A

Small dead-end tubes
Fluid filled at the ends next to muscle fibre
Extend throughout all the body tissues

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12
Q

How does a diffusion gradient affect in the tracheal system?

A

Muscle fibre cells use O2 for aerobic respiration
Creates a conc. gradient for O2 to diffuse to cells
CO2 produced creates a conc. gradient to cause it to diffuse to the atmosphere

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13
Q

Is diffusion faster in gas or liquid?

A

Gas - less molecules to hit therefore moves faster

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14
Q

How is mass transport done in insects?

A

Contractions of muscles can squeeze the trachea
Enables mass movement of air
This is also the movement of the external environment

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15
Q

Why are the ends of the tracheoles filled with water in insects?

A

Anaerobic respiration produces lactate
Lactate is soluble and lowers water potential in cells
Water moves into cells from tracheoles by osmosis
Vol. of water decreases in tracheoles and draws air further into them
Diffusion is in gas phase rather than liquid
Increases rate at which air moves but leads to greater water loss

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16
Q

What is a spiracle?

A

Tiny pores on the body surface
Can be opened or closed by valves
When open water can evaporate but gas exchange can occur

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17
Q

What is the limitation of the tracheal system?

A

Relies on diffusion
Requires short pathway
Therefore requires small size of insects

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18
Q

Why are hairs found in the spiracle?

A

Traps moist air & humidity

Lowering concentration gradient so water cannot diffuse out as easily

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19
Q

Where is a gill found?

A

Behind the head of the fish

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20
Q

What are the gill filaments?

A

Thin plates which have a large SA for exchange of gases

Stacked in a pile

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21
Q

What is a gill lamellae?

A

Gill filaments covered with them, at right angles
Contain lots of blood capillaries
Thin surface later of cells to speed up diffusion

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22
Q

What is the counter-current flow system?

A

Blood flows through lamellae in one direction
Water flows over them in the opposite direction
Maintains a large conc. gradient

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23
Q

Why does counter-current flow system work?

A

Larger conc. of oxygen in water than blood

Maintains conc. gradient as water moves over lamellae

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24
Q

What is the main surface of gas exchange in plants?

A

Mesophyll cells

They have a large SA

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25
Q

What are the pores in the plant called?

A

Stomata

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26
Q

When do the stomata open and close?

A

Open in the day - when photosynthesis occurs

Closed at night

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27
Q

Where are the stomata found?

A

Bottom side of the plant - in the shade so less evaporation
Guard cells turgid when H2O available - opens stoma
Flaccid when less H2O available - closes stoma

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28
Q

Name some adaptations of gas exchange in plants?

A

No cells far from stoma - short diffusion pathway
Air spaces in mesophyll - gases can easily come in contact with cells
Large SA of mesophyll cells - rapid diffusion

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29
Q

How are insects adapted to reduce water loss?

A

Small SA:V ratio - minimise area over which water is lost
Waterproof covering - waterproof cuticle prevents water loss
Spircales - valve can be closed to reduce water loss

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30
Q

What is a xerophyte?

A

Plants specifically adapted in warm, dry or windy habitats, where water loss is a problem

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31
Q

Why are stomata sunken in pits and hairy leaves?

A

Traps moist air - high water potential therefore reduces conc. gradient
Reduces the amount of water diffusing out of leaf and evaporating away

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32
Q

Why are leaves rolled up in xerophytes?

A

Protects them from the wind

Traps moist air - high water potential therefore reduces conc. gradient

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33
Q

Why is there a thick cuticle in xerophytes?

A

Waterproof barrier - prevents the water loss from this route

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34
Q

Why is there a reduced SA:V ratio in xerophytes?

A

Reduces the surface area which allows water to leave the plant

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35
Q

Why is gas exchange required in humans?

A

Oxygen needed for aerobic respiration to release ATP

Carbon dioxide is produced in respiration and if builds up is harmful in the body

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36
Q

Why is a large amount of air required to be moved in or out of the human body?

A

Large organisms with large volume of living cells

Maintain a high body temp. which is related to high metabolic and respiratory rates

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37
Q

Why are the lungs located in the body?

A

Air is not dense enough to support and protect delicate structures
Body would lose a great deal of water

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38
Q

What is the route of the air going into the body?

A 
Mouth/nostril
Pharynx
Epiglottis
Larynx
Trachea
Bronchi
Bronchioles
Alveoli
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39
Q

What is the pharynx?

