Energy Flashcards
6Co2 + 6O2 =
C6H12O6 + O2
Photosynthsis
686 kcal/ mol [endergonic/ energy required]
C6H12O6 + O2 =
6Co2 + 6O2
Oxidation
-686 kcal/ mol [exergonic/ erergy released]
Flow of energy through biosphere
Sun [ Solar energy] Plant [ Photpsynthesis] [Chemical energy] Animal [chemical energy released in catabolism] [Heat loss/ --> Work] Mechanical Work/ Chemical synthesis --> Transport across membrane
Joule
S.I unit
Energy expended when 1 kg is moved 1 m by a force of 1 Newton
1 MJ= 10^3 kJ
Kilo - calories (kcal)
The amount of heat required to raise the temperature of 1 L water from 15C to 16C
Bomb Calorimeter
An electrical heating device starts the reaction inside a sealed reaction vessel.
The temperature rise of the water which surrounds it is measured.
Energy of marconutrient
Lipid = 9 kcal/g CHO = 4 kcal/ g/ Protein = 4kcal/ g Alcohol = 7 kcal/ g
Sources of energy in the British diet
47% CHO
30% Fat
15% Protein
8% Alcohol
Calories source ~ 1965 & 1995
[Developing country]
Developing Countries
Less cereals, pulse, roots & tubers,
More meat, fruit & veg, oil crops, ,fish & seafood, dairy & eggs
More calories intake
Calories source ~ 1965 & 1995
[Developed country]
Developed Countries
Less cereals, pulse, roots & tubers,
More oil crops, ,fish & seafood, dairy & eggs
meat, fruit & veg relative the same
More calories intake
Calories source ~ 1965 & 1995
[World]
More oil crops
Less pulse
Others relative the same
More calories intake
Calories source ~ Female & Male
Female has a few more % of CHO (cereals/ potatoes/ savory snack), dairy, veg, fish
Less meat, sugar, drinks (inc alcohol) than male
Energy density of food
Weight of food per 1000 kcal
Energy density change
Prehistoric/Subsistence diet = low energy density
Modern/western diet = high energy density
Indirect Calorimetry
Estimates heat production by determing O2 consumption or CO2 production
Provides a means of estimating the composition of oxidized fuels
carried out on an individual basis, which makes this a fairly time-consuming process ideal for smaller studies
Indirect calorimetry in closed circuit
Analyzer (i.e. animals) in respiration chamber (closed environment)
Measure O2 consumption or CO2 production over time?
Indirect calorimetry in open circuit
measurement of oxygen consumption (VO2) to assess the metabolic intensity of the exercise.
Indirect Gas Analysis Calorimetry
Fundamental Principles
- the volume of oxygen consumed (VO2) by the body is
equal to the difference between the volumes of inspired and expired oxygen. - the volume of carbon dioxide produced ( VCO2) by the body is equal to the difference between the volumes of expired and inspired carbon dioxide
Limitation of Indirect calorimetry
Measuring the whole body - the sum of all active tissue in body, not just contracting skeletal muscle.
Needs sophisticated and expensive equipment.
Highly sensitive to measurement error.
.
Can only be accurately used for metabolic intensities, economy, efficiency, and energy expenditure during steady state exercise
Requires subjects to wear apparatus on face or in
mouth
Energy cconomy & efficiency
Economy - refers to the energy cost of an exercise condition.
Efficiency -the mechanical energy produced relative to the metabolic energy expenditure
Doubly Labelled Water
The DLW method uses the natural occurring stable isotopes of water (D2O and H218O) to assess energy expenditure, body composition and water flux in humans
[Hydrogen replaced with deuterium
16Oxygen replaced with 18O]
Measure:
18O in CO2 exhaled
Deuterium in excreted water
As 18O is lost from the body in the form of water and carbon dioxide (CO2), whereas deuterium is lost only as water, the difference in loss from the body reflects the CO2 production during the period.
[CO2 production is the result of fat, carbohydrate and protein oxidation/ an index of energy expenditure.]
used samples of urine, blood or saliva for analysis
(urine is most commonly used)
Estimated average requirement (EAR) for Male & Female
M 75kg 19-59 yrs = 2553kcal
F 60kg 19-50 yrs = 1940 kcal
F 63kg 51-59 yrs = 1912 kcal
Estimated average requirement (EAR) for children and adolescents
0 - 3 months F= 515 M= 545
10- 12 months F= 865 M= 920
7- 10 yrs F= 1740 M= 1970
15- 18 yrs F= 2110 M= 2755
Average daily total energy intake and percentage of EAR – UK (2003)
M = 92% of EAR F = 85% of EAR
Energy usage
Metabolism and homeostasis
- Thermogenesis
- Tissue turnover
- Biochemical reactions
- Basal metabolic rate (75 % of energy usage)
Work
(25 % of energy expenditure)
BMR
When is it measured?
