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AQA A level biology <33 > Topic 3- exchange of substances > Flashcards

Topic 3- exchange of substances Flashcards

1
Q

insect tracheoles have thin walls. How does this increase the efficiency of gas exchange?

A

it means there is a short diffusion distance to cells

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2
Q

Insects have a large number of highly branched tracheoles. How does this increase the efficiency of gas exchange?

A

it means there is a short diffusion distance to cells and a large surface area for gas exchange

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3
Q

Insect tracheae are full of air. How does this increase the efficiency of gas exchange?

A

it means that gases diffuse quickly into tissues

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4
Q

Fluid in the ends of tracheoles moves out into tissues during exercise. How does this increase the efficiency of gas exchange?

A

the final diffusion pathway is gas rather than liquid, so diffusion to the gas exchange surface is faster and the surface area for gas exchange is larger

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5
Q

Insects can use their muscles to move air through tracheae. How does this increase the efficiency of gas exchange?

A

maintains a steep diffusion gradient for oxygen and carbon dioxide

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6
Q

define counter-current flow

A

When two materials flow in opposite directions to maintain a concentration gradient

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7
Q

What is a stoma?

A

A pore, usually found in the lower epidermis of a leaf, through which gases diffuse

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8
Q

In the mammalian gas exchange system, what is the trachea?

A

A flexible airway lined with cells, and supported by rings of cartilage, through which air moves towards and away from the lungs

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9
Q

In humans, the trachea and large bronchi are supported by cartilage. How does this adaptation support their function?

A

It prevents airways from collapsing when air pressure drops when breathing in

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10
Q

In humans, the trachea and bronchi are lined with cilia. How does this adaptation support their function?

A

cilia move mucus towards the throat

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11
Q

How are alveoli adapted for efficient gas exchange?

A

the alveolar epithelium is one cell thick which creates a short diffusion pathway for gas exchange

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12
Q

What is maltase?

A

an enzyme that hydrolyses maltose to form glucose

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13
Q

What is an endopeptidase?

A

an enzyme which acts in the middle of a polypeptide and hydrolyses peptide bonds to produce shorter polypeptides

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14
Q

What is an exopeptidase?

A

an enzyme which acts at the end of a polypeptide and hydrolyses peptide bonds to form dipeptides and amino acids

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15
Q

What is a dipeptidase?

A

an enzyme which acts on a dipeptide and hydrolyses peptide bonds to form amino acids

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16
Q

What is haemoglobin and its structure?

A

A protein enabling transport of oxygen in the blood. It has a quaternary structure and four prosthetic haem groups which are able to bind oxygen.

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17
Q

Define myocardial infarction.

A

Blood flow in the coronary arteries reduces, so the amount of oxygen reaching the heart muscle reduces. So cells respire less and start to die.

17
Q

Blood vessels generally contain an outer layer of collagen. What is its function?

A

it resists changes in pressure

18
Q

Blood vessels generally contain a muscle layer. What is its function?

A

to contact to control the flow of blood

18
Q

Blood vessels generally contain an elastic layer. What is its function?

A

to stretch and recoil to maintain blood pressure

19
Q

Blood vessels are lined with an endothelium layer. How is it adapted to its function?

A

it is smooth to reduce friction with the blood

it is one layer thick for rapid diffusion

19
Q

How is the muscle layer in arteries adapted to its function?

A

It is thicker than the muscle layer in veins so that small arteries can constrict and dilate to control the volume of blood passing to the tissue

20
Q

How is the elastic layer in arteries adapted to its function?

A

it is thicker than the elastic layer in veins to maintain high blood pressure so that blood reaches the extremities. The stretch and recoil of the elastic wall helps to smooth the pressure surges resulting from the heartbeat.

21
Q

How is the artery wall adapted to its function?

A

it is thick to help prevent the artery bursting under pressure

22
Q

How is the valve system in arteries adapted to its function?

A

there are no valves in the arteries, as the constant high pressure helps prevent blood from flowing backwards

23
Q

How is the lumen in veins adapted to its function?

A

it is large so it can carry a large volume of slow-moving blood

24
Q

How is the muscle layer in veins adapted to its function?

A

It is thinner than the muscle layer in arteries.

Veins carry blood away from tissues and so constriction and dilation can’t affect the volume of blood passing to tissues.

25
Q

how is the elastic layer in veins adapted to its function?

A

it is thinner than the elastic layer in arteries.

Lower blood pressure reduces the risk of bursting and does not create a recoil action.

26
Q

How is the vein wall adapted to its function?

A

it is thinner as low pressure reduces the risk of bursting

27
Q

How is the valve system in veins adapted to its function?

A

valves ensure that, despite low blood pressure, blood does not flow backwards

28
Q

Capillaries are numerous and highly branched. How does this support their function?

A

provides large surface area for exchange

29
Q

Capillaries have a narrow diameter. How does this support their function?

A

they permeate tissues, so all cells are close to a capillary, reducing the diffusion distance and increasing the rate of diffusion.

30
Q

Capillaries have a narrow lumen. How does this support their function?

A

It means that blood cells press against the side wall, reducing the diffusion distance to nearby cells and increasing the rate of diffusion.

31
Q

Capillaries have spaces between endothelial cells. How does this support their function?

A

It allows white blood cells to escape and tackle infections in nearby tissues.

32
Q

Capillaries have extremely thin walls. How does this support their function?

A

Reduces the diffusion distance to nearby cells and increases the rate of diffusion.

33
Q

what is the xylem?

A

dead, hollow, elongated tube which transports water in most plants

34
Q

The xylem contains cells joined end to end with no end wall. Why does this make it a good transport system in plants?

A

it forms one continuous tube, which is essential for the cohesion-tension theory.

35
Q

the xylem contains dead cells. Why does this make it a good transport system in plants?

A

The cells do not use metabolic energy to move the water.

Movement of water would be slowed by the membrane and cytoplasm of a living cell.

36
Q

The xylem has thick walls containing lignin. Why does this make it a good transport system in plants?

A

it helps strengthen the xylem and prevents collapse

37
Q

What is phloem?

A

A tissue that transports the products of photosynthesis from the leaves to the rest of the plant.

AQA A level biology <33 (12 decks)

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