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Human Biosciences > Bioenergetics part 2 > Flashcards

Bioenergetics part 2 Flashcards

1
Q

What is energy released from macronutrients harnessed by our bodies to do?

A

Synthesise ATP

So ATP is carrier of energy from macronutrients

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2
Q

What is Adenosine triphophate made up of?

A

Adenine
Ribose
Phophate chain

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3
Q

How does ATP produce energy basically?

A

When you break phosphate bond lots of energy released

It’s the only compound that transfers chemical energy to energy requiring processes

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4
Q

Why do we use ATP?

A

Phosphate bonds trap large portion of potential energy from food

Easily transfers to other compounds to fuel endergonic reactions or raise compounds to higher activation levels (means that eventually energy release will be greater)

Example of this is storing glucose as glycogen

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5
Q

Explain how ATP is the energy currency, and reasons which it isn’t aswell?

A

Simplifies the coupling of energy producing reactions to energy requiring reactions (ATP can be used by all)

However, ATP cannot be accumulated, or transferred from cell to cell

Once the ATP has been used and no more can be generated, the cell dies (can’t go in debt)

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6
Q

What mechanisms do cells have to prevent death when run out of ATP?

A

Fatigue in ,muscle arrests ATP utilisation during physical activity

Maintenance of the ATP to ADP concentration ratio

This take precedence over cell function

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7
Q

Features about the ATP-ADP ratio?

A

Not equillibrium, 50/1 in favour of ATP

A system that is far from equilibrium is capable of doing work

Breakdown of ATP increases ADP concentration, but ATP is rapidly reformed

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8
Q

What are luxury reactions?

A

Physiological functions of the cells, that aren’t essential for that cell to survive (body may die)

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9
Q

What type of reaction is the breakdown of ATP?

A

Hydrolysis reaction, a Phosphate bond (terminal) is broken down when joined with water

ATP + H2O = ADP + Pi (inorganic Phosphate)

-(delta)G7.3kcal.mol^-1 amount of energy released

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10
Q

What enzyme catalyses ATP breakdown?

A

Adenosine triphosphatase (ATPase)

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11
Q

What can happen to ADP to release more energy?

A

A further phosphate group can be cleaved releasing more energy

Catalyzed by adenosine diphosphatase

This leaves adenosine monophosphate - AMP

Is a rare occurrencre as turnover of ATP (hydrolysis-re synthesis) is so effective

So only used in exhaustive situations

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12
Q

What does the enzyme adenylate kinase do?

A

Catalyse ATP regeneration from ADP

2ADP = ATP + AMP

Most important at beginning of exercise

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13
Q

Does ATP hydrolysis require oxygen?

A

No, Oxygen would take too lung too get to cells

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14
Q

Why haven’t human evolved to store more ATP instead of relying on re synthesis?

A

It would be too heavy, and therefore inefficient

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15
Q

How much ATP stored in the body at any given time?

A

80-100g

3mmol of ATP per kg wet weight muscle tissue

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16
Q

How is instant replenisment of ATP achieved?

A

PCr - phosphate phosphocreatine

Provides Phosphate group

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17
Q

Formula for ATP being used for biological work?

A

ATP = ADP + Pi + Energy

Catalysed by ATPase

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18
Q

Formula for ADP being turned into ATP?

A

PCr + ADP = Cr + ATP

Catalysed by creatine kinase

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19
Q

Where is Creatine Kinase found in abundance?

A

Locations of ATP hydrolysis and regeneration

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20
Q

How long does it take for PCr to theoretically deplete?

A

8-12 sec

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21
Q

What does PCr creating a buffer mean?

A

Gives time for other energy pathways to get going

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22
Q

What is the stimulus for Creatine Kinase activity?

A

Increase in ADP concentration (thus ATP Hydrolysis)

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23
Q

Describe the PCR shuttle?

A

Made in centre of Mitochondria

ATP leaves inner mitochondrial membrane, and binds to MiCK (mitochondrial creatine Kinase) in the inter membrane space

Then outside the mitochondrial membrane MMCK (muscle machinery Creatine Kinase) gives a Cr to MiCK, then PCr goes to MMCK,

Which then goes to ATPase and then the myofibril for contraction

The ATP has turned into ADP and returned inside the mitochondrial membrane to be re-synthesised into ATP

This reduces the distance ADP and ATP have to travel as they are very heavy, and Cr and PCr are lighter

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24
Q

What are the 3 macronutrients?

A

Carbs
Protein
Fat

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25
Q

What are the important 3 micronutrients?

A

Vitamins
Water
Minerals

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26
Q

Order from smallest to largest of energy production per gram?

A

Carbs
Protein
Lipid

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27
Q

Features of carbohydrate molecules?

