Topic 3

Question 1

Why might mitochondria be found closer to the cell surface membrane in larger cells

Answer 1

Larger cells have smaller SA:Vol ratio

Diffusion pathway is longer

Question 2

What is the advantage for larger animals having a specialised system that facilitates oxygen uptake

Answer 2

Larger organisms have smaller SA:Vol ratio

Faster diffusion

Question 3

Mammals such as a mouse and a horse are able to maintain a constant body temperature.

Use knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse.

Answer 3

Mouse has larger SA:Vol ratio

More heat loss

Faster rate of metabolism releases heat

Question 4

Relationship between size and surface area to volume ratio of organisms

Answer 4

As size increases, surface area to volume ratio decreases

Question 5

Why is oxygen uptake a measure of metabolic rate

Answer 5

Oxygen used in respiration WHICH is a metabolic process

Question 6

Features of the alveolar epithelium that makes the epithelium wall adapted as a surface for gas exchange

Answer 6

Single layer of cells
Reduces diffusion distance

Permeable
Allows diffusion of oxygen

Question 7

How does the counter current principle allow efficient oxygen uptake

Answer 7

Blood and water flow in opposite directions

Maintains diffusion gradient of oxygen

Concentration gradient maintained along length of lamella

Question 8

How is pressure generated inside phloem

Answer 8

Sucrose actively transported into phloem

Lowering water potential

Water moves into phloem by osmosis

Question 9

Why is phloem pressure reduced during hottest part of the day

Answer 9

High rate of transpiration

Water lost through stomata

Causes less water movement from xylem to phloem

Question 10

Describe and explain the mechanism that causes the lungs to fill with air

Answer 10

Diaphragm contracts AND external intercostal muscles contract

Causes pressure decrease

Air moves down a pressure gradient

Question 11

How could the death of alveolar epithelium cells reduce gas exchange

Answer 11

Reduced surface area

Increased distance for diffusion

Reduced rate of gas exchange

Question 12

Why do plants grown in soil with very little water grow only slowly

Answer 12

Stomata close

Less carbon dioxide for less photosynthesis

Question 13

Pathway taken by an oxygen molecule from an alveolus to the blood

Answer 13

Across alveolar epithelium

Across capillary endothelium

Question 14

Ways which the structure of fish gills is adapted for efficient gas exhange

Answer 14

Many lamellae SO large surface area

Thin surface SO short diffusion distance pathway

Question 15

Evaluate the statement

‘It is dangerous to smoke when a child is in the car. Higher levels of deadly toxins can build up, even on short journeys, and children breathe faster than adults, meaning they inhale more of the deadly toxins.’

Answer 15

For:
Significantly higher concentrations of CO with closed window

Any increase in CO could be dangerous

Higher levels after 5 minutes

Against:
Don’t know if concentration of CO is deadly

No significant difference with open window as SD overlaps

No data on child breathing rates

Question 16

Describe the gross human gas exchange system and how we breathe in and out

Answer 16

Trachea, Bronchi, Bronchioles, Alveoli

Breathing in - Diaphragm contracts and external intercostal muscles contract

Ribcage is pulled outwards

Causes volume increase and pressure decrease in thoracic cavity

Air moves down pressure gradient

Breathing out - Diaphragm relaxes and internal intercostal muscles contract

Ribcage moves down

Causes volume decrease and pressure increase in thoracic cavity

Question 17

Ways which the insects tracheal system is adapted for gas exchange

Answer 17

Tracheoles have thin walls SO short diffusion distance to cells

Highly branched SO large surface area

Body can be moved to move air SO maintains concentration gradient for oxygen

Tracheae provides tubes full of air SO fast diffusion

Question 18

Pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs

Answer 18

Renal vein

Vena cava to right atrium

Right ventricle to pulmonary artery

Question 19

Explain how water from tissue fluid is returned to the circulatory system

Answer 19

Plasma proteins remain in blood

Decreases water potential

Water enters blood by osmosis

Water re-enters the lymphatic system

Question 20

Effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin

Answer 20

Increasing carbon dioxide concentration leads to higher acidity

Lower affinity for oxygen meaning that the rate of dissociation would increase

Question 21

Role of micelles in the absorption of fats into the cells lining the ileum

Answer 21

Micelles contain bile salts and fatty acids

Makes fatty acids more soluble in water

Which allows it to diffuse across the membrane

Question 22

How does the structure of the insect gas exchange system provide cells with sufficient oxygen

Answer 22

Tracheoles are highly branched - Large surface area

Tracheoles are thin - Short diffusion distance

Spiracles can open - Allow more air in

Question 23

How does the structure of the insect gas exchange system limit water loss

Answer 23

Waterproof exoskeleton - Reduces evaporation

Spiracles can close - Prevent water vapor from escaping by evaporation

Question 24

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels

Answer 24

Micelles contain bile salts and fatty acids

Make fatty acids soluble in water

Fatty acids absorbed by diffusion

Triglycerides reformed in cells

Vesicles move to cell membrane

Question 25

Function of ATP hydrolase

Answer 25

Releases energy Energy allows ions to be moved against a concentration gradient

Question 26

How does the movement of sodium out the cell allow the absorption of glucose into the cell lining the ileum

