Ultrastructure of a generalised cell

Question 1

What are all membranes thought to have?

Answer 1

The same structure

Question 2

What are membranes composed of?

Answer 2

They are composed of phospholipids and proteins

Question 3

What type of phosphate and lipid groups do phospholipids have?

Answer 3

A water-hating lipid group and a water-loving phosphate group

Question 4

How are phospholipids arranged?

Answer 4

They are arranged into double layers (bilayers) The phosphates are on the exposed outer surfaces with the lipids in the middle

Question 5

Name four functions of membranes

Answer 5

1. retain the cell contents
2. Recognise molecules that touch them
3. Control what enters and leaves the cell
4. Give some support to the cell

Question 6

What is the nucleus surrounded by?

Answer 6

It is surrounded by a double membrane with numerous nuclear pores.

Question 7

What does the double membrane with numerous nuclear pores surrounding the nucleus do?

Answer 7

They allow the controlled entry and exit of molecules into and out of the nucleus.

Question 8

What does the nucleus contain?

Answer 8

It contains strands of deoxyribonucleic acid (DNA). and it is arranged into structures called chromosomes

Question 9

Why is the nucleus of a stained cell darker than the other parts of the cell?

Answer 9

As the DNA in the nucleus readily absorbs many stains and becomes darkly coloured under the microscope.

Question 10

What does every organism have a definite number of in each nucleus? Give this number for humans nuclei

Answer 10

A definite number of chromosomes. (humans have 46)

Question 11

Where are genes located?

Answer 11

They are located randomly along chromosomes

Question 12

Define chromatin

Answer 12

Chromatin is the name given to chromosomes when they are elongated and not dividing

Question 13

What are genes? What do they control?

Answer 13

Genes are the structures that inform the cell how to make certain proteins.

They control features such as the number of fingers, colour of eyes and production of enzymes

Question 14

What are genes also known as?

Answer 14

Units of inheritance

Question 15

When cells are not dividing what do they look like?

Answer 15

They are very elongated and interwoven. In this form they are called chromatin

Question 16

What do nuclear pores allow?

Answer 16

They allow a type of RNA called mRNA to pass in and out of the nucleus.

Question 17

What does the nucleolus make?

Answer 17

It makes ribosomes

Question 18

Where is the nucleolus located?

Answer 18

In an area in the nucleus that stains very darkly.

Question 19

What is cytoplasm?

Answer 19

It is a jelly-like substance that surrounds the nucleus. A number of organelles are suspended in it.

Question 20

What do mitochondria provide?

Answer 20

They supply energy to the cell

Question 21

What cells produce lots of energy? Give an example in both animals and plants

Answer 21

Cells with many mitochondria produce lots of energy. An example is muscle and liver in animals, meristems in plants.

Question 22

What cells produce less energy? Give an example in both animals and plants

Answer 22

Cells with few mitochondria produce less energy. An example is fat in humans, ground tissue in plants.

Question 23

Mitochondria are the sites of what?

Answer 23

The sites of respiration

Question 24

What are mitochondria surrounded by?

Answer 24

A double membrane.

Question 25

Where is energy released in mitochondria?

Answer 25

It is on the inner membrane, especially the infoldings, that energy is released.

Question 26

What affects cellular respiration in mitochondria?

Answer 26

The more infoldings that are present the greater the surface area for cellular respiration

Question 27

What does each mitochondrion contain?

Answer 27

Its own loop of DNA

Question 28

What causes the number of infoldings in mitochondria to increase?

Answer 28

Exercise

Question 29

Answer the following in terms of chloroplasts: 1. What are they surrounded by? 2. What do they have that contains the green pigment chlorophyll? 3. What do they also have similar to mitochondria? 4. What are chloroplasts?

Answer 29

1. Double membranes. 2. They have membrane stacks that contain chlorophyll. 3. They have a loop of DNA. 4. Chloroplasts are green structures in plants in which photosynthesis takes place

Question 30

Answer the following in terms of cell walls: 1. What are they made of? 2. Are they impermeable or permeable? 3. What is the cell walls function?

Answer 30

1. Cellulose (a structural polysaccharide) 2. They are fully permeable. 3. The function of the cell walls is to support and strengthen the cell.

Question 31

What do plants have that animals don't?

Answer 31

Chloroplasts, cell walls, a large vacuole

Question 32

Answer the following in terms of ribosomes: 1. What is the function of ribosomes? 2. What are ribosomes made of? 3. They work by combining what to form what?

Answer 32

1. The function of ribosomes is to make proteins. 2. They are made of RNA and protein. 3. They work by combining a sequence of amino acids to from a protein.

Question 33

Name all the parts of an animal cell (9)

Answer 33

``` Cell membrane Nucleus Nuclear membrane Nucleolus Chromatin Nuclear Pore Cytoplasm Ribosome Mitochondrion ```

Question 34

Name all the parts of a plant cell (12)

Answer 34

``` Mitochondrion Cell wall Cell membrane Nucleus Cytoplasm Vacuole Chloroplast Ribosomes Nuclear pore Nucleolus Chromatin Nuclear membrane ```

Question 35

Name the differences between a plant and animal cell

Answer 35

Plant Cells: Have a cell wall, may have chloroplasts, have a large vacuole Animal cells: Don't have a cell wall or chloroplasts or a large vacuole.