Energy Reactions in Cells Flashcards
Define 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.
Where does food go after it’s eaten?
GI tract
What is the overall purpose of food?
To supply the energy needs of the cell
What is food broken down into?
Nutrients
What happens once food has been broken down into nutrients in the GI tract?
They pass into the blood
What happens to food not absorbed into blood?
It is lost as faeces
What happens to the nutrients in the blood?
They are taken up by the tissues
What happens to nutrients in the tissue?
- Interconversion
- Storage (packaging nutrients into stores)
- Synthesis
- Utilisation
What happens to utilised nutrients in the tissues?
They can pass back into blood for transport
How can nutrients be used for energy?
They can be oxidised
What happens to any waste produced from the oxidation of nutrients?
It’s passed back into the blood, and then lost from the kidneys or lungs
How does biological chemistry occur?
In small, controlled, step-wise chemical changes
What are metabolic reactions organised into?
Metabolic pathways
Describe the nature of the metabolic pathways
Distinct but integrated
What allows for the interconnectivity of metabolism?
Staging points on pathways where nutrients can enter or leave
Do the metabolic pathways occur in all cells?
Some do, but some restricted to certain cell types, or compartments of cells
Give an example of a pathway that occurs in all cells
Glycolysis
What is which metabolic pathways occur in which cells related to?
Function
What do all pathways have?
- Start point
- End point
- Interconnections
- Intermediates
What are the intermediates in metabolic pathways known as?
Metabolites
What are the two main types of metabolic pathway?
NAME?
What do catabolic pathways do?
Break down larger molecules into smaller ones
What are smaller molecules produced in catabolic processes known as?
Intermediary metabolites
What do catabolic processes release?
Large amounts of free energy
How do catabolic processes release free energy?
Breaking chemical bonds
Are catabolic processes oxidative or reductive?
NAME?
What is meant by catabolic processes being oxidative?
They release H atoms- ‘reducing power’
What are the H atoms released by oxidative processes used for?
Can be used to fuel production of energy currency, or fuel biosynthesis in another pathway
What is the result of the metabolic steps being small?
Release small amounts of energy per step
What is the advantage of releasing small amounts of energy per step?
It can be captured for the future
What do we need catabolism for?
To allow synthesis within cells
What do anabolic processes do?
Synthesise larger cellular components from intermediary metabolites
What do anabolic processes need?
Energy in the form of ATP released from catabolism
Are anabolic processes oxidative or reductive?
NAME?
What is meant by anabolic processes being reductive?
They use H’s
Give the 4 products of catabolic metabolism
- Building block materials
- Organic precursors
- Biosynthetic reducing power
- Energy for cell function
Give 3 examples of building block materials
NAME?
What is meant by there being a dynamic state of cellular components?
There is interconversion between each other to meet cells needs
What are building block materials needed for?
- Cell growth
- Division
- Repair
Give an example of an organic precursor
Acetyl CoA
What is Acetyl CoA required for?
Interconversion of building block materials
Give two examples of molecules that capture biosynthetic reducing power
NAME?
What do molecules that capture biosynthetic reducing power do?
Capture H atoms
What is the energy content of fat?
37kJ/g
What is the energy content of carbohydrate?
17kJ/g
What is the energy content of protein?
16kJ/g
What is the energy content of alcohol?
29kJ/g
What is the basal metabolic rate for a 70kg man/ 58kg woman?
1700/1400kcal
What is meant by basal metabolic rate?
The energy required by an awake individual during physical, emotional and digestive rest at 18ºc by all the body tissues
How much energy is required for activity?
1000-3000kcal
How much energy is required for the specific dynamic action of food?
150kcal
What is the specific dynamic action of food?
The energy cost of ingestion, digestion and absorption of food- extracting molecules in a form that we can get into body
How long can we survive without food?
20-70 days, if given water
What do food regulatory mechanisms do?
Govern supply, storage and utilisation of energy
What can happen to the different forms of energy?
They’re all interconvertible
What type of energy does biology predominantly use?
Chemical bond energy
How is chemical bond energy used?
NAME?
What is meant by man being isothermal?
They cannot use heat energy for work
What are all cellular activities expressions of?
Chemical reactions in which chemical bonds are broken or formed
What is meant by exergonic?
Releases energy
Are exergonic reactions catabolic or anabolic?
NAME?
What is the sign for ∆G in exergonic reactions?
Negative
Are exergonic reactions spontaneous?
Yes
What is meant by endergonic?
Requires energy
What is the sign for ∆G in endergonic reactions?
Positive
Are endergonic reactions spontaneous?
No
What do endergonic reactions require?
Energy input
What is the intermediate energy position?
The high energy as a result of activation energy, caused by the necessity to bring things together
What are the conditions for standard free energy change (∆Gº)?
25ºc, 101kPa, 1 molar concentrations of reactants and products
What additional condition exists for ∆Gº ’ ?
At pH 7.0
What is ∆G equal too in non-standard conditions?
∆Gº + RT . log n ([products]/[reactants])
Where may non-standard conditions be found?
In a cell
What determines free energy?
The ratio of products to reactants in the body
What does the ∆G sign indicate?
If the reaction is spontaneous or not
Why does the ∆G sign not indicate rate?
It may be that a reaction has a very high activation energy, or a very low rate.
