B2 Exam Questions
Different parts of the human digestive system help to break down molecules of fat so that they can be absorbed into the body. Describe how. To gain full marks you should refer to: • the enzyme and where the enzyme is produced • the products of digestion • any other chemicals involved. 6 marks
mechanical breakdown in mouth and stomach, lipase turns lipids into fatty acids or glycerol, produced by pancreas and small intestine, break down occurs in small intestine, bile produced by the liver neutralises the acid from the stomach so there are alkaline conditions in the small intestine which absorbs the products
Nearly every organism on earth has an even number of chromosomes in its body cells. Suggest why. 1 mark
chromosomes in pairs
chromosomes contain DNA molecules. Describe the function of DNA. 2 marks
code forming specific proteins
Use information from the diagram to explain how cell C is adapted for producing this enzyme. 2 marks
contains many ribosomes for protein synthesis
Explain how oxygen passes from the blood to part A. 3 marks
diffuses from a high to a low concentration across a cell membrane
What happens to the genetic material before the cell divides? 1 mark
doubles
The lipase in the beads does not digest the lipid coating around the capsule. Suggest why. 1 mark
enzymes only work in solution
How do fossils provide evidence that species alive today have evolved from simpler organisms? 3
fossil is remains of organism that lived a long time ago, show changes over time, also has similar features to present day species
Why is it important that the sperm cell has this number of chromosomes? 2 marks
fuses with egg cells and restores number of chromosomes to 46
A gardener wanted to produce a new variety of onion. Explain why sexual reproduction could produce a new variety of onion. 3 mark
fusion of the gametes, mixing of genetic information, one copy of chromosomes from each parent
In the 1850s, Gregor Mendel carried out breeding experiments using peas. (a) The importance of Mendel's work was not recognised until the early 1900s. Explain why. 2 marks
genes and chromosomes not discovered, other scientists not aware of work
Explain why it will not be identical to either of its parents. 2 marks
genes from two parents, alleles may be different
Explain why it will look similar to its parents. 1 mark
genes passed on from parents
What is meant by the term species? 2 marks
group of organisms that can successfully interbreed
Why is the ability of body cells to divide important? 1 mark
growth and repair
Explain why these parts of the fossill have been preserved. 2
hard parts do not decay
what is the structure of DNA
has a double helix structure
Explain how the information in the diagrams supports the theory of evolution.2 2
horses today evolved from earlier species over long period of time
It is very difficult to get red-flowering pea plants that breed true. Explain why you cannot guarantee to breed, by self-pollination, pea plants that only have red flowers. 2
if recessive of white allele present, there is a chance of a white flower
Explain why Ted did not inherit cystic fibrosis. 2
inherited dominant gene of not having cystic fibrosis from carol
Apart from protease enzymes, give one other use of a named enzyme in industry. 2 marks
isomerase used to turn glucose into fructose for slimming products
Scientists are uncertain about how life started on Earth. Explain why. 2
lack of valid and reliable evidence, early organisms soft bodied/ evidence destroyed by geological activity
The table gives some information about these two species of palm tree. Howea forsteriana Howea belmoreana Optimum pH of the soil for growth of the palm tree pH 8 pH 6 Height above sea level of most common habitat 30 to 60 metres above 120 metres Month when most palm trees flower October December Method of pollination Wind carries pollen Wind carries pollen Scientists believe that these two species of palm tree began to evolve from a single species over 2 million years ago. Suggest how these two different species developed. In your answer you should use information from the table and your own knowledge 5 marks
live at different heights and grow in soils with a different ph as genetic variation in the isolated population led to natural selection acting differently on each population which results in interbreeding no longer being possible
In industry, trypsin is used to pre-treat some baby foods. In their experiment, the students used 1- 5% trypsin at 20°C. The baby food manufacturers make most profit if they use 0.5% trypsin at 35°C. Suggest why the manufacturers make most profit with these conditions. 4 marks
lower concentration is cheaper, higher temp means a faster rate of reaction so less time to make product and extra heating cost outweighed by enzyme cost
Using a heart monitor is better than taking the pulse by hand. Why? 1 mark
more accurate
