Fundamentals of Metabolism I & II lectures Flashcards
What a cell does to exist?
What is necessary for it?
Cells continually build
up & break down molecules & expend cellular energy.
Existence depends on
CONTINUOUS PROVISION OF ENERGY …
FOR maintenance of
structure & function
Cellular energy
enables:
- mechanical
- transport
- chemical
Run out of energy - cells die.
In photosynthetic organisms…
- light energy is used to synthesise carbohydrates from CO2.
2.Carbohydrates (& other
fuels) are metabolised
to CO2 & H2O providing
energy, for example as
ATP.
- These metabolic
pathways are very
similar in bacteria & us!
What is Metabolism?
For energy supply,
essentially it is the
conversion of food
into energy &/or
components required by cells, & thus the body, to
function
2 TYPES OF METABOLISM?
REQUIRES?
- Catabolism
- Anabolism
Requires enzymes
Basis of metabolic reactions…
Conversion of substrate(s) (reactants) into product(s).
Substrate (S) –> Product (P)
Even the simplest reactions need enzymes…
— Hydration of carbon dioxide, spontaneous rate about 2-5 molecules per minute, add an enzyme…
CO2 + H2O —carbonic anhydrase –>H2CO3
1 molecule of carbonic anhydrase hydrates
100 000 CO2 every second (blood pH)
Characteristics of Metabolic pathways = 4
- multistep: Several reactions linked form a metabolic pathway
2.open systems…Product of each reaction becomes substrate for next, so reactions don’t reach equilibrium, & system is in
continual flux.
3 .Often, the product of one reaction can influence another reaction in the sequence
- Enzyme activity controlled in numerous ways … – e.g.,
feedback inhibition, protein shape altered by
de/phosphorylation.
Enzymes do not change the equilibrium of a reaction.
EXPLAIN
If a reaction ‘can’t’ take place, an enzyme ‘won’t’ make it happen,
but they do SPEED UP reaction rate…
Fuels can be oxidised to CO2 & H2O explain…
- Main fuels = carbohydrates, fats, proteins, (alcohol!)
2.Oxidise the carbons in fuels to CO2
C-H
C-C
C-N (amino acids)
“Reduced Bonds”: foundational meaning of oxidation…
Metabolic pathways are
Complex network of reactions
Examples of Macromolecules as Fuels..
- Glucose
- Stearic acid
- Alanine
Energy Generating Reactions: Glycogen + Triglyceride and Protein
OVERVIEW
Oxidation of Fuels (Cellular Respiration)…
Fuels gradually broken down to CO2 & H2O, i.e., oxidising
the “reduced bonds” in fuels.
FOCUS ON GLUCOSE:
C6H12O6 (glucose) + 6O2 (OXYGEN) —> —> 6CO2 (CARBON DIOXIDE) = 6H20 (WATER)
Oxidation; Glucose loses electrons (and hydrogens)
Reduction: Oxygen gains electrons (and hydrogens)
Energy in cells: how
- OXIDATION of foods RELEASES ENERGY , which is stored in OTHER MOLECULES that are USED TO PERFOM WORK…
- Examples of cellular “high energy” compounds
—– Activated carrier:
1. ATP
2. NADH, FADH2
3. Acetyl CoA
- Energy can also be STORED as ION GRADIENTS & in other HIGH ENERGY BONDS TOO,
e.g., PPi (pyrophosphate)
- Energy can be transferred between these
Examples of cellular “high energy” compounds
Activated carrier: High-energy component
- ATP = phosphoanhydride bond
- NADH, FADH2 = electrons & hydrogens
- Acetyl CoA = thioester bond
Understanding Oxidation and reduction…
- During catabolism, oxidation of fuels (loss of
electrons) eventually produces CO2 & H2O. - This is oxidative metabolism – we need O2 to make enough ATP in our cells.
3.In “original” terminology, “reduced bonds” (C-C, C-H) in
the fuels eventually share electrons with oxygen (C=O)
to become “oxidised bonds”
Redox Reactions
Often Catalysed by…INVOLVES…
- Often Catalysed by Dehydrogenases
- In cells often involves transfer of H (atom has electron)
- Hydride ions, H- (2 electrons) are being transferred
Explain NADH…
- NADH = (nicotinamide adenine dinucleotide)
- Electron carrier
- Cellular currency of REDUCTIVE POTENTIAL ENERGY produced during RESPIRATION
Explain NADH process…
- NADH = 2 high-energy electrons from sugar oxidation
- ELECTRON DONATION
– unstable isomer
- BOND REARRANGEMENT
- NAD+
- hydride ion
- 2 Electrons to electron-transport chain in membrane
ETC.
ATP Energy….
- ATP
= (PHOSPHATE = phosphoanhydride bonds, phospoanhydride bond + ribose, adenine) - ADP + Phosphate
= NEW BOND, ENERGY RELEASED
What is ATP? HOW DOES IT WORK
- ATP = adenosine triphosphate, contains two “high energy” phosphate group bonds.
- When a phosphate group is cleaved from ATP, ADP (adenosine diphosphate) is formed,
- the energy released can be used to drive reactions in the cell.
When does Reactions occur in cells?
- Reactions occur all the time in cells, generating ATP
when foods are catabolised, & hydrolysing ATP to ADP
(or AMP) when energy is required by the cell.
2.Cells produce ATP & continually break it down &
reform it, as required.
- Each ATP equivalent recycled 500-750 times a day
- Energy: from food catabolism
—> ATP hydrolysis yields = approx 30kj/mol energy
Energy: e.g, for anabolism
5.Cells produce ATP & continually break it down &
reform it, as required.
— Each ATP equivalent recycled 500-750 times a day
ADP TO ATP
ADP+P —-> PHOSPHORYLATION —> ATP
AND
ATP —–> HYDROLYSIS —-> ADP+ P
UNDERSTANDING Cellular Work
- Sufficient ATP levels (1 - 10 mM) must be maintained,
- or the
cell quickly loses its ability to function - this is what happens when cells are deprived of oxygen. - Energy coupling is a key feature of how cells manage their energy resources.
- ATP powers cellular work by coupling energy-generating reactions to energy-requiring reactions.
- This energy can be used to drive other reactions, such as formation of new bonds & molecules… this is metabolism & it
occurs in multiple reactions in various cellular compartments
Organised & Disorganised Energy Release…
A. STEPWISE OXIDATION OF SUGAR IN CELLS
- Sugar + O2
- Small activation energies overcome at body temperature owing to the presence of enzymes
- CO2 +H2O
- Activated carrier molecules store energy (NADH)
B. DIRECT BURING OF SUGAR
1. SUGAR + O2
2. Large activation energy overcome by the heat from a fire
3. all free energy is released as heat; none is stored
4. CO2 + H2O
Integration of Metabolism: 6
- Metabolic processes are coordinated
- Opposing pathways cannot operate simultaneously
- Cell must respond to constant changes
—- ‘External conditions e.g., availability of nutrients’
—- ‘Internal conditions e.g., genetics’
- In multi-cellular organisms, cells must communicate & cooperate, simplified by “division of labour” between tissues & cells
- Different pathways operate in different tissues &
cellular compartments - Consider glucose catabolism as an example…
