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MEH My own decs > Lecture 2: Energy reactions in cells > Flashcards

Lecture 2: Energy reactions in cells Flashcards

1
Q

What is Metabolism?

A

Metabolism is 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

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2
Q

How does biological chemistry occur? (unlike chemistry in the lab)

A

By making small chemical changes, one after the other

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3
Q

Why can we understand biochemistry relatively easily?

A

(Because there are many reactions) but only a relatively few reaction types

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4
Q

What are the chemical reactions for a particular substrate arranged into?

A

Reactions are organised into metabolic pathways,
which are distinct but integrated:

– Some metabolic pathways occur in all cells (e.g. glycolysis)
– Others are restricted to some cell types
– Some may be further restricted to compartments within cells (e.g. fatty acid synthesis occurs in cytoplasm, fatty acid break down occurs in mitochondria)

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5
Q

What are the important steps to note about metabolic pathways?

A
  • Start Points
  • End Points
  • Intermediates (metabolites)
  • Interconnections between pathways
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6
Q

What are the 2 main types of Metabolic Pathways?

A
  • Catabolic

- Anabolic

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7
Q

Describe what catabolic pathways do

A

– Break down larger molecules into smaller ones
(e.g break down building blocks into intermediary metabolites that can then feed out into other pathways)

– Release large amounts of free energy (from the bonds they are breaking)

– Oxidative meaning during the reaction, electrons are lost from the substrate. Most of the time, a Hydrogen atom (proton) will be removed from the molecule with the electron. If we can capture that hydrogen atom, it gives us some reducing power that we can put back into the system to derive other forms of energy or to drive biosynthesis

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8
Q

Describe what anabolic pathways do

A

– Synthesise larger important cellular components
from intermediary metabolites

– Use energy released from catabolism to drive that biosynthesis ( That energy might be in the form of hydrogen atoms that have been removed from substrates or through the use of ATP, which is an energy currency within a cell

– Reductive - we are putting back on Hydrogen atoms onto the substrate

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9
Q

Describe the products of catabolic metabolism

A

Fuel molecules are metabolised to supply:

  1. Building block materials (sugars, amino acids, fatty acids)
    – dynamic state of these cellular components (turnover)
    – (building block materials used for) cell growth and division
    – (building block materials used for) repair of tissues
  2. If we break building blocks down further, we yield Organic precursors like AcetylCoA
    – allow for inter-conversion of building block material (between fats and carbs for example)
  3. Biosynthetic reducing power in the form of NADH, NADPH, FAD2H
  4. Energy for cell function in the form of Adenosinetriphosphate ATP
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10
Q

What sort of work do we require energy for?

A
  1. Biosynthetic work (anabolism) - synthesis of cellular components
  2. Transport work - membranes
    (a) maintenance of ion gradients (Na+, K+, Ca2+)
    (b) nutrient uptake
  3. Specialised functions

(a) Mechanical work - muscle contraction
(b) Electrical work - nervous impulse conduction
(c) Osmotic work - kidney

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11
Q

In a normal, healthy adult, what will be equal?

A

Average daily energy intake (in food) = Average daily expenditure (in work and heat)

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12
Q

Give the order of dietary components in order of energy value

A

Fats
Alcohol
Carbohydrate
Protein

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13
Q

What is the actual definition of basal metabolic rate?

A

Energy required by an awake individual during physical, digestive and emotional rest at 18oC

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14
Q

What is diet - induced thermogenesis?

A

The energy required to process food: energy cost of ingestion, digestion and absorption of food

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15
Q

How do you convert from kcal required in 24 hours to kilojoules

A

1kcal = 4.2kj

so X4.2

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16
Q

What are the energy requirements of the body and how many kcal and kJ are required for each thing? State the values for males (70kg) and females (58kg)

A
  1. Basal Metabolic rate approx 1,700kcal (M) 1,400kcal (F) / ( 7000/5800kJ)
  2. Physical activity (depends on type, intensity and duration of activity) approx 1000 - 3000 kcal (4000 - 12000kJ)
  3. Diet Induced thermogenesis approx 150kcal / 650kJ
  4. Energy lost as heat
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17
Q

What happens when energy intake from food is greater than the energy expenditure (on DIT, BMR, PAL and energy lost as heat)?

