Exchange and Transport Systems

Question 1

Explain the surface area : volume ratio

Answer 1

SA:V effects how quickly substances are exchanged.

Smaller organisms have higher surface area: volume ratios than larger organisms

Question 2

You may need to calculate volume

give equation for cylinder

give equation for sphere

Answer 2

cylinder = pi x r^2 x h

sphere = 4/3 x pi x r^3

Question 3

How do single cell organisms allow substances to enter?

Answer 3

The substances can diffuse directly into or out of the cell across the cell surface membrane. The diffusion rate is quick because of the small distances the substances have to travel.

Question 4

How do multicellular organisms allow substances to enter?

Answer 4

Diffusion is too slow because some cells are deep within the body and larger animals have a low surface area to volume ratio.

Multicellular organisms need specialised exchange organs and an efficient system to carry substances to and from their individual cells - this is mass transport.

In mammals, ‘mass transport’ normally refers to the circulatory system, which uses blood to carry glucose and oxygen around the body.

Mass transport in plants involves the transport of water and solutes in the xylem.

Question 5

Explain how the body size effects heat exchange

Answer 5

larger organisms = large v:sa ratio
This makes it harder for it to lose heat from its body.

smaller organism = smaller v:sa ratio
This makes it easier for them to lose heat.
This means smaller organisms need a relatively high metabolic rate, in order to generate enough heat to stay warm.

Question 6

Explain how the body shape effects the heat exchange

Answer 6

Animals with a compact shape have small SA:V - minimising heat loss from their surface

Animals with a less compact shape have a larger SA:V - this increases heat loss from their surface

Question 7

Explain how an animal has adapted for heat exchange

Answer 7

Example

Arctic fox = small ears and round head to reduce SA:V ratio and heat loss

Question 8

How have behavioural and physiological adaptations occurred to aid exchange?

Answer 8

Animals with high SA:V tend to lose more water as it evaporates from their surface. This is a problem for those living in hot environments. Some small animals in desert have kidney structure adaptations so that they produce less urine to compensate.

To support high metabolic rates, small mammals living in cold regions need to eat large amounts of high energy foods such as seeds and nuts

Smaller mammals may have thick layers of fur or hibernate when the weather gets cold

Large organisms in hot environments find it hard to keep cool as their heat loss is slow. Elephants have developed large flat ears allowing a larger surface area to increase heat loss.

Question 9

How to have an increased rate of diffusion?

Answer 9

• Large surface area
  -One cell thick so short diffusion pathway
• Maintain a steep conc gradient

Question 10

There is a lower concentration of _______ in water than in air

Answer 10

oxygen

Question 11

Explain the structure of gills

Answer 11

Water enters the fish through the mouth and passes out through the gills. Each gill is made of lots of thin plates called gill filaments, which give a large surface area for exchange of gases. The gill filaments are covered in lots of tiny structures called lamellae, which increases surface area even more. The lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion, between water and the blood.

Question 12

What is the counter current flow system?

Answer 12

Blood flows through the lamellae in one direction and water flows over them in the opposite direction.
This means that the water with a high oxygen concentration always flows next to blood with a low concentration of oxygen.
This means that a steep concentration gradient it maintained between water and the blood so as much oxygen as possible diffuses into the blood.

Question 13

Explain gas exchange in plants

Answer 13

The main gas exchange surface is the surface of the mesophyll cells in the leaf.
Gases move in and out through pores in the epidermis called stomata. The stomata can open to allow exchange of gases and close if the plant is losing too much water.
Guard cells control the opening and closing of stomata.

Question 14

Explain gas exchange in insects

Answer 14

Insects have air filled spaces called trachea which are used for gas exchange.
Air moves into the trachea through pores on the surface called spiracles.
Oxygen travels down the concentration gradient towards the cells.
The trachea branch off into trachioles which have thin permeable walls and go to individual cells.
This means that oxygen diffuses directly into respiring cells - the insects circulatory system doesn’t transport O2.
Carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere.
Insects use rhythmic abdominal movements to move air in and out of the spiracles.

Question 15

How do insects control water loss?

Answer 15

If they are losing too much water, they close spiracles using muscles.
They have a waterproof, waxy cuticle all over their body and tiny hairs around their spiracles, both of which reduce evaporation

Question 16

How are plants adapted for controlling water loss ?

Answer 16

Water enters the guard cells, making them turgid, which opens the stomatal pore. If the plant gets dehydrated, the guard cells lose water and become flaccid which close the pore.

Question 17

Some plants are adapted to live in warm, dry or windy habitats where water loss is a problem.

