2023 past paper bio

Define a tissue

A group of cells with a similar function

Name the type of tissue in plants that contains stem cells

Meristem

Which plant does aspirin originate from?

Willow

The scientists usually extract chemical A from the berries of the deadly nightshade plant. Suggest one reason why berries are used instead of leaves or roots.

The berries are easy to access/pick.

Suggest one reason why the leaves of the deadly nightshade plant have chlorosis.

Lack of chlorophyll

It is important for drugs to be tested in clinical trials before the drugs are approved for use by the public. Give two reasons why

To check dosage and efficacy (also allow toxicity)

How can scientists be sure that claims about new drugs are valid?

Have the claims peer reviewed

Suggest one reason why a report making claims about the effects of chemical A may be biased.

Companies may get financial gain

A group of cells called the pacemaker controls the resting heart rate. Where in the heart is the pacemaker found?

Right atrium

Describe two ways that the structure of an artery is different from the structure of a vein.

Artery has a thicker muscle tissue. Artery was a narrower lumen.

Explain the effect of a partly blocked coronary artery on the human body. [6 marks]

• reduced blood flow to heart

• therefore less oxygen and glucose to heart

• less aerobic respiration in cells (so more anaerobic respiration)

• less energy produced

• slower flow in blood

• results in tiredness

• anaerobic respiration causes lactic acid

• build up of lactic acid causes muscle fatigue and pain

There are different treatments for a blockage in a coronary artery. Explain how one treatment for a blockage in a coronary artery works.

Insert stents to open up coronary artery

How do Salmonella bacteria in food cause the symptoms of vomiting and diarrhoea?

Bacteria produces toxins

Explain how:

• the immune systems of animals respond to a vaccination

• the immune response in farm animals prevents an outbreak of food poisoning in humans. (4)

• animals white blood cells produced antibodies that are specific to Salmonella antigens

• If infected, specific antibodies are produced quickly, killing Salmonella

• so fewer/no pathogens in animal products

• Therefore fewer pathogens consumed by humans, so fewer toxins produced in humans.

Describe two aseptic techniques the scientists should have used in the investigation. (petri-dish practical)

• disinfect hands/work surface

• sterilise the culture

The scientists incubated the bacteria at 37 °C. Students in school laboratories incubate bacteria at 25 °C. Explain why scientists use 37 °C but students must use 25 °C to incubate bacteria

• 37C is human body temperature

• Salmonella grows best at 37C

• 25C prevents growth of bacteria that are harmful to students

What is the purpose of the paper disc with no antibiotic? (petri dish practical)

acts as a control/allows for comparison

Antibiotics treat food poisoning because they kill Salmonella bacteria inside the human body. Some antibiotics work because they damage the bacterial cell wall. The bacteria die because the cells burst. Explain why the cells burst

• Water enters the bacterial cell by osmosis

• Damaged cell wall cannot withstand the pressure of water

During vigorous exercise, anaerobic respiration occurs in a person’s body. Explain two effects of anaerobic respiration on the person’s body.

• muscle fatigue due to production of lactic acid

• heavy/fast breathing to produce oxygen to break down the lactic acid

Design an investigation to show the effect of different types of exercise on the heart rate of athletes. [6 marks]

• test a group of athletes, using at least 2 intensities of exercise

• record heart rate for each athlete before and after exercise

• compare mean increase of heart rate in the 2 types of exercise

• control: same biological sex, same age, same length of time for exercise, always return to rest before starting the next exercise.

Explain how taking anabolic steroids could improve an athlete’s performance

Athlete is faster/stronger so more/stronger muscle contractions.

Describe how scientists make monoclonal antibodies using the cell created when a mouse lymphocyte and a tumour cell combine.

• cell is cloned

• all the cells make the same antibody

• the antibody is collected and purified

What property makes a monoclonal antibody useful in detecting the presence of an anabolic steroid in urine?

a monoclonal antibody only binds to the anabolic steroid

What term describes an organism that passes a pathogen from one person to another person?

vector

The malarial protist is a eukaryotic cell. Describe three ways the structure of the malarial protist is different from the structure of a prokaryotic cell. Do not refer to size in your answer.

• protist has a mitochrondria

• protist has a nucleus

• protist does not have plasmids/cell wall

Explain why the bursting of red blood cells causes tiredness.

• less oxygen carried in blood

• less energy released in respiration

give three differences between sexual reproduction and asexual reproduction.

sexual: (say opposite for asexual)

• slower

• mixing of genetic material

• more energy required

One drug for treating malaria prevents mitosis occurring in the malarial protist. The drug stops the synthesis of new DNA bases in the cell. Suggest how the drug prevents mitosis occurring.

DNA replication cannot occur

Describe the process of cell division by mitosis.

• after DNA replication

• one set of chromosomes is pulled to each side of the cell

• nucleus divides

• cytoplasm divides to form two cellsd