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A Level - Biology > 6: Exchange > Flashcards

6: Exchange Flashcards

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
What are the pores in the plant called?
Stomata
26
When do the stomata open and close?
Open in the day - when photosynthesis occurs | Closed at night
27
Where are the stomata found?
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
28
Name some adaptations of gas exchange in plants?
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
29
How are insects adapted to reduce water loss?
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
30
What is a xerophyte?
Plants specifically adapted in warm, dry or windy habitats, where water loss is a problem
31
Why are stomata sunken in pits and hairy leaves?
Traps moist air - high water potential therefore reduces conc. gradient Reduces the amount of water diffusing out of leaf and evaporating away
32
Why are leaves rolled up in xerophytes?
Protects them from the wind | Traps moist air - high water potential therefore reduces conc. gradient
33
Why is there a thick cuticle in xerophytes?
Waterproof barrier - prevents the water loss from this route
34
Why is there a reduced SA:V ratio in xerophytes?
Reduces the surface area which allows water to leave the plant
35
Why is gas exchange required in humans?
Oxygen needed for aerobic respiration to release ATP | Carbon dioxide is produced in respiration and if builds up is harmful in the body
36
Why is a large amount of air required to be moved in or out of the human body?
Large organisms with large volume of living cells | Maintain a high body temp. which is related to high metabolic and respiratory rates
37
Why are the lungs located in the body?
Air is not dense enough to support and protect delicate structures Body would lose a great deal of water
38
What is the route of the air going into the body?
``` Mouth/nostril Pharynx Epiglottis Larynx Trachea Bronchi Bronchioles Alveoli ```
39
What is the pharynx?
Part of the throat that air and food goes through
40
What is the epiglottis?
Flap which prevents the food from entering the trachea
41
What is the larynx?
After the epiglottis, where the vocal chords are found
42
What are the adaptation of the bronchioles?
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
What is the adaptation of the trachea?
C-shaped cartilage rings | Allows flexibility, gives structure when the pressure reduces
44
Why is smooth muscle present in the bronchioles?
Allows them to constrict so they can control flow of air in and out of the alveoli
45
What is the alveoli?
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
What is ventilation in and out called?
Inspiration | Expiration
47
What things are used for ventilation?
Diaphragm Internal and External intercostal muscles Ribcage
48
What occurs in inhalation?
``` 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
What is the diaphragm?
Sheet of muscles that separates the thorax and abdomen Curved/concave when relaxed Contracts to a downwards and flattened state
50
What occurs during passive expiration?
``` 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
What is passive and active ventilation?
Passive doesn't require any energy | Active requires energy
52
What occurs in active expiration?
External intercostal muscles relax and internal intercostal muscles contract Pulling the ribcage further down and in Intercostal muscles move in an antagonistic way
53
What does antagonistic movement mean?
When two sets of muscles is said to be moving in an opposing direction
54
What is tidal volume?
Volume of air normally taken in at each breath when the body is at rest - typically 0.5 dm3
55
What is breathing/ventilation rate?
The number of breaths taken in 1 minute - typically 12-20 breaths in healthy adult
56
What is pulmonary ventilation and what is it measured in?
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
What is the equation of pulmonary ventilation rate?
Pulmonary ventilation rate = tidal volume x breathing rate | dm3 min-1 = dm3 x min-1
58
What is an alveolus made of?
Microscopic air sacs | Made from a single later of thin, flat cells called alveolar epithelium
59
How is there a short diffusion pathway in a human lung?
Diffusion is across thin squamous epithelium (one cell thick) and capillary cell wall
60
What is the advantage of having a thin pulmonary capillaries?
Slows RBCs - increasing time spent at the exchange surface and flattens them decreasing the short diffusion pathway
61
How are the lungs protected?
Delicate membranes internalised by ribs for protection
62
How does a large capillary and alveoli have a large SA?
Due to the large number of them
63
How is the movement of the environment done in the lungs?
