Cells

Question 1

What is the site of respiration?

Answer 1

Mitochondria

Question 2

How to measure magnification in a microscope ?

Answer 2

Magnification = size of image / size of real object

Question 3

What is the function of the cell membrane?

Answer 3

It is selectively permeable which forms a boundary for the cell and controls what enters and leaves

Question 4

What is the function of the nuclear membrane?

Answer 4

Surrounds the nucleus

Question 5

What is the function of cytoplasm?

Answer 5

Where chemical reactions take place

Question 6

What is the function of the nucleus (A.K.A. Control centre of the cell)?

Answer 6

This contains chromosomes and genetic information for the cell

Question 7

What is the function of chromosomes?

Answer 7

Found in the nucleus. Made up of the molecule DNA which contains the genetic information for the organism

Question 8

What is the function of the cellulose cell wall?

Answer 8

Stiff structure just outside of the membrane that provides support

Question 9

What is the function of the chloroplast?

Answer 9

Contain chlorophyll which traps light used in the process of photosynthesis. Only found in the green parts of the plant

Question 10

What is the function of the Large Permanent Vacuole

Answer 10

Contains cell sap

that when full pushes the cell membrane against the cell wall making the cell more rigid which provides more support

Question 11

What is a stem cell?

Answer 11

Stem cells are simple cells in animals and in plants that has the ability to divide to form more cells of the same type

Question 12

Where can stem cells be harvested from in animal cells?

Answer 12

In animals stem cells can be harvested from (embryonic) umbilical cord or bone marrow (adult)

Question 13

What is the difference between embryonic stem cells and adult stem cells?

Answer 13

Embryonic stem cells form a full range of cell types while adult stem cells form a limited range of cell types

Question 14

What do most animal stem cells change permanently into?

Answer 14

Most stem cells change permanently at an early stage into specialised cells with structures that adapt them to a particular function

Question 15

What do plant stem cells originate from?

Answer 15

In plants, stem cells originate from meristems at the apices of the root and stems and many of these cells retain the ability to divide and so can be used in cloning techniques

Question 16

What potential benefits come from using stem cells in medicine?

Answer 16

Bone marrow transplant in treating leukaemia

Question 17

What are the potential risks in using stem cells in medicine?

Answer 17

Ethical implications, including pre-treatment using radiotherapy or chemotherapy, transfer of viruses or diseases from other animals, formation of tumours or development of unwanted cell types

Question 18

What is there not in bacteria cells that are in plant and animal cells?

Answer 18

There is no cellulose cell wall but there is a non-cellulose cell wall, absence of nucleus but there is presence of plasmids in the bacterial cell

Question 19

What can multicelled organisms’ form

Answer 19

Multicelled organisms’ can form specialised tissues, organs and organ systems

Question 20

Why do multicelled organisms need a exchange surface? (eg alveoli in the lungs)

Answer 20

Surface area affects the rate at which particles can enter and exit the cell

Volume affects the rate at which materials are made or used within the cell

As the volume of the cell increases, so does the surface area, but not to the same extent. When the cell gets bigger its surface area to volume ratio gets smaller

And if the surface area to volume ratio gets too small:
Substances won’t be able to enter the cell fast enough to fuel the reactions.
Waste products will start to accumulate within the cell as they will be produced faster than they can be excreted
Cells will not be able to lose heat fast enough and so may overheat

This is why multicelled organisms need an exchange surface.
In addition, a transport system is required in order to supply nutrients to the cell fast enough and remove waste products quickly to prevent them building up to dangerous levels

Question 21

What is diffusion?

Answer 21

Diffusion is the movement of molecules from a region of high concentration to a area of low concentration

Question 22

What is diffusion affected by?

Answer 22

The rate of diffusion is affected by temperature, surface area and concentration gradient