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A-Level Biology- Y12 > 3.3- Organisms exchanging substances > Flashcards

3.3- Organisms exchanging substances Flashcards

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1
Q

What needs to be exchanged between an organism and the environment?

A

Oxygen, waste products, nutrients, heat

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2
Q

exchange surfaces

A

surfaces over which materials are exchanged from one area to another.

Lungs, roots, leaves, intestines

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3
Q

Factors affecting rate of exchange

A

Surface area, temperature, conc gradient

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4
Q

how to measure surface area

A

(BxH) x number of sides

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5
Q

How to measure volume

A

B x H x L

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6
Q

Single Celled Organisms- exchange

A

Can use diffusion alone to provide their nutrients

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7
Q

Multi Celled Organisms- exchange

A

Require transport systems and specialised exchange surfaces to provide the cells nutrients

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8
Q

What happens as an object gets smaller?

A

The sa:v increases

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9
Q

Why can’t insects use their body surface to transport?

A

They are multicellular so have a large distance between cells and outside

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10
Q

What can an efficient gas exchange surface also mean?

A

An efficient water loss surface

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11
Q

What do terrestrial insects have to do?

A

Balance their needs to conserve water with the need to exchange gases

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12
Q

How do insects limit water loss?

A

-small surface area to volume ratio

-waterproof coverings

-spiracles which can close

-Hairs that reduce air movement

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13
Q

Tracheae

A

tiny tubes in insect body that deliver oxygen directly to metabolizing tissues

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14
Q

Spiracles

A

openings in the abdomen of an insect that are used for breathing- allow gases in and out and controlled by valves

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15
Q

Why aren’t insects bigger?

A

More cells=more oxygen demand. Insects wouldn’t be able to meet that oxygen demand

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16
Q

Limitations of the tracheal system

A

Insects rely on diffusion rather than a transport system.

It limits the size insects can grow to

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17
Q

How do gases move in and out of the tracheal system?

A

Diffusion gradient, muscle contractions, water filled tracheoles

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18
Q

Diffusion gradient

A

Respiring cells use oxygen and thus reduces its concentration in the object compared to outside. Same happens to CO2 but in reverse

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19
Q

Muscle contraction & the tracheae

A

Squeezing the tracheae through abdominal pumping causes contracting of insect muscle which reduces volume in tracheae and expels air

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20
Q

Water filled tracheoles

A

Anaerobic respiration produces lactate which is water soluble- this lowers water potential of muscle cells. Water moves into muscle cells from tracheoles. Volume in tracheole end decreases, draws the air in.

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21
Q

What happens when the spiracles close?

A

Oxygen levels decrease in the tracheae as oxygen is used up by the respiration and there is no more entering the tracheae.

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22
Q

What causes spiracles to open ?

A

an increase in CO2 as there may be less volume to keep the waste products.

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23
Q

What do both plants and animals have to reduce water loss?

A

a waterproof cuticle/surface

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24
Q

Are fish adapted to exchange materials via their surface?

A

No they are large and multicellular

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25
Q

Coating of fish

A

Waterproof and gas tight

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26
Q

Specialised internal exchange surface in fish

A

gills

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27
Q

Gill structure

A

Gill cover protects gills.

Gills are made of gill filaments that are stacked on top of each other

Filament is covered in lamellae that are at right angles to the filaments

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28
Q

What does parallel flow mean?

A

Water and blood flow in the same direction in the gills

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29
Q

How does water enter the fish?

A

By the mouth then passed out over the gills

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30
Q

countercurrent flow

A

flow of water opposite that of the flow of blood in a fish’s gills

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31
Q

Why is parallel flow not beneficial for fish?

A

the most oxygen rich water meets the least oxygen rich blood meaning lots of diffusion occurs in the beginning and by the middle of the gill, equilibrium is met. Half of the exchange surface is wasted.

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32
Q

How is countercurrent flow beneficial for fish?

A

The most oxygen rich water meets the most oxygen rich blood. This controls the diffusion of oxygen, preventing an equilibrium from being met. A favourable O2 gradient is maintained.

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33
Q

Where is there always a higher oxygen concentration?

A

Water

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34
Q

What does countercurrent flow result in?

A

This results in the maintenance of a favourable O2 gradient across the whole gill.

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35
Q

Dicotyledonous plants

A

Plants that produce seeds that contain two cotyledons. They have two primary leaves.

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36
Q

What gases do plants need?

A

carbon dioxide and oxygen

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37
Q

What is the respiration equation?

A

oxygen + glucose > carbon dioxide + water + energy

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38
Q

What is the photosynthesis equation?

A

Carbon dioxide + water > glucose + oxygen

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39
Q

How are the leaves of a plant adapted for gas exchange?