A

Excess energy is stored:

a) by the growth/synthesis of new tissue (repair, children, pregnancy)
b) If those things are satisfied, the surplus energy is put into store as adipose tissue/fat

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18
Q

What happens when energy intake is less than the energy requirements?

A
  • Energy stores deplete and tissue is lost:
  • First fat stores deplete
  • If we are really in starvation, protein stores deplete
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19
Q

How long can humans survive without food? (providing water is given)

A

20-70 days

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20
Q

What is the main energy type that is predominantly used to drive energy requiring activities?

A

Chemical bond energy

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21
Q

What is important about the utilisation of chemical bond energy?

A

It is important that it is used directly without prior conversion to heat

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22
Q

Man is what? What does this mean?

A

Isothermal and thus can’t use heat energy for work

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23
Q

Define the terms endergonic and exergonic

A

Exergonic : a reaction where the energy released is greater than the energy input

Endergonic: a reaction where the energy input is greater than the energy released

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24
Q

What is special about exergonic reactions?

A

They are the only reactions that occur spontaneously

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25
Q

What do you call the useful energy released from exergonic reactions, and what is the symbol for it?

A
  • Gibb’s free energy

- G

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26
Q

What symbol is given for change in free energy?

A

Delta (triangle)G

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27
Q

Is the value for delta G negative or positive for exergonic reactions?

A

Negative - your EX is bad vibes

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28
Q

Contrast exergonic reactions with endergonic reactions

A

Exergonic reaction:
• Delta G < 0 (-ve)
• Reaction is spontaneous

Endergonic reaction:
• Delta G > 0 (+ve)
• Reaction is not spontaneous
• Requires energy input

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29
Q

Sketch the graph for both exergonic and endergonic reactions

A
30
Q

What is the standard free energy largely controlled by?

A

The amount of products and reactants that are normally present in the cell (rather than at 1 molar concentrations)

31
Q

If Delta G is negative, is the reaction spontaneous or not?

A

It is spontaneous - just imagine fire starting

32
Q

How is chemical bond energy of food molecules released?

A

By oxidation reactions

33
Q

Give the 2 definitions of oxidation

A
  • removal of electrons (e-) or

- removal of H-atoms (H+ + e-)

34
Q

What are redox reactions?

A

All oxidation reactions accompanied by a reduction

reaction

35
Q

What can you use to remember what oxidation and reduction are?

A

OIL RIG = Oxidation is loss of e-, reduction is gain

36
Q

In biochemistry, If we are going to do an oxidation reaction, what do we need to be looking for?

A

The associated reduction reaction

37
Q

What happens when fuel molecules are oxidised?

A

electrons and protons are transferred to carrier molecules

38
Q

Name the 3 major (hydrogen) carrier molecules

A

NAD
NADP
FAD

39
Q

What do hydrogen carrier molecules do?

A

They capture the hydrogen atoms from whatever substate it’s being released from

40
Q

What are the oxidised forms of the hydrogen carrier molecules?

A

NAD - NAD+
NADP - NADP+
FAD - FAD

41
Q

What are the reduced forms of the hydrogen carrier molecules?

A

NAD - NADH + H+
NADP - NADPH + H+
FAD - FADH2

42
Q

What is constant? So what must be present?

A
  • Total concentration of ‘oxidised and reduced’ carriers is constant
  • Therefore, must be a cycle between oxidative processes and reductive processes
43
Q

What do hydrogen carrier molecules act as?

A

• Act as carriers of ‘reducing power’ for

a) ATP production (NADH + H+) and
b) Biosynthesis (NADPH)

44
Q

If you see NADPH in a system, what do you know?

