Fundamentals of Metabolism 3 - How cells work Flashcards
(33 cards)
Essential Characteristics of Living Cells
- Information of storage
- Compartmentation
- Controlled Reactions
Essential Characteristics of Living Cells:
EXPLAIN INFORMATION STORAGE
HOW?
A mechanism for storing and using the information
required for the cell to work and passing it to offspring
→ NUCLEIC ACIDS
Essential Characteristics of Living Cells:
COMPARTMENTATION = 2
HOW?
- Keeping the contents of cells separate from their environment
- Controlled interaction with environment
→ MEMBRANES WITH SELECTIVE PERMEABILITY
Essential Characteristics of Living Cells: CONTROLLED REACTIONS
- Reactions that occur in an aqueous environment under MILD conditions.
→ STEPWISE OXIDATION AND REDUCTASE REACTIONS AVOIDING LARGE CHANGES IN FREE SINGLE STEP
- Made possible by the use of ENZYMES
- Storing information and passing to offspring = EXPLAIN HOW 3.
1 * DNA replication is SEMI-CONSERVATIVE
(each parent strand copied)
2 * PROTEIN STRUCTURE IS ENCODED BY DNA
3 * PROTEINS FOLD IN A MANNER DICTATED BY THIER PRIMARY STRUCTURE
Molecular Composition of Cells:
6 - general
- MAJOR ATOMS
- MOLECULES
- MARCROMOLECULES
- SMALL MOLECULES
- INORGANIC IONS
- TRACE ELEMENTS
Molecular Composition of Cells: MAJOR ATOMS
H
C
O
N
P
S
Molecular Composition of Cells: MOLECULES
- WATER (70%)
- Macromolecules (23%)
- Protein
- Nucleic Acids (DNA and RNA)
- Carbohydrates - SMALL MOLECULES (6%)
- Amino acids
- Sugars
- Nucleotides
- Lipids
Molecular Composition of Cells: INORGANIC IONS
= 1% approx
Na+, Cl-, H2PO4-, HCO3-, Ca+2, K+
Molecular Composition of Cells: TRACE ELEMENTS
Fe, Cu, Zn, Mg, Mn, Mo, Co, Se, I
amino acids to
Proteins
fatty acids to
Lipids
Sugar residues to…
- Glycerol
to Lipids - Mono-saccharides
to Carbohydrates
or
- Sugar residues to monosaccharides to Nucleotides = DNA/RNA
Nucleobases to
nucleotides to DNA/RNA
Why is Water a solvent?
due to Hydrogen Bonds in Water
1 * Water forms H-bonds due to the interaction
between the δ+ on the H and the δ- on O
2 * Each water molecule can form up to 4 H-bonds
(4 in ice)
3 * Continually breaking and reforming
Water’s polar nature and ability to H-bond gives water its unique solvent properties… WHAT ARE THEY?
1 – Polar (high dielectric constant)
2 – Dense
3 – High melting and boiling point
4 – Viscous with high surface tension
5 – Can act as proton donor or acceptor:
Explain water Can act as proton donor or acceptor:
H2O ⇋ H+ + OH-
[H+][OH-] = 10^-14 M^2
H+ + H2O ⇋ H3O+ (hydronium ion)
Water tends to exclude hydrophobic molecules because?
disrupt H-bonding
EXPLAIN COMPARTMENTATION IN DETAIL….3
1 * Cells (and organelles) can maintain a SPECIALISED ENVIRONMENT consistent with the function of the cell- via phospholipid membranes
2 * Membranes have SELECTIVE PERMEABILITY to POLAR and CHARGED molecules via SPECIFIC TRANSPORTERS in their PLASMA and ORGANELLE MEMBRANES
3 * Energy (‘ATP’) must be used to MAINTAIN ORDER in a cell, including for TRANSPORT OF ESSENTIAL MOLECULES AGAINST A CONCENTRATION GRADIENT.
Understanding SELECTIVELY MEMBRANE TRANSPORT…
EXAMPLE K+ channel = 5
- Hydrated K+ and Na+ ions in Solution, ENTRY AT PORE
- Na+ is smaller than K+
- K+ (but not Na+) co-ordinate perfectly with carbonyl ( -C=O) oxygens in channel
- ACTIVATION ENERGY = for K+ to MOVE THROUGH PORE IS LOW.
ACTIVATION for Na+ to MOVE THROUGH PORE REMAINS HIGH
- K+ transported 1000 x faster than Na+
CONTROLLED REACTIONS:
AIM? HOW?
AIM: avoid a large release in free energy in a single step
∴ Fuels oxidized stepwise (e.g. β-oxidation)
- Enzymes permit reactions to proceed RAPIDLY in the aqueous environment of
cells under mild conditions
Controlled Reactions: SPEED UP REACTION BY: 2
a) Holding reactants in correct ORIENTATION
b) Promoting attainment of the TRANSITION STATE
Specificity in Binding - BETWEEN MACROMOLECULES
- Between a macromolecule and a SMALL MOLECULE
eg. ENZYME BINDING TO ITS SUBSTRATE
2.SPECIFIC MATCHING of FUNCTIONAL GROUPS ENABLES SPECIFIC PROTEIN-PROTEIN INTERACTION
- Collective bond energies –> strong interaction;
- N bond, Ionic bond, Hydrophobic and van der Waals interactions
Chemical ENERGY in Cells …
Understanding ATP - the energy currency in cells
A large release of free energy accompanies ATP HYDROLYSIS
1.* Can be COUPLED to REACTIONS that NEED ENERGY to PROCEED in
the FORWARD DIRECTION:
e. g.
glucose + Pi ⇀, <——– glucose-6-P
2* COUPLED to ATP HYDROLYSIS, PHOSPHORYLATION of GLUCOSE proceeds in the
FORWARD DIRECTION:
glucose + ATP <↽, ——-> glucose-6-P + ADP
