2.1 Cell Theory

Question 1

State the 3 main points of cell theory

Answer 1

Cells are the smallest units of life
Living organisms are composed of cells
Cells come from pre-existing cells

Question 2

Define ‘cell’

Answer 2

A functional unit of cytoplasm surrounded by a membrane and containing genetic material

Question 3

Name the functions of life that all organisms, including unicellular organisms, carry out

Answer 3

Metabolism
Response
Homeostasis
Growth
Reproduction
Nutrition

Question 4

State the main points of organismal theory

Answer 4

Some organisms aren’t divided into cellular compartments e.g. fungi
Some cells lack the basic components e.g. red blood cells
Removing cells from a complete multicellular organism requires complex support systems to keep them alive
Homeostatic control and coordination are needed to keep an organism alive whether it is uni or multicellular

Question 5

How many metres is a millimetre, micrometre, and nanometre?

Answer 5

Millimetre (mm) = 10(-3) m
Micrometre = 10(-6) m
Nanometre = 10(-9) m

Question 6

What is the rough size of a molecule?

Answer 6

1nm

Question 7

What is the rough size of a membrane’s thickness?

Answer 7

10nm

Question 8

What is the rough size of a virus?

Answer 8

100nm

Question 9

What is the rough size of a bacteria?

Answer 9

1 micrometre

Question 10

What is the rough size of an organelle?

Answer 10

Up to 10 micrometres

Question 11

What is the rough size of a cell?

Answer 11

Up to 100 micrometres

Question 12

Explain how to calculate magnification using a scale bar

Answer 12

Measure the scale bar in mm
Convert this number to the same units as the scale bar
Divide this number by the number on the scale bar

Question 13

Explain how to calculate the actual size of something when you are given the magnification

Answer 13

Measure the dimension you’re interested in on the diagram in mm
Divide this number by the magnification
Convert this number to a sensible unit (so the number is in single or double digits rather than lots of decimal places)

Question 14

State how the surface area:volume ratio of an organism changes as it increases in size.

Answer 14

As an organism increases in size, its surface area:volume ratio decreases.

Question 15

How does surface area:volume ratio limit cell size?

Answer 15

Surface area provides an exchange surface for heat and substances. The bigger the cell is (more cytoplasm), the more heat and waste products are generated and the more nutrients and oxygen are needed from outside the cell. As the cell gets bigger, however, there is less surface area relative to volume, so at some point the cell generates more waste and requires more nutrients than can diffuse across the surface area it has, limiting cell size.

Question 16

What are emergent properties?

Answer 16

“The whole is greater than the sum of its part”; i.e. they are properties that arise from the fact that different components of an organism can work together to be more effective than each individual part would be alone. All multicellular organisms show emergent properties.

Question 17

Summarise what differentiation of cells is.

Answer 17

Differentiation of cells is where cells become different from each other and can specialise in particular functions. Cells differentiate in multicellular organisms.

Question 18

How do cells differentiate?

Answer 18

They express some of their genes but not others; the genes that code for functions the cell does not do are ‘switched off’.

Question 19

What is special about stem cells?

Answer 19

They retain their capacity to divide and can differentiate along different pathways.

Question 20

Give an example of a therapeutic use of stem cells

Answer 20

Leukaemia is a cancer of leukocytes. Leukocytes come from adult stem cells in bone marrow, so a donor bone marrow transplant can be used to provide stem cells to produce new, healthy leukocytes after a course of chemotherapy has wiped out the normal and abnormal bone marrow stem cells.