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A-level Biology > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

What’s the SA :V

A

The relationship between the size of an organism or structure and its surface area to volume ratio plays a significant role in the types of adaptations an organism will have.

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2
Q

Small organisms & SA:V

A

Small organisms e.g amoeba, very large surface area in comparison to volume.

big surface for exchange of substances, but also there is a smaller distance from the outside of the organisms to the middle of it.

As a result, very small organism can simply exchange substances across their surface.

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3
Q

Larger organisms and SA:V

A

larger an organism, smaller its SA compared to vol and larger the distance from middle to outside.

typically have higher metabolic rate, which demands efficient transport of waste out of cells and reactants into cells.

have adaptations help make exchange across surfaces more efficient.

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4
Q

Adaptations of larger organisms to increase SA:V

A

Villi and microvilli - Absorption of digested food

Alveoli and bronchioles - Gas exchange

Spiracles and tracheoles - Gas exchange

Gill filaments and lamellae - Gas exchange

Thin wide leaves - Gas exchange

Many capillaries -capillary network

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5
Q

What happens during digestion

A

large biological molecules hydrolysed to smaller molecules that can be absorbed across cell membranes.

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6
Q

What enzymes do carbohydrates require to hydrolyse them into monosaccharides

A

Amylases

Membrane-bound disaccharidases

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7
Q

Where is amylase produced

A

Pancreas and salivary glands

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8
Q

What does amylase do

A

It hydrolyses polysaccharides into disaccharide maltose by hydrolysing glycosidic bonds.

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9
Q

What are examples of membrane-bound enzymes

A

Sucrose and lactase

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10
Q

What do membrane-bound enzymes(sucrase and lactase) do

A

hydrolyse sucrose and lactose into monosaccharides.

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11
Q

How many enzymes can protein be hydrolysed by

A

3

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12
Q

What are the 3 enzymes proteins can be broken down by

A

Endopeptidases

Exopeptidases

Membrane-bound dipeptidases

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13
Q

What d Endopeptidases do

A

hydrolyse peptide bonds between amino acids in middle of polymer chain

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14
Q

What do Exopeptidases do

A

hydrolyse peptide bonds between amino acids at end of polymer chain

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15
Q

What do Membrane-bound dipeptidases

A

hydrolyse peptide bonds between 2 amino acids

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16
Q

Where are proteins digested

A

Protein digestion starts in stomach, continues in the duodenum and is fully digested in ileum.

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17
Q

Where are lipids digested

A

Lipids are digested by lipase and the action of bile salts.

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18
Q

Where is lipase produced and what does it do

A

Lipase is produced in the pancreas and it can hydrolyse the ester bond in triglycerides to form the monoglycerides and fatty acids.

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19
Q

Where are bile salts produced and what do they do

A

Bile salts are produced in the liver and can emulsify lipids to form tiny droplets, micelles. This increases the surface area for lipase to act on.

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20
Q

What are the 2 stages in lipid digestion

A

Physical (emulsification & micelle formation)

Chemical (Lipase)

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21
Q

What happens in the 1st stage of lipid digestion

A

Physical (emulsification & micelle formation)
Lipids are coated in bile salts to create an emulsion.
Many small droplets of lipids provides a larger surface area to enable the faster hydrolysis action by lipase.

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22
Q

What happens in the 2nd stage of lipid digestion

A

Chemical (Lipase)

Lipase hydrolyses lipids into glycerol and fatty acids (some monoglycerides) .

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23
Q

What are micelles

A

Micelles are water soluble vesicles formed of the fatty acids, glycerol, monoglycerides and bile salts.

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24
Q

What do micelles do

A

Micelles deliver the fatty acids, glycerol and monoglycerides to the epithelial cells of the ileum for absorption.

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25
Q

How does micro villi maximise absorption

A

by increasing SA, decreasing diffusion distance and maintaining concentration gradient.

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26
Q

What is the ileum covered in

A

The ileum wall is covered in villi, which have thin walls surrounded by a network of capillaries and epithelial cells have even smaller microvilli

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27
Q

In mammals the products of digestion are absorbed where

A

Across the cells lining the ileum

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28
Q

What are lipids digested into and by what

A

monoglycerides and fatty acids by the action of lipase and bile salts.

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29
Q

Describe process of lipid absorption

A

Lipids digested into monoglycerides and fatty acids by action of lipase and bile salts.

These form tiny structures called micelles

When micelles encounter ileum epithelial cells, due to non-polar nature of fatty acids and monoglycerides, they can simply diffuse across cell surface membrane to enter cells of epithelial cells.

Once in cell, these will be modified back into triglycerides inside of endoplasmic reticulum and Golgi body.

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30
Q

Describe how digested lipids are absorbed and then transport to the ileum and lymphatic system. [5]

A
  1. Micelles are made of bile salts, fatty acids and monoglycerides
  2. Micelles carry the fatty acids to the epithelial cells of the ileum
  3. Fatty acids are absorbed into the cells of the ileum by simple diffusion
  4. Triglycerides or chylomicrons are formed
  5. Vesicles are removed by exocytosis
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31
Q

Describe the importance of micelles in absorbing lipids into the epithelial cells of the ileum. [3]

A
  1. Micelles are made of bile salts, fatty acids and monoglycerides/glycerol
  2. Micelles make fatty acids more soluble in water
  3. Micelles carry fatty acids to the epithelial cells of the ileum
  4. The fatty acids are released from the micelle and are absorbed into the cell by simple diffusion
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32
Q

When lipids are digested, they first form smaller droplets and then micelles are formed.

