9700 Biology November 2025 Question Paper 13

The diagram shows a stage micrometer, with divisions 0.1 mm apart, viewed through an eyepiece containing a graticule. 10 20 30 40 50 60 70 80 90 100 The same eyepiece is now used to examine a blood smear. How many graticule divisions will cover the diameter of a lymphocyte of 10 m?

Cell structures can be isolated by centrifuging the cells in a sucrose density gradient. This breaks up the cells and separates the cell structures into fractions. The diagram shows the positions of some of these fractions in a sucrose density gradient. fraction 1: ribosomes fraction 2: lysosomes fraction 3: mitochondria fraction 4: chloroplast sucrose density gradient Which fractions contain cell structures that carry out protein synthesis?

The diagram shows a plant cell.

Which labelled organelles would contain nucleotides?

Bacterial ribosomes consist of two subunits and a total of three rRNA molecules per ribosome. An analysis of all the 70S ribosomes from a single cell of the bacterium Escherichia coli showed that there were: ● 57 000 rRNA molecules ● three types of rRNA molecule ● 19 000 copies of each type of rRNA molecule. How many 70S ribosomes were there in the E. coli cell?

Radioactively labelled amino acids are introduced into a tracheal cell that uses them to make mucus (a glycoprotein). Which route will the amino acids take? first last

Which features shown in the diagram can be present in viruses? feature DNA RNA protein coat 70S ribosomes

The diagram shows some steps in a laboratory method used to identify the presence of non-reducing sugars in a food sample. Some terms are missing. step X step Y end colour Z Which terms are correct for the expected result for a very low concentration of non-reducing sugar? X Y Z

Many biological molecules exist as polymers made up of monomer subunits. Which row correctly identifies the monomer in each of the biological molecules? collagen glycogen cellulose

Which statement correctly explains the result when the two molecules shown in the diagram react together? CH2OH H OH HO O O H2O

Which row describes amylopectin? -1,4 glycosidic bonds -1,6 glycosidic bonds shape of molecule function of molecule

What is a feature of triglyceride molecules?

An unsaturated fatty acid molecule has 17 carbon atoms in the tail which is attached to its carboxyl group. The tail contains three double bonds. How many hydrogen atoms does the tail contain?

Which statement about phospholipids in the bilayer of a cell surface membrane is correct?

Which descriptions of enzymes that use the lock-and-key hypothesis are correct? The active site is complementary to the substrate the enzyme acts on. Bonds that form in the enzyme–substrate complex change the shape of the active site. Most of the amino acids in an enzyme help to maintain the specific shape of the enzyme.

The graph shows the results of an investigation into the effect of amylase on starch at three different temperatures. concentration of reducing sugar time / minutes 50 °C 60 °C 70 °C Which statements are correct conclusions using these results? The optimum temperature is 50 °C. The initial rate of reaction is highest at 70 °C. The higher the temperature the more quickly the enzyme denatures.

The rate of enzyme-catalysed reactions in human cells is regulated. What may be involved in this regulation? a change in enzyme concentration a change in substrate concentration inhibition by the final product of the reaction

Proteins in the cell surface membranes of human cells and mouse cells were labelled with fluorescent dyes. The human cells were labelled with a red dye and the mouse cells were labelled with a green dye. A human cell and a mouse cell were then fused to form a hybrid cell. At first, the different dyes remained separate. After 40 minutes, the two dyes were evenly distributed in the hybrid cell surface membrane. What explains this observation?

Which statements about the cell surface membrane are correct? Channel proteins allow water soluble ions and molecules across the membrane. Glucose can pass into the cell via carrier proteins. Oxygen passes freely through the membrane as it is soluble in lipids. Some glycoproteins act as antigens.

The diagram shows two cylinders of agar. The agar cylinders are placed into a solution of dye at the same time. The time taken for the dye to diffuse into the centre of each cylinder is recorded. 2 cm 1 cm 5 cm 3 cm X Y Which statement explains why the dye reaches the centre of one agar cylinder faster than the other agar cylinder?

