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AS AQA BIOLOGY > Exchange > Flashcards

Exchange Flashcards

(72 cards)

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1
Q

What does passively mean

A

No metabolic energy is required

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2
Q

What does actively mean

A

Metabolic energy is required

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3
Q

Where does exchange take place?

A

At the surface of an organism

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4
Q

Describe a small organisms SA:V ratio

A

Large

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5
Q

Describe a large animals SA:B ratio

A

Small

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6
Q

What features have evolved to allow all cells to exchange?

A

A flattened shape
- so no shape is ever far from the surface

Specialised exchange surfaces
- large surface areas to increase the SA:V ratio

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7
Q

How to calculate the SA:V ratio

A

Calculate SA
Calculate V
Simplify the ratio

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8
Q

Features of specialised exchange surfaces

A

Large surface area relative to organism volume
- increases exchange rate

Thin to great short diffusion pathway
- increases exchange rate

Selectively permeable
- allows specific materials to cross

Transport system
- Maintained diffusion gradient

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9
Q

Describe the relationship between diffusion, surface area, concentration, and length of the diffusion pathway

A

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

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10
Q

Why does an organism with specialised exchange surfaces need to have a means of moving the medium over its surface?

A

Specialised exchange surfaces are easily damaged and dehydrated
So they are located inside the organism for protection

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11
Q

Name two general things that need to be exchanged between organisms and their environments

A

Respiratory gases (CO2, O2)
Nutrients
Excretory products
Heat

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12
Q

Name three factors affecting the rate of diffusion

A

Surface area
Thickness of cell membrane
Permeability of cell membrane to the substance attempting diffusion
Concentration gradient across the membrane
Temperature

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13
Q

How does gas exchange occur in single celled organisms?

A

Oxygen is absorbed by diffusion
Across the body surface

Carbon dioxide diffuses out
Across the body surface

Due to a small SA:V ratio

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14
Q

Describe the route taken by oxygen in insect gas exchange

A 
Air enters the spiracles 
Into the trachea 
Down to the diffusion gradient
To the tracheoles
Oxygen diffuses 
Across the cell surface membrane to muscle cells
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15
Q

Describe the route taken by carbon dioxide in insect gas exchange

A 
Carbon dioxide diffuses across the cell surface membrane
Into the tracheoles
Moves down the diffusion gradient
To the trachea 
And out of the spiracle
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16
Q

Why are insects small

A

Their tracheal system relies on diffusion
So every cell must be close to the system
To create a short diffusion pathway

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17
Q

What are the three ways respiratory gases move in an insect

A

Along a diffusion gradient

Mass transport

Tracheole ends are filled with water

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18
Q

Describe how a diffusion gradient is created in a tracheal system

A

Resourcing cells use up oxygen
Dropping O2 concentration
Creating a concentration gradient from the atmosphere to the cells

Repairing cells produce CO2
Increasing CO2 concentration
Creating a concentration gradient from the cells to the stomp sphere

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19
Q

How does mass transport of gasses occur in insects?

A

Muscles contract in the insect
Squeezing the trachea
Moving mass amounts of air in and out
Speeding up exchange

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20
Q

How does the ends of an insects tracheoles being filled with water assist in gas exchange?

A

Muscle cells anaerobically respire
Producing SOLUABLE lactate
Lactate lowers the water potential of muscle cells
Water moves into the muscle cells by osmosis
Decreasing the volume of the tracheoles
Drawing air further into the system

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21
Q

What is a consequence of insects having water in the ends of their tracheoles?

A

Increased water evaporation

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22
Q

what state are the spiracles typically in? Why?

A

Closed - to prevent water loss

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23
Q

Explain why there’s a conflict in insects between gas exchange and water conservation

A

Gas exchange requires a thin permeable surface with a large area

Conserving water requires thick water proof surfaces with a small area

Therefor both cannot occur together

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24
Q

What is the specialised gas exchange surface of a fish?

