1. Cell biology

What are eukaryotic cells?

Cells that contain a nucleus and membrane-bound organelles.

Give three examples of organisms with eukaryotic cells

Animals, plants, fungi.

What are prokaryotic cells?

Cells that do not contain a nucleus or membrane-bound organelles.

How is genetic material found in eukaryotic cells?

In a nucleus, enclosed by a membrane.

How is genetic material found in prokaryotic cells?

As a single circular strand of DNA in the cytoplasm.

How does the size of eukaryotic and prokaryotic cells compare?

Eukaryotic cells are larger than prokaryotic cells.

Explain why bacteria do not have mitochondria

They are prokaryotes and lack membrane-bound organelles.

Which five sub-cellular structures are found in most animal cells?

Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.

Which three sub-cellular structures are often found in plant and algal cells, but not animal cells?

Chloroplasts, permanent vacuole, cell wall.

What is the function of the nucleus?

Controls cell activities and contains genetic material.

What occurs in the cytoplasm?

Chemical reactions.

What is the function of the cell membrane?

Controls the movement of substances in and out of the cell.

What is the function of the mitochondria?

Site of aerobic respiration.

What is the function of the ribosomes?

Site of protein synthesis.

What is the function of the chloroplasts?

Site of photosynthesis.

What is the vacuole filled with?

Cell sap.

What is the function of the cell wall?

Provides strength and support.

What is the cell wall made from?

Cellulose.

What is meant by "specialised"?

A cell adapted to carry out a specific function.

Describe how sperm cells are specialised

Long tail for movement, many mitochondria for energy, acrosome with enzymes to penetrate egg.

Describe how nerve cells are specialised

Long axons for signal transmission, branched ends for connections, lots of mitochondria.

Describe how muscle cells are specialised

Can contract, contain lots of mitochondria, long and flexible.

Describe how root hair cells are specialised

Long extension increases surface area for water and mineral absorption.

Describe how xylem cells are specialised

Hollow, strengthened by lignin, transport water.

Describe how phloem cells are specialised

Sieve plates and companion cells, transport sugars.

Compare the specialisation of animal and plant cells

Both have specialised cells, but plants also transport water and nutrients.

What is a stem cell?

An undifferentiated cell that can become specialised.

Name three places that stem cells are found

Embryos, bone marrow, meristems in plants.

Give one type of specialised cell that can be made from adult bone marrow

Blood cells.

Give two conditions that can be treated using stem cells

Diabetes, paralysis.

What is meant by therapeutic cloning?

Using an embryo with the same DNA as the patient.

Why are stem cells from the embryo not rejected by the patient's body?

They have identical DNA to the patient.

Give two disadvantages of stem cell medicine

Ethical concerns, risk of infection.

Give two uses of plant stem cells

Cloning plants, growing rare species.

What is meant by magnification?

How much larger an image is compared to the actual object.

What is meant by resolution?

The ability to distinguish between two points.

Which formula connects image size, actual size and magnification?

Image size = actual size × magnification.

When carrying out microscopy why is it important to use a stain?

To highlight structures.

When carrying out microscopy how would you correct an image in which the structures were too small to be seen?

Increase magnification.

When carrying out microscopy how would you correct an image that was blurry?

Adjust focus.

How does a light microscope produce an image?

By passing light through the specimen.

When was the light microscope first used?

17th century.

How many lenses does a typical light microscope used in school have?

Two.

What name is given to this type of light microscope?

Compound microscope.

How do you calculate the overall magnification of a light microscope?

Eyepiece lens × objective lens.

What are the differences between light microscopes and electron microscopes?

Electron microscopes have higher magnification and resolution.

What is the maximum magnification of a light microscope?

Around ×1500.

What is the maximum resolution of a light microscope?

200 nanometres.

What is the maximum magnification of an electron microscope?

Around ×2,000,000.

What is the maximum resolution of an electron microscope?

0.2 nanometres.

What are the two types of electron microscope?

Transmission, scanning.

What is the difference between these types of electron microscope?

Transmission gives internal structure, scanning gives surface image.

What does the nucleus contain?

Chromosomes.