What are roles of adult stem cells in humans? repair other cells by mitosis divide to replace cells in tissues differentiate into a new organism

Which statements are correct for the mitotic cell cycle? DNA is replicated semi-conservatively during mitosis. DNA is never changed from one generation of cells to the next generation. The daughter cells at the end of a mitotic cell division have the potential to produce the same enzymes as the parent cell. The same quantity of DNA is distributed to the nuclei of two new cells at the end of a mitotic cell division.

The photomicrograph shows a stage of the cell cycle. Which stage is shown in the photomicrograph?

The diagram represents a molecule of ATP. J K L What are the components of ATP labelled J, K and L? J K L

Which statements about complementary base pairing are correct? It occurs during translation. Purines and pyrimidines are the same size. The base pairs are of equal length. Uracil forms three hydrogen bonds with adenine.

Which statement is correct for protein synthesis?

A mutation occurred in this original DNA nucleotide sequence. C T A G A A T C C T C T C C C After the mutation occurred, the new DNA nucleotide sequence coded for the amino acids Asp, Leu, Gly and Glu. The table shows the amino acids that are coded for by each DNA triplet. AAA AAG AAT AAC

The photomicrograph shows a longitudinal section of part of a plant stem. Q P R Which row correctly identifies structures P, Q and R? P Q R

Which statement about the pathway taken by a water molecule travelling from the soil to the xylem is correct?

Amino acids move from a phloem sieve tube element into a root cell. What are the changes to the water potential and the volume of liquid in the phloem sieve tube element at the sink, when this event is happening? water potential in the phloem sieve tube element volume of liquid in the phloem sieve tube element

The table shows the comparison of blood pressure in three main blood vessels during diastole. vessel 1 vessel 2 vessel 3 blood pressure in the vessel during diastole low very high high Which row identifies the three blood vessels? vessel 1 vessel 2 vessel 3

Red blood cells may contain a molecule known as 2,3-bisphosphoglycerate (2,3-BPG). When 2,3-BPG binds to haemoglobin, a higher partial pressure of oxygen is needed to bring about 50% saturation of haemoglobin with oxygen. Which statements about the effect of 2,3-BPG are correct? 2,3-BPG in red blood cells causes the oxygen dissociation curve to shift to the right. The binding of 2,3-BPG to haemoglobin reduces the Bohr effect. The binding of 2,3-BPG to haemoglobin lowers the affinity of the haemoglobin for oxygen.

A person has a small hole in the septum between the ventricles. This is called a ventricular septal defect (VSD). The person has no other heart defects. What is the direction of the net flow of blood during ventricular systole in the heart of this person?

The diagram shows a transverse section through a human bronchus. Which labelled tissue is the cartilage?

What helps to maintain a concentration gradient between blood and the air in the alveolus?

Which row correctly identifies the pathogens causing malaria and TB? malaria TB

What could be used to help prevent an outbreak of cholera in a town?

The graph shows the percentage of tuberculosis (TB) patients who were also known to be infected with HIV, from 2004 to 2011. 2004 2005 2006 2007 2008 2009 2010 2011 percentage of TB patients year region P global regions outside region P Which statement about the graph is correct?

Four different treatments were tested in a human volunteer during a year. One of these treatments was a vaccine. The treatments were injected into the volunteer and blood samples were taken after two weeks. The samples were analysed to obtain a cell count for four types of cell. The results are shown in the table. Which treatment was the vaccine? (Assume the volunteer's baseline blood cell count was the same before each treatment.) cell count / cells per cm3 monocytes neutrophils plasma cells macrophages

A bacterial pathogen produces a protein that acts as a toxin. This toxin is harmful to humans. People can be vaccinated to protect them from the effects of this pathogen. Which statement describes the sequences of events that occur in a vaccinated person to protect them from the effects of this pathogen?