A

gills

  • Gill filaments
    • Gill lamellae
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25
What is the purpose of gill filaments and Gill lamellae
To increase the surface area of the gills
26
What is countercurrent flow?
The flow of water and blood in opposing directions (in fish) across Gill lamellae
27
What are the advantages of countercurrent flow?
Maintains a diffusion gradient along the entire gill lamellae More oxygen diffuses from the water into the blood
28
Why is water flow in fish one way but exchange in the lungs is two way?
Less energy is required As the flow doesn't need to reversed As water is dense and difficult to move
29
What is the difference between gas exchange in animals and plants?
Photosynthesis occurs in plants but not animals
30
How does gas exchange during photosynthesis differ from when the plant is not photosynthesising?
Some CO2 produced by respiration is used in photosynthesis Some O2 used in respiration is a product of photosynthesis But most gas exchange occurs by diffusion into and out of the leaf
31
What are the similarities between gas exchange in an insect and a plant?
No living cell is far from the external air Diffusion occurs in gas phase Both have pores for gas exchange Pores close to avoid excessive water loss
32
What adaptations does the leaf have for gas exchange?
Stomata - short diffusion pathway Air spaces - increases gas contact with Mesopotamia cells Mesophyll cells have large SA - rapid diffusion
33
What differences are there between gas exchange in a plant and an insect?
Insects can create mass air flow but plants cannot Insects have a smaller SA:V ratio than plants Insects have tracheae for gases to diffuse along but plants do not Insects do not interchange gases between respiration and photosynthesis but plants do
34
What is the function of closing the stomata?
Help control water loss by evaporation/transpiration
35
How do insects limit water loss?
Have a small SA:V ratio Waterproof coverings Close spiracles
36
How does a small SA:V ratio limit water loss?
Minimises h e area over which water is lost
37
How do waterproof coverings limit water loss?
Water cannot leave via osmosis as easily
38
How does closing the spiracles limit water loss?
Water cannot exit via the spiracles down the water potential gradient via osmosis
39
Define xerophyte
A plant adapted to living in areas where water is in short supply Eg. Dry, windy, hot conditions
40
Name three adaptations does a plant have to prevent water loss
A thick cuticle Leaves that roll up Hairy leaves Stomata in pits or grooves Reduced SA:V ratio
41
How does a thick cuticle limit water loss
Reduces water loss by evaporation by increasing the diffusion pathway length
42
How does rolling up leaves limit water loss?
Stomata become trapped inside a pocket of air This region becomes saturated with water vapour increasing its water potential There is no water potential gradient therefore no water loss
43
How does hairy leaves limit water loss?
Traps still moist air next to the leaf surface Reducing the water potential gradient So less water is lost by evaporation
44
How does having stomata in pits or grooves prevent water loss?
Traps still moist air next to the leaf surface Reducing the water potential gradient So less water is lost by evaporation
45
How does having a reduced SA:V ratio limit water loss?
Slower rate of diffusion Must be balanced with need for photosynthesis
46
Why must the volume of oxygen absorbed and carbon dioxide removed large in mammals?
Large organisms with a large number of cells High body temperature due to high metabolic rate
47
Describe the route taken by inhaled air from the atmosphere to the blood stream
``` Nasal cavity / mouth Trachea Bronchi Bronchioles Alveoli Capillaries ```
48
Describe the lungs features
Lobed structures Consisting of branches tubules Called bronchioles Ending in tiny air sacs called alveoli
49
Describe the features of the trachea
Flexible airway Supported by cartilage To prevent the trachea collapsing due to pressure drop Ciliates epithelium and goblet cells Prevent infection
50
Describe the features of the bronchi
Two leading to each lung Flexible airway Supported by cartilage To prevent the trachea collapsing due to pressure drop Mucus and cilia to remove dirt and prevent infection
51
Describe the features of the bronchioles
Many branches from bronchi Muscle tissue allows constriction To control flow of air in and out of alveoli
52
Describe the features of alveoli
Large supply For increased SA for faster rate of diffusion Elastic fibres allow alveoli to stretch to fill with air
53
Define ventilation
The movement of air into and out of the lungs
54
Describe inspiration
External intercostal muscles and diaphragm muscle contract Internal intercostal muscles relax Ribs move up and out Increasing thorax volume This reduces the pressure in the lungs Creating a pressure gradient So air is forced into the lungs
55
Describe expiration
External intercostal muscles and diaphragm muscle relax Internal intercostal muscles contract Ribs move down and in Decreasing thorax volume This increases the pressure in the lungs Creating a pressure gradient So air is forced out of the lungs
56
In ventilation which process is active and which is passive?
Inspiration is active Expiration is largely passive
57
Define tidal volume
The volume of air skin in a breath (at rest) Typically 0.5dm3
58
Define ventilation rate
The number of breaths per minute Typically 12-20
59
Define pulmonary ventilation rate
The amount of air taken into the lungs in a minute
60
How to calculate luminary ventilation rate?
PVR=TVxVR
61
Name 3 adaptations of the alveoli that increase diffusion rate
Large surface area Thin cells One cell layer thick Close to capillaries High O2 concentration
62
What factors increase the risk of lung disease
Smoking Air pollution Genetic make up Infection Occupation
63
List the major parts of the digestive system
``` Oesophagus Stomach Ileum/Small intestine Large intestine Rectum Salivary Glands Pancreas Liver ```
64
What is digestion?
The physical and chemical breakdown of food
65
Outline physical digestion
Mastication/Chewing of food into smaller pieces Providing a larger surface area for chemical digestion Churning of the stomach also breaks up food
66
Outline chemical digestion
Enzymes hydrolyse large insoluble molecules into smaller soluble ones
67
Outline carbohydrate digestion
Amylase (produced in mouth and pancreas) hydrolyses starch into maltose Maltase (lining of ileum) hydrolyses maltose into alpha glucose Sucrase hydrolyses sucrose into glucose and fructose Lactase hydrolyses lactose into glucose and galactose
68
Outline lipid digestion
Lipids are hydrolused into micelles by bile salts (liver) in emulsification to increase the surface area of lipids
69
Outline protein digestion
Endopeptidases hydrolyse bonds in the central region to form a series of peptide molecules Exopeptidases hydrolyse terminal amino acids to form dipeptides and amino acids Dipeptidases hydrolyse dipeptides into amino acids
70
Outline the features of villi in the ileum
Increase surface area for diffusion Thin walled to reduce diffusion pathway length Muscle to move to maintain diffusion gradients Rich blood supply to carry away absorbed olecules and maintain a diffusion gradient Microvilli to increase surface area for diffusion
71
Outline the absorption of amino acids and monosaccharides
Diffusion and co-transport From the ileum Into the bloodstream
72
Briefly outline the absorption of triglycerides
1. lipid droplets are hydrolysed into micelles 2. Micelles carry monoglycerides and fatty acids to ileum 3. Monoglycerides and fatty acids diffuse into the cell 4. The smooth ER reforms triglycerides 5. Golgi associates triglycerides with cholesterol and lipoproteins to form chylomicrons 6. Chylomicrons exits cell by exocytosis into the lacteals

AS AQA BIOLOGY (8 decks)

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