Extended Response (AS & A Level) (AQA A Level Biology): Exam Questions

When food passes to the small intestine, starch molecules are broken down to maltose by pancreatic amylase. This process takes place at normal body temperature.

Explain why amylase only breaks down starch and why amylase allows this reaction to take place at normal body temperature.

Amylase is an enzyme that can break down starch into maltose. Biologists have investigated how competitive and non-competitive inhibitors affect amylase.

Describe competitive and non-competitive inhibition of enzymes.

Once amylase has broken starch down into maltose, maltase can then break maltose down into glucose. 

Describe how glucose is then absorbed so it can be used by the body.

Some white blood cells are known as phagocytes.

Describe how these cells destroy bacteria.

Contrast active and passive immunity.

Vaccines designed to protect people from Covid-19 are currently being developed by many different scientific research laboratories around the world.

Explain how vaccines can protect humans from disease-causing organisms

Starch and cellulose are both polysaccharides made up of many glucose molecules, but they have different structures and functions.

Describe and explain how the structure of starch and cellulose molecules relate to their functions.

Plants have to transport substances, such as water and sugars, along their stems. 

Describe how sugars are transported in plant stems.

The cohesion-tension theory explains how water is transported in the xylem.

Describe this theory.

Give similarities and differences between the DNA in a eukaryotic cell and the DNA in a prokaryotic cell.

Describe the production of mRNA in an animal cell.

The mRNA in part (b) can now be used to form a polypeptide via a process known as translation.

Describe how this occurs.

Compare and contrast the digestion of carbohydrates and the digestion of proteins in mammals.

Describe the digestion of lipids in mammals.

Describe the process by which the products of lipid digestion are absorbed by cells lining the ileum.

Describe the structure of cell surface membranes, including the functions of the main membrane components.

Outline the mechanisms by which substances can be transported across cell membranes.

Cells lining the ileum absorb glucose into the blood.

Describe the mechanism by which glucose is absorbed.

Describe how gas exchange occurs in plants.

Explain how the structure of the lungs enables efficient gas exchange in mammals.

Explain how haemoglobin allows oxygen to be delivered from the lungs to the respiring tissues.

Describe how the process of natural selection can lead to adaptation in a population.

Explain how organisms are classified into groups based on their evolutionary relationships.

Describe how the biodiversity of plant species in two grassland communities could be compared.

Plants produce ATP in two ways: photosynthesis and respiration. Explain why it is necessary for plants to produce ATP during respiration as well as during photosynthesis.

Describe the role of electron carrier proteins and the electron transport chain (ETC) in the light-dependent reactions of photosynthesis.

Predict whether the increase in dry mass of a plant over 15 months will be greater or less than the mass of hexose sugars produced during the same time period. Justify your answer.

Describe and explain the role of the loop of Henle in osmoregulation, specifically the absorption of water from the glomerular filtrate.

Describe and explain the role of ADH in urine production.

Some diabetic individuals do not produce insulin. Explain how an inability to produce insulin would affect the reabsorption of glucose within the kidneys.

Describe the mechanism by which a heartbeat is initiated and coordinated.

Exercise causes an elevated heart rate. Describe the role of nervous system and receptors in causing an increased heart rate.

Explain how a one-way flow of blood from the left atrium to the aorta is maintained.

Biologists were carrying out research on several small islands off the coast of Papua New Guinea. They discovered that there are over 20 species of frogs belonging to the same genus on the islands. They believe that these species evolved from two ancestral species found on mainland Papua New Guinea.

Explain how the island frog species could have evolved.

A lot of the frog species on the islands have a similar appearance. The biologists must see the frogs in close detail in order to identify what species they are.

Describe how the mark-release-recapture method could be used to estimate the number of a particular frog species on one of these islands.

The biologists were also studying the different plant species present on all the islands. One of the biologists stated that they thought succession had occurred on two of the Islands. Succession can occur naturally in ecosystems.

Describe and explain how it occurs.

DNA replication must be very accurate to ensure normal growth and development of organisms. Describe and explain how the structure of DNA results in a high level of accuracy during replication.

DNA replication is part of the process of cell replication during mitosis. Describe how chromosomes behave during mitosis and explain how two genetically identical cells are produced as a result of this.

When food passes to the small intestine, starch molecules are broken down to maltose by pancreatic amylase. This process takes place at normal body temperature.

Explain why amylase only breaks down starch and why amylase allows this reaction to take place at normal body temperature.

Once amylase has broken starch down into maltose, maltase can then break maltose down into glucose.

Describe how glucose is then absorbed so it can be used by the body.

Some white blood cells are known as phagocytes. Describe how these cells destroy bacteria.

A biologist wanted to view the cell structure of a phagocyte using a transmission electron microscope (TEM). Explain the possible limitations of using a TEM to do this.

Starch and cellulose are both polysaccharides made up of many glucose molecules.
However, they both have different structures and functions. Describe and explain how the structures of starch and cellulose molecules relate to their functions.

Amylase is an enzyme that can break down starch into maltose. Biologists have investigated how competitive and non-competitive inhibitors affect amylase.

Describe competitive and non-competitive inhibition of enzymes.

Describe the production of mRNA in an animal cell.

The mRNA in part (b) can now be used to form a polypeptide via a process known as translation.

Describe how this occurs.

Plants have to transport substances, such as water and sugars, along their stems. The cohesion-tension theory explains how water is transported in the xylem. Describe this theory.

Describe how sugars are transported in plant stems.

Cell fractionation and ultracentrifugation are techniques that can be used to isolate organelles from a suspension of cells. Describe and explain how these techniques can be used to isolate mitochondria from animal cells.

The mitochondria in part (a) contain their own DNA. Give similarities and differences (stating at least two of each) between the DNA in a eukaryotic cell and the DNA in a prokaryotic cell.

Contrast active and passive immunity.

Vaccines designed to protect people from Covid-19 are currently being developed by many different scientific research laboratories around the world.

Explain how vaccines can protect humans from disease-causing organisms.

Sodium ions and oxygen are two substances that are able to diffuse across cell-surface membranes. The diffusion of Sodium ions requires a membrane protein, whereas the diffusion of oxygen does not

Explain why.

The fact that oxygen can diffuse across cell-surface membranes allows us to respire.
Our lungs have many adaptations to ensure the fast exchange of oxygen between air in the alveoli and blood in the capillaries around them.

Describe and explain these adaptations.

The process of meiosis begins with the chromosomes condensing. Describe what happens to the chromosomes next.

Meiosis results in genetic variation in gametes. This leads to variation in the offspring formed by sexual reproduction. Explain why this variation is advantageous for a species.

Microorganisms may secrete cellulase enzymes to break down cellulose in dead plant material.

Explain why cellulase only breaks down cellulose.

Environmental scientists have investigated how competitive and non-competitive inhibitors affect cellulase activity in soil ecosystems.

Describe competitive and non-competitive inhibition of enzymes.

Mucus, produced by epithelial cells in the human gas exchange system, contains glycoproteins. One of the glycoproteins is a modified polypeptide that has the sugar lactose attached to it.

Describe how the sugar lactose is formed, and state the location within the cell where the polypeptide is attached to lactose to form a glycoprotein.

Describe the anatomy of the human gas exchange system and the mechanism of inhalation and exhalation.