M22 Biology Paper 1

Timezone 1 and Timezone 2, in order. Questions and markscheme.

A cell contains chloroplasts, plasma membrane and 80S ribosomes. What type of cell could it be?

A cell contains chloroplasts, plasma membrane and 80S ribosomes. What type of cell could it be?

Bryophyte

More than 90% of cellular cholesterol is located in the cell's plasma membrane. What is the main role of cholesterol in the plasma membrane of mammalian cells?

To regulate membrane fluidity

What is required for facilitated diffusion?

A concentration gradient A channel protein

Which cell component arose first during the formation of the earliest cells?

Plasma membrane

In the chimpanzee, the haploid number of chromosomes is 24. How many sister chromatids are present in the G2 phase of a somatic cell, such as a cell in the bone marrow of the chimpanzee?

96

What are linked by hydrogen bonds?

Hydrogen and oxygen in different water molecules

Which reaction occurs when a dipeptide is formed from amino acids?

Condensation

The graph shows enzyme activity plotted against temperature. What is the reason for the drop in enzyme activity above 40 degrees?

Changes to the conformation of the enzyme

A molecule of DNA is found to contain 200 guanine bases, representing 25% of the total number of bases. How many phosphate groups does this molecule of DNA contain?

800

What is the minimum number of nucleotides needed to code for a polypeptide composed of 210 amino acids?

630

This graph shows the changes in lactate measures in an athlete's blood during exercise. Which hypothesis provides the most likely explanation for the curve?

Anaerobic exercise results in high levels of lactate

The graph shows how the rate of photosynthesis of a green plant varies with CO2 concentration at two different light intensities. The temperature is kept constant at 20 degrees Celsius. What is the limiting factor of X?

Light intensity

The table shows the estimated total number of genes in several organisms. What can be deduced from the information in this table?

The number of genes does not determine evolutionary success.

Chromosome numbers vary between species. Which statement refers to humans?

An egg cell has 22 autosomes

What is produced by meiosis in a cell of a male animal?

Four gametes, each with the same number of chromosomes

Huntington's disease is an autosomal dominant genetic disease. What are the chances of two parents that are heterozygous for the gene having a child with Huntington's disease?

75%

What is a community?

A group of populations interacting with each other within a given area

The table contains information about the diet of some animals. Which pyramid of energy represents this information?

Eagles, snakes, mice, seeds

The diagram shows a simplified carbon cycle. Which processes are taking place at X and Y?

X = respiration, Y = combustion

Mammals, birds and reptiles have an embryonic tail that may disappear during development. What is the most likely explanation?

All vertebrates have a common ancestor

The graph shows the proportion of a bacterial population displaying resistance to the antibiotic tetracycline. What can be deduced from this graph?

Bacteria with beneficial adaptations survive and pass on their genes

The plant in the diagram has vascular tissue and reproduces by spores. To which phylum does the plant belong?

Filicinophyta

Data regarding the presence or absence of five traits in several different species are shown in the table. Which cladogram best represents the relationship between the five species?

QTSRP

Which process describes starch metabolism in humans?

Glucose produced by the digestion of starch can be stored as glycogen

Which structures are part of the walls of both capillaries and veins?

Cells

What is a method of transmission of HIV and its effects on the immune system?

Breastfeeding + decrease in number of active lymphocytes

A cell from the lungs, observed under a microscope, contains a large number of secretory organelles. Which conclusion can be drawn about the cell?

It is a type II pneumocyte

The image shows a neuron. What is the function of X?

Increases the speed of transmission along the axon

Leptin helps to regulate body mass in humans and mice. The image shows an obese mouse (O) and a normal mouse (N). What hypothesis could account for the differences between the mice?

Leptin binds to receptors in the hypothalamus of mouse N

What is most likely to increase in the presence of insulin?

The uptake of glucose by muscles

Cell metabolism involves anabolic and catabolic reactions. Which process directly involves anabolism?

Production of intracellular enzymes

The images of radiolarian, a single-celled marine organism, were produced using a light microscope and a scanning electron microscope. What is a reason for the difference in quality of these images?

The resolution of an electron microscope is higher

In an experiment on osmosis, red blood cells were immersed in a salt solution for two hours. The micrographs show the appearance of these cells before and after immersion in the salt solution. What explains the observed changes?

The salt solution was hypertonic and water moved into it from the red blood cells

What is the evidence against the spontaneous generation theory?

No microorganisms grew in flask F (boiled), but many grew in flask G (not boiled)

How does cisplatin prevent cancer cells from dividing?

It inhibits the replication of DNA

The micrograph of a section through a plant stem shows at least ten different types of cells. What explains the difference between these cells?

Different genes are expressed in each cell type

Which feature allows transport of glucose in blood plasma?

It's polar

Lipids are more efficient energy stores than carbohydrates. What is a reason for this?

Lipids release more energy per gram than carbohydrates

People who suffer from night blindness cannot sett well at night because their retinal cells produce an abnormal form of protein pigment. Which protein is this?

Rhodopsin

Which curve shows the concentration of a product during the course of an enzyme-catalyzed reaction?

A (steady curve)

What is a function of the enzyme helicase?

It breaks hydrogen bonds between DNA strands

The apparatus shown was used to investigate the effect of varying carbon dioxide concentration on the rate of photosynthesis. What is the dependent variable in this investigation?

Volume of oxygen produced

Which statement defines alleles?

They are various forms of a gene with slight differences in their base sequences

What can be deducted from this karyogram?

The person is male with a genetic disorder

The pedigree chart shows the inheritance of hemochromatosis, a genetic disease which causes an excessive accumulation of iron in the body. What can be deduced about this genetic disease from the pedigree chart?

It is autosomal recessive

A cloning method used for livestock involves in vitro fertilization (IVF) with selected male and female gametes. The diagram shows the steps followed after IVF. What does X represent?

An embryo

The calculated value of the chi-square test was below the critical value. What can be deduced from the results of the chi-squared test?

The distribution of one species is independent from the other

The diagram shows part of a food chain. Which forms of energy are represented by X and Y?

X = light energy Y = chemical energy

Which activity directly contributes the most to recent increases in atmospheric CO2 concentrations?

Burning of fossil fuels

What is the name of the process that was used to produce modern corn?

Selective breeding

Which encircled area shows a clade?

A (fourth box, left)

Which phyla are represented by R, S and T?

R = filicinophyta S = coniferophyta T = angiospermophyta

Which factor would favor evolution by natural selection?

Variation within a species

The graph shows the amounts of two substances present in food ingested by a healthy person as it moves along their gut. Which substances could X and Y be?

X = cellulose Y = vitamin C

Which structure sends messages to the sinoatrial node of the heart to cause changes in heart rate?

Medulla of the brain

The light microscope shows two blood vessels, an artery and a vein, in transverse section. What explains the different shapes of these blood vessels?

There are fewer elastic fibers in the walls of veins

What causes forced movement out of the lungs at T (upturn)?

Internal intercostal muscles contract Abdominal muscles contract

What is the fate of acetylcholine immediately after binding to the receptor?

It is broken down in the synaptic cleft

What is an example of negative feedback in the menstrual cycle?

High levels of estrogen inhibits FSH secretion

Which labeled structure of the male reproductive system contributes to formation of semen?

B (little pouch in back)