Compare between F/ M
Children / Adults
Rate of BMR change vs age
Adults/ Elderly
How many % of energy requirement
Basal metabolic rate
Energy expenditure in the post-absorptive state, under standardised conditions of thermal neutrality, awake but completely at rest.
BMR is measured when a person is at complete rest
Infants and young children have a proportionately high BMR for their size due to their rapid growth and development. After 20 years, it drops about 2 per cent, per decade.
Men usually have a higher BMR than women since they tend to have more muscle.
Older adults usually have a lower BMR than the young since the amount of muscle tends to decrease with age.
The BMR accounts on average for about three quarters of an individual’s energy needs.
PAR
Physical activity ratio
Energy cost of physical activities, as a ratio of BMR (per minute)
PAL
Physical activity level
Sum of PAR x time spent for each activity over 24h, as a ratio of BMR (per 24 hours)
Factors that affect BMR
Age: higher in young. Less “lean body mass” (LBM) in old.
Height: greater BMR for tall, thin people.
Growth: greater BMR in children and during pregnancy
Body composition: greater BMR with more LBM.
Fever/stress: increase BMR
Temp. of environment: both extreme cold and heat increase BMR
Fasting/starvation: lowers BMR
Thyroxin: key factor in BMR regulation
Metric BMR Formula
Women: BMR = 655 + ( 9.6 x weight in kilos ) + ( 1.8 x height in cm ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 13.7 x weight in kilos ) + ( 5 x height in cm ) - ( 6.8 x age in years )
Classification of occupational work by PAR
Light work: PAR = 1.7
professional, clerical workers, administrative staff
Moderate work: PAR = 2.2 (men) 1.7 (women)
students, sales staff, domestic service
Moderate-Heavy work: PAR = 3.0(men) 2.3 (women)
machine operators, labourers with machines
Heavy work: PAR = 3.8(men) 2.8(women)
labourers without machines, bricklaying, agricultural workers
Total Energy Expenditure
TEE = BMR x PAL
Main catabolic processes
- Break down of macromolecules to TCA cycle precursors –> TCA cycle– the central pathway to catabolism
- Release of electrons for the electron transport chain
& Production of ATP in the electron transport chain
Phosphorylation
ADP –> ATP
Substrate-level phosphorylation = Transferring a phosphate directly to ADP from another molecule
Oxidative phosphorylation = Use of ATP synthase and energy derived from a proton (H+) gradient to make ATP
Glycolysis
Substrate-level phosphorylation
Break down of 1 glucose molecule into 2 pyruvate molecules
Citric Acid cycle/ TCA cycle
Substrate-level phosphorylation
1 x pyruvate + 1 x NAD+ –> 1 x acetyl CoA + 1 x CO2 + 1 x NADH
1 x acetyl CoA –> 1 x CoA + 1 x citric acid (6C)
1 x citric acid + 2 x NAD+ --> 2 x CO2 + 2 x NADH 1 x (4C) + 1 x ADP + Pi --> 1 x ATP 1 x (4C) + 1 x FAD --> 1 x FADH2 1 x (4C) + 1 x NAD+ --> 1 x NADH + 1 x Oxaloacetate (4C) --> + 1 x acetyl = 1 x citric acid (6C)
Chemiosmosis
Electron transport chain & oxidative phosphorylation at inner mitochondrial membrane
Catabolism -> Macronutritient to energy
Bulk food is digested in the mouth, stomach and small intestine to yield small molecules
Sugar/ fatty acid/ amino acids are degraded in the cytoplasm to yield acetyl- CoA
Acetyl CoA is oxidized inside mitochondria by citric acid cycle to yield CO2 and reduced coenzymes
The energy transferred to the reduced coenzymes in stage 3 is used to make ATP by the coupled pathways of electron transport and oxidative phosphorylation.
Lipid metabolism
Break down to glycerols and fatty acid
–> Fatty acid oxidation–> Acetyl CoA
CHO metabolism
Break down to glucose and other sugars
–>Glycolysis [ ATP & pyruvate] –> Acetyl CoA
Protein metabolism
Break down to amino acids
–> Amino acid catbolism [ pyruvate] or straight into Acetyl CoA/ Citric acid cycle
Metabolism in liver
Glycolysis– > pyruvate [outside liver]
–> Acetyl CoA [synthesis fatty acid] –> Citric acid cycle
The Cori Cycle [ Liver muscle]
The Cori Cycle
[In Liver] 2 x Lactate –> 2x pyruvate–> 1 x glucose (6 ATP required)
[Transfer to muscle by red blood cells]
[ In muscle ]
1 x glucose –> 2 x ATP & 2 x pyruvate –> 2 x Lactate
[Transfer to Liver]
Metabolism in brain
% of basal metabolic rate
Glycolysis– > pyruvate –> Acetyl CoA [synthesis