Life at a Cellular Level 1

Question 1

What is a cell?

Answer 1

Functional unit of all living things

Question 2

Describe a prokaryotic cell.

Answer 2

• Bacteria
• Lack nuclear membrane
• No mitochondria
• No membrane bound structures

Question 3

Describe a eukaryotic cell

Answer 3

• Human cells
• Multicellular animals and plants
• Nucleus with membrane
• Membrane bound structures

Question 4

What are stem cells?

Answer 4

• Multipotent: Cells that can differentiates into many cells

- Pluripotent: Cells that can differentiate into all cell types of the body

Question 5

What are changes in gene expression reflected in?

Answer 5

The alteration of cell structure and behaviour

Question 6

What process can some cells go through during differentiation?

Answer 6

Cell fusion

Question 7

What are cancer cells?

Answer 7

• Cells that divide without any control and fail to coordinate with normal cells.
• Fail to differentiate into specialised cells
• Displace and replace the normal cells

Question 8

What is apoptosis?

Answer 8

• A process of programmed cell death

- A central mechanism controlling multicellular development

Question 9

What are tissues?

Answer 9

Functional arrangements of cells

Question 10

What are organs?

Answer 10

Mixture of different tissues

Question 11

What are systems?

Answer 11

Cells or organs with similar functional roles

Question 12

What is the cell membrane?

Answer 12

-Selective barrier

Question 13

What does the plasma membrane detect?

Answer 13

Chemical messengers and signalling molecules from surrounding cells or other organs

Question 14

How can membrane lipids be described.

Answer 14

Amphipathic

-Hydrophilic head and hydrophobic tail

Question 15

What are the functions of the plasma membrane?

Answer 15

• Transport
• Surface of enzymatic activity
• Receptors for signal transduction
• Intercellular joining
• Cell-cell recognition
• Attachment to cytoskeleton and ECM

Question 16

Describe passive diffusion.

Answer 16

• Concentration gradient needed

- Lipid-soluble molecules pass freely (non-polar)

Question 17

Describe facilitated diffusion

Answer 17

• Concentration gradient needed

- Requires carrier molecules

Question 18

What do tight junctions do?

Answer 18

Seals gap between epithelial cells

Question 19

What do adheren junctions do?

Answer 19

• Connects actin filament bundle in one cell with that in the next cell
• Link actin filaments in two different cells

Question 20

What do desmosomes do?

Answer 20

• Connect intermediate filaments in one cell to those in the next cell
• Link keratin filaments in two different cells

Question 21

What do gap junctions do?

Answer 21

• Allows the passage of small water soluble molecules from cell to cell
• Links two cells cytoplasm together

Question 22

Where would you find tight junctions?

Answer 22

• Intestine
• Kidney
• Blood brain barrier

Question 23

What are tight junctions dependent on?

Answer 23

Calcium

Question 24

Where would you find gap junctions?

Answer 24

• Heart muscle
• Liver
• Pancreas

Question 25

What are gap junctions composed of?

Answer 25

Connexions (6 subunit membrane spanning proteins)

Question 26

What are the 4 types of cell signalling?

Answer 26

- Contact-dependent - Paracrine (cell only signals local cells) - Synaptic (specific to neurones) - Endocrine (signal gets carried around body and has mass effect

Question 27

What does fast cell signalling involve?

Answer 27

Adrenaline or nerves

Question 28

What does slow cell signalling involve?

Answer 28

Genes being switched on/off

Question 29

Describe the structure of a mitochondria?

Answer 29

- Porous outer membrane - Inner membrane with cristae - Matrix containing calcium binding sites and enzymes for oxidation of food molecules. - Circular DNA - Ribosomes

Question 30

What does the nucleus contain?

Answer 30

- DNA - Nucleoprotein - RNA

Question 31

What are nucleoli?

Answer 31

Sites of ribosomal RNA synthesis and ribosomal assembly

Question 32

What 2 forms does DNA come in?

Answer 32

- Heterochromatin | - Euchromatin

Question 33

Describe the nuclear membrane of the nucleus.

Answer 33

- Phospholipid bilayer - Encloses the nucleus - Contains pores - Closely associated with the ER

Question 34

Describe the ER.

Answer 34

- Membrane bound | - RER has ribosomes

Question 35

What is the ER responsible for?

Answer 35

Protein modification and transport coordinated by the RER and Golgi body

Question 36

What does the smooth ER do?

Answer 36

Mainly breaks down compounds such as drugs and glycogen or synthesises some compounds such as lipids

Question 37

What are lysosomes used for?

Answer 37

- Used to separate enzymes from the rest of the cell | - Used in autophagy or digestion of engulfed particles.

Question 38

What does the cytoskeleton do?

Answer 38

- Supports and maintains cell shape - Holds organelles in position - Moves organelles - Involved in cytoplasmic streaming - Interacts with extracellular structures to hold cell in place

Question 39

What are the 3 different divisions to the cytoskeleton?

Answer 39

- Microfilaments - Intermediate filaments - Microtubules

Question 40

What are microfilaments involved in?

Answer 40

Cell dynamics

Question 41

What are intermediate filaments involved in?

Answer 41

Hold organelles in place

Question 42

What are microtubules involved in??

Answer 42

Mitosis and meiosis

Question 43

What are cilia and flagella made from?

Answer 43

Microtubules

Question 44

What are cilia?

Answer 44

- Short - Usually many present - Move with stiff power stroke and flexible recovery stroke

Question 45

What are flagella?

Answer 45

- Longer - Usually one or two present - Movement is snakelike