Topic 1.1: Introduction to Cells

Question 1

Principles of Cell theory

Answer 1

a) All living things are composed of cells
b) The cell is the smallest unit of life
c) Cells only arise from pre-existing cells

Question 2

Caveats to cell theory

Answer 2

a) Striated muscle fibres
b) Aseptate fungal hyphae
c) Giant algae

Question 3

Striated muscle fibres

Answer 3

a) Have multiple nuclei despite being surrounded by a continuous plasma membrane.
b) Challenges the idea that cells always function as autonomous units.

Question 4

Aseptate fungal hyphae

Answer 4

a) Not partitioned by septa and have a continuous cytoplasm along the length of the hyphae.
b) Challenges the idea that living structures are composed of discrete cells.

Question 5

Giant algae

Answer 5

a) Grow very large sizes

b) Challenges the idea that larger organisms are always made of many microscopic cells.

Question 6

Unicellular organisms

Answer 6

Smallest organisms capable of independent life

Question 7

Functions of Life

Answer 7

Metabolism
Reproduction
Sensitivity
Homeostasis
Excretion
Nutrition
Growth

Question 8

Metabolism

Answer 8

Undertaking chemical reactions

Question 9

Reproduction

Answer 9

Producing offspring either sexually or asexually

Question 10

Sensitivity

Answer 10

Responsive to internal and external stimuli

Question 11

Homeostasis

Answer 11

Maintain a stable internal environment

Question 12

Excretion

Answer 12

Removal of waste products

Question 13

Nutrition

Answer 13

Exchange of material and gases with the environment

Question 14

Growth

Answer 14

Change shape or size

Question 15

Paramecium

Answer 15

a) Food is enclosed within small vacuoles that contain enzymes for digestion
b) Surrounded by small hairs (cilia) which allow it to move
c) Solid wastes removed via an anal pore
d) Gas exchange via diffusion
e) Divide asexually or by conjugation

Question 16

Scenedesmus

Answer 16

a) Exchange gases and other materials via diffusion
b) Organic molecules produced via photosynthesis
c) Non-motile autospores via the internal asexual division of the parent cell

Question 17

What do cells need to survive?

Answer 17

a) Production of chemical energy to survive

b) Exchange of materials with the environment

Question 18

Rate of metabolism

Answer 18

A function of the cell’s volume

Question 19

Rate of exchange of materials

Answer 19

A function of its surface area

Question 20

SA : Vol ratio as a cell grows

Answer 20

As a cell grows, volume increases faster than surface area, leading to a decreased SA:Vol ratio

Question 21

What happens if metabolic rate exceeds the rate of exchange of materials?

Answer 21

Cell will eventually die

Question 22

Why do cells divide and remain small?

Answer 22

To maintain a high SA:Vol ratio

Question 23

Magnification

Formula

Answer 23

Magnification = Image size / Actual size

Question 24

Emergent Properties

Answer 24

The interaction of individual component produces new functions such as thinking

Question 25

Organization of Multicellular Organisms

Answer 25

Cells -> 
Tissues -> 
Organs -> 
Organ systems -> 
Organism

Question 26

Differentiation

Answer 26

Process where newly formed cells become more specialized and distinct from one another as they mature

Question 27

What involves differentiation?

Answer 27

Expression of some genes and not others in a cell’s genome

Question 28

Stem cells properties

Answer 28

Self-Renewal – They can continuously divide and replicate

Potency – Capacity to differentiate into specialized cell types

Question 29

Types of stem cells

Answer 29

a) Totipotent – Can form any cell type, as well as extra-embryonic tissue
b) Pluripotent – Can form any cell type
c) Multipotent – Can differentiate into a number of closely related cell types
d) Unipotent – Cannot differentiate, but are capable of self renewal

Question 30

Uses of Stem Cells

Answer 30

Necessary for embryonic development as well as therapeutic uses

Question 31

Therapeutic Use of Stem Cells

Answer 31

Stem cells can be used to replace damaged or diseased cells with healthy, functioning ones

Question 32

Example of Stem Cell Therapy

Answer 32

a) Stargardt’s Disease is an inherited form of macular degeneration that causes progressive vision loss to the point of blindness.
b) Caused by a gene mutation in photoreceptor cells
c) Treated by replacing dead cells in the retina with functioning ones derived from stem cells.