6.Exchange

Question 1

What is tissue fluid

Answer 1

The environment around the cells of multicellular organisms

Question 2

What common things are interchanged between organism and its environment?

Answer 2

Respiratory gases
Nutrients
Excretory products
Heat

Question 3

For exchange to be effective what must exchange surfaces be?

Answer 3

Large compared to volume

Question 4

How do you work out ratio of surface area to volume?

Answer 4

Surface area➗volume

Question 5

What are features of specialised exchange surfaces

Answer 5

• large SA relative to volume which increases rate of exchange
• very thin short diffusion distance rapid diffusion
• selectively permeable to allow selected materials across
• movement of environmental median to maintain diffusion grad
• transport system for internal median to maintain diffusion grad

Question 6

Gas exchange in single called organisms

Answer 6

Small
Large surface to volume
Oxygen absorbed by diffusion across body surface
Carbon dioxide diffuses out across body surface

Question 7

What are spiracles

Answer 7

Tiny pores on body surface
Gases enter and leave through
When open water vapour can evaporate

Question 8

What is the exchange system in insects made of

Answer 8

Internal network of trachea-supported by strengthened rings to prevent collapsing
Tracheoles-branch off trachea, extended through out bodytissue, gas brought directly to respiring tissues

Question 9

In insects what does the diffusion gradient do

Answer 9

• When respiring cells use up oxygen, creates diffusion grad, draws gaseous oxygen from atmosphere along trachea and tracheoles
• carbon dioxide is created so creates diff grad in opposite direction

Question 10

What is mass transports role in respiration of insects

Answer 10

Interaction of muscles in insects squeezes trachea, enabinling mass movements of air in n out
Speeds up exchange

Question 11

What is the function of end of tracheoles being filled worth water

Answer 11

During periods of major activity, muscle cells carry out anaerobic
Produces lactate, it’s soluble and lowers w.p of cells
Water moves into cells by osmosis
Water in tracheoles decreases in volume so further draws air in
Final diffusion is in gas phase which is more rapid than in liquid

Question 12

Structure of gills

Answer 12

• Gill bar
• Branching of gill bar are Gill filaments
• At right angle to filament are gill lamellae
• Flow of water over gills is opposite to flow of blood within them (countercurrent flow)

Question 13

What’s the countercurrent exchange principle

Answer 13

• Opposite flow direction of blood and water
• Blood is well loaded with oxygen when meets water, meets water with max conc of oxygen so diffusion of oxygen from water to blood occurs
• blood with little oxygen meets water with little oxygen left, diffusion oxygen from water to blood occurs
• diffusion grad maintained whole width of gill lamellae

Question 14

Structure of plant gas exchange

Answer 14

Stomata-allow gaseous diffusion
Interconnecting air spaces-allowgases readily contact with mesophyll cells
Large surface area of mesophyll cells-rapid diffusion

Question 15

How is water loss limited in insects

Answer 15

• Small surface are to volume ratio-minimise area over which water is lost
• waterproofing coverings-rigid outer skin eg chitin that’s cover d with waxy cuticle
• spiracles-can be closed to reduce water loss

Question 16

What are xerophytes

Answer 16

Plants adapted to living in areas where water is in short supply

Question 17

What adaptations do xerophytes have

Answer 17

• Thick cuticle-thicker the waxy cuticle the less water loss
• Rolling up of leaves-protects lower epidermis, region gets saturated with water vapour, no w.p gradient no water loss
• hairy leaves-thick layer traps still moist air, water potential between inside and outside cell reduced less water loss
• stomata in pits of grooves-trap still moist air
• reduces SA to volume-smaller SA slower diffusion

Question 18

Why is the volume of oxygen absorbed and volume of carbon dioxide removed so large in mammals?

Answer 18

• large organisms with large volume of living cells

- maintain high body temperature which is related to high metabolic and respiratory rates

Question 19

What features make up the respiratory system in mammals

Answer 19

Rib cage
Lungs
Trachea
Bronchi 
Bronchioles
Alveoli

Question 20

What is the structure and function of the lungs

Answer 20

Pair of lobed structures
Made up of highly branched tubules (bronchioles)
End up as tiny air sacs called alveoli

Question 21

What is the structure and function of the trachea

Answer 21

• Flexible airway supported by rings of cartilage
• Cartilage prevents collapsing as pressure inside falls when breathing in
• tracheal walls made of muscle, lined with ciliates epithelium and goblet cells

Question 22

What is the structure and function of the bronchi

Answer 22

Two divisions of trachea
Lead to lung
Similar in structure to trachea produce mucus to trap dirt and use cilia to move trapped particles towards throat
Amount of cartilage reduced as bronchi get smaller

Question 23

What is the structure and function of bronchioles

Answer 23

• Series of branching subdivisions of bronchi
• Walls made of muscle lined with epithelial cells
• Muscle allows them to construct so can control flow of air in n out of alveoli

Question 24

What is the structure and function of the alveoli

Answer 24

• minute air sacs at end of bronchioles
• between alveoli is collagen and elastic fibres
• lined with epithelium
• Elastic fibres allow the alveoli to stretch and spring back during breathing
• gas exchange surface

Question 25

What is inspiration

Answer 25

When air pressure of atmosphere is greater than air pressure inside of the lungs, so air is forced in

Question 26

What’s expiration

Answer 26

When air pressure is greater inside of lungs than the air pressure of atmosphere, air is forced out of lungs