Explain the advantages of these two stages. [3]

A
  1. Lipid droplets the increase surface areas for lipase
  2. This speeds up hydrolysis / digestion
  3. The micelles bring the fatty acids, monoglycerides and glycerol to the epithelial cell
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33
Q

How are Golgi apparatus involved in the absorption of lipids? [3]

A
  1. They modify triglycerides
  2. They combine proteins with triglycerides to form chylomicrons
  3. These are packaged into vesicles
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34
Q

How do micelles help with lipid absorption?

A

They make the fatty acids more soluble in water

They carry the fatty acids to epithelial cells of the ileum

They help to maintain a higher concentration of fatty acids compared to the epithelial cells of the ileum

The fatty acids are then released from the micelle and enter the epithelial cell by simple diffusion

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35
Q

Why do fatty acids enter by simple diffusion?

A

They are non-polar (lipid soluble)

So they can dissolve and diffuse through the phospholipid bilayer.

36
Q

What happens once fatty acids are in the cell?

A

The fatty acids.and monoglycerides are modified back into triglycerides inside of the endoplasmic reticulum and Golgi body.

Sometimes a protein is added to the lipid, making it a chylomicron.

37
Q

How do modified lipids leave the epithelial cell?

A

Vesicles containing the triglyceride/chylomicron are released and move towards the cell membrane.

• They are released by exocytosis
• Then the triglycerides/chylomicrons enter the lacteal.

38
Q

Why is active transport and co-transport required to absorb glucose and amino acids from the lumen to the gut.

A

To absorb glucose and amino acids from the lumen to the gut there must be a higher concentration in the lumen compared to the epithelial cell (for facilitated diffusion).

BUT

There is usually more in the epithelial cells.

39
Q

What’s Tissue fluid

A

Fluid containing water, glucose, amino acids, fatty acids, ions and oxygen which bathes the tissues.

40
Q

How is tissue fluid formed

A

Capillaries have small gaps in the walls so that liquid and small molecules can be forced out.

As blood enters the capillaries from arterioles, the smaller diameter results in a high hydrostatic pressure so water, glucose, amino acids, fatty acids, ions and oxygen are forced out. This is known as ultrafiltration.

Large molecules remain in the capillaries and therefore create a lowered water potential.

Towards the venule end of the capillaries, hydrostatic pressure is lowered due to loss of liquid, but water potential is very low.

Water re-enters capillaries by osmosis.

41
Q

What is forced out when forming tissue fluid

A

Water molecules

Dissolved minerals and salts

Glucose

Small proteins and amino acids

Fatty acids oxygen

42
Q

What remains in the capillary when forming tissue fluid

A

Red blood cells

Platelets

Large proteins

43
Q

The lymph

A

Not all the liquid will be reabsorbed by osmosis, as equilibrium will be absorbed.

The rest of the tissue fluid is absorbed into the lymphatic system and eventually drains back into the bloodstream near the heart.

44
Q

What is breathing

A

movement of air into and out of the lungs.

45
Q

What is respiration

A

chemical reaction to release energy the form of ATP.

46
Q

What is ventilation

A

the scientific word for breathing.

47
Q

What is gaseous exchange

A

diffusion of oxygen from the air in the alveoli into the blood and of carbon dioxide from the blood into the air in the alveoli.

48
Q

Why is Breathing an active process

A

It uses energy

49
Q

Describe the process of inspiration

A

external intercostal muscles contract, internal intercostal muscles relax.

ribs pulled upwards and outwards, increasing volume of thorax.

diaphragm muscles contract, causing it to flatten, which also increases volume of thorax.

• increased volume of thorax results in reduction of pressure in lungs.

• Atmospheric pressure now greater than pulmonary pressure, and so air is forced into lungs.

50
Q

Describe the process of expiration

A

internal intercostal muscles contract, external intercostal muscles relax.

ribs move downwards and inwards, decreasing volume of thorax.

diaphragm muscles relax and so it’s pushed up again by contents of abdomen that were compressed during inspiration.

volume of thorax is therefore further decreased.

decreased volume of thorax increases pressure in lungs.

pulmonary pressure is now greater than that of atmosphere, and so air forced out of lungs.

51
Q

What is tidal volume

A

Volume of air that enters and leaves the lungs at normal resting breath (0.5dm3)

52
Q

What is Vital capacity

A

Max volume of air we can inhale and exhale

53
Q

What is Residual volume

A

Volume of air left in lungs after the strongest exhalation

54
Q

What’s total lung capacity

A

Vital capacity + residual capacity (normally 5-6dm3)

55
Q

What’s pulmonary ventilation

A

the total volume of air that is moved into the lungs during one minute (dm min-‘).

