Topic 5: Energy Reactions in cells Flashcards
What is cell metabolism
The set of processes which derive energy and raw materials from food stuffs and use them to support repair, growth, and activity of the tissues of the body to sustain life
By making small chemical changes of few types
Reactions are organised into metabolic pathways - some are in all, or multiple cells or restricted to compartments
What are the functions of metabolism
Conversion of food to energy to run cellular processes
Conversion of food to cellular blocks for proteins, lipids, nuclei acids and carbs
Elimination of metabolic waste
Describe the relationship between catabolism and anabolism
Catabolic - break down larger molecules to smaller, releasing free energy. It is oxidative so releases hydrogen atoms - ‘reducing power’
Anabolic - synthesise larger components from intermediary metabolites with the use of energy released from catabolism (atp). Reductive - use H released in catabolism
Why do cells need a continuous supply of energy
- Bio synthetic work (anabolism ) - synthesise components
- Transport - maintain ion gradients, nutrient uptake
- Mechanical - muscle contraction
- Electric - nervous impulse
- Osmotic - kidney
What is a redox reaction
Both oxidation and reduction
Oxidation - removal of electrons or H atoms
Accompanied by reduction
Reduction - gain
OILRIG
What is the the role of redox reactions and H carrier molecules in metabolism
When undergoing redox, electrons and protons are transferred to carrier molecules
Include: NAD+, NADP+, FAD
In reduced form: NADH +H+, NADPH + H+, FADH2
concentration of opposing forms of carriers constant - cycle between oxidative and reductive processes
What are the roles of ATP?
Must be recycled as limited
It is stable in the absence of specific catalysts - Enables flow of energy to be controlled, when energy levels high, negative feedback, so stop
What are the roles of other molecules containing high energy
Energy is melt often stored in form of glycogen or triglyceride
Creating phosphate is used when cells undergo increased metabolic activity and this reserve of energy is used - creatine kinase - phosphocreatine + ATP
When ATP - creatine phosphate is formed + ADP
If low ATP - reaction reversed to form creatine + ATP
Explain the role of high and low energy signals in the regulation of metabolism
When there is lots of ATP = anabolic pathways are activated When there is little ATP, ADP high, AMP high = catabolic pathways activated Adenylate kinase(myokinase): 2ATP -> ATP + AMP AMP = lower energy signal High energy(energy levels high) - anabolic pathways so ATP, NADH, NADPH, FADH2 Low energy - catabolic pathways (energy used up) so ADP, AMP, NAD+, NADP+, FAD
What is a metabolic pathway
Start pointe Intermediates (metabolites) End points Interconnections between different pathways Two types - catabolic and anabolic
What are the waste products of cell metabolism
Carbon dioxide
Water
Urea
What are the products of catabolic metabolism
- Building block materials (sugars, amino acids)- allow fo cell growth, division and repair
BREAKDOWN INTO - Organic precursors (acetyl coA) - allow for inter conversion of building block material
- Bio synthetic reducing power (NADH, NADPH)
- Energy for cell function (ATP)
What are the energy contents of food
Fat - 37g-1
Carb - 17
Protein - 16
Alcohol - 29
What does the body need energy for
- Basal metabolic rate - 1700/1400kcal- awake, sitting
- Activity - 1000-3000
- Specific dynamic action of food - 150 - ingestion, digestion etc
Energy is lost as heat
What happens if energy intake > energy required
Excess energy stored for growth such as synthesis of new tissue
And production of adipose tissue
What happens if energy intake< energy requirement
Tissue is lost
What forms do energy exist in
Heat, light, mechanical, electrical, osmotic, chemical bond
Biology uses chemical bond energy predominately without producing heat as can not use that
Describe chemical bond energy
All cellular activities involve chemical bonds being broken or formed
If exergonic - release energy
Endergonic - require energy
Which reactions can only occur spontaneously
Exergonic
Useful energy = free energy, G (gibbs)
Delta G = negative = exergonic
What is an exergonic reaction
Spontaneous
Reactants of a higher energy level that products
DeltaG is negative
What is an endergonic reaction
Not spontaneous
Reactants of lower energy level than products so energy needed to put into the system
Delta G = positive
What are the standard conditions for free energy
25 degrees
1atm
1 mol
pH= 7
What are the standard conditions fo free energy in the cell
Change in G = change in G in standard conditions + RT x logn(products)/(reactants)
Value indicates ether spontaneous or not
Not rate
What processes are H carrier molecules used for
ATP production - (NADH + H+)
Biosynthesis (NADPH)
What happens to H carrier molecules
Contain components from B vitamins
Converted to reduced form by adding two H atoms
One - h+ dissociates into solution
One - present in the molecule
How can energy released during oxidative metabolism be used to drive processes?
Energy released by oxidation of food - exergonic
Directly - use of NADPH in biosynthesis, oxidised back, substrate reduced by H (bio synthetic Reduction)
Indirectly - mitochondrial system to couple NADH to form ATP(ATP synthesis)
What is the structure of ATP
Adenine
Ribose
Triophosphate
How can ATP release energy
The phosphate bond can be hydrolysed to release an inorganic phosphate and ADP ATP + H2O -> ADP + Pi -31kjmol-1 ADP can then hydrolysed to AMP ADP + H2O -> AMP + Pi -31kjmol-1
Catabolism involves the breakdown of chemicals to release..
Reducing power
Energy (ATP)
Reducing,power is converted to ATP by
Oxidative phosphorylation
Clinical markers related to creatine metabolism
Creatine kinase is a marker of myocardial infarcation
One subunit is made of CK-MM and other is CK-MB - specific to heart
CK is released from cardiac cells when damaged in heart attack, present in blood, diagnosed if in correct combination
Creatine and phosphocreatine can randomly break down to form
Creatinine
Constant formation
How is creatinine used as a clinical marker
Excreted via kidneys
Creatinine excretion per 24hr = muscle mass
Creatinine concentration in urine = urine dilution (high creatinine - urine concentrated)
Can be used to estimate urinary loss of many substances such as hormones in pregnancy
Which phosphate group on ATP is hydrolyzed when energy is needed to drive cellular work?
Gamma phosphate
Which substance is used to supply the electron transport chain with high-energy electrons derived from metabolic substrates?
NADH
When ATP levels are high in skeletal muscle, energy may be temporarily stored in which substance?
Phosphocreatine
How much atp is produced by glycolysis
2
Exergonic reactions,
Delta g less than 0
Spontaneous
Catabolism - oxidation
Endergonic reactions
Delta G more than 0
Not spontaneous
Requires energy
Catabolism
NAD+ -> NADH
Low creatinine
Lots of urine formed