A

Large Surface Area

Thin

Selectively Permeable

Diffusion Gradient

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40
Q

How are plants and animals different in terms of gas exchange?

A

Plants photosynthesise and respire

41
Q

What reduces the gas exchange with the outside environment?

A

Gases produced in photosynthesis and respiration are used in other processes. Rates of reaction change the volume and types of gases being exchanged.

42
Q

Gas Exchange in plants during the day

A

Respiration provides some CO2 for photosynthesis however most of it is taken from the environment. Some O2 from photosynthesis is used in respiration however most diffuses out.

43
Q

Gas exchange in plants at night

A

Dark. No photosynthesis occurs without light. Respiration still occurs as o2 diffuses into the leaf and CO2 diffuses out.

44
Q

stomata (stoma)

A

small pores on underside of leaf allow water in and out- also allows co2 and o2 movement

45
Q

Waxy cuticle

A

Forms a waterproof layer to stop water loss through evaporation

46
Q

Palisade cells

A

closely packed photosynthetic cells within leaves. Many chloroplasts to trap light

47
Q

Guard cells

A

control the opening and closing of stomata

48
Q

Xylem

A

vascular tissue that carries water and minerals upward from the roots to every part of a plant

49
Q

Phloem

A

Living vascular tissue that carries sugar and organic substances throughout a plant

50
Q

Upper epidermis cells

A

Upper layer of the cells, covers with a waxy waterproof cuticle that reduces water loss from leaf. Transparent

51
Q

Spongy mesophyll cells

A

Rounded, loosely packed cells, with air spaces between them. They are found below the palisade cells. Allow gas exchange

52
Q

When do stomata open and close?

A

open during the day and close at night. Photosynthesis occurs during the day so O2 is required, hence why stoma open

53
Q

How does exchange of gases also cause loss of water in leaves?

A

Large sa allow lots of gas exchange and absorption of sunlight. This also promotes loss of water through desiccation

54
Q

The Transpiration Stream

A

the movement of water through a plant from the roots until it is lost by evaporation from the leaves. Happens because of cohesion tension theory

55
Q

cohesion-tension theory

A

theory that explains how the physical properties of water allow it to move through the xylem of plants- water sticks together.

56
Q

Xerophytes

A

Plants adapted to living in areas with a short supply of water

57
Q

Adaptations- thick waxy cuticle

A

Acts as a thick waterproof barrier preventing evaporation and osmosis

58
Q

Adaptations- rolled up leaves

A

Protects the stomata on lower epidermis. Still, moist air is trapped holding water against the stomata. Water potential gradient is lowered, preventing the movement of water out.

59
Q

Adaptations- hairs on leaves

A

Still, moist air is trapped holding water against the stomata. Water potential gradient is lowered, preventing the movement of water out.

60
Q

Adaptations- Sunken stomata

A

Still, moist air is trapped holding water against the stomata. Water potential gradient is lowered, preventing the movement of water out.

61
Q

Adaptations- reduce SA:Vol ratio

A

Slower rate of diffusion as there is limited space for movement/evaporation of water out the cell. Still allows photosynthesis

62
Q

Why do we breathe?

A

To get O2 & get rid of CO2, they are equally important during respiration

63
Q

Alveoli structure

A
  • layer of thin flattened epithelial cells → short diffusion pathway
  • elastin + collagen → stretch and recoil
  • large surface area
  • surrounded by capillaries → good blood supply
  • good ventilation
64
Q

Structures of the lungs

A

Trachea, bronchi, bronchioles, alveoli

65
Q

What features allow for fast diffusion?

A

Slowed rbc, rbc flattened against capillary wall, thin walls, large surface area

66
Q

Difference between epithelial and endothelial

A

Epithelial- alveoli

Endothelial- capillaries

67
Q

Describe inspiration

A
  • External intercostal muscles contract, pulling the ribcage up and out
  • Diaphragm contracts, pulling it from a domed to a flattened shape
  • Combined effect is:

Volume of thorax and lungs increases

Pressure is reduced

Air enters and goes down the pressure gradient

68
Q

Where must gases diffuse?

A

Across the alveoli wall and capillary wall

69
Q

Tuberculosis

A

An infectious disease that may affect almost all tissues of the body, especially the lung- caused by bacterium

Infection course- inhaled TB bacteria enters lungs and multiplies causing a lung infection- lymph nodes may be enlarged. Immune system reacts by forming scar tissue around bacteria, hardening and thickening tissue

70
Q

Tuberculosis symptoms

A

productive cough, fatigue, fever, weight loss (anorexia, weight loss) night sweats

71
Q

Pulmonary Fibrosis

A

formation of scar tissue in the connective tissue of the lungs. An autoimmune disorder. Air sacs of lungs become replaced by fibrotic tissue- making them thicker and increasing diffusion pathway.

