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Biology A-level > exchange surfaces > Flashcards

exchange surfaces Flashcards

1
Q

Tracheae

A

internal network of tubes supported by strengthened rings to prevent collapse.

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2
Q

Tracheoles

A

smaller dead end tubes leading from tracheae. Extend through the body of the insect direct to respiring tissues providing a short diffusion pathway from air to cells.

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3
Q

Spiracles

A

pores on surface of insect leading to tracheae, can be opened and closed

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4
Q

Describe the structure of
fish gills

A

Gill filaments stacked on top of each other.
Gill lamellae project at right angles to the gill filaments, this increases the surface area of the gills.
The gill filaments and lamellae have a good blood supply.

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5
Q

Describe how a fish
exchanges gases (mechanism)

A

Water is taken in through the mouth of the fish and forced out over the gills. through an opening on the side of the body. Gases are exchanged between the water and the blood vessels in the gills.

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6
Q

Explain the difference
between parallel flow and
counter-current flow

A

In parallel flow the blood and the water flow in the same direction. In countercurrent flow the blood and the water flow in opposite directions.

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7
Q

Explain how
counter-current flow
increases the rate of gas
exchange

A

Rate of gas exchange is increased because
counter-current flow maintains a diffusion gradient between the water and the blood over the whole length of the gill.

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8
Q

Describe the SA:vol of a fish

A

small

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9
Q

Describe how plants exchange gases

A

Gas exchange occurs by diffusion in the leaves of plants and volumes and types of gases depend on the balance between the rates of photosynthesis and respiration.

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10
Q

Explain the adaptations of leaves for efficient gas exchange

A

Leaf is designed so that cells are close to external air and diffusion occurs in the gas phase.
Stomata: found on the underside of the leaf and allow gases to enter. Many stomata so short diffusion pathway to cells
Spongy mesophyll: has air spaces so large surface area compared with tissue volume, gases readily come into contact with cells, rapid diffusion

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11
Q

Inhalation/Inspiration (active process - requires energy)

A

External intercostal muscles contract - internal
intercostal muscles relax
Ribs pulled upwards and outwards
Diaphragm contracts and flattens
Volume of thorax increases
Pressure in lungs decreases
Atmospheric pressure greater than pulmonary pressure
- air moves in to lungs

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12
Q

Exhalation/Expiration (passive process - does not require
energy)

A

Internal intercostal muscles contract - external
intercostal muscles relax
Ribs move downwards and inwards
Diaphragm relaxes and moves upwards
Volume of thorax decreases
Pressure in lungs increases
Pulmonary pressure greater than atmospheric pressure
- air moves out of lungs

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13
Q

Explain what is meant by pulmonary ventilation and how it is calculated

A

Pulmonary ventilation rate is the total volume of air that is moved into the lungs during one minute.
Calculated by: tidal volume x breathing rate

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14
Q

Describe the structure of the human gas exchange system

A

Contained within the ribcage for protection and to allow ventilation to occur
Trachea - flexible airway from mouth to bronchi, has cartilage for support. Walls made of ciliated epithelium and goblet cells
Bronchi - two branches of trachea, similar structure to trachea
Bronchioles - branches from bronchi, muscular walls control air flow to alveoli
Alveoli - tiny air sacs at the end of bronchioles. made of epithelium with elastic fibres and collagen between alveoli

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15
Q

Explain the functions of the human gas exchange system

A

To allow a large volume of oxygen and carbon dioxide to be exchanged between the blood and the environment. The gases are needed and produced by respiration

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16
Q

Describe the features of the gas exchange surface in humans

A

Large surface area, thin, movement of internal and environmental medium to maintain diffusion gradient

17
Q

Explain how the alveolar epithelium is adapted to maximise gas exchange

A

Single layer of cells for short diffusion pathway
Millions of alveoli allowing a very large surface area
Good blood supply with many capillaries whose walls are one cell thick for a short diffusion pathway

18
Q

Describe the purpose of digestion

A

To hydrolyse large molecules into small ones for absorption from the ileum into the blood

19
Q

Describe structure and function of organs of the digestive system

A

Salivary glands: near mouth. Pass amylase via a duct into the mouth
Oesophagus: carries food from mouth to stomach
Stomach: muscular sac, produces enzymes to digest protein, stores and digests food
Pancreas: gland secreting pancreatic juice containing protease, amylase and lipase
Ileum: long muscular tube, walls and glands secrete enzymes. villi and microvilli to increase surface area
Large intestine: absorbs water
Rectum: stores faeces and egests them via the anus

20
Q

Explain how food is physically and chemically digested

A

Physical digestion: large pieces of food to small pieces by chewing and churning of stomach - increases SA for enzyme action
Chemical: Enzymes hydrolyse large insoluble molecules into small soluble molecules

