Cell Biology

Question 1

Name the 5 parts of an animal cell

Answer 1

Nucleus, Cytoplasm, Cell Membrane, Mitochondria, Ribosomes

Question 2

What type of cell are animal and plant cells?

Answer 2

Eukaryotic cells

Question 3

Name the 3 parts of a plant cell that are not in an animal cell

Answer 3

Rigid cell wall, Permanent vacuole, Chloroplasts

Question 4

Describe the nucleus and give its function

Answer 4

Contains genetic material that controls the activities of the cell.

Question 5

Describe the cytoplasm and give its function

Answer 5

Gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions.

Question 6

Give the function of the cell membrane

Answer 6

Holds the cell together and controls what goes in and out.

Question 7

Describe the mitochondria and give their function

Answer 7

Where most of the reactions for aerobic respiration take place.

Question 8

Give the function of ribosomes

Answer 8

Where proteins are made in the cell.

Protein synthesis?

Question 9

Describe the rigid cell wall and give its function

Answer 9

Made of cellulose. It supports the cell and strengthens it.

Question 10

Describe the permanent vacuole and give its function

Answer 10

Contains cell sap, a weak solution of sugar and salts.

Question 11

Describe the chloroplasts and give their function

Answer 11

Where photosynthesis occurs, which makes glucose (food) for the cell. They contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis.

Question 12

Name the 5 parts of a bacterial cell

Answer 12

Single circular strand of DNA (instead of a nucleus), Plasmids (small rings of DNA), Cytoplasm, Cell membrane, Cell wall

Question 13

Compare electron microscopes to light microscopes

Answer 13

Electron microscopes have a higher magnification and a higher resolution (sharper image) and therefore let us see smaller things in more detail.

Question 14

What is the equation for magnification?

Answer 14

Magnification = Image size ÷ Real size

Question 15

Define differentiation

Answer 15

The process by which a cell changes to become specialised for its job.

Question 16

Describe how a sperm cell is specialised for its function

Answer 16

It has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed. It also carries enzymes in its head to digest through the egg cell membrane.

Question 17

Describe how a nerve cell is specialised for its function

Answer 17

These cells are long (to cover more distance) and have branched connections at their ends to connect to other nerve cells to form a network throughout the body.

Question 18

Describe how a muscle cell is specialised for its function

Answer 18

These cells are long ( so that they have space to contract) and contain lots of mitochondria to generate the energy need for contraction.

Question 19

Describe how a root hair cell is specialised for its function

Answer 19

They grow into long “hairs” that stick out into the soil. This gives the plant a big surface area for absorbing water and mineral ions from the soil.

Question 20

How many chromosomes are there in a normal human cell

Answer 20

46 chromosomes (23 pairs)

Question 21

Describe the events of the cell cycle that need to occur before mitosis can begin.

Answer 21

Before it divides (by mitosis), the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes. It then duplicates its DNA, the DNA is copied and forms X-shaped chromosomes.

Question 22

Describe the stages of mitosis

Answer 22

Once the contents of DNA have been copied, a cell is ready for mitosis.
The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell. Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has divided. Lastly, the cytoplasm and cell membrane divide. The cell has now produced two daughter cells.

Question 23

Describe the stages of binary fission

Answer 23

1) The circular DNA and plasmid(s) replicate
2) The cell gets bigger and the circular DNA strands move to opposite ‘poles’ (ends of the cell.
3) The cytoplasm begins to divide and new cell walls begin to form.
4) The cytoplasm divides and two daughter cells are produced. Each cell has one copy of the circular DNA, but can have a variable number of copies of the plasmid(s).

Question 24

What are stem cells?

Answer 24

Stem cells are undifferentiated cells that can divide to produce lots more undifferentiated cells and can differentiate into different types of cell.

Question 25

Describe a difference between stem cells from embryos and those from bone marrow.

Answer 25

Stem cells from embryos can differentiate into any type of cell whereas stem cells from bone marrow can only differentiate into a certain type of cell (e.g. blood cells).

Question 26

What is diffusion?

Answer 26

Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.

Question 27

What are three factors that can affect the rate of diffusion?

Answer 27

The bigger the concentration gradient (the difference in concentration), the faster the diffusion rate. A higher temperature will also give a faster diffusion rate because the particles have more energy, so move around faster. The larger the surface area of a membrane, the faster the diffusion rate (in diffusion through a cell membrane).

Question 28

What is osmosis?

Answer 28

Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

Question 29

What is active transport?

Answer 29

The process in which particles are transferred from a region of lower concentration to a region of higher concentration, against a concentration gradient. It is used in root hair cells (the particles being mineral ions and water) and sometimes between the gut and the blood stream (the particles being nutrients).

Question 30

True or False, the larger an organism is, the smaller its surface area is compared to its volume?

Answer 30

True

Question 31

How are exchange surfaces adapted to maximise effectiveness?

Answer 31

They have a thin membrane, so substances only have a short distance to diffuse. They have a large surface area so lots of a substance can diffuse at once. Exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly. Gas exchange surfaces in animals (e.g. alveoli) are often ventilated too - air moves in and out.

Question 32

How are alveoli specialised to maximise the diffusion of oxygen and carbon dioxide.

Answer 32

Alveoli have an enormous surface area, a moist lining for dissolving gases, very thin walls and a good blood supply.

Question 33

What is the function of villi and how are they specialised for their function?

Answer 33

They increase the surface area in a big way so that digested food is absorbed much more quickly into the blood. They have a single layer of surface cells and a very good blood supply to assist quick absorption.

Question 34

How is a leaf adapted to improve the rate of diffusion?

Answer 34

The flattened shape of the underneath of a leaf increases the area of this exchange surface so that it's more effective. The walls of the cells inside the leaf form another exchange surface. The air spaces inside the leaf increase the area of this surface so there's more chance for carbon dioxide to get into the cells.

Question 35

How are gills in a fish specialised for their function?

Answer 35

Each gill is made of lots of thin plates called gill filaments which give a big surface area for exchange of gases. The gill filaments are covered in lots of tiny structures called lamellae, which increase the surface area even more. The lamellae have lots of blood capillaries to speed up diffusion. They also have a thin surface layer of cells to minimise the distance that the gases have to diffuse. Blood flows through the lamellae in one direction and water flows over in the opposite direction. This maintains a large concentration gradient between the water and the blood increasing the amount of oxygen that can diffuse.