Life at the Cellular Level Flashcards
Tight junction function
Physical barrier to diffusion across layers of cells
Types of adhesive junctions
- Adherens: link actin filaments in two different cells
- Desmosomes: link keratin filament in two different cells
Gap junction function
Channels linking two cell cytoplasms
Types of cell signalling
- Contact dependent: i.e. receptors
- Paracrine
- Synaptic: neurotransmitter
- Endocrine
What 4 element are 99% of humans made from?
H, O, N and C
List 5 chemical reactions occurring in living organisms
- Redox reactions
- Making and breaking C-C bonds
- Internal arrangements
- Group transfers
- Condensation and hydrolysis reactions
Outline redox reactions and give an example
- 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
Example of making/breaking C-C bonds
Cleavage of glucose in glycolysis pathway
Example of internal rearrangements
Occurs in glycolysis; a rearrangement of G 6-P to F 6-P
Example of group transfers
Occurs in glycolysis; phosphate group transferred
Example of conditions and hydrolyses
Sub-units of proteins, polysaccharides and nucleic acids joined by condensation and broken by hydrolysis reactions
Nucleic acid components
Polymers of nucleotide monomers linked by 3’,5’-phosphodiester bonds
Describe the two types of bases in nucleic acids
- Pyrimidines (flat, single rings): C, T and U
- Purines (flat, double rings): A and G
Why is D-glucose a reducing sugar
Linear form has an aldehyde group which can be oxidised
Accepts electrons from molecule being oxidised
1st Law of Thermodynamics
Energy can be converted from one form to another but total energy remains constant
2nd Law of Thermodynamics
Energy transformation leads to more disorder - increase the entropy
What is entropy?
Randomness and chose with a closed system
As usable energy is lost, chaos and randomness increase
Do cell defy the 2nd Law?
No - the chemical reactions that generate the cell’s order produce heat which is released into the surrounding environment and increases its entropy
Describe Gibbs Free Energy
- Enthalpy, H - released heat
- Entropy, S - disorder
- Absolute temp., T
G = H - TS
Describe entropy in a spontaneous reaction
Increase
-Can only occur if change in free energy is NEGATIVE
What is an exergonic pathway?
Catabolic pathway that saves free energy within a system by forming ATP
What is endergonic pathway?
Anabolic pathway that is supplied with free energy within a system through conversion of ATP to ADP
Describe ATP-ADP interconversion
ATP to ADP + Pi hydrolysis - decrease in free energy (exergonic)
ADP + Pi to ATP condensation - requires free energy (endergonic)
Characteristic of water
- Polar
- Hydrophilic
- Hydrogen bonding
In what structure are hydrogen bonds the strongest?
Linear
Define amphipathic and give an example
Molecule that contains both hydrophobic and hydrophilic parts
-phospholipids
What is the dissociation for water?
1x10 to -14 (mol/L)2
What is the concentration of H+ and OH- in water?
Both are 1x10 to -7 mol/L
Equation for pH of water
-log[H+]=-log[OH-]= 7
or
pH=pOH=7
pH scale for acids
below pH 7
pH scale for alkalis
above pH 7
Define strong acids and alkalis
Fully dissociate into ions
- HCl
- NaOH
Define weak acids and alkalis
Partially dissociate
Buffer function
- Maintain optimal pH
- Solutions of weak acids
Acid characteristic
- Proton donors
- Stronger acids have greater tendency to lose protons
Name the buffer in the blood and its importance
HCO3 - ensures pH doesn’t fluctuate wildly as cellular products of acids (i.e. lactic acid, ketone bodies) decrease blood pH
What to do if patient has high acid levels
Monitor:
- blood pH (7.4)
- [HCO3]
- [CO2]
