igcse-edexcel-biology-4bi1-May-22-P2R-QP

Question 1

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Human kidney disease

Human kidney disease can be caused by infection, high blood pressure, high blood cholesterol levels or diabetes. There is no cure for kidney disease, but suitable treatment can reduce the symptoms and stop the disease getting worse.

The treatments include lifestyle and dietary changes to help you remain as healthy as possible. Medicine is also used to control associated problems such as high blood pressure and high cholesterol levels. Other treatments need to be used for severe kidney disease when the kidneys stop working. These are dialysis and kidney transplants.

Dialysis carries out the excretory function of the kidney. There are two types of dialysis that are commonly used, haemodialysis and peritoneal dialysis. Haemodialysis involves diverting blood into an external machine, where it is filtered before being returned to the body. Peritoneal dialysis (PD) involves pumping dialysis fluid into a space inside your abdomen. Haemodialysis is usually done about three times a week, either at hospital or at home. PD is normally done at home, several times a day or overnight. If the patient does not have a kidney transplant, treatment with dialysis will usually need to continue for life.

PD became an alternative to haemodialysis a few years ago. Many patients prefer the independence PD lets them have. In PD, a soft tube called a catheter is used to fill the abdomen with a dialysis solution. The composition of the dialysis solution is water, glucose, and mineral ions at the same concentration that occurs naturally in the blood. The dialysis solution is prepared according to the individual patient’s needs to
help regulate their ion balance and remove metabolic waste products.

Inside the abdominal cavity is a natural membrane lining called the peritoneum. This membrane is partially permeable. The waste products and extra fluid and salts pass from the blood through the peritoneum into the dialysis solution. They then leave the body when the dialysis solution is drained. This used solution is thrown away.

The process of draining and filling is called an exchange and takes about 30 to 40 minutes. The period that the dialysis solution is in your abdomen is called the dwell time. A typical schedule is four exchanges a day, each separated by a dwell time of four hours.

One form of PD, continuous ambulatory peritoneal dialysis (CAPD), does not require a machine and it is possible to walk around with the dialysis solution in your abdomen. Another form of PD, automated peritoneal dialysis (APD), requires a machine to fill and drain your abdomen. Three to five exchanges are performed during the night while you sleep. The whole process lasts a total of nine hours each night.

(a) Give one way that a person can change their diet to lower their risk of developing high cholesterol (lines 4 to 6).

(b) One function of the kidney is excretion (line 9). Another function is osmoregulation.
Explain what is meant by the term osmoregulation.

(d) The peritoneum acts as a partially permeable membrane.
(i) Explain what is meant by a partially permeable membrane (lines 23 to 24).

(ii) Explain why the dialysis solution must contain purified water, glucose and mineral ions (lines 19 to 21).

(e) Explain how the composition of the dialysis solution results in the waste products being removed from the blood (lines 21 to 22).

(f) (i) A person is using APD.
Calculate the percentage of their time used for treatment in a week (lines 33 to 35).

percentage = …………………………………………………….. %

(ii) Suggest why people may prefer to use CAPD instead of haemodialysis (lines 31 to 32).

(g) Describe how the structures in a human kidney result in the correct substances being retained in the blood.

▶️Answer/Explanation

1(a) An answer that makes reference to one of the following points:

balanced diet / eq (1)
less lipid / fat / oil / eq (1)
less foods that contain cholesterol eg eat fewer eggs that contain cholesterol /eq (1)

1(b) An answer that includes :

maintains water level/ water of body / body fluids /plasma / blood / cells / eq (1)
maintains salt and water levels / salt and water balance / concentration / water potential in body / body fluids / blood/ plasma cells / eq (2)

1(c) An explanation that makes reference to two of the following points:

(body produces) urea / salt / toxins / water / metabolic waste / eq
need to be excreted / removed / prevent build up / prevent poisoning / become toxic eq (1)
kidneys cannot recover / no cure / incurable / (until) transplant /eq (1)

1(d)(i) An explanation that makes reference to the following points:

(only) lets / allows some molecules / substances / water pass through (stops others) eq (1)
does not let large ones / charged ones / pass through / eq (1)

1(d)(ii) An explanation that makes reference to two of the following points:

so that substances do not leave blood / so they can return to blood / eq (1)
by diffusion / down concentration gradient / eq (1)
as cells require water for water balance / ions for water balance / water for metabolic reactions / eq (1)
glucose for respiration /energy / allow named mineral ion for correct function / (1)

1(e) An explanation that makes reference to two of the following points:

lower concentration of / no urea / salts / waste products in dialysis fluid (1)
by diffusion / (from blood / into solution) (1)

1(f)(i)

9 ÷ 24 = 0.375 or 63÷168

0.375 × 100 = 38 %

37.5 or 38 % (2)

1(f)(ii)

you can walk around / can be done at home / when travelling / does not require machine/ eq (1)

1(g) A description that makes reference to three of the following points:

proteins / large molecules can’t leave glomerulus / can’t go into Bowman’s capsule /eq (1)
reabsorption of glucose /amino acids / glucose absorbed (back) into blood eq (1)
by proximal convoluted tubule / eq (1)
water reabsorbed from collecting duct / eq (1)

Question 2

A student uses this method to measure the energy value of a sample of bread.
• measure the mass of a sample of bread
• put 20cm³ of water in a boiling tube

• place a thermometer in the boiling tube and record the initial temperature of the water
• place the sample of bread on a mounted needle
• light the bread sample in a Bunsen flame
• quickly move the burning bread sample and place it directly under the boiling tube
• if the bread stops burning, relight the bread in the Bunsen flame
• place it back under the boiling tube
• repeat until the bread does not burn
• record the final temperature of the water in the boiling tube

The student repeats the experiment 3 times.