A

Only Carbon Hydrogen and Oxygen

Has a Carbonyl group CHO, and a carbon skeleton

Isomers have same molecular formula and mass (C6H12O6)

Will either be mono, di or polysaccharides

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28
Q

Why do carbs provide energy?

A

We strip hydrogens from them and then strip electrons for electron transport chain

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29
Q

General formula for Carb?

A

Cn(H2O)n

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30
Q

Examples of monosachharides

A

Glucose
galactose
fructose

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31
Q

Example of a disaccharide?

A

Glucose + fructose = sucrose

Glucose + glucose = maltose

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32
Q

Example of polysaccharide?

A

Starch in plants, amylose and amylopectin

Glycogen in animals

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33
Q

Features of blood glucose?

A

Regulated by hormones
Primary cerebral fuel
Storage of carbs

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34
Q

What are the 3 storages of glycogen?

A

Blood glucose
Liver glycogen
Muscle glycogen

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35
Q

What’s glycogenenis?

A

Synthesis of glycogen from sugar molecules

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36
Q

What’s glyconeogenesis?

A

Formation of glycogen from amino acids, fats and other non carbohydrates

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37
Q

What’s glycogenolysis?

A

Breakdown of glycogen into glucose, to use it for energy transfer

Catalysed by glycogen phosphorylase

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38
Q

3 stages of extraction of energy from carbs?

A

Glycolysis
TCA cycle (Krebs)
Oxidative phosphorylation

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39
Q

Features of glycolysis?

A 
Oxidation of glucose
Start product can also be glycogen
Takes place in the cytoplasm
Aerobic glycolysis produces pyruvate
Anaerobic glycolysis produces lactate
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40
Q

What does glycolysis require?

A

Glucose
Enzymes
Co enzymes
ADP

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41
Q

What does glycolysis produce?

A

Pyruvate
NADH
ATP

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42
Q

Does glycolysis require oxygen?

A

No but further stages do

43
Q

1-3 steps of glycolysis?

A

Energy investment to recouped later:

  1. Catalysed by the enzyme hexokinase
  2. Catalysed by phosphofructokinase

ONLY STEP 3 REQUIRES ATP WHEN GLYCOGEN IS USED AS A SUBSTRATE

44
Q

What is the primary regulator of the speed of glycolysis?

A

Phosphofructokinase

45
Q

Steps 4-5 of glycolysis?

A

Cleavage of 6-carbon sugar to 2 3-Carbon sugars:

So rest of reactions will occur in duplicate

46
Q

Steps 6-7 of glycolysis?

A

Energy generation: (remember all these steps are occurring in duplicate now)

  1. If the metabolic rate is high, the NAD+ can become saturated with H+, so that there is not enough free NAD+ available. This can cause a bottleneck at step 6 which will slow the rate of glycolysis
47
Q

Steps 8-10

A

Remember all still in duplicate

Energy generation:

  1. pyruvate + ATP formed, catalysed by the enzyme pyruvate kinase
48
Q

Net result of glycolysis?

A

1 molecule of glucose is turned into 2 pyruvate (or 2 lactate)

2ADP goes to 2 ATP (will be 3 for glycogen)

2NAD+ goes to 2NADH + H+

49
Q

What can happen to pyruvate once it’s formed?

A

Can be turned into lactate, which also produces NAD+, which can then be used in step 6 of glycolysis

Can turn into Acetyl-CoA, produces NADH + H+, which can then be used in the mitochondrial electron transport chain

So what is made depends on if there is high NAD+ in the cell (Acetly-coA is made) or if there is high NADH + H+ in the cell (Lactate is made)

50
Q

Overall energy yield of glycolysis?

A

2 ATPs

51
Q

In glycolysis what are the rate limiting steps?

A

PFK at step 4

NAD+ in step 6

52
Q

What are the ATP generating steps in glycolysis?

A

7 and 10

53
Q

TCA cycle=

A

Krebs cycle

54
Q

What happens directly after glycolysis?

A

If fatigued

Pyruvate turned into lactate, via lactate dehydrogenase

If not fatigued, pyruvate turned into Acetly-CoA + CO2, which then goes into the TCA cycle

Add more notes

55
Q

Why do we make lactate when fatigued?

A

Glycolysis is faster than TCA and ETC

When metabolic rate is high NADH availability is high and NAD+ availability is low

This favours pyruvate to lactate

NAD+ produced will help maintain the glycolysis rate

H+ ions are released though, increasing acidity effecting enzymes can denature early ones in glycolysis

56
Q

When is Acetly-CoA made?

A

When metabolic rate low and O2 availability high and so is NAD+

Favours the transport of of pyruvate to the mitochondrion where it is converted to Acetyl-CoA

57
Q

Location of carbohydrate metabolism in a cell?

A

Cytosol for glycolysis, and therefore substrate level phosphorylation (Phosphocreatine hydrolysis and glycolysis)

TCA cycle and oxidative phosphorylation occurs in mitochondrion

58
Q

Features of the TCA cycle?