Suggest how receiving more sunlight could result in the plants producing more flowers per stalk. 2 mark
more glucose from photosynthesis so more energy for growth
The students suggested the following hypothesis: 'The difference in the modes is due to the plants receiving different amounts of sunlight.' Suggest why 2 mqrks
more light in field a, faster rate of photosynthesis
Explain how an increase in heart rate helped the student during exercise. 4 minutes
muscles respire faster, more oxygen supplied, more glucose supplied, more carbon dioxide and lactic acid removed
The lipid coating on the capsule makes sure that the enzymes are not released until the capsule reaches the small intestine. Explain how. 2 marks
no lipase produced in the stomach or mouth
What controls the rate of chemical reactions in the cytoplasm? 1 mark
nucleus/enzymes
Red blood cells contain haemoglobin. Explain how this enables red blood cells to pick up oxygen from the alveoli and release it to cells in other parts of the body. 4
oxygen diffuses, forms oxy-haemoglobin in areas of high oxygen concentration, breaks down to oxygen and haemoglobin in areas of low concentration
Why should the students place the quadrats randomly in the field? 1
to avoid bias
Explain why Mendel made the first generation of plants self-pollinate. 2
to stop cross pollination and to control the gene pool
Suggest how the students could test their hypothesis for the two habitats
use light meter to measure light intensity/ take many measurements at the same time of day
Explain why the athlete breathes at a faster rate than normal for two minutes after finishing a 100 metres race. 2 marks
there is an oxygen debt, lactic acid needs to be oxidised
The diagram shows the inheritance of cystic fibrosis in a family. The allele that produces cystic fibrosis is recessive. Explain why Alice inherited cystic fibrosis. 2 marks
2 recessive genes from both parents
How do scientists know when they lived? 1
age of rock
What is a dominant allele? 1 mark
allele expressed if only one copy of allele present
Use words from the box and your own knowledge to describe how carbohydrates are digested. (amylase, sugars, starch) 5 marks
amylase breaks down starch into sugars, amylase produced in salivary glands/small intestine/pancreas, starch is broken down in the mouth and small intestine
Oxygen is transported round the body by the blood. Blood leaving the human lung can carry about 250 milligrams of oxygen per litre. However, only 7 milligrams of oxygen will dissolve in one litre of water at body temperature. (a) Suggest an explanation for the difference. 2
blood has haemoglobin which carries blood as oxyhaemoglobin
Describe the effect trypsin, a protease enzyme, would have on the baby food. 2 marks
breaks down food and protein into amino acids making it softer
Breathing allows large amounts of oxygen to enter the blood. Explain how breathing does this. 2
brings more oxygen into lungs and keeps oxygen level high in alveoli/
Originally, there was only one species of salamander in the country. Suggest an explanation for the development of the four different species. 5
populations of salamanders becomes isolated by areas between mountains, genetic variation in isolated communities, natural selection affects isolated population differently and eventually results in interbreeding being no longer possible between populations as new species has formed
The students wanted to collect valid data. Describe how the students should have sampled the bluebell plants at each habitat to collect valid data. 2marks
randomly placing a quadrat
In terms of oxygen passing into the blood from the lungs, why is the movement of blood important? 2
removes oxygen that has diffused from the lungs and keeps difference in concentration gradient high
What happens in the mitochondria? 1 mark
respiration
The pancreas cell makes enzymes. Enzymes are proteins. Describe how the ribosomes and part A help the cell to make enzymes. 3 marks
ribosomes make proteins from amino acids and the mitochondria provides the energy for this
Suggest one cell part that you would expect to find a lot of in the cytoplasm of goblet cells. Explain your answer. 3 marks
ribosomes, protein synthesis, for production of sticky mucus
what are genes? 3
section of DNA which code for a particular combination of amino acids which make a specific protein
Why do the scientists use stem cells? 2 marks
stem cells can differentiate and can form any cell through division
Describe the structure of the leaf and the functions of the tissues in the leaf. You should use the names of the tissues in your answer. 6 marks
waxy cuticle reduces water loss, the epidermis has no chloroplasts so allows light to penetrate, the stomata and guard cells allows co2 in and o2 out, palisade mesophyll layer has many chloroplasts for photosynthesis and is near the top to receive more light, the spongy mesophyll layer has air spaces for rapid movement of gases