Organisation

Question 1

A person has a tumour blocking the tube leading from the gall bladder to the small intestine.
Explain why this person would have difficulty digesting fat.
[5marks]

Answer 1

-Less bile reaches the small intestine
-So less emulsification of fat
-So smaller surface area for lipase to break down fat
-Ph of small intestine is not neutralized
-So lipase is not at its optimum pH to breakdown fat

Question 2

Compare the structure and function of xylem tissue and phloem tissue.
[6marks]

Answer 2

STRUCTURE:
-Xylem is made of dead cells and phloem is made of living cells
-Xylem is hollow or does not contain a cytoplasm and phloem does contain a cytoplasm
-Xylem contains lignin and phloem does not
-Both tubular
FUNCTION:
-Xylem is involved in transpiration and phloem is involved in translocation
-Xylem transports water/mineral ions and phloem transports dissolved sugars
-Xylem transports unidirectionally and phloem transports bidirectionally
-Both transport substances through the stem,leaves and roots of plants

Question 3

Amylase is an enzyme that breaks down starch.
Amylase is a polymer of smaller molecules.
Name the type of smaller molecule.
[1 marks]

Answer 3

Amino acids

Question 4

Diffusion also happens in the human lungs. Figure 3 shows the human breathing system.
Explain how the human lungs are adapted for efficient exchange of gases by diffusion.
[6 marks]

Answer 4

• Many alveoli to provide a large surface area (: volume)
• alveoli / capillary walls are thin or one cell thick or capillaries are close to the alveoli
• which provides short diffusion path (for oxygen / carbon dioxide)
• breathing (mechanism) moves air in and out or lungs are ventilated
• to bring in (fresh) oxygen
• to remove carbon dioxide
• to maintain a concentration / diffusion gradient
• large capillary network (around alveoli) or good blood supply
• to remove oxygen(ated blood) quickly
• to bring carbon dioxide to the lungs quickly
• to maintain a concentration / diffusion gradient

Question 5

Lipases break down lipids.
Which two products are formed when lipids are broken down? [2 marks]

Answer 5

-Glycerol
-Fatty acids

Question 6

Explain the ‘lock and key theory’ of enzyme action.
[3 marks]

Answer 6

-enzyme binds to the substrate because they are complementary (shapes)
-(so) substrate is broken down (into products)
-(so) products are released or enzyme is not changed and can be used again

Question 7

Cirrhosis of the liver leads to liver failure.
Describe the effects of liver failure on the human body.
[4 marks]

Answer 7

• no bile made (in the liver)
  -fats / lipids are not emulsified
  -surface area of fats / lipids not increased
  -pH of small intestine will not be alkaline/neutralised
  -enzymes (in small intestine) will not work effectively or (named) food not digested / absorbed
  -so may lose weight
• lactic acid not broken down / oxidised
  -accumulation of lactic acid in blood / body
• lactic acid is toxic or body will be poisoned
  -oxygen debt higher/prolonged
  -so muscle pain / fatigue
• proteins / amino acids will not be broken down (in liver)
  -(amino acids) not deaminated
  -amino acids not made into urea or will not form ammonia
• (however)any ammonia formed is toxic
• so accumulation of amino acids in blood / body
• liver does not break down / remove other toxins (like alcohol)
  -toxins accumulate in blood / body
  -body will be poisoned
  -so pain or jaundice or swollen liver
• glycogen stores will not be formed
• cannot control blood glucose
• so diabetes / coma may occur

Question 8

Coeliac disease is a disease of the digestive system.
It damages the lining of the small intestine when foods that contain gluten are eaten.
When people with coeliac disease eat foods that contain gluten:
1. their immune system forms antibodies to gluten
2. these antibodies attack the lining of the small intestine
3. this causes inflammation in the intestines and damages the villi.
Symptoms of coeliac disease include poor growth.
Suggest why a person with coeliac disease might have this symptom
[4 marks]

Answer 8

-Damage to the villi will decrease area for absorption of food molecules
-therefore fewer amino acids and glucose is absorbed
-and less glucose transfer of energy from respiration is reduced
-and fewer amino acids available to make new proteins

Question 9

Sometimes a valve in the heart can start to leak.
Explain why a person with a leaking heart valve has difficulty exercising.
[4 marks]

Answer 9

• backflow can occur or some blood flows backwards
• less blood leaves the heart or less blood is pumped around the body or some blood stays in the heart (instead of being pumped out) or reduced blood pressure or reduced flow rate
• less oxygen supplied to muscles / cells
• (so) less aerobic respiration
• (so) less energy released
• (so) less (efficient) muscle contraction
• anaerobic respiration takes place
• less (efficient) removal of lactic acid or lactic acid builds up or oxygen debt occurs
• (lactic acid building up) causes muscle fatigue
• less (efficient) removal of carbon dioxide (from blood)

Question 10

The pancreas produces digestive enzymes.
What is an enzyme?
[2 marks]

