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as aqa biology > Exchange > Flashcards

Exchange Flashcards

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AP® Biology flashcards
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
Q

What is the purpose of gill filaments and Gill lamellae

A

To increase the surface area of the gills

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26
Q

What is countercurrent flow?

A

The flow of water and blood in opposing directions (in fish) across Gill lamellae

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27
Q

What are the advantages of countercurrent flow?

A

Maintains a diffusion gradient along the entire gill lamellae

More oxygen diffuses from the water into the blood

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28
Q

Why is water flow in fish one way but exchange in the lungs is two way?

A

Less energy is required
As the flow doesn’t need to reversed
As water is dense and difficult to move

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29
Q

What is the difference between gas exchange in animals and plants?

A

Photosynthesis occurs in plants but not animals

30
Q

How does gas exchange during photosynthesis differ from when the plant is not photosynthesising?

A

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
Q

What are the similarities between gas exchange in an insect and a plant?

A

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
Q

What adaptations does the leaf have for gas exchange?

A

Stomata
- short diffusion pathway

Air spaces
- increases gas contact with Mesopotamia cells

Mesophyll cells have large SA
- rapid diffusion

33
Q

What differences are there between gas exchange in a plant and an insect?

A

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
Q

What is the function of closing the stomata?

A

Help control water loss by evaporation/transpiration

35
Q

How do insects limit water loss?

A

Have a small SA:V ratio

Waterproof coverings

Close spiracles

36
Q

How does a small SA:V ratio limit water loss?

A

Minimises h e area over which water is lost

37
Q

How do waterproof coverings limit water loss?

A

Water cannot leave via osmosis as easily

38
Q

How does closing the spiracles limit water loss?

A

Water cannot exit via the spiracles down the water potential gradient via osmosis

39
Q

Define xerophyte

A

A plant adapted to living in areas where water is in short supply

Eg. Dry, windy, hot conditions

40
Q

Name three adaptations does a plant have to prevent water loss

A

A thick cuticle

Leaves that roll up

Hairy leaves

Stomata in pits or grooves

Reduced SA:V ratio

41
Q

How does a thick cuticle limit water loss

A

Reduces water loss by evaporation by increasing the diffusion pathway length

42
Q

How does rolling up leaves limit water loss?

A

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
Q

How does hairy leaves limit water loss?

A

Traps still moist air next to the leaf surface

Reducing the water potential gradient

So less water is lost by evaporation

44
Q

How does having stomata in pits or grooves prevent water loss?

A

Traps still moist air next to the leaf surface

Reducing the water potential gradient

So less water is lost by evaporation

45
Q

How does having a reduced SA:V ratio limit water loss?

A

Slower rate of diffusion

Must be balanced with need for photosynthesis

46
Q

Why must the volume of oxygen absorbed and carbon dioxide removed large in mammals?

A

Large organisms with a large number of cells

High body temperature due to high metabolic rate

47
Q

Describe the route taken by inhaled air from the atmosphere to the blood stream

A 
Nasal cavity / mouth
Trachea
Bronchi
Bronchioles
Alveoli
Capillaries
48
Q

Describe the lungs features

A

Lobed structures

Consisting of branches tubules

Called bronchioles

Ending in tiny air sacs called alveoli

49
Q

Describe the features of the trachea

A

Flexible airway

Supported by cartilage

To prevent the trachea collapsing due to pressure drop

Ciliates epithelium and goblet cells

Prevent infection

50
Q

Describe the features of the bronchi

A

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
Q

Describe the features of the bronchioles

A

Many branches from bronchi

Muscle tissue allows constriction

To control flow of air in and out of alveoli

52
Q

Describe the features of alveoli

A

Large supply

For increased SA for faster rate of diffusion

Elastic fibres allow alveoli to stretch to fill with air

53
Q

Define ventilation

A

The movement of air into and out of the lungs

54
Q

Describe inspiration

A

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
Q

Describe expiration

A

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
Q

In ventilation which process is active and which is passive?

A

Inspiration is active

Expiration is largely passive

57
Q

Define tidal volume

A

The volume of air skin in a breath (at rest)

Typically 0.5dm3

58
Q

Define ventilation rate

A

The number of breaths per minute

Typically 12-20

59
Q

Define pulmonary ventilation rate

A

The amount of air taken into the lungs in a minute

60
Q

How to calculate luminary ventilation rate?

A

PVR=TVxVR

61
Q

Name 3 adaptations of the alveoli that increase diffusion rate

A

Large surface area

Thin cells

One cell layer thick

Close to capillaries

High O2 concentration

62
Q

What factors increase the risk of lung disease

A

Smoking

Air pollution

Genetic make up

Infection

Occupation

63
Q

List the major parts of the digestive system

A 
Oesophagus
Stomach
Ileum/Small intestine
Large intestine
Rectum
Salivary Glands
Pancreas
Liver
64
Q

What is digestion?

A

The physical and chemical breakdown of food

65
Q

Outline physical digestion

A

Mastication/Chewing of food into smaller pieces
Providing a larger surface area for chemical digestion
Churning of the stomach also breaks up food

66
Q

Outline chemical digestion

A

Enzymes hydrolyse large insoluble molecules into smaller soluble ones

67
Q

Outline carbohydrate digestion

A

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
Q

Outline lipid digestion

A

Lipids are hydrolused into micelles
by bile salts (liver) in emulsification
to increase the surface area of lipids

69
Q

Outline protein digestion

A

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
Q

Outline the features of villi in the ileum

A

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
Q

Outline the absorption of amino acids and monosaccharides

A

Diffusion and co-transport
From the ileum
Into the bloodstream

72
Q

Briefly outline the absorption of triglycerides

A
  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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