A

Part of the throat that air and food goes through

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40
Q

What is the epiglottis?

A

Flap which prevents the food from entering the trachea

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41
Q

What is the larynx?

A

After the epiglottis, where the vocal chords are found

42
Q

What are the adaptation of the bronchioles?

A

C-shaped cartilage rings
Allows flexibility, gives structure when the pressure reduces
Made of smooth muscles and lined with ciliated epithelium and goblet cells

43
Q

What is the adaptation of the trachea?

A

C-shaped cartilage rings

Allows flexibility, gives structure when the pressure reduces

44
Q

Why is smooth muscle present in the bronchioles?

A

Allows them to constrict so they can control flow of air in and out of the alveoli

45
Q

What is the alveoli?

A

Minute air-sacs at the end of bronchioles
Between alveoli collagen and elastic fibres allowing them to stretch as they fill with air
Alveolar membrane is the surface of gas exchange

46
Q

What is ventilation in and out called?

A

Inspiration

Expiration

47
Q

What things are used for ventilation?

A

Diaphragm
Internal and External intercostal muscles
Ribcage

48
Q

What occurs in inhalation?

A 
External intercostal muscles and diaphragm contract
Causes ribcage to move up and out
Thoracic cavity increases in volume
Lung pressure decreases
Air flows from high->low pressure
Active process as requires energy
49
Q

What is the diaphragm?

A

Sheet of muscles that separates the thorax and abdomen
Curved/concave when relaxed
Contracts to a downwards and flattened state

50
Q

What occurs during passive expiration?

A 
External intercostal and diaphragm relax
Ribcage moves down and inwards
Thoracic cavity decreases in volume
Lung pressure increases
Air flows out of the lungs
51
Q

What is passive and active ventilation?

A

Passive doesn’t require any energy

Active requires energy

52
Q

What occurs in active expiration?

A

External intercostal muscles relax and internal intercostal muscles contract
Pulling the ribcage further down and in
Intercostal muscles move in an antagonistic way

53
Q

What does antagonistic movement mean?

A

When two sets of muscles is said to be moving in an opposing direction

54
Q

What is tidal volume?

A

Volume of air normally taken in at each breath when the body is at rest - typically 0.5 dm3

55
Q

What is breathing/ventilation rate?

A

The number of breaths taken in 1 minute - typically 12-20 breaths in healthy adult

56
Q

What is pulmonary ventilation and what is it measured in?

A

Total volume of air that is moved into the lungs that is moved into the lungs during 1 minute
Measured in dm3 min-1

57
Q

What is the equation of pulmonary ventilation rate?

A

Pulmonary ventilation rate = tidal volume x breathing rate

dm3 min-1 = dm3 x min-1

58
Q

What is an alveolus made of?

A

Microscopic air sacs

Made from a single later of thin, flat cells called alveolar epithelium

59
Q

How is there a short diffusion pathway in a human lung?

A

Diffusion is across thin squamous epithelium (one cell thick) and capillary cell wall

60
Q

What is the advantage of having a thin pulmonary capillaries?

A

Slows RBCs - increasing time spent at the exchange surface and flattens them decreasing the short diffusion pathway

61
Q

How are the lungs protected?

A

Delicate membranes internalised by ribs for protection

62
Q

How does a large capillary and alveoli have a large SA?

A

Due to the large number of them

63
Q

How is the movement of the environment done in the lungs?

A

External environment is managed by ventilation

Internal environment is managed by circulation

64
Q

How is a moist coated inner surface of the alveolus advantageous?

A

Reduces surface tension

Enables gases to dissolve before diffuses to speed up movement

65
Q

What is forced expiratory volume (FEV1)?

A

Max volume of air that can be breathed out in 1 second

66
Q

What is the forced vital capacity (FVC)?

A

Max volume of air it is possible to breathe forcefully out of lungs after a really deep breath in

67
Q

What are the processes in the digestive system?

A 
Ingestion
Digestion
Absorption
Assimilation
Egestion
68
Q

Is the contents of the digestive system internal or external?

A

External

69
Q

What is an endocrine?

A

Chemicals which are secreted into the bodies systematic circulation
E.g Hormones

70
Q

What is an exocrine?

A

Chemical which are secreted outside of your body

E.g tear ducts, gastro-intestinal tract

71
Q

What forms of mechanical digestion are there in the digestive system?

