Diet and nutrition

Human blood contains red blood cells and white blood cells. Different situations can cause changes in the numbers of these blood cells. The table shows some of these changes.

Explain why poor diet can cause a change in the number of red blood cells.

Suggest why athletes often live at high altitude before competing in a long distance race.

Explain how the change in the number of white blood cells during therapy for cancer could be a risk to the patient.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow. Omega-3 Excess lipids (fats and oils) in the human diet can increase the risk of health problems such as obesity, heart disease and strokes. However, a balanced diet needs to contain fats and oils because they are needed in the human body for many important functions. Scientists have recently discovered that a type of fatty acid contained in oils can also benefit human health. The fatty acids that provide benefits to human health are called omega-3 fatty acids. A diet rich in these fatty acids is thought to lower blood pressure and reduce the risk of heart disease. Fish oils are known to contain high levels of omega-3 fatty acids. Fish farmers know that the fish they produce are of more value to the consumer if they contain oils rich in omega-3. As a result, about 80% of the fish oil produced globally from the oceans is used as food in fish farms. Small fish called anchovies live in our oceans. They eat microscopic plants called plankton that contain high levels of omega-3. As the anchovies grow, they also contain high levels of omega-3 in their oil. Fishing boats catch billions of these small fish, that are then ground up to be fed to bigger fish such as salmon, on fish farms. Fish farms consume vast quantities of anchovies. The increase in the number of fish farms is one reason why wild fish stocks of anchovies are declining. It takes about 5 kg of anchovies to produce 1 kg of farmed salmon. The high cost of this source of fish oil has encouraged fish farmers to use less, so the fish they produce contain lower levels of omega-3 in their oil, which is not good for human health. Recently, scientists have discovered another way to obtain high levels of omega-3 to feed to fish on fish farms. The scientists genetically modified a plant called Camelina to produce seeds containing omega-3 fatty acids. This discovery will enable these seeds to be fed to salmon in fish farms and could reduce overfishing of the oceans.

Suggest how excess lipids (fats and oils) increase the risk of heart disease (lines 1 and 2).

Fats and oils are large, insoluble molecules needed in a balanced diet (lines 2 and 3). Give the names of two small, soluble molecules needed in a balanced diet.

State a function of lipid in the human body.

Fatty acids are one component of a lipid molecule. Name another component.

Use the information in the passage to draw a food chain that includes anchovies (lines 13 to 17).

Suggest why wild fish stocks are declining.

Explain why 5 kg of anchovies only produce 1 kg of farmed salmon (line 20).

The genetic modification of Camelina plants involves the use of enzymes and a vector (lines 24 and 25).

Explain how enzymes are used in genetic modification.

Describe the role of a named vector in genetic modification.

The fungus Fusarium venenatum is grown in a fermenter to make a food product called mycoprotein.

Name the molecule that a fungus uses to store carbohydrate.

Name the thread-like structures that make up the mycelium of a fungus.

Mycoprotein contains low levels of fats and is high in protein. Suggest the benefits of each of these to a human diet.

Food production can be increased by using genetically modified plants that are resistant to disease. Explain how enzymes can be used to genetically modify plants.

A student wants to make yoghurt. The diagram shows what she did.

Which two stages help to improve the production of yoghurt by killing bacteria that compete with Lactobacillus ?

Explain why the milk needed to be cooled to 45 °C in stage 3.

Explain what could happen to the production of yoghurt if the jars used in stage 5 had not been sterilised in stage 2.

Explain what would happen to the production of yoghurt if the water cooled below 35 °C in stage 6.

The student added fruit to her yoghurt to improve the taste. Suggest how adding fruit to yoghurt also helps to maintain healthy skin.

A teacher set up an experiment to investigate the factors required for seed germination. He set up four test tubes containing cotton wool and cress seeds as shown in the diagram.

layer of oil

tube A tube B tube C tube D

He placed tubes A, B and C in an incubator at 20°C and tube D in a fridge at 4°C. He left the tubes for four days then returned to look at them. He asked his students to produce a table to show the factor being tested and whether the seeds germinated.

Complete the table to show the factor being tested and whether the seeds are likely to germinate.

Suggest how the students could see if germination had taken place.

Name two other variables the teacher should control in his experiment.

Other seeds such as beans or peas contain larger food stores.

Suggest a food molecule that seeds could use as a food store.

Explain why it is important for seeds to have a food store.

Describe an experiment you could carry out to determine the energy content of a seed.

A calorimeter is a piece of apparatus used to calculate the energy content of a food sample. The diagram shows a calorimeter.

Food is placed in the dish and burnt in air with high levels of oxygen. The temperature rise of the water is measured using the thermometer. The energy content of the food is measured in joules per gram of food.

The oxygen gas inlet allows the food to burn in air with high levels of oxygen. Suggest why this gives a more accurate value of the energy content than burning food in normal air.

Suggest why the calorimeter has an insulated outer container.

Table 1 shows the mass of fat in five different types of food. The mass is measured in grams of fat per 100 grams of each food.

A student measures the energy content of the five different foods. Table 2 shows her results.

The student wrote three conclusions in her notebook.

• I think that the energy in food is all contained in fat. • The more fat in food the more energy the food contains. My results are reliable because I did not get an anomaly.

The student is wrong to believe that ‘the energy in food is all contained in fat’. Name two other large insoluble molecules in food that contain energy.

1_........ 2_........

Explain whether the student’s results support her conclusion that food with more fat contains more energy.

The student states that her results are reliable because she did not get an anomaly. What is meant by the term anomaly ?

(a) The diagram shows a piece of apparatus called a calorimeter.

The calorimeter is used to investigate the energy content of one gram of glucose. The glucose burns in the calorimeter and the energy released heats the water.

Suggest why oxygen gas is passed into the calorimeter.

Suggest why the waste gas pipe is coiled.

Suggest why stirring the water will improve the data collected.

The calorimeter contains 200 g of water. The graph shows the rise in temperature of the water in the calorimeter during the investigation.

Use the graph to find out the increase in the temperature of the water during the investigation.

Use the formula to calculate the energy content of the 1 g of glucose.

In mammals, males have two different sex chromosomes (X and Y) and females have two similar sex chromosomes (X and X). However, in birds males have two similar sex chromosomes (Z and Z), while females have two different sex chromosomes (Z and W).

Complete the genetic diagram to show how sex is inherited in birds.

Genotype of male parent Genotype of female parent

Gametes from male parent Gametes from female parent

Genotypes of offspring

Sex of offspring

In birds, the egg is extremely large and contains food molecules that the growing embryo needs in order to develop.

Suggest one food molecule that is present in a bird’s egg and describe the role of this molecule in the growth of the bird embryo.

Suggest an advantage of the shell of the egg being made of a hard substance.

Chicken eggs are a rich source of vitamin A. Give another source of vitamin A and describe the function of vitamin A in humans.

The number of chromosomes in eggs and in sperm is less than the number of chromosomes in the body cells of animals. Explain how the number of chromosomes in animals is maintained in their offspring.

Describe an investigation to find out the most suitable amount of calcium ions needed to get the best growth in rats.

The diagram shows the label on a packet of a new kind of food for people who want to lose weight.

The food is a powder which is added to water to make a liquid drink. The label on the packet claims that the food provides a complete balanced diet.

What is meant by the term balanced diet ?

A pregnant woman decides that this food does not provide her with a complete balanced diet. Use the information on the packet to give two reasons why the pregnant woman may be right.