Answer 26

Maintains a concentration gradient for sodium from ileum into the cell Sodium moving in by co transport, brings glucose with it

Question 27

Role of micelles in the absorption of fats into cells lining the ileum

Answer 27

Micelles include bile salts and fatty acids Make the fatty acids more soluble in water Carry fatty acids to cell Maintain high concentration of fatty acids to cell Fatty acids absorbed by diffusion

Question 28

Role of enzymes in the digestion of proteins in a mammal

Answer 28

Hydrolysis of peptide bonds Endopeptidase - Act in middle of polypeptide Exopeptidase - Act at end of polypeptide Dipeptidase - Acts between 2 amino acids

Question 29

How can animals eating their own caecal droppings help digestion of dietary protein

Answer 29

Undigested protein breaks down More amino acids absorbed As protein passes again through stomach

Question 30

Advantages of lipid droplet and micelle formation

Answer 30

Droplets increase surface area So faster hydrolysis of lipids Micelles carry fatty acids and glycerol to epithelial cell

Question 31

How is golgi apparatus involved in lipid absorption

Answer 31

Modifies triglycerides Combines triglycerides with proteins Packaged for release

Question 32

Explain how cells lining the ileum of mammals absorb glucose by co-transport with sodium ions

Answer 32

Sodium ions actively transported from ileum cell to blood Maintains diffusion gradient for sodium to enter cells from gut Glucose enters by facilitated diffusion with sodium ions

Question 33

Features of vein

Answer 33

Wide lumen Thin wall

Question 34

Features of artery

Answer 34

Small lumen Thick wall

Question 35

Precautions to take when dissecting blood vessels

Answer 35

Carry sharp instruments by holding handle Disinfect instruments Disinfect hands Put organs in a seperate bag to dispose

Question 36

How can an arteriole reduce blood flow into capillaries

Answer 36

Muscle contracts Narrows lumen

Question 37

Heart muscle activity between ventricles and arteries during diastole

Answer 37

Ventricle muscles relaxed No blood backflow into ventricles

Question 38

Heart muscle activity between ventricles and atria

Answer 38

Atria muscle contracted Blood movement from atria into ventricles

Question 39

Advantage of the bohr effect during intense exercise

Answer 39

Increases dissociation of oxygen For aerobic respiration at the muscles

Question 40

How can an increase in red blood cells cause a heart attack

Answer 40

Blood begins to thicken Thickened blood slows blood flow

Question 41

Effect of increasing carbon dioxide concentration of oxyhaemoglobin dissociation

Answer 41

Increases oxygen dissociation By increasing blood acidity

Question 42

How can a dissociation curve shifted to the left be adapted for intense exercise

Answer 42

Higher affinity for Oxygen Delays anaerobic respiration

Question 43

Safety precautions when dissecting a heart

Answer 43

Use sharp scalpel Wash hands Disinfect bench Cover any cuts Safe disposal

Question 44

How does atrioventricular valve maintain unidirectional flow of blood

Answer 44

Pressure in atrium is higher than in ventricle CAUSING valve to open Pressure in ventricle is higher than in atrium CAUSING valve to close

Question 45

Blood vessels which carry blood to heart muscle

Answer 45

Coronary arteries

Question 46

How does binding of one oxygen molecule make it easier for second oxygen molecule to bind

Answer 46

Binding of first oxygen changes tertiary structure of haemoglobin Creates another binding site

Question 47

Role of the heart in the formation of tissue fluid

Answer 47

Contraction of ventricles produces high blood pressure Forces water out of blood capillaries

Question 48

How could a blockage in the lymphatic system lead to side effects

Answer 48

Excess tissue fluid builds up

Question 49

How does a change in the shape of haemoglobin result in S shaped dissociation curve

Answer 49

First oxygen binds causing change in shape Shape change allows more O2 to bind easily

Question 50

Why is a dissociation curve shifted to the left beneficial

Answer 50

Lower affinity for O2 at low partial pressures Easier unloading of O2 for respiration

Question 51

Measurements to take when calculating rate of water movement

Answer 51

Time taken Initial and final mass Number of xylem vessels

Question 52

How does water move up the stalks

Answer 52

Water is transpired Lowers water potential Cohesion maintains column

Question 53

Cohesion tension theory of water transport in the xylem

Answer 53

Water lost from leaf because of evaporation of water Lowers water potential of leaf cells Water pulled up xylem Water molecules cohere Forming continuous water column Adhesion of water to walls of xylem

Question 54

Mass flow hypothesis of translocation in plants

Answer 54

In leaf sugars actively transported into phloem By companion cells Lowers water potential of sieve cell and water enters by osmosis Increase in pressure causes mass movement Sugars used for respiration for storage