External environment is managed by ventilation | Internal environment is managed by circulation
64
How is a moist coated inner surface of the alveolus advantageous?
Reduces surface tension | Enables gases to dissolve before diffuses to speed up movement
65
What is forced expiratory volume (FEV1)?
Max volume of air that can be breathed out in 1 second
66
What is the forced vital capacity (FVC)?
Max volume of air it is possible to breathe forcefully out of lungs after a really deep breath in
67
What are the processes in the digestive system?
``` Ingestion Digestion Absorption Assimilation Egestion ```
68
Is the contents of the digestive system internal or external?
External
69
What is an endocrine?
Chemicals which are secreted into the bodies systematic circulation E.g Hormones
70
What is an exocrine?
Chemical which are secreted outside of your body | E.g tear ducts, gastro-intestinal tract
71
What forms of mechanical digestion are there in the digestive system?
Chewing/Mastication Stomach churning Small intestine/oesophagus - peristalsis
72
What is the purpose of the oseophagus?
Carries food from mouth to stomach | Smooth muscle pushes down food by peristalsis
73
What is peristalsis?
Smooth muscle causes wave like contractions creating a squeezing motion downwards
74
What chemical digestion is there is the digestive system?
Enzymes | Hydrochloric acid
75
What is the stomach?
Muscular sac with an inner layer that produces enzymes Stores and digests food Produces hydrochloric acid
76
What is the role of the large intestine?
Absorbs water
77
What is the rectum?
Final section of the intestines | Faeces stored here before being removed via the anus by egestion
78
What is the role of the oesophagus?
Smooth muscle - peristalsis
79
What is secreted in the stomach?
Pepsin secreted by chief cells Goblet cells produce mucus for protective barrier against acid and proteases HCl secreted
80
What affect does HCl have in the stomach?
Kill pathogens or bacteria | Break down ionic/hydrogen bonds to disrupt tertiary structure to make it primary
81
What are the salivary glands and the roles?
Situated near the mouth Pass secretions via a duct in the mouth Contains amylase which hydrolyses starch into maltose
82
What is the pancreas and its role?
Large gland situated behind the stomach Produces pancreatic juice (exocrines) Contains pancreatic protease, carbohydrases, and lipase Secretes enzymes and alkaline salts
83
What is the role of alkaline salts?
Allows enzymes to work at their optimum pH by lowering pH | Emulsifies fats
84
What is the purpose of enzymes?
Hydrolyses a molecule into smaller sections and into their molecules
85
What does amylase do?
Hydrolyse glycosidic bond Starch into maltose (disaccharides) Produced in salivary glands, pancreas, and ileum Optimum pH is 7
86
Why does amylase not work in the stomach?
Low pH would denature the enzymes
87
What is maltase, lactase, and sucrase?
Membrane bound disaccharidases in small intestine cells (enterocyte)
88
How are carbohydrates absorbed by the small intestine?
Diffusion or co-transport
89
How are proteins digested in the digestive system?
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
What are endopeptidases?
Hydrolyses peptide bonds in the central region of a protein
91
What are expopeptidases?
Hydrolyses peptide bonds on the terminal ends of the protein
92
What is a dipeptidase?
Membrane bound peptidases | Hydrolyses single peptide bonds in disaccharides
93
How is absorption in digestion follow the exchange principles?
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
What do lipases do to triglycerides?
Hydrolyse ester bonds from triglycerides -> monoglycerides + two fatty acids
95
What is the process of emulsification?
Bile salts break large droplets into smaller droplets
96
Where are bile salts made transported and stored?
Produced in liver Stored in gall bladder Transported in bile ducts
97
How are triglycerides absorbed into the enterocytes?
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
What is a chlyomicron?
Triglyceride + cholesterol + protein | Formed in golgi body
99
How is fructose absorbed?
Facilitated diffusion | Through a transporter protein
100
What is a micelles?
Small globules of monoglycerides and fatty acids Very small with large SA:V Must break down to diffuse across
101
How do spiracles work?
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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