These are called xerophytes

Explain adaptations these have

Answer 17

• Stomata sunk in pits to trap water vapour, reducing the conc gradient of water between the leaf and the air. This reduces evaporation of water
• A layer of ‘hairs’ on the epidermis to trap water vapour round the stomata.
• Curled leaved with the stomata inside, protecting them from wind
• Reduced number of stomata so there are fewer places for water to escape
• Thicker waxy waterproof cuticles on leaves and stems to reduce evaporation

Question 18

Explain the human gas exchange system

Answer 18

Air enters the trachea.
The trachea splits off into two brochi.
Each bronchus the branches off into smaller tubes called bronchioles.
The bronchioles end in small air sacs called alveoli.
This is where gases are exchanged.
The ribcage, intercostal muscles and diaphragm all work together to move air in and out.

Question 19

Explain inspiration

Answer 19

External intercostal muscles and diaphragm contract.
This causes the ribcage to move up and out and the diaphragm flattens, increasing the volume of the thoracic cavity.
As the volume increase, the lung pressure decreases.
Air will flow down the trachea and into the lungs
Active process so requires energy

Question 20

Explain expiration

Answer 20

External intercostal and diaphragm relax.
The ribcage moves downwards and inwards, the diaphragm curves upwards again.
The volume of the thoracic cavity decreases causing air to be forced down the pressure gradient and out of the lungs.

Normal expiration is a passive process
Expiration can be forced

During forced expiration, external intercostal muscles relax and internal intercostal muscles contract pulling the ribcage further down and in.
During this the movement of the two sets of intercostal muscles is said to be antagonistic (opposing)

Question 21

Lungs contain millions of air sacs where gas exchange occurs - called ________

These are surrounded by a network of _____________

Answer 21

alveoli

capillaries

Question 22

Explain the structure of alveoli

Answer 22

Wall of each alveolus is made from a single layer of thin flat cells called alveolar epithelium.
The walls of the capillaries are made from capillary endothelium.
The walls contain a protein called elastin.
Elastin is elastic and helps the alveoli to recoil to the normal shape after inhaling and exhaling air.

Question 23

Air containing oxygen moved down the trachea, bronchi and bronchioles into the alveoli. The movement happens down a _______ gradient.

Oxygen moves into the blood where it can be transported around the body - this movement happens down a _______ gradient.

Answer 23

pressure

concentration

Question 24

Describe gas exchange in alveoli

Answer 24

Oxygen diffuses out of the alveoli, across the alveolar epithelium and the capillary endothelium , into haemoglobin in the blood

Carbon dioxide diffuses into the alveoli from the blood.

Question 25

Factors affecting the rate of diffusion:

Answer 25

• Thin exchange surface - one cell thick so short diffusion pathway
• Large surface area - there are millions of alveoli meaning a large surface area for gas exchange

There is a steep concentration gradient of oxygen and carbon dioxide between the alveoli and capillaries, increasing the rate of diffusion. This is constantly maintained by the flow of blood and ventilation.

Question 26

Define tidal volume

Answer 26

volume of air in each breath

Question 27

Define ventilation rate

Answer 27

number of breaths per minute

Question 28

Define forced expiratory volume

Answer 28

maximum volume of air that can be breathed out in 1 second

Question 29

Define forced vital capacity

Answer 29

maximum volume of air it is possible to breathe forcefully out of the lungs after a deep breath in

Question 30

Explain how tuberculosis effects lung function

Answer 30

Tubercles form from bacteria. The infected tissue within the tubercles dies and the gaseous exchange surface is damaged so tidal volume is decreased.

A reduced tidal volume means less air can be inhaled. Increased breathing rate.

Question 31

Explain how fibrosis effects lung function

Answer 31

Scar tissue in lungs. Scar tissue is thicker and less elastic so lungs are less able to expand so cant hold as much air as normal. Tidal volume is reduced and so is FVC.

Reduction of rate of gaseous exchange so sufferers have a faster ventilation rate to get enough oxygen.

Question 32

Explain how asthma effects lung function

Answer 32

Airways become inflamed and irritated.

Smooth muscle lining the bronchioles contracts and a large amount of mucus is produced. This causes constriction of the airways. Air flow in the lungs is severely reduced so less oxygen enters. Reduced FEV

Question 33

Explain how emphysema effects lung function

Answer 33

Caused by smoking or long time exposure to air pollution. Causing inflammation which attracts phagocytes. Phagocytes break down elastin. This is elastic and helps alveoli to return to normal shape. Loss of elastin means alveoli cant expel air as well. Rate of gaseous exchange is reduced.

Question 34

One effect of lung diseases means that ___ ______ is released and sufferers often feel tired and weak

Answer 34

less energy

Question 35

How are carbohydrates digested?

Answer 35

Amylase is the digestive enzyme used.