56
Q

Pulmonary ventilation equation

A

Pulmonary ventilation = tidal volume x ventilation rate
(dm min-1). (dm3). (min-1)

57
Q

What are examples of lung diseases

A

Pulmonary fibrosis
Asthma
Emphysema
Bronchitis

58
Q

Example exam question style
A student concluded the data shows more cigarettes smoked per day will increase deaths.
Do you agree?

A

There is a positive correlation between lung cancer deaths and cigarettes smoked

However:
The data overlaps
Correlation does not prove causation - other factors, such as genetics or pollution could cause the deaths
There is no correlation coefficient statistic to know if the correlation is significant.

59
Q

Why do fish require a gas exchange surface

A

Fish are waterproof and the have a small surface area to volume ratio.

60
Q

What’s the gas exchange surface in fish

A

Gills

61
Q

Why do fish have a special adaptation to maintain conc gradient to enable diffusion to occur.

A

As Fish obtain oxygen from water, but there’s 30 time less oxygen in water than air,

62
Q

Features of gas exchange surfaces

A

Large surface area to volume ratio

Short diffusion distance

Maintained a concentration gradient

63
Q

What law can be used to calculate the rate of diffusion

A

Diffusion (alpha sign)

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

64
Q

How many layers of gills are on both sides of the head

A

4

65
Q

What are the gills made up of

A

Stacks of gill filaments

66
Q

What is each gill filament covered in

A

Each gill filament is covered in gill lamellae, position at right angles to the filament.

67
Q

What do gill lamellae do

A

Create a large SA

68
Q

What happens when fish open their mouth

A

When fish open their mouth

water rushes in and over the gills

and then out through a hole in the sides of their head.

69
Q

Terrestrial insects features

A

• Insects have an exoskeleton made of hard fibrous material for protection and a lipid layer to prevent water loss.

• Insects do not have lungs, and instead have a tracheal system.

70
Q

What gas exchange system do insects have

A

Tracheal system (trachea, tracheoles and spiracles

71
Q

What are spiracles and what do they do

A

Spiracles are round, valve like openings, running along the length of the abdomen. Oxygen and carbon dioxide enter and leave via the spiracles. The trachea attach to these openings.

72
Q

What are trachea

A

The trachea is a network of internal tubes.

The trachea tubes have rings within them to strengthen the tubes and to keep them open.

73
Q

What do the trachea do

A

The trachea branch into smaller tubes, deeper into the abdomen of the insect called tracheoles.

These extend throughout all the tissues in the insect to deliver oxygen to all respiring cells.

74
Q

How many methods of moving gases in the tracheal system are there

A

3

75
Q

What’s the 1st method of moving gases in the tracheal system

A

Gas can exchange by diffusion, as when cells respire, they use up oxygen and produce carbon dioxide, creating a concertation gradient from the tracheoles to the atmosphere.

76
Q

What’s the 2nd method of moving gases in the tracheal system

A

The second method of gas exchange is mass transport, in which an insect contracts and relaxes their abdominal muscles to move gases on mass.

77
Q

What’s the 3rd method of moving gases in the tracheal system

A

When the insect is in flight the muscle cells start to respire anaerobically to produce lactate. This lowers the water potential of the cells, and therefore water moves from the tracheoles into the cells by osmosis. This decreases the volume in the tracheoles and as a result more air from the atmosphere is draw in.

78
Q

What happens once the gases are in the alveoli

A

gas exchanges between the epithelium and the blood.

79
Q

Features of alveolar epithelium for efficient gas exchange

A

Alveoli are tiny air sacks, and there are 300 million in each human lung - creates very large SA for gas exchange.

alveoli epithelium cells very thin, to minimise diffusion distance.

Each alveolus is surrounded by network of capillaries to remove exchanged gases, and therefore maintains conc gradient.

80
Q

5 features of the human gas exchange system

A

alveoli

bronchioles

bronchi

trachea

lungs

81
Q

Which enzyme are proteins broken down to aminonacids

A

Proteases

82
Q

Insect adaptations to limit water loss

A

Insects have a small surface area to volume ratio where water can evaporate from

Insects have a waterproof exoskeleton

Spiracles, where gases enter and water can evaporate from, can open and close to reduce water loss.

83
Q

Adaptations for efficient diffusion in insects

A

Large number of fine tracheoles - large surface area

Walls of tracheoles are thin and short distance between spiracles and tracheoles - short diffusion pathway

Use of oxygen and production of carbon dioxide sets up steep diffusion gradients

84
Q

Adaptations for efficient gas exchange in fish

A

Large surface to volume ratio created by many gill filaments covered in many gilli lamellae

Short diffusion distance due to a capillary network in every lamellae and very thin gill lamellae

Maintaining concentration gradient
countercurrent flow mechanism.

85
Q

What is the countercurrent exchange principle

A

This is when water flows over the gills in the opposite direction to the flow of blood in the capillaries.

86
Q

What does countercurrent flow ensure

A

Countercurrent flow ensures that equilibrium is not reached

This ensures that a diffusion gradient is maintained across the entire length of the gill lamellae.

A-level Biology (15 decks)

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