How is the chemical bond energy of fuel molecules released?
Oxidation reactions
What is oxidation?
Removal of e - or removal of H + atoms
What are all oxidation reactions accompanied by?
Reduction
Why do oxidation reactions have to be accompanied by reduction reactions?
H atoms must be passed on
What happens when fuel molecules are oxidised?
e - and H + are transferred on to carrier molecules
Why does the cell have a choice of how to use reduced power?
Because it’s not in a linear pathway
Give the 3 major H carrier molecules in their oxidised forms
- NAD +
- NADP +
- FAD
Give the 3 main H carrier molecules in their reduced forms
- NADH + H +
- NADPH + H +
- FADH 2
Why is NAD(P)H and H + formed?
One H + quickly dissociates
How does the total concentration of oxidised and reduced carriers vary?
It doesn’t- it remains constant
Why does the total concentration of oxidised and reduced carriers remain constant?
The carriers are converted back and forth so they can pick up more energy in a cycle
What does NADH + H + act as the reducing power for?
ATP production
What does NADPH act as the reducing power for?
Biosynthesis
What do H carrier molecules contain?
Certain components from B vitamins
How are oxidised H carriers converted to their reduced form?
Adding 2 H atoms
What happens to H + in solution with H carriers?
It dissociates, leaving one electron behind on the carrier
What does NAD(P) + contain?
NAME?
Why is the nicotinamide group with conjugated ring important?
Because the ring can pick up electrons to redistribute them
What is the result of the conjugated ring’s ability to redistribute electrons?
It allows the H atom to bind
How does FAD + differ from the other two carrier molecules?
It is similar, but has different electron capturing structure
What kind of process is the release of energy from food?
Exergonic
How has the oxidation of food captured bond energy?
Onto reducing equivalents
How can reducing equivalents drive energy requiring activities?
By coupling systems
What is meant by coupling systems?
Coupling carriers to other processes
Give an example of when coupling systems can be used directly
The use of NADPH drives biosynthesis
Give an example of where coupling systems can be used indirectly?
In the mitochondria electron transport system
What happens in the mitochondrial electron transport system?
NADH is coupled to production of ATP- electrons are fed into system, energy stripped out to drive ATP production
What bond in ATP is hydrolysed?
The bond between the terminal phosphate and the rest of the molecule
What happens when the terminal phosphate bond is hydrolysed?
It releases a phosphate and energy
What can be used to drive ATP synthesis?
Energy released in an exergonic reaction
How is part of the free energy released in a exergonic reaction conserved?
As chemical bond energy in the terminal phosphate of ATP
How much supply of ATP does a cell have?
A few seconds
What is the consequence of only having a few seconds supply of ATP?
It must cycle
Is ATP stable?
Yes, in the absence of a specific catalyst
What is the result of ATP being stable?
In controls the energy flow to prevent wasteage
When does catabolism slow?
When there is nowhere for the energy to go
What happens to catabolism when the energy has been used?
It restarts
What happens when [ATP] is high?
Anabolic pathways are activated
Why are anabolic pathways activated when [ATP] is high?
It is a high energy signal, so they know they have enough energy for biosynthesis
What happens when [ATP] is low, and [AMP] and [ADP] is high?
Catabolic pathways are activated
What is the effect of adenylate kinase (myokinase)?
2 ADP are converted to AMP and ATP
Give 4 high energy signals
- ATP
- NADH
- NADPH
- FADH 2
Give 5 low energy signals
- ADP
- AMP
- NAD +
- FAD +
- NADP +
What happens when supply > demand?
Energy most often stored in form of polymer macromolecules of fuel molecules
Give an example of a cell type that may need to increase metabolic activity very quickly?
Skeletal muscle
What is required for cell types that may need to increase their metabolic rate very quickly?
A high energy store reserve for emergencies
What is the high energy store reserve for emergencies?
Creatine phosphate
When is creatine phosphate produced in cells?
When ATP levels are high
Give the equation for the formation of creatine phosphate
Creatine + ATP -> Creatine Phosphate + ADP
What enzyme is required for the production of creatine phosphate?
Creatine kinase
What happens if [ATP] suddenly drops?
The creatine phosphate reaction reverses, producing a short term boost of [ATP]
How can creatine kinase (CK) be used clinically?
As a myocardial infarction (MI) marker
Why can CK be used as a MI marker?
CK is made up of 2 sub units. Different isoform combinations are found in different tissues, as there are 2 different proteaceous sub units of 2 genes that could form CK. One of the isoform combinations is CK-MM at 70% and CK-MB at 25-30%, which is specific to heart muscle. Normally CK is not in the muscle, so if it is present in a blood test in that isoform combination, it shows you there has been heart muscle damage, as CK is released from myocytes when damaged in MI.
Other than MI, what can CK be used as a clinical marker for?
Muscle infarction
What isoform is found in blood if there has been a muscle infarction?
98% MM and 1% MB
What happens to creatine and phosphocreatine spontaneously?
They break down slowly, at a steady rate, to creatinine
When is the breakdown of creatine and phosphocreatine not slow and steady?
In the case of muscle wasteage
How is creatinine excreted?
Via the kidneys
How can creatinine measurements be used clinically?
- Excretion per 24 hours is proportional to muscle mass
- Concentration in urine can be a marker of urine dilution
- Can be used to standardise other tests