It catalyses hydrolysis reactions that break the glycosidic bonds.

It is produced in the salivary glands and in the pancreas which releases amylase into small intestines.

Question 36

What are membrane bound disaccharides?

Answer 36

Enzymes that are attached to the cell membranes of epithelial cells lining the ileum. They help to break down disaccharides into monosaccharides involving hydrolysis of glycosidic bonds.

The monosaccharides can be transported across the epithelial cell membranes in the ileum via specific transporter proteins

Question 37

What are the disaccharidases and monosaccharides for each disaccharide?

-sucrose
-maltose
-lactose

Answer 37

sucrase = glucose + fructose

maltase = glucose + glucose

lactase = glucose + galactose

Question 38

How are lipids digested?

Answer 38

Lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids . This involves the hydrolysis of the ester bonds.
Enzymes mainly made in the pancreas and are secreted into the small intestine where the act.

Question 39

Explain how bile salts work

Answer 39

Bile salts are produced in the liver and emulsify lipids. Several small lipid droplets have a bigger surface area than a single large droplet. So the formation of small droplets greatly increases the surface area of lipid that lipases to work on.

Once the lipid has been broken down by lipase, the monoglycerides and fatty acids sick with bile salts to form micelles. These help the products of lipid digestion to be absorbed.

Question 40

How are proteins digested ?

Answer 40

Broken down by a combination of different peptidases. Catalyse the conversion of proteins into amino acids by hydrolysing the peptide bond.

Endopeptidases
Hydrolyse the peptide bond within a protein.

Exopeptidases
Hydrolyse peptide bonds at the end of protein molecules. They remove single amino acids from proteins.

Dipepidases
Exopeptidases that work specifically on dipeptides. Separate two amino acids that make up a dipeptide by hydrolysing a peptide bond.

Question 41

How are monosaccharides absorbed?

Answer 41

Glucose is absorbed by active transports with sodium ions via a co transporter protein. Galactose is absorbed in the same way. Fructose is absorbed by facilitated diffusion through a transporter protein.

Question 42

How are monoglycerides and fatty acids absorbed?

Answer 42

Micelles help to move monoglycerides and fatty acids towards the epithelium. Because micelles constantly break up and reform they can release the products allowing them to be absorbed - whole micelles are not taken across the epithelium.

Monoglycerides and fatty acids are lipid soluble so can diffuse directly across the epithelial cell membrane.

Question 43

How are amino acids absorbed?

Answer 43

Via co transport
Sodium ions are actively transporting out of the epithelial cells into the blood creating a conc gradient. Sodium ions can then diffuse from the lumen of the ileum into the epithelial cells through transport proteins carrying the amino acids with them.

Question 44

Why is haemoglobin so important?

Answer 44

Role is to carry oxygen around the body

Question 45

What is haemoglobin and oxyhaemoglobin?

Answer 45

Haemoglobin is a large protein with a quaternary structure. 4 polypeptide chains. Each chain has a haem group which contains an iron ion and gives it the red colour. Each can carry 4 oxygen molecules.

When oxygen joins to Hb in the lungs it forms oxyhaemoglobin. This is a reversible reaction

Hb + 4O2 yields HbO8

Question 46

What is oxygen association?

Answer 46

oxygen molecule joining to haemoglobin

Question 47

What is oxygen dissociation?

Answer 47

When oxygen leaves oxyhaemoglobin

Question 48

Affinity for oxygen?

Answer 48

Tendency for a molecule to bind with oxygen

Question 49

As pO2 (partial pressure of oxygen) increases, haemoglobins affinity for oxygen also increases as:

Answer 49

O2 loads onto haemoglobin to form oxyhaemoglobin where theres a high pO2

Oxyhaemoglobin unloads oxygen at a lower pO2.

Alveoli have high pO2 so oxygen loads

Respiring tissue have low pO2 so oxygen is unloaded.

Question 50

Haemoglobin gives up oxygen more readily in a higher pCO2

How does this effect the curve

Answer 50

When cells respire they produce CO2 which raises pCO2. Increasing unloading and therefore shifting curve to the right

Question 51

How does haemoglobin differ for organisms in low oxygen environments?

Answer 51

Higher affinity for oxygen than humans.
There isn’t much oxygen available so loading needs to be very good

Question 52

How does haemoglobin differ for organisms with high activity levels?

Answer 52

High oxygen demand have haemoglobin with a lower affinity for oxygen than humans. Need oxygen to be easily unloaded .

Question 53

How does haemoglobin differ for organisms with size?

Answer 53

High SA:V for small mammals so lose heat quickly so high metabolic rate - high oxygen demand so lower affinity so it can easily unload to meet high demands.