Answer 10

-A biological catalyst that speeds up reactions in living organisms
-reduces activation energy
-is a protein

Question 11

One symptom of pancreatic cancer is weight loss.
Explain how pancreatic cancer may cause a person to lose weight. Do not refer to hormones in your answer.
[4 marks]

Answer 11

-Pancreas tissue is damaged from cancer so there is reduced enzyme production
-food is not broken down fully

-less glucose/sugar absorbed in the bloodstream
-so less glucose available for respiration
-so more body fat used in metabolism/respiration

-Protease would not break down into amino acids so fewer amino acids to make new proteins for repair

-Lipase would not break down fully so fewer fatty acids are absorbed
-so less fat stored in the body

-chemotherapy causes loss of appetite
-so less food intake

Question 12

A monoclonal antibody has been produced to treat pancreatic cancer. Explain how the monoclonal antibody works to treat pancreatic cancer.
[3 marks]

Answer 12

-Monoclonal antibody is attached to drug/chemical/toxin

-M.A will only attach/target the antigen on the cancer cells/tumour

-so drug/chemical/toxin will bind to cancer cells and stop them from dividing uncontrollably

Question 13

Define the term double circulatory system.
[1 mark]

Answer 13

Blood is pumped to the lungs on the right side of the heart AND blood is pumped to the body on the left side of the heart

Question 14

Explain why having only one ventricle makes the circulatory system less efficient than
having two ventricles.
[2 marks]
(same answer if there is a hole in the heart)

Answer 14

-oxygenated and deoxygenated blood mixes

-so less oxygen reaches the body / tissues / cells

Question 15

Explain why an axolotl may die in water with a low concentration of oxygen. [4 marks]

Answer 15

-concentration gradient of
oxygen is less steep
-(therefore) less oxygen diffuses into blood / cells / gills
-(so) less (aerobic) respiration occurs so less energy is released / available
or
-(so more) anaerobic respiration occurs so less energy is released / available
-(so) less metabolism
or
-(so when) anaerobic respiration occurs, lactic acid is produced (and is toxic)

Question 16

Evaluate the use of mechanical replacement heart valves and biological replacement heart valves.
Use information from Table 4 and your own knowledge.
[6 marks]

Answer 16

MECHANICAL VALVES:
* longer lasting or more durable or don’t wear out as easily or
less likely to need replacing (within 6 years)
* blood clots (on the brain) are more likely (after surgery)
* patient has to take anti-clotting medication (for the rest of their
lives)
* if medication not taken (correctly), clots can lead to blood clots
on brain / heart attack
* medication can lead to excessive bleeding (after injury)
* some patients say they can hear the valves opening and
closing
* survival rate at 5 years is slightly higher for mechanical valve
* lower percentage of deaths due to heart-related problems
BIOLOGICAL VALVES:
* no additional medication required
* ethical issues surrounding use of animal tissue
* valve may harden
* more likely to need further operation or another new valve * more likely to be rejected
* more likely to need (immuno-suppressant) medication
BOTH VALVES:
* both are readily available * little wait time

Question 17

Why does our heart rate increase during exercise?

Answer 17

-Increased heart rate leads to more blood being pumped tor respiring cells
-More blood means more glucose and oxygen is produced
-so more respiration for energy for muscles
-removes waste such as carbon dioxide more quickly

Question 18

Explain how the human circulatory system is adapted to:
* supply oxygen to the tissues
* remove waste products from tissues.
[6 marks]

Answer 18

• dual / double circulatory system which means that it has higher blood pressure and a greater flow of blood to the tissues
• heart made of specialised (cardiac) muscle cells which have long protein filaments that can slide past each other to shorten the cell to bring about contraction for pumping blood
• heart pumps blood to lungs in pulmonary artery so that oxygen can diffuse into blood from air in alveoli
• blood returns to heart via pulmonary vein where muscles pump blood to the body via aorta
• oxygen carried by specialised cells / RBCs which contain haemoglobin to bind oxygen and have no nucleus so there is more space available to carry oxygen
• arteries carry oxygenated blood to tissues where capillaries deliver oxygen to cells for respiration and energy release
• thin walls allow for easy diffusion to cells
• large surface area of capillaries to maximise exchange
• waste products removed eg CO2 diffuse from cells into the
  blood plasma
• blood goes back to the heart in veins which have valves to
  prevent backflow
• cardiac output can vary according to demand / is affected by
  adrenaline

Question 19

Differences between veins and arteries

Answer 19

ARTERIES:
Carries blood away from the heart
Have a narrow lumen
Has a thick muscular wall with lots of elastic fibres Has a thick muscular layer
Does not have valves
Blood travels in pulses
Blood is under high pressure
VEINS:
Blood travels to the heart Have a wide lumen
Has a thin wall with few elastic fibre Has a thin muscular layer
Has valves
Blood travels constantly Blood under lower pressure

Question 20

How does smoking increase the risk of cardiovascular disease?

