Extended Response (AS Only) (AQA AS Biology): Exam Questions

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.

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.

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.

Describe the production of mRNA in an animal cell.

The mRNA in part (a) 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.

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.

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.