Which chemical are chromosomes made from?

DNA.

How does the size of a gene relate to the size of a chromosome?

A gene is a small section of a chromosome.

How many chromosomes does each cell of the human body have?

46.

How many of each type of chromosome does the human body have?

2 of each, 23 pairs.

What is the cell cycle?

The sequence of growth and division of a cell.

What name is given to the process of cell division that can take place in any cell of the body?

Mitosis.

What are the three overall stages of the cell cycle for mitosis?

Growth, DNA replication, mitosis.

Which two processes is mitosis necessary for?

Growth, repair.

Define diffusion

The movement of particles from a high to low concentration.

Describe the process of diffusion in the lungs

Oxygen diffuses from alveoli into the blood.

Give one example of diffusion that occurs in the kidneys

Urea diffuses from blood into the kidney tubules.

Name three factors that affect the rate of diffusion

Temperature, concentration gradient, surface area.

Relate the structure of the lungs to the need for rapid diffusion

Large surface area, thin walls, good blood supply.

Relate the structure of the small intestine to the need for rapid diffusion

Villi increase surface area, thin walls, good blood supply.

Relate the structure of gills to the need for rapid diffusion

Large surface area, thin layers, good blood supply.

Relate the structure of a plant's roots to the need for rapid diffusion

Root hairs increase surface area.

Describe how the structure of a single-celled organism negates the need for a transport system such as blood vessels

Large surface area to volume ratio allows diffusion.

Which formula can be used to calculate the surface area of a cube?

Area = 6 × side².

Which formula can be used to calculate the volume of a cube?

Volume = side³.

Define osmosis

The diffusion of water through a partially permeable membrane.

Describe how you would calculate the rate of water uptake by plant roots

Rate = change in mass ÷ time.

Describe what happens to plant tissue when placed in a very concentrated solution

Water leaves the cells, tissue shrinks.

Describe what happens to plant tissue when placed in a very dilute solution

Water enters the cells, tissue swells.

How would you calculate the percentage change of a piece of potato that has been placed into a solution?

% change = (final mass - initial mass) ÷ initial mass × 100.

Explain why it is important during the required practical to dry the potato cores before their mass is measured

To remove excess water and avoid errors.

Define active transport

Movement of substances against a concentration gradient using energy.

Give two features of cells undertaking active transport

Many mitochondria, carrier proteins.

Give an example of where active transport is used in the human body

Absorption of glucose in the small intestine.

Give an example of where active transport is used in plants

Absorption of mineral ions by root hair cells.

Give two examples of ions moved by active transport

Nitrate ions, phosphate ions.

State the function of nitrate and phosphate ions in plants

Nitrate for protein synthesis, phosphate for DNA and ATP.

Explain why active transport is not used when a substance will move by diffusion

Diffusion requires no energy, so it is used when possible.

By what process do bacteria divide?

Binary fission.

How rapidly can bacteria divide?

Every 20 minutes under ideal conditions.

What two things do bacteria require in order to divide this rapidly?

Nutrients, suitable temperature.

Give two ways that bacteria can be cultured

On agar plates, in nutrient broth.

Give two reasons why uncontaminated culture of microorganisms are required

To avoid harmful microbes, ensure accurate results.

Why must petri dishes and culture media be sterilised before use?

To kill unwanted microorganisms.

Why must inoculating loops used to transfer microorganisms to the media be sterilised by passing them through a flame?

To prevent contamination.

Why must the lid of the Petri dish be secured with adhesive tape and stored upside down?

Prevent contamination and condensation.

Why in school laboratories should cultures generally be incubated at 25°C?

To reduce risk of growing harmful pathogens.

Which mathematical formula can be used to calculate the area of a bacterial colony?

Area = π × radius².

What is an antiseptic?

A substance that kills or prevents the growth of microorganisms.

What is the zone of inhibition?

The clear area around an antiseptic where bacteria do not grow.

How would you introduce antiseptics to a colony of bacteria in order to determine which is the most effective?

Place soaked paper discs on the agar.

How would you identify the most effective antiseptic in this case?

Measure and compare the size of the zone of inhibition.