A

Occur in mitochondrial matrix

Starts off with acetly-CoA

A cyclical process of 8 steps

Main purpose is to oxidise acety-CoA groups and strip off their electrons

Finishes with oxaloacetate

59
Q

What’s cristae?

A

Folds in the mitochondrial matrix

60
Q

Key steps of TCA cycle?

A

Step 1. Oxaloacetate reacts with acetyl CoA to form a 6-carbon molecule citrate

Step 3 produces CO2 and NADH

Step 4 produces CO2 and NADH

Step 5 produces one GTP

Step 6 produces one FADH2

Step 8 produces one NADH and regenerates oxaloacetate

61
Q

What is net yield from one molecule of glucose?

A

36 ATP

Glycolysis 2
TCA 2
ETC 32

62
Q

Ways to generate ATP and features of it?

A

PCr
Low capacity
Fast rate

Glycolysis
Intermediate capacity
Intermediate rate

Oxidative phosphorylation = etc

High capacity
Low rate

63
Q

What are the differences between substrate level phosphorylation and oxidative phosphorylation?

A

Substrate level occurs in cytoplasm, PCR hydrolysis and glycolysis

Oxidative is in mitochondria energy comes from electron transport chain

64
Q

Features of fat?

A

Composed of carbon , hydrogen and oxygen

Contain more hydrogen than carbohydrates

65
Q

Types of fat?

A

Nuetral lipids - triglycerides

Compound lipids - phospholipids in cell membranes

Derived lipids cholesterol

66
Q

More features of triglycerides?

A

Made up of 1 glycerol and 3 fatty acids

Hydrocarbon chain of fatty acid can vary - longer it is the more energy rich as more hydrogen and therefore more electrons

67
Q

Where are triglycerides stored?

A 
It's stored in adipose tissue:
Subcutaneous fat (fat directly under the skin)
Internal fat (Deposits internal organs)

In muscle cells

68
Q

How are triglycerides made?

A

Condensation reaction releasing water between glycerol and fatty acid chain

Facilitated by substrate availability and hormonal regulation

69
Q

Cells that form adipose tissue are?

A

adipocytes

70
Q

Describe fat mobilisation?

A

Release of fatty acids from adipose tissue, triggered by hormone sensitive lipase (HSL)

Glycerol diffuses out

Free fatty acids travel in circulation bound to protein albumin

Triglycerides travel in lipoprotein complexes

71
Q

What is lipolysis and what catalsyes it?

A

It’s the breakdown of triglycerides, catalysed by lipoprotein lipase

72
Q

Equation for triglyceride catabolism?

A

Triglyceride + 3 H2O = Glycerol + 3 fatty acids

73
Q

Describe how fats are used to generate ATP?

A

Catabolism occurs, glycerol and 3 fatty acids produced

Glycerol turned into Glyceraldehyde 3-phosphate, which is also the substrate in step 6 of glycolysis

Will then carry on the same path as glucose from there

The 3 Fatty acids are activated costing each an ATP

They then go into Beta- Oxidation producing 2 carbon Acyl groups which then react with CoA to form Acetly-CoA which is the substrate which goes into the TCA cycle so can just follow glucose from there

Also Beta Oxidation produces 2 H+ which will be used in the electron transport chain (transported by FAD and NAD+)

74
Q

Features of Beta oxidation?

A

Occurs in mitochondrial matrix

75
Q

Limiting rate of fatty acids entering TCA cycle?

A

There needs to be sufficient oxaloacetate to combine with the acetyl-CoA formed during Beta oxidation

76
Q

What is Oxaloacetate regenerated from?

A

Pyruvate

77
Q

What’s gluconeogenesis?

A

Glycerol, lactate and certain amino acids being converted to glucose in the liver

78
Q

What’s the cori cycle?

A

2 lactate goes to 2 pyruvate goes to 1 glucose

Requires 6 ATP which is expensive so normally occurs resting after exercise

79
Q

What’s lipogenesis?

A

Liver cells and adipose cells can synthesise lipids from glucose and amino acids

80
Q

Can fatty acids be converted into pyruvate or oxaloacetate to synthesise glucose?

A

No

81
Q

Protein functions?

A

There are Structural proteins - Actin and myosin in skeletal muscle

Transportation from the proteins haemoglobin and myoglobin as oxygen binds to them

Enzymes for all metabolic pathways

Hormones:
Neurotransmitters
Immune function

82
Q

Structure of an amino acid?

A

alpha Carbon in middle

One side amino group (NH2)

Other side is carboxyl group (COOH)

Hydrogen above

Organic side chain bellow (C, O, H, N, S)

83
Q

What happens when 2 amino acids bind together?

