topic 1 - cell biology: cell structure

Question 1

what is a eukaryotic cell?

Answer 1

a cell that has a cell membrane, cytoplasm and genetic material enclosed in a nucleus.

Question 2

what is a prokaryotic cell?

Answer 2

a cell that has a cytoplasm and cell membrane enclosed by a cell wall, genetic material is not enclosed in a nucleus.

Question 3

what is the size of an animal cell?

Answer 3

10-30 micrometers

Question 4

what is the size of a plant cell?

Answer 4

10-100 micrometers

Question 5

what is the formula for magnification?

Answer 5

magnification = image size / actual size

Question 6

what parts are in an animal cell?

Answer 6

nucleus, cytoplasm, cell membrane, mitochondria, ribosomes

Question 7

what parts are in a plant cell?

Answer 7

nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, chloroplasts, permanent vacuole.

Question 8

what is the function of ribosomes?

Answer 8

site of protein synthesis.

Question 9

what is the function of mitochondria?

Answer 9

controls the enzymes for respiration, and where most energy is released in respiration.

Question 10

what is the function of the cell membrane?

Answer 10

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

Question 11

what is the function of the cytoplasm?

Answer 11

a jelly like material where chemical reactions happen.

Question 12

what is the function of the nucleus?

Answer 12

contains genetic material, including DNA, which controls the cell’s activities.

Question 13

what is the function of a chloroplast?

Answer 13

contains the enzymes needed for photosynthesis.

Question 14

what is the function of a cell wall?

Answer 14

strengthens the cell and supports the plant.

Question 15

what is the function of a permanent vacuole?

Answer 15

filled with cell sap to help keep the cell turgid.

Question 16

how is the sperm cell adapted for its function?

Answer 16

The head of the sperm contains the genetic material for fertilisation. The acrosome in the head contains enzymes so that the sperm can penetrate an egg. The middle piece is packed with mitochondria to release energy needed to swim and fertilise the egg. The tail enables the sperm to swim.

Question 17

how is the nerve cell adapted for its function?

Answer 17

The nerve cell is extended, so that nerves can run to and from different parts of the body to the central nervous system. The cell has extensions and branches, so that it can communicate with other nerve cells, muscles and glands. The nerve cell is covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse.

Question 18

how is the muscle cell adapted for its function?

Answer 18

Muscle cells contain filaments of protein that slide over each other to cause muscle contraction. The arrangement of these filaments causes the banded appearance of heart muscle and skeletal muscle. They contain many well-developed mitochondria to provide the energy for muscle contraction. In skeletal muscle, the cells merge so that the muscle fibres contract in unison.

Question 19

how is the root hair cell adapted for its function?

Answer 19

large surface area to provide contact with soil water, thin walls so as not to restrict the movement of water.

Question 20

how is the xylem cell adapted for its function?

Answer 20

There are no top and bottom walls between xylem vessels, so there is a continuous column of water running through them. Their walls become thickened and woody. They therefore support the plant.

Question 21

how is the phloem cell adapted for its function?

Answer 21

Dissolved sugars and amino acids can be transported both up and down the stem. Companion cells, adjacent to the sieve tubes provide energy required to transport substances in the phloem.

Question 22

what is the importance of cell differentiation?

Answer 22

cells become specialised in order to perform a particular role in the body.

Question 23

what is the difference between an electron microscope and a light microscope?

Answer 23

An electron microscope has much higher magnification and resolution than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures.

Question 24

how often do bacteria multiply by simple cell division (binary fission)?

Answer 24

as often as every 20 minutes if they have enough nutrients and a suitable temperature.

Question 25

give two examples of culture mediums that can be used when growing bacteria.

Answer 25

nutrient broth solution or agar jelly.

Question 26

what are uncontaminated cultures of microorganisms required for?

Answer 26

investigating the action of disinfectants and antibiotics.

Question 27

describe how to prepare an uncontaminated culture using aseptic technique.

Answer 27

1. pour hot agar jelly into a petri dish
2. when the jelly is set, use an inoculating loop to transfer microorganisms to the culture medium.
3. lightly tape the lid on and store the culture upside down
4. wait for the microorgamisms to multiply

Question 28

why must petri dishes and culture medium be sterilised before use?

Answer 28

to kill any unwanted bacteria.

Question 29

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

Answer 29

fire kills any harmful bacteria.

Question 30

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

Answer 30

to stop microorganisms from the air getting in and to stop drops of condensation falling on the agar surface.

Question 31

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

Answer 31

because above this temperature harmful pathogens can grow.