21
Q

Describe how carbohydrates are digested

A

Saliva contains amylase which hydrolyses starch to maltose and mineral salts to maintain pH7
Stomach denatures amylase from mouth
Pancreas secretes pancreatic juice containing amylase and alkaline salts to neutralise stomach acid
Ileum produces the membrane bound disaccharidase maltase which hydrolyses maltose to alpha glucose
Additional disaccharidases: lactase and sucrase

22
Q

Describe how lipids are digested

A

Lipases hydrolyse triglycerides (lipids) into monoglycerides and fatty acids
Bile salts emulsify lipids to increase the surface area for enzyme action

23
Q

Describe how proteins are digested

A

Endopeptidases: hydrolyse peptide bonds between amino acids in the middle of a polypeptide producing shorter polypeptides
Exopeptidases: hydrolyse peptide bonds on the ends of the polypeptide producing single amino acids and dipeptides
Dipeptidases: membrane bound, hydrolyse dipeptides into single amino acids

24
Q

Explain how triglycerides are absorbed

A

Micelles (containing monoglycerides, bile salts and fatty acids) come into contact with epithelial cells lining ileum and break open.
Monoglycerides and fatty acids diffuse into epithelial cell through phospholipid bilayer (they are lipid soluble).
Monoglycerides and fatty acids reform triglycerides in the endoplasmic reticulum.
Chylomicrons (triglycerides, lipoproteins, cholesterol) formed in the golgi apparatus
Chylomicrons leave cell by exocytosis into the lacteal (lymphatic capillary) in the villus
Chylomicrons move from the lymphatic vessels into the blood stream
Triglycerides hydrolysed by enzymes in endothelial cells of blood capillaries from where they diffuse into cells

25
Q

SA to Volume ratio

A

To survive organisms transfer material between internal and external environment

26
Q

Name the excretory products that need to be exchanged between an organism and its environment

A

urea and carbon dioxide

27
Q

Name the nutrients that need to be exchanged between an organism and its environment

A

glucose, fatty acids, amino acids, vitamins, minerals

28
Q

Name the respiratory gases that need to be exchanged between an organism and its environment

A

carbon dioxide and oxygen

29
Q

Explain why tissue fluid is important in exchange

A

most cells are too far from exchange surfaces for substances to arrive or be removed by diffusion. Substances move through the tissue fluid

30
Q

Describe how larger organisms increase their surface area to volume ratio

A

Larger organisms require specific exchange surfaces with large surface areas to obtain the substances they need.

31
Q

Describe the relationship between SA:vol and metabolic rate

A

Organisms with a high metabolic rate exchange more materials and therefore need a larger surface area to volume ratio

32
Q

Features of a specialised exchange system

A

-large SAVR compared to organism which increases the rate of exchange
-very thin so diffusion distance is short and exchange occurs rapidly
-selectively permeable to allow selected materials to cross
-movement of the environmental medium
-A transport system

33
Q

Describe how single celled organisms exchange gases

A

Single celled organisms are small and therefore have a large surface area to volume ratio. This is sufficient to exchange the substances required

34
Q

Describe how an insect
exchanges gases

A

Tracheae - internal network of tubes supported by strengthened
rings to prevent collapse.
Tracheoles - smaller dead end tubes leading from tracheae.
Extend through the body of the insect direct to respiring tissues
providing a short diffusion pathway from air to cells.
Spiracles - pores on surface of insect leading to tracheae, can be
opened and closed

35
Q

Explain how insects exchange
gases

A
  1. Diffusion gradient - respiration in cells uses oxygen,
    concentration falls in ends of tracheoles, produces a diffusion
    gradient causing oxygen to diffuse from the atmosphere. The
    opposite applies to carbon dioxide
  2. Mass transport - contraction of muscles squeezes trachea and
    enables mass movement of air
  3. Water in tracheoles - intense activity causes muscle cells to
    respire anaerobically, producing soluble lactic acid which lowers
    water potential of muscle cells, water moves into cells from
    tracheoles by osmosis, lowering volume in tracheoles, drawing air
    further in and allowing it to diffuse in gas phase rather than liquid
    which is more rapid.
36
Q

How is water loss limited in insects

A

-Small surface area to volume ratio to minimise the area water is lost
-Waterproof covering of chitin
-Spiracles that open and close

37
Q

How is water loss limited in plants

A

They have a waterproof covering that covers part of the leaves and the ability to close stomata

38
Q

How is water loss limited in xerophytes

A

-a thick cuticle- so less water can escape
- rolling up of leaves to trap air and create a high water potential
-hairy leaves to trap moisture
-stomata in pits to trap moisture
-Reduced SA:VR

39
Q

State two reasons why humans need to absorb large volumes of oxygen from the lungs

A
  • high body temperature
    -high metabolic rate
    -large organisms

Biology A-level (31 decks)

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