Cell Structure and Division

Question 1

What is the function of the cell surface membrane?

Answer 1

Regulates movement of substances into and out of the cell, it also has receptor molecules on it allowing it to respond to chemicals such as hormones.

Question 2

What is the function of the nucleus and the nuclear envelope?

Answer 2

Large organelle surrounded by a nuclear envelope containing chromosomes. Controls the cell activity, contains DNA which controls protein making. The nuclear envelope contains pores which lets substances in and out of the nucleus.

Question 3

What is the function of the RER?

Answer 3

System of membranes enclosing a fluid filled space covered in ribosomes. Folds, processes, and packs proteins made by ribosomes.

Question 4

What is the function of the SER?

Answer 4

System of membranes enclosing a fluid filled space does not have ribosomes, Synthesis, and processes lipids.

Question 5

What is the function of the golgi body?

Answer 5

A group of long flattened fluid filled sacs that processes and packages proteins and makes lysosomes

Question 6

What is the function of the golgi vesicle?

Answer 6

A small fluid filled sac in the cytoplasm produced by apparatus, stores lipids and proteins made by apparatus to transport them around the cell.

Question 7

What is the function of a lysosome and lysozomes?

Answer 7

Round organelle surrounded by membrane. Contains digestive enzymes called lysozymes used to digest invading cells or break down worn out components of cell.

Question 8

What is the function of a ribosome?

Answer 8

A small organelle that floats in the cytoplasm and attached to the RER, made up of proteins and RNA, where proteins are made.

Question 9

What is the function of mitochondria?

Answer 9

Oval shaped with a double membrane, inner one folded to form cristae, contains a matrix which has enzymes involved in respiration. The site of aerobic respiration and the production of ATP., and the cells energy source

Question 10

What is the function of the vacuole?

Answer 10

Membrane bound organelle found in the cytoplasm containing cell sap surrounded by tonoplast membrane. Helps to maintain pressure inside cell.

Question 11

What is the function of the cytoplasm?

Answer 11

A jelly-like material that contains dissolved nutrients and salts and organelles. It is where many of the chemical reactions happen.

Question 12

What is the function of the cell wall?

Answer 12

A rigid structure that supports the cells and prevents the changing of the shape.

Question 13

What is the function of the chloroplast?

Answer 13

A small, flattened structure surrounded by a double membrane and thylakoid membranes which are stacked up to form grana which are linked together by lamellae. Where photosynthesis takes place.

Question 14

What is the capsule?

Answer 14

Surrounds the cell made up of secreted slime, helps protect bacteria from attack by cells of the immune system

Question 15

What is the flagellum?

Answer 15

Long hair like structure that rotates to help the prokaryotic cell move

Question 16

What are plasmids?

Answer 16

Small loops of DNA that contain genes and can be passed between prokaryotes.

Question 17

How are cells organised into an organ system?

Answer 17

A group of specialised cells form a tissue, the tissues from an organ, and multiple organ together form an organ system.

Question 18

What is the name of which prokaryotic cells replicate and how does this process take place?

Answer 18

Binary fission
1. The circular DNA and plasmids replicate, the main DNA loop is only replicated once but the circular DNA can be replicated as many times as possible.
2. The cell gets bigger, and the DNA loops move to opposite poles of the cell.
3. The cytoplasm begins to divide, and new cell walls begin to form
4. The cytoplasm fully divides, and two daughter cells are produced

Question 19

What is in the structure of a virus?

Answer 19

Capsid, attachment proteins, protein coat and a DNA core.

Question 20

What happens during viral replication?

Answer 20

1. Virus attaches to the host cell receptor proteins.
2. Genetic material is released into the host cell.
3. Genetic material and proteins are replicated by host cells machinery.
4. Viral components assemble.
5. Replicated viruses released from the host cell.

Question 21

What is the equation for magnification?

Answer 21

Magnification = Size of Image/Actual size of object

Question 22

How does an optical light microscope work and what are its limitations?

Answer 22

Visible light passes through the specimen and is bent through the lens system, allowing the user to see a magnified image.
- They have a maximum magnification of 0.2 micrometres.

Question 23

How does a transmission electron microscope work and what are its limitations?

Answer 23

An electron source at the top of the microscope emits electrons that travel through a vacuum in the column of the microscope. Electromagnetic lenses are used to focus the electrons into a very thin beam, and this is then directed through the specimen of interest.
- Can only be used on non-living and thin specimens and in a vacuum.

Question 24

How does a scanning electron microscope work and what are its limitations?

Answer 24

Scan a beam of electrons across the specimen, knocking of electrons from the specimen which are gathered in a cathode ray tube to form an image. Can be used of thick specimen and can be 3D.
- Give lower resolution images to TEMs and only used on non-living specimens.

Question 25

What are the three phases of cell fractionation?

Answer 25

Homogenisation, filtration and ultracentrifugation.

Question 26

What is homogenisation?

Answer 26

By vibrating the cells or grinding them in a blender to break up the membrane and release the organelles.

Question 27

What are the three things that must be kept constant during homogenisation?

Answer 27

Must be kept ice cold to reduce enzyme activity, should be kept isotonic to maintain same concentration, and a buffer solution should be added to maintain pH.

Question 28

What is filtration?

Answer 28

Solution is filtered through a gauze to separate large cell debris or tissue debris whilst the organelles pass the through the gauze.

Question 29

What is ultracentrifugation?

Answer 29

The cell fragments are poured into a tube which is then put into a centrifuge and is spun at a low speed. The heaviest organelles get released first forming a thick sediment at the bottom of the tube like a pellet. Repeat.

Question 30

What is mitosis needed for?

Answer 30

Growth and repair.

Question 31

What are the names of the 4 phases of mitosis?

Answer 31

Prophase.
Metaphase.
Anaphase.
Telophase.

Question 32

What happens during prophase?

Answer 32

The chromosomes condense getting shorter and fatter. Tiny bundles of proteins called centrioles start moving to opposite ends of the cell forming spindles. The nuclear envelope breaks down and chromosomes lie free in the cytoplasm.

Question 33

What happens during metaphase?

Answer 33

The chromosomes line up on the middle of the cell and become attached to the spindle by the centromere.

Question 34

What happens during anaphase?

Answer 34

The centromeres divide separating each pair of sister chromatids. The spindles contract pulling chromatids to opposite ends of the spindle.

Question 35

What happens during telophase?

Answer 35

The chromatids reach opposite ends of the poles, uncoiling becoming long and thin again. The nuclear envelope forms around each group of chromosomes so there are now two new nuclei. The cytoplasm divides (cytokinesis) and two genetically identical daughter cells are produced.

Question 36

How do you figure out the mitotic index?

Answer 36

Mitotic Index = Number of cells with visible chromosomes/Total number of cells observed.

Question 37

How is cancer caused?

Answer 37

If there is a mutation in the gene that controls cell division, the cells can grow out of control, the cells keep on dividing to make more cells which forms a tumour.