Question 27

What’s the process of inspiration

Answer 27

1-external intercostal muscles contract, while the internal intercostal muscles relax 2-ribs pulled upwards and outwards increasing volume of thorax 3-diaphragm muscles contract, it flattens,further increases thorax volume 4-increased volume results in reduction of pressure in lungs 5-atmospheric pressure greater,air forced in

Question 28

What’s the process of expiration

Answer 28

1-internal intercostal muscles contract, external intercostal muscles relax 2-ribs move downwards and inwards, decreasing volume of thorax 3-diaphragm muscles relax causing it to dome, pushed up by contents of abdomen, volume of throws further decreased 4-decreased volume means pressure increased in lungs 5-greater pressure in lungs than atmosphere so air forced out lungs

Question 29

Why is diffusion across alveoli rapid

Answer 29

- one cell thick wall for short diffusion pathway - large capillary network, narrow capillaries so red blood cells flattened against wall reduces diffusion pathway - red blood cells slowed as pass through pulmonary cappliaries allowing more time for diffusion - breathing movements constantly ventilate lungs, heart constantly circulates blood around alveoli so steep con grad maintained

Question 30

What are the major parts of the digestive system

Answer 30

``` Oesophagus Stomach Ileum Large intestine Rectum Salivary glands Pancreas ```

Question 31

What’s the role of the stomach

Answer 31

Muscular sac with an inner layer that produces enzymes Role is to store and digest food eg protein Has glands that produce enzymes which digest protein

Question 32

What’s the role of ileum

Answer 32

- Long muscular tube - Food further digested by enzymes produced by its walls and by glands that our secretions into it - inner walls of ileum are folded into villi =large SA - microvilli further increases SA - adapts for the absorption of products of digestion into bloodstream

Question 33

What’s the role of large intestine

Answer 33

Absorbs water | Most of water absorbed is water from the secretions of many of the digestive glands

Question 34

What’s the role of the rectum

Answer 34

Faeces are stored befor periodically being removed via the anus in process called egestion

Question 35

What’s the role of salivary glands

Answer 35

Situated near mouth Pass their secretion via a duct into mouth Contain amylase which hydrolyse starch into maltose

Question 36

What’s the role of pancreas

Answer 36

Large gland situated below stomach Produces pancreatic juice Secretion contains proteases, lipase, and amylase

Question 37

What is the physical breakdown in digestion

Answer 37

Large molecules broken down into smaller molecules by teeth Creates larger SA for chemical disgestion Food is churned by stomach walls which further breaks it down

Question 38

What is chemical digestion

Answer 38

Hydrolyse large insolubk molecules into smaller soluble ones Carried out by enzymes 3 main types of enzyme Carbohydrases-carbs into monosaccharides Lipases-lipids into glycerol and fatty acids Proteases-proteins into amino acids

Question 39

What is the process of carb digestion in humanse

Answer 39

1-saliva in mouth, from salivary glands, mixed with food in chewing 2-salivary amylase, hydrolyse starch into maltose, mineral salts maintain pH around neutral 3-food swallowed, enter stomach, acid denatures amylase 4-moves into small intestine, pancreatic juices from pancreas mix with food 5-pancreatic amylase hydrolyse remaining starch, alkaline salts neutralise acidic conditions from stomach 6-muscles in intestine walls push food along ileum, Maltase is membrane bound enzyme turning maltose to a-glucose

Question 40

What are the other two common disaccharides in the diet that are hydrolysed

Answer 40

Sucrose - sucrase hydrolysed it onto glucose and fructose Lactose - lactase hydrolysed it into glucose galactose

Question 41

What happens in lipid digestion

Answer 41

- Lipases produced by pancreas and hydrolyse Ester bond in triglycerides - firstly emulsification occurs to form micelles increases surface area so action of lipases speed up

Question 42

What’s the process of protein digestion

Answer 42

3 types of peptidases 1-endopeptidases hydrolyse peptide bonds in central region forming series of peptide molecules 2-exopeptidases hydrolyse peptide bonds on terminal amino acids forming dipeptides and single amino acids 3-dipeptidases hydrolyse dipeptides into amino acids (membrane bound in ileum)

Question 43

Describe structure of ileum

Answer 43

``` Folded Finger like projections- villi Microvilli Thin walls lined with epithelial cells Rich network of blood capillaries Situated at intersurface between lumen and blood and other tissues ```

Question 44

How does the ileum and villi increase the efficiency of absorption

Answer 44

- Villi increase SA for diffusion - Thin walled reducing diffusion pathway - Contain muscle so can move, movement mixes contents of ileum so new material replaces material that’s been absorbed - well supplied with blood vessels, Carry about absorbed molecules main diff grad - microvilli increase SA

Question 45

How are amino acids and monosaccharides absorbed

Answer 45

Diffusion and co transport

Question 46

Absorption of triglycerides

Answer 46

- When micelles come into contact with epithelial cells on ileum they break down releasing monoglycerides and fatty acids - non polar so diffuse across cell surface memabrne into epithelial - transported to endoplasmic reticulum and recombined to triglycerides - continue to Golgi, associated with cholesterol and lipoproteins forming chylomicrons, specialised for transport of lipids - exocytosis out of epithelial cells enter lymphatic capillaries called lacteals, then pass into blood system - triglycerides in chylomicrons hydrolysed by enzyme in endothelial cells and diffuse into cells