Answer 20

-Smoking damages the lining of the
arteries, including the coronary
arteries. The damage encourages the build-up of fatty material in the arteries. This can lead to a heart attack
or a stroke
-Inhalation of carbon monoxide in cigarette smoke reduces the amount of oxygen that can be carried by the blood.
-The nicotine in cigarette smoke increases the heart rate, putting strain on the heart.
-Chemicals in cigarette smoke increase the likelihood of the blood clotting
, resulting in a heart attack or stroke.

Question 21

What are the effects of smoking on babies?

Answer 21

-smoking increases the risk of miscarriage
-the babies and children are more likely to suffer from respiratory infections and an increased risk of asthma
-the long-term physical growth and intellectual development of the baby/child is affected
-there is an increased risk of birth defects
-the birthweight of the baby is reduced

Question 22

Effects of alcohol on the brain

Answer 22

-slows reaction time
-causes difficulty walking
-can impair memory
-causes slurred speech
-causes changes in sleep patterns and mood, including increased anxiety and depression

Question 23

What are the long term effects of alcohol on the brain?

Answer 23

causes brain shrinkage
leads to memory problems
leads to psychiatric problems
may result in the patient requiring long-term care

Question 24

What are the effects of alcohol on unborn babies?

Answer 24

-is smaller in size
-has a smaller brain with fewer neurones
-will have long-term learning and behavioural difficulties
-has distinct facial features

Question 25

Describe how the alveoli and vili are adapted to increase absorption
[4 marks]

Question 26

Propose the advantage of your body of having many blood capillaries surrounding the alveoli

Answer 26

The massive surface area of the capillaries surrounding your alveoli ensures that inhaled oxygen is absorbed quickly into the bloodstream and poisonous CO2 is removed from the bloodstream just as quickly.

Question 27

some lung infections cause a build of fluid in the lungs and the infected person is short of breath. propose a reason for this system

Answer 27

If there is a build-up of fluid in the lungs then it takes longer for oxygen to pass from the alveoli into the bloodstream and CO2 to pass out.

Question 28

Explain how the human circulatory system is adapted to:
-supply oxygen to the tissues
-remove waste products from tissues
(6 marks)

Answer 28

-dual / double circulatory system which means that it has higher blood pressure and a greater flow of blood to the tissues
-heart made of specialised (cardiac) muscle cells which have long protein filaments that can slide past each other to shorten the cell to bring about contraction for pumping blood
-heart pumps blood to lungs in pulmonary artery so that oxygen can diffuse into blood from air in alveoli
-blood returns to heart via pulmonary vein where muscles pump blood to the body via aorta
-oxygen carried by specialised cells / RBCs which contain haemoglobin to bind oxygen and
have no nucleus so there is more space available to carry oxygen
- arteries carry oxygenated blood to tissues where capillaries deliver oxygen to cells for
respiration and energy release
- thin walls allow for easy diffusion to cells
- large surface area of capillaries to maximise exchange
- waste products removed eg CO 2 diffuse from cells into the blood plasma
- blood goes back to the heart in veins which have valves to prevent backflow
cardiac output can vary according to demand / is affected by adrenaline

Question 29

Describe the test you would use to find out if protein is present in food.
(2 marks)

Answer 29

-Add biuret reagent to food sample
-Observe colour change from blue to purple if protein is present

Question 30

How can damaged to the small intestine and villi cause someone to have poor growth?

Answer 30

-damaged villi reduce surface area for absorption (of food molecules)
-(therefore) fewer amino acids and glucose absorbed
-with less glucose transfer of energy from respiration is reduced and fewer
-amino acids available to build new proteins

Question 31

Describe the route taken by oxygenated blood from the lungs to the body cells.
(4 marks)

Answer 31

-(blood) travels through (the) pulmonary vein
-(blood) enters left atrium
-(blood) enters (the) left ventricle
-(blood) leaves the heart via / through (the) aorta

Question 32

Explain how the villi and the alveoli are adapted to absorb molecules into the bloodstream?
(6 marks)

Answer 32

ALVEOLI:
-arranged in clusters to increase S.A to maximise the diffusion of gases
-Thin walls for a short diffusion pathway
-Capillaries surrounding the alveoli so it has a good blood supply and maintains diffusion gradient

VILLI:
-Have microvilli to create a large S.A so it maximises absorption of food molecules
-Villi have mitochondria to provide energy for active transport
-Thin walls for a short diffusion pathway
-Capillaries are close to villi to provide a good blood supply so maintains a concentration gradient

Question 33

Enzymes speeds up chemical reactions.Explain how amylase breaks down starch.
(3 marks)

Answer 33

-The enzyme amylase has an active site which has a specific complementary shape to the substrate starch
-Substrate starch fits into the active site of enzyme amylase when they bind together
-Chemical reaction takes place and bonds within starch are broken down into simple sugars

Question 34

Give uses for glucose in the body

Answer 34

-for respiration
-converted to glycogen which is stored
-converted to new carbohydrates
-converted to proteins or fat