The table shows some of the student’s results.

(a) To calculate the energy released from the burning bread the student uses this formula.
energy (in J) = mass of water (in g) × 4.2 × increase in temperature (in °C)
They then calculate the energy in joules released by 1g of bread.
(i) Calculate the increase in water temperature for the third sample of bread.

temperature increase = …………………………………………………….. °C
(ii) Calculate the energy released in joules by the third sample of bread.
[1cm³ of water has a mass of 1g]

energy released = …………………………………………………….. J
(iii) Calculate the energy released in joules by 1g of bread for the third sample of bread.
energy released by 1g = …………………………………………………….. J

(b) The energy value given on the packaging of the bread is 10400J for 1g of bread.
Comment on why the student’s method gives a different value.

(c) Give two ways that the student could modify this apparatus to achieve an answer
nearer to the energy value given on the packaging of the bread.

▶️Answer/Explanation

2 (a) (i) Clip table with (i) (ii) and (iii) increase in temperature 15 (1)

(ii) Clip table with (i) (ii) and (iii) energy released 20 × 4.2 × 15 1260 (J) (1)

(iii) Clip table with (i) (ii) and (iii) energy released by 1 g 1260 ÷ 0.20 = 6300 (J) (1)

2(b) An answer that makes reference to five of the following points:

student value much lower / eq (1)
not all energy released from food (1)
not burnt in oxygen / not completely combusted (1)
energy / heat not all transferred to tube / some energy / heat lost ( to atmosphere )/ eq (1)
energy lost / heat to atmosphere when moving food / flame (1) energy lost as light / eq (1)
flame / affected by draught / eq (1)
water not evenly heated/ not stirred / eq (1)
only repeated 3 times / eq (1)
different / distances from tube / distance not fixed / eq (1)
variation in results / parallax error / eq (1)

2(c) An answer that makes reference to two of the following points

fix position of food / clamp needle (1)
use stirrer/ stir contents / eq (1)
use heat shield / eq (1)
use lid / eq (1)
insulate tube / eq (1)

Question 3

The diagram shows a cell found in the lining of the human small intestine .

(a) (i) Which of the labelled structures is a microvillus?

A
B
C
D

(ii) Which of the labelled structures produces ATP?
A
B
C
D

(b) These cells form the lining of the small intestine.
Explain how the structure of the small intestine is adapted for absorption.

▶️Answer/Explanation

3(a)(i)

The only correct answer is C as they are the microvilli

A is not correct as it is not the microvilli
B is not correct as it is not the microvilli
D is not correct as it is not the microvilli

3(a)(ii)

The only correct answer is B as this is a mitochondrion

A is not correct as it is not a mitochondrion
B is not correct as it is not a mitochondrion
D is not correct as it is not a mitochondrion

3(b) An answer that makes reference to four of the following points:

folded / long to increase surface area / (1)
contains many villi to increase surface area (1)
contains microvilli to increase surface area (1)
contains lacteal to absorb lipid / eq (1)
contains capillaries to absorb glucose /amino acids / minerals /eq (1)
capillaries / blood flow maintain diffusion /concentration gradient / eq (1)
thin wall/ one cell thick for fast diffusion/short diffusion distance / eq (1)

3(c) A description that makes reference to three following points:

oxygen to foetus from mother / eq (1)
digested food / nutrients /amino acids / glucose /fatty acids to foetus from mother / eq (1)
removes waste (products) /urea / carbon dioxide from foetus to mother / eq (1)
provides antibodies for baby / foetus /eq (1)
produces hormones /progesterone / eq (1)

Question 4

4 Sewage pollution affects the distribution of organisms in a river.
Scientists measured the oxygen level, the number of bacteria, the number of mayfly nymphs and the number of tubifex worms in the river.
The mayfly nymph is an immature form of an insect and the tubifex is a small worm usually growing to a length of about 10cm.

The scientists recorded how these measurements changed at different distances from the sewage outlet.

(a) Comment on the changes in the measurements as the distance from the sewage outlet increases.
You should use information from the graphs and your own knowledge in your answer.

(b) Scientists often use information about the organisms present in a habitat as an indication of the level of pollution and as a measure of biodiversity.
(i) Explain what is meant by the term biodiversity.

(ii) Suggest how the number of mayfly nymphs and the number of tubifex worms can be used to indicate the level of pollution.

