Biology P1

2025 mocks

Differences between asexual and sexual reproduction

Sexual - gametes involved, mitosis AND meiosis, 2 haploid (23 chromosomes) turn into 23 pairs of 46 chromosomes in a zygote

Asexual - no gametes involved, genetically identical clones, mitosis ONLY, one parent needed

Describe the process of breathing in

1. Diaphragm contracts and flattens, moving down during inspiration

2. External intercostal muscles contract and rib moves outwards/up

3. Thorax increases in volume

4. Pressure in chest decreases

5. Air moves from high to low pressure in pressure gradient

Dangers of smoking

Nicotine - narrows blood vessels and increases heart rate, increased blood pressure: can lead to blood clots in arteries and heart attacks

Carbon monoxide - Binds irreversibly to haemoglobin, reducing capacity of blood to carry oxygen. Strain on breathing system, breathing frequency and depth increases. Circulatory system needs to pump blood faster, raising blood pressure and risk of CHD

Tar - Carcinogen can cause cancer and contributes to COPD; bronchitis and emphysema

Why do cells which carry out active transport and movement need many mitochondria?

Active transport/movement requires energy

Energy is released through aerobic respiration

Mitochondria is the site of aerobic respiration

Describe the role of enzymes in the breakdown of starch to glucose

Amylase (produced in salivary gland and pancreas) digest starch to maltose

Maltase (small intestine, ileum) converts maltose to glucose

Describe and explain progesterone in menstrual cycle

Progesterone builds up in the second half of the menstrual cycle

Helps maintain uterus lining

So the embryo can implant into the uterine lining

Describe and explain the adaptations of the placenta

Large surface area (many villi) to maximize exchange of gases

Dense capillary network for steep concentration gradient

Short distance between baby and mother’s blood so shorter diffusion distance

Function of placenta

Exchanges substances between mother and foetus:

CO2, urea, oxygen, nutrients

What effect does temperature have on movement of particles in diffusion/osmosis?

The particles move more quickly

Because they have more kinetic energy

Diffusion occurs faster

Why may a sporty person need more glucose than an fatty?

They need more energy for muscle contraction

More glucose is needed for more energy through respiration

Why would a plant kept in the dark be unlikely to be tested positive for starch?

Plant can’t photosynthesise in the dark, so it can’t produce glucose

As glucose is needed for respiration, it uses its starch stores and converts into glucose

Roots absorb mineral ions by active transport. Why do root cells require a source of oxygen?

Active transport needs more energy

Which is released through respiration

Aerobic respiration requires oxygen

How does the blood respond to pathogens?

Phagocytes engulf and digest pathogens (non specific)

Lymphocytes produce antibodies

Antibodies are specific to a pathogen

Antibodies attach to pathogens and cause them to burst

Immunity and vaccinations

Memory cells are produced in response to a foreign antigen.

They remain in the body and remember a specific antigen.

They can reproduce very fast again if it enters again

Vaccines have dead or inactive pathogens to trigger an immune response.

Describe the process of seed formation

1. Pollen grain lands on stigma

2. Pollen tube grows out of pollen grain and down through style to ovary and ovule

3. Nucleus from male gamete moves down the tube and fuses with female gamete in ocule

4. Each fertilised female gamete forms a seed.

The ovary develops into a fruit around the seed

The ovule develops into a seed coat

Explain the response of increasing light in the pupils

Pupil constricts to limit light

Circular muscles contract

Radial muscles relax

Less light enters the eye

Prevents retina damage

Why may an increase in wind lead to increased water loss in a plant?

Water molecules are moved away from the leaf more quickly

Increases the concentration gradient

More transpiration

More water loss

Why is the presence of glucose and protein not expected in healthy urine?

In a healthy person there should be no glucose after proximal convoluted tubule

If there is then it’s because blood glucose levels are higher than normal (e.g diabetes)

If proteins are present it could be due to high blood pressure, which causes damage to the glomerulus and protein molecules are squeezed out of the glomerulus into Bowman’s

It cannot be reabsorbed, so it ends up in urine.

How can a change in pH affect enzyme activity?

At a pH above or below optimum pH, enzyme may start to denature

Therefore, shape of the active site changes

Substrate is no longer complementary to active site, and cannot bind

Compare DNA and mRNA

DNA is double stranded, RNA is single stranded

DNA has T, RNA has U

DNA is a helix, RNA is not a helix

DNA has deoxyribose, RNA has ribose

Describe the process of protein synthesis

Transcription makes mRNA

mRNA leaves the nucleus and enters ribosome in cytoplasm

tRNA brings specific amino acids by binding anticodon to a codon on mRNA

Amino acids join together in polypeptide, joined by peptide bonds