A

That that carrier is going to take that reducing power and put it into a biosynthetic process

45
Q

If you see NADH or FADH2 in a system, what do you know

A

That that carrier is going to take that reducing power and use it for ATP production

46
Q

State a word that describes the hydrogen carrier molecules

A

Complex molecules

47
Q

What do Hydrogen carrier molecules contain, and what does this prove the importance of?

A
  • Contain components from B vitamins

- Proves the importance of (B) vitamins in our diets as we can’t make them from scratch

48
Q

How are Hydrogen carrier molecules converted to a reduced form?

A

By adding two H atoms (H+ + e-)

49
Q

What happens

A
50
Q

What happens during the conversion of NAD+ to the reduced form?

A
  • 2 H atoms are added onto the carrier
  • It’s not stable
  • One of the H+ dissociates into water, so we end up with (NADH + H+)
51
Q

Describe how reducing power is used to drive biosynthesis and for ATP synthesis

A
  • Reduced fuels are oxidised
  • H atom gets released
  • H atoms are picked up either by NADP+ or NAD+
  • If we form NADPH, that’s reducing power for biosynthesis
  • If we form NADH or FAD2H, they are substrates for ATP synthesis
52
Q

What is ATP?

A

The energy currency of the cell

53
Q

What does ATP consist of?

A
  • Adenine ring
  • Ribose sugar
  • 3 phosphates
54
Q

Where is the energy being carried in ATP?

A

In the bond that links the terminal phosphate to the ADP

55
Q

What is the energy released in exergonic reactions used to drive?

A

ADP + Pi ——-> ATP ( The production of ATP)

56
Q

When we produce ATP, what is the reducing power that we released, conserved as?

A

As the chemical bond energy of the terminal phosphate group (PO4^4-) of ATP

57
Q

Is ADP a carrier or a store? Explain

A
  • A carrier
  • Because there is only a limited amount of ADP in a cell, so if we charged up all our ADP to ATP, there would only be enough for a few seconds of life, therefore must cycle
58
Q

What is one important feature of ATP?

A

ATP is stable in the absence of specific catalysts ( if we made some ATP, but there’s no immediate requirement to use it, it will maintain the phosphate in the 3rd position and hold onto it till it’s required- it docent break don spontaneously) Enables flow of energy to be controlled

59
Q

Is ATP a currency or a store?

A

A currency

60
Q

Why do we need fuel oxidation to be occurring all the time?

A
  • Because ATP is not a store so we constantly need to be oxidising fuels to be releasing the energy to produce the ATP to allow us to do work
  • Theres only limited amounts of adenosine nucleotides
  • We need the ATP/ADP cycle to be running to maintain the ATP supply in the tissue
61
Q

What activates anabolic pathways?

A

[ATP] is high

62
Q

What activates catabolic pathways?

A

When [ATP] is low , and ADP is high and AMP is high

63
Q

What do high energy signals do?

A

Activate anabolic pathways

64
Q

What do low energy signals do?

A

Activate catabolic pathways

65
Q

List the high energy signals within a cell

A

ATP (as you have piked up that energy)
NADH (as you have picked up that reducing power from substrate)
NADPH
FAD2H

(ATP and reduced Hydrogen carrier molecules)

66
Q

List the low energy signals within a cell

A

ADP, AMP
NAD+
NADP+
FAD

67
Q

What does AMP stand for?

A

Adenosine monophosphate

68
Q

Name the important enzyme when energy levels are low and describe what it does.

A

When energy levels are low,
the cell looks for a way of creating a bit more ATP using
the enzyme Adenylate kinase (myokinase).
It brings 2 ADP molecules together and transfers the terminal al phosphate from one of them to the other, to make ATP and AMP.
AMP signals low energy levels in the cell

69
Q

What is reducing power converted to, and by which process?

A
  • To energy currency ATP

- By oxidative phosphorylation

70
Q

What is energy and reducing power use to do?

A
  • To drive the synthesis of new molecules (anabolism)

- Or to produce work (e.g. exercise)

MEH My own decs (13 decks)

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