72
Q

Pulmonary Fibrosis symptoms

A

shortness of breath, dry hacking cough, fatigue, chest discomfort or pain

73
Q

Emphysema

A

a condition in which the air sacs of the lungs are damaged and enlarged, causing breathlessness. Mainly caused by smoking. Tobacco smoke temporarily paralyses the cilia so irritants enter the alveoli and inflame and damage alveoli tissue

74
Q

Emphysema symptoms

A

shortness of breath, chronic cough, fatigue, excess mucus, blue tint to skin

75
Q

Asthma

A

episodes of breathing difficulty due to narrowed or obstructed airways. Can be inherited or due to a lack of exposure to certain substances. Can be life threatening if airways are severely restricted

76
Q

Asthma symptoms

A

shortness of breath, wheezing, coughing, excessive mucus production

77
Q

Digestion

A

The process by which the body breaks down food into small nutrient molecules. Large insoluble molecules are hydrolysed by enzymes into small soluble molecules which can be absorbed and assimilated

78
Q

Salivary glands

A

Glands of the mouth that produce saliva, a digestive secretion. Saliva provided to mouth and contains amylase

79
Q

Oesophagus

A

Carries food to the stomach

80
Q

stomach

A

Muscular sac- lining produces enzymes. Stores and digests food by having glands

81
Q

Pancreas

A

Large gland that produces pancreatic juices containing protease, lipase and amylase

82
Q

ileum (small intestine)

A

Long muscular tube. Walls and glands produce enzymes. Walls folded into villi and microvilli

83
Q

Large intestine

A

The last section of the digestive system, where water is absorbed from food and the remaining material is eliminated from the body

84
Q

Rectum

A

Final section of intestines. Stores faeces which is egressed by the Anus

85
Q

physical digestion

A

The mechanical breakdown of large food particles into smaller ones. Chewing of food, churning of the stomach

86
Q

Chemical digestion

A

Enzymes break down food into smaller molecules using hydrolysis. Uses 3 main enzymes: protease, carbohydrase, lipase.

87
Q

Importance of physical digestion?

A

Larger SA:V ratio which aids enzyme action

88
Q

Lipid digestion

A

Hydrolysed by lipases. Ester bonds are hydrolysed to form fatty acids and monoglycerides.

Lipids first hydrolysed into micelles and then to fa and mg.

Called emulsification

89
Q

Why does emulsification aid lipid absorption?

A

Breaks down larger fats into smaller ones therefore increasing surface area. More SA means more space for enzyme actions to occur

90
Q

Bile salts

A

compounds in bile that aid in emulsification. One side is hydrophilic/lipophobic and the other side is hydrophobic/lipophillic . They prevent the fats from sticking back together

91
Q

Protein digestion

A

Peptidases hydrolysed peptide bonds in proteins. 3 main forms: endopeptides, exopeptides and dipeptides.

92
Q

Endopeptidases

A

Hydrolyse in the central region forming smaller polypeptides. Move freely

93
Q

Exopeptidases

A

Hydrolyse at terminal/end amino acids of the peptide molecules formed by endopeptides. Move freely

94
Q

Dipeptidases

A

Hydrolyse the bonds between 2 amino acids of a dipeptides. Membrane bound

95
Q

Absorption of triglycerides

A

Micelles break down when in contact with epithelia cells, releasing monoglycerides and fatty acids (non- polar so diffuse)

Once in epithelial cells, transported to endoplasmic reticulum where they rejoin to form triglycerides

Triglycerides associate with cholestrol and lipoproteins to form Chylomicrons

These move out of E cells by exocytosis, entering lacteals

Chylomicrons pass into blood system

Triglycerides in chylomicrons are hyrdolysed by enzyme and then diffuse into cells

96
Q

Chylomicrons

A

Small milky globules. Fat globules composed of proteins and lipids. Transport fat from the intestine to adipose tissue.

97
Q

Explain how the structure of the ileum is adapted to maximise exchange (5 marks)

A

Villi and Microvilli- hair like structures, folds of the cell walls. Increases the surface area so there is more space for exchange to occur.

Muscles layers- maintain the concentration gradient by constantly pushing food through ileum. Means there is a constant stream of nutrients that can diffuse

Capillary bed- Maintain concentration gradient of the bloodstream by meaning there is always a constant blood supply

Thin walls lined with epithelial cells- ensure a short diffusion pathway

98
Q

Describe the process of co-transport

A

-Sodium is actively transported into the blood by the sodium potassium pump. Potassium leaves the blood and enters the cell

-Now a high concentration of sodium in the lumen compared to epithelial cell. Sodium diffuses into the cell

-When sodium diffuses in, it brings aa or glucose with it

-Glucose/AAs pass into the blood plasma by facilitated diffusion

A-Level Biology- Y12 (14 decks)

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