A

Chewing/Mastication
Stomach churning
Small intestine/oesophagus - peristalsis

72
Q

What is the purpose of the oseophagus?

A

Carries food from mouth to stomach

Smooth muscle pushes down food by peristalsis

73
Q

What is peristalsis?

A

Smooth muscle causes wave like contractions creating a squeezing motion downwards

74
Q

What chemical digestion is there is the digestive system?

A

Enzymes

Hydrochloric acid

75
Q

What is the stomach?

A

Muscular sac with an inner layer that produces enzymes
Stores and digests food
Produces hydrochloric acid

76
Q

What is the role of the large intestine?

A

Absorbs water

77
Q

What is the rectum?

A

Final section of the intestines

Faeces stored here before being removed via the anus by egestion

78
Q

What is the role of the oesophagus?

A

Smooth muscle - peristalsis

79
Q

What is secreted in the stomach?

A

Pepsin secreted by chief cells
Goblet cells produce mucus for protective barrier against acid and proteases
HCl secreted

80
Q

What affect does HCl have in the stomach?

A

Kill pathogens or bacteria

Break down ionic/hydrogen bonds to disrupt tertiary structure to make it primary

81
Q

What are the salivary glands and the roles?

A

Situated near the mouth
Pass secretions via a duct in the mouth
Contains amylase which hydrolyses starch into maltose

82
Q

What is the pancreas and its role?

A

Large gland situated behind the stomach
Produces pancreatic juice (exocrines)
Contains pancreatic protease, carbohydrases, and lipase
Secretes enzymes and alkaline salts

83
Q

What is the role of alkaline salts?

A

Allows enzymes to work at their optimum pH by lowering pH

Emulsifies fats

84
Q

What is the purpose of enzymes?

A

Hydrolyses a molecule into smaller sections and into their molecules

85
Q

What does amylase do?

A

Hydrolyse glycosidic bond
Starch into maltose (disaccharides)
Produced in salivary glands, pancreas, and ileum
Optimum pH is 7

86
Q

Why does amylase not work in the stomach?

A

Low pH would denature the enzymes

87
Q

What is maltase, lactase, and sucrase?

A

Membrane bound disaccharidases in small intestine cells (enterocyte)

88
Q

How are carbohydrates absorbed by the small intestine?

A

Diffusion or co-transport

89
Q

How are proteins digested in the digestive system?

A

HCl denatures hydrogen and ionic bonds in proteins
Tertiary to primary like structure
Endopeptidases, Exopeptidases, and Dipeptidases break peptide bonds
Diffusion and co-transport

90
Q

What are endopeptidases?

A

Hydrolyses peptide bonds in the central region of a protein

91
Q

What are expopeptidases?

A

Hydrolyses peptide bonds on the terminal ends of the protein

92
Q

What is a dipeptidase?

A

Membrane bound peptidases

Hydrolyses single peptide bonds in disaccharides

93
Q

How is absorption in digestion follow the exchange principles?

A

Short diffusion pathway - only through enterocyte
Internal movement - blood flow takes away nutrients
External movement - peristalsis takes away food in the lumen
High SA - villi and microvilli
Membrane permeability - carrier/protein channel

94
Q

What do lipases do to triglycerides?

A

Hydrolyse ester bonds from triglycerides -> monoglycerides + two fatty acids

95
Q

What is the process of emulsification?

A

Bile salts break large droplets into smaller droplets

96
Q

Where are bile salts made transported and stored?

A

Produced in liver
Stored in gall bladder
Transported in bile ducts

97
Q

How are triglycerides absorbed into the enterocytes?

A

Emulsification by bile salts to form micelles
Lipase breaks down triglycerides to monoglycerides and fatty acids
Micelles break down and contents diffuse into enterocytes
Free fatty acids and monoglycerides repackaged in the endoplasmic reticulum into triglyceride
Chylomicron formed in the golgi body
Chylomicron goes by excocytosis into the lacteal

98
Q

What is a chlyomicron?

A

Triglyceride + cholesterol + protein

Formed in golgi body

99
Q

How is fructose absorbed?

A

Facilitated diffusion

Through a transporter protein

100
Q

What is a micelles?

A

Small globules of monoglycerides and fatty acids
Very small with large SA:V
Must break down to diffuse across

101
Q

How do spiracles work?

A

Can be opened or closed by valves

When open water can evaporate but gas exchange can occur

A Level - Biology (22 decks)

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