Life at the Cellular Level

Question 1

Tight junction function

Answer 1

Physical barrier to diffusion across layers of cells

Question 2

Types of adhesive junctions

Answer 2

• Adherens: link actin filaments in two different cells

- Desmosomes: link keratin filament in two different cells

Question 3

Gap junction function

Answer 3

Channels linking two cell cytoplasms

Question 4

Types of cell signalling

Answer 4

• Contact dependent: i.e. receptors
• Paracrine
• Synaptic: neurotransmitter
• Endocrine

Question 5

What 4 element are 99% of humans made from?

Answer 5

H, O, N and C

Question 6

List 5 chemical reactions occurring in living organisms

Answer 6

• Redox reactions
• Making and breaking C-C bonds
• Internal arrangements
• Group transfers
• Condensation and hydrolysis reactions

Question 7

Outline redox reactions and give an example

Answer 7

• Oxidation: loss of electrons with reducing agent
• Reduction: gain of electrons with oxidising agent

Glucose to pyruvate is oxidation reaction
Pyruvate to lactate is reduction reaction

Question 8

Example of making/breaking C-C bonds

Answer 8

Cleavage of glucose in glycolysis pathway

Question 9

Example of internal rearrangements

Answer 9

Occurs in glycolysis; a rearrangement of G 6-P to F 6-P

Question 10

Example of group transfers

Answer 10

Occurs in glycolysis; phosphate group transferred

Question 11

Example of conditions and hydrolyses

Answer 11

Sub-units of proteins, polysaccharides and nucleic acids joined by condensation and broken by hydrolysis reactions

Question 12

Nucleic acid components

Answer 12

Polymers of nucleotide monomers linked by 3’,5’-phosphodiester bonds

Question 13

Describe the two types of bases in nucleic acids

Answer 13

• Pyrimidines (flat, single rings): C, T and U

- Purines (flat, double rings): A and G

Question 14

Why is D-glucose a reducing sugar

Answer 14

Linear form has an aldehyde group which can be oxidised

Accepts electrons from molecule being oxidised

Question 15

1st Law of Thermodynamics

Answer 15

Energy can be converted from one form to another but total energy remains constant

Question 16

2nd Law of Thermodynamics

Answer 16

Energy transformation leads to more disorder - increase the entropy

Question 17

What is entropy?

Answer 17

Randomness and chose with a closed system

As usable energy is lost, chaos and randomness increase

Question 18

Do cell defy the 2nd Law?

Answer 18

No - the chemical reactions that generate the cell’s order produce heat which is released into the surrounding environment and increases its entropy

Question 19

Describe Gibbs Free Energy

Answer 19

• Enthalpy, H - released heat
• Entropy, S - disorder
• Absolute temp., T

G = H - TS

Question 20

Describe entropy in a spontaneous reaction

Answer 20

Increase

-Can only occur if change in free energy is NEGATIVE

Question 21

What is an exergonic pathway?

Answer 21

Catabolic pathway that saves free energy within a system by forming ATP

Question 22

What is endergonic pathway?

Answer 22

Anabolic pathway that is supplied with free energy within a system through conversion of ATP to ADP

Question 23

Describe ATP-ADP interconversion

Answer 23

ATP to ADP + Pi hydrolysis - decrease in free energy (exergonic)

ADP + Pi to ATP condensation - requires free energy (endergonic)

Question 24

Characteristic of water

Answer 24

• Polar
• Hydrophilic
• Hydrogen bonding

Question 25

In what structure are hydrogen bonds the strongest?

Answer 25

Linear

Question 26

Define amphipathic and give an example

Answer 26

Molecule that contains both hydrophobic and hydrophilic parts -phospholipids

Question 27

What is the dissociation for water?

Answer 27

1x10 to -14 (mol/L)2

Question 28

What is the concentration of H+ and OH- in water?

Answer 28

Both are 1x10 to -7 mol/L

Question 29

Equation for pH of water

Answer 29

-log[H+]=-log[OH-]= 7 or pH=pOH=7

Question 30

pH scale for acids

Answer 30

below pH 7

Question 31

pH scale for alkalis

Answer 31

above pH 7

Question 32

Define strong acids and alkalis

Answer 32

Fully dissociate into ions - HCl - NaOH

Question 33

Define weak acids and alkalis

Answer 33

Partially dissociate

Question 34

Buffer function

Answer 34

- Maintain optimal pH | - Solutions of weak acids

Question 35

Acid characteristic

Answer 35

- Proton donors | - Stronger acids have greater tendency to lose protons

Question 36

Name the buffer in the blood and its importance

Answer 36

HCO3 - ensures pH doesn't fluctuate wildly as cellular products of acids (i.e. lactic acid, ketone bodies) decrease blood pH

Question 37

What to do if patient has high acid levels

Answer 37

Monitor: - blood pH (7.4) - [HCO3] - [CO2]