A

COOH terminal reacts with Amino terminal of other amino acid

Condensation reaction

Peptide bond formed

84
Q

Describe Protein structure?

A

Primary:
Amino acid sequence

Secondary:
Hydrogen bonds between amino acids with the peptide chain
Alpha helices, beta sheets

Tertiary:
Attractions between a helices and beta sheets

Quaternary:
interactions between 2 or more peptide chains

85
Q

Denaturation in protein?

A

Loss of structure and biological activity

However peptide bonds remain intact

Caused by temp or pH

86
Q

Features of protein metabolism?

A

Unlike CHO and fats, protein is not stored as an energy substrate

Fast turnover rate

Rapid response to starvation and training

Regulated by hormones

87
Q

Why is it difficult to determine energy yield of protein oxidation?

A

Nitrogen excretion requires ATP

88
Q

Describe protein catabolism?

A

Amino acid is deaminated (removal of nitrogen)

Then will enter the TCA cycle at various stages:

  • Pyruvate ( then go on to form acetyl-coA)
  • Acetoacyl-coA ( then go on to form acetyl-coA)
  • Acetyl-coA
  • Intermediaries in the TCA cycle
89
Q

Describe the process of nitrogen balance ?

A

Nitrogen removal from amino acids

Transported by alanine and glutamine

Urea cycle (ATP cost)

Dietary N input = N excetion to maintain balance

Negative Nitrogen balance means net loss of muscle mass

90
Q

When we will protein contribute more to energy expenditure?

A

When CHO stores decrease

91
Q

What is cellular oxidation?

A

Process aimed at providing energy to rynthesise ATP (oxidative phosphorylation) in the presence of Oxygen

Accomplished through the breakdown of CHO lipids and protein

92
Q

What do we need for cellular oxidation?

A 
Fuel
Citric Acid cycle
Co-enzymes (Cartier’s, NAD and FAD)
The electron transport chain
Oxygen

In the exam?

93
Q

Describe electron transport?

A

Hydrogen atoms are stripped from CHO, lipids and protein (Citric acid cycle)

Co-enzymes NAD+ and FAD transport hydrogen to the ETC

Electrons are temporarily stripped from hydrogen and passed onto the ETC

The ETC is composed of 4 cytochromes (membrane bound proteins). Electrons are passed down them

At cytochrome 4 oxygen accepts the electrons and rejoins with H2 to form water

94
Q

Describe ATP generation in ETC?

A

In 3 of 4 cytochromes the free energy release of electron transfer is accosiated with proton pumping from the matrix to the intermembrane space

This is a kind of active transport, as the protons accumulate outside the mitochondrial matrix

When they flow back down their concentration gradient, enough energy to phosphorylate ADP into ATP

(Happens in 1,3,4)

95
Q

Where does FAD drop electrons?

A

Complex 2
So doesn’t help out at first complex

So net gain only 2ATP

96
Q

Where does NAD drop electrons off?

A

First complex

Net gain is therefore 3 ATP

97
Q

Equation for resynthesis of ATP?

A

NADH + H{+} + 3ADP + 3Pi + 1/2 O2. = NAD{+} + H2O + 3 ATP

98
Q

What would happen if oxygen is limited in ETC?

A

Can no longer move electrons down the chain as C4 cannot be oxidised, so the rest will be backed up

NADH accumulates

NAD+ reduces

Flux through Krebs cycle is reduced

99
Q

How do we continue exercise after O2 becomes limited?

A

Increase anaerobic energy turnover

Hydrogen removed from NADH by pyruvate resulting in lactate formation which generates more NAD+ which can be used in glycolysis and processes like this to generate more ATP, meaning pH will drop

Low pH is associated with reduced muscle function, so exercise tolerance is compromised

100
Q

What’s an easy way to measure the rate of xeullar oxidation?

A

Consumption of oxygen

101
Q

Explain the role of PCr hydrolysis at the onset of intense exercise?

A

Buffering - ATP replenishment

Signalling - early reactions involving PCr hydrolysis switch on glycolysis and oxidative phosphorylation1

102
Q

How do kidneys regulate the acid-base balance?

A

Renal buffering is the only pathway to excrete H+ ions and thus neutralise acids other than the carbonic acid

Kidneys also facilitate the chemical buffering in the blood by releasing bicarbonate back into the back into circulation to mop up H+

103
Q

Explain how ATP can be considered as an energy currency with 2 inconsistencies?

A

ATP simplifies the coupling of energy producing reactions to energy requiring actions

Unlike currency ATP can’t be accumulated or transfered

Credit is not permited, once ATP is gone cell function declines

104
Q

What are the 4 main steps in the reciever donor cycle?

A

Extraction of potential energy from food
Conservation of this energy within ATP
Extraction of energy from ATP to perform biological work
ATP resynthesis via energy from food

Human Biosciences (69 decks)

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