▶️Answer/Explanation

4(a) An answer that makes reference to five of the following points:

oxygen decreases / eq (1)
bacteria increase as present in sewage (1)
bacteria feed on nutrients / sewage (1)
mayfly numbers drop (1)
bacteria use oxygen for respiration / mayfly larvae need oxygen for respiration / eq (1)
tubifex numbers increase as use nutrients from / feed on sewage / eq (1)
tubifex can survive in low oxygen / eq (1)
then bacteria decrease / eq (1)
(so) oxygen increases (1)
mayfly increase / tubifex decrease / eq (1)

4(b)(i) An explanation that makes reference to two of the following points

variation shown by organisms in an ecosystem (1)
number of / how many (different) species (1)
number / abundance / how many of each species / eq (1)

4(b)(ii)

An answer that makes reference to the following points

mayfly (only) found in oxygen rich /unpolluted water /no / few mayfly in polluted / eq (1)
tubifex (can be) found oxygen deprived / polluted water / no /few tubifex in unpolluted / eq (1)

Question 5

(a) The table gives some information about different hormones.

Complete the table by giving the missing information.

(b) Give three differences between hormones and neurotransmitters.

▶️Answer/Explanation

5(a)

5(b) An answer that makes reference to three of the following points

hormone produced in endocrine cells / glands / eq (1)
carried in blood stream / plasma /eq (1)
all around body / affects many target cells / eq (1)
long term effect / response / eq (1)

Question 6

Scientists can now produce farm animals by cloning. Since Dolly the sheep was born in 1996 many different species have been cloned.
The form of cloning used is called somatic cell cloning.
The first ever clone of a champion racehorse was announced in 2005 in Italy.
The foal was cloned from Pieraz, a world champion in long-distance horse races.
(a) Describe the stages scientists could use to clone a male horse.

(b) Pieraz was castrated (had his testicles removed) at a young age.
Explain why this stopped him reproducing normally but did not stop him being used to produce a foal by cloning.

(d) State one difference between cloning an organism and genetically modifying an organism.

▶️Answer/Explanation

6(a) A description that makes reference to four of the following points:

nucleus from (body) cell of male horse (1)
insert this (nucleus) into enucleated egg cell / empty egg cell / eq (1)
electric shock / electricity (1)
mitosis / cell division / cell divides /eq (1)
embryo into uterus / womb (1)
surrogate mother (1)

6(b)

An explanation that makes reference to three of the following points

no sperm / gametes produced / eq (1)
no fertilisation / cannot impregnate female / eq (1)
but in cloning all chromosome / genes / DNA / nucleus comes from body cells (diploid male) / cloning uses body cell /eq (1)

6(c)

An answer that makes reference to one of the following points

to keep value of male / sire /eq (1)
prevent inbreeding /maintain genetic diversity /maintain genetic variation /prevent genetic disease /disorder / eq
limit number of offspring from each sire / stallion / eq (1)
to prevent fraud / confirm paternity / eq / (1)
ethical issues use of embryo / eq (1)
many attempts needed to get successful clone / eq (1)
idea of unfairness/ unequal competition / cheating / eq (1)

6(d)

An answer that makes reference to the following

clones are genetically identical / have same genotype / eq (1)

Question 7

A student uses this method to investigate the water loss from leaves.

• select 4 leaves of equal size from the same species of plant

• wrap thin wire around the leaf stalk of each leaf and use the remaining wire to produce a hook

• cover the upper surface on leaf 1 with petroleum jelly

• cover the lower surface on leaf 2 with petroleum jelly

• cover the upper surface and the lower surface on leaf 3 with petroleum jelly

• do not cover leaf 4 with petroleum jelly

• record the mass of each leaf

• attach the leaves, by their wire hooks, at intervals along a horizontal string

• remove the leaves from the string after 3 hours

• record the new mass of each leaf

(a) (i) Which of these is the independent variable in this experiment?
A leaf size
B leaf surface covered
C mass lost
D time
(ii) State why leaves of the same species were selected.

(b) The table shows some of the student’s results.

(i) Calculate the percentage change in mass for leaf 3.

(ii) Explain the differences in water loss from the four leaves in the student’s experiment.

▶️Answer/Explanation

7(a)(i)

The only correct answer is B leaf area covered

A is not correct as leaf size is not varied
C is not correct as mass lost is the dependent variable
D is not correct as time is not varied

7(a)(ii)

An answer that makes reference to the following

same density / number of stomata / different species may have different transpiration rates/ valid experiment / make it a fair test / make results accurate / comparable / eq (1)

7(b)(i)

3.1 – 3 = 0.1
(0.1 ÷3.1) ×100

3.2 % (2)

7(b)(ii) An explanation that makes reference to three of the following points:

most mass lost / water loss from leaf when no surface is covered /both exposed (1)
water lost from stomata (on leaf surfaces) / eq (1)
more mass lost / more water lost from lower surface / most water /most mass lost when lower exposed / eq (1)
lower surface has most stomata / upper has fewest / eq (1)
(upper surface) has waxy cuticle (1)

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