Question 54

MAKE FLASHCARDS ON CIRCULATORY AND ARTERIES ETC

Question 55

Explain what tissue fluid is and how it moves

Answer 55

Fluid that surrounds cells in tissues made from oxygen water and nutrients.

The hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid. The difference in pressure means an overall outward pressure forces fluid out of capillaries and into spaces surrounding cells, forming tissue fluid. As fluid leaves the hydrostatic pressure reduces in the capillaries.

Due to fluid loss, some water may reenters the capillaries from tissue fluid by osmosis. Any excess tissue fluid is drained into the lymphatic system.

Question 56

FLASHCARDS ON HEART

Question 57

What is cardiovascular disease?

Answer 57

General term to describe diseases associated with the heart and blood vessels

Coronary artery disease is an example

Question 58

How is an atheroma formed?

Answer 58

If the endothelium gets damaged, wbc and lipids accumulate to form layers. Over time this builds up and hardens to for a plaque called an atheroma.

This partially blocks the lumen restricting blood flow, causing blood pressure to increase.

Question 59

How does an aneurysm occur?

Answer 59

Atheroma damages and weakens the artery. When the blood travels through at a higher pressure it may push the inner layers of the artery out to form an aneurysm . Balloon like and can burst causing a haemorrhage.

Question 60

How does thrombosis occur?

Answer 60

Formation of a blood clot. Atheroma plaque ruptures the endothelium leaving a rough surface. Platelets and fibrin accumulate at the site to form a blood clot. Can cause complete lockage of the artery

Question 61

How does a heart attack occur?

Answer 61

If the coronary artery becomes blocked, an area of the heart will be cut off from blood supply so no oxygen causing a heart attack.

Can cause damage or death of the heart muscle.

Question 62

What are some risk factors for cardiovascular disease?

Answer 62

High BP
Increase risk to artery walls so increased likelihood of atheroma formation

High blood cholesterol and poor diet
Cholesterol is one of the main components that form an atheroma which can lead to increased blood pressure and blood clots

Smoking
Carbon monoxide and nicotine increase risk of cardiovascular disease and heart attack.
CO combines with haemoglobin to inhibit oxygen from binding

Question 63

What is the xylem?

Answer 63

Tissue which transports water and mineral ions in solution. These move up the plant from the roots to the leaves.

Question 64

What is the phloem?

Answer 64

Tissue which transports organic substances like sugars both up and down the plant.

Question 65

Describe structure of the xylem

Answer 65

Long tube like structures formed from dead cells joined end to end. There are no end walls on these cells making it uninterrupted so water can pass through easily.

Question 66

How does cohesion and tension work in moving water up a plant?

Answer 66

1. Water evaporates from the leaves at the top of the xylem. This is called transpiration
2. This creates tension which pulls more water into the leaf
3. Water molecules are cohesive so when some are pulled up other follow
4. Water then enters the stem through the roots

Question 67

What is transpiration?

Answer 67

Evaporation of water from a plants surface. When the stomata open it moves out of the leaf down the water potential gradient .

Question 68

Factors affecting transpiration rate ?

Answer 68

Light intensity - Increased light = increased transpiration rate as stomata open when light to allow CO2 to enter for photosynthesis.

Temperature = Higher temp = faster transpiration rate as the molecules have more energy so evaporate from cells faster

Humidity= Lower humidity = faster transpiration rate as if the air is dry around plant the water potential gradient is increased

Wind = More wind = faster transpiration rate as air movement blows away water molecules from stomata

Question 69

Describe structure of phloem

Answer 69

Formed from cells in tubes but have sieve tube elements and companion cells

Sieve tube = living cells that form the tube for transporting solutes they have no nucleus and few organelles so

Companion cells = carry out living functions for sieve cells

Question 70

What is translocation?

Answer 70

Movement of solutes in a plant. Solutes are sometimes called assimilates. Requires energy to occur. Moves solutes from source to sink
Source = where they are produced
Sink = where they are used up
Enzymes maintain a conc gradient from source to sink by changing solutes at the sink. This makes sure there is always a lower conc in the sink.

Question 71

What is the mass flow hypothesis?

Answer 71

1. Source
   Active transport is used to actively load the solutes from companion cells to sieve tubes. This lowers the water potential inside the sieve tubes so water enters the tubes by osmosis from the xylem and companion cells. This creates a high pressure inside the sieve tubes and at the source end of the phloem.
2. Sink
   Solutes are removed from the phloem. This increases water potential inside the sieve tubes so water leaves the tubes by osmosis lowering pressure inside the sieve tubes
3. Flow
   The result is a pressure gradient from the source end to the sink end. This gradient pushes solutes towards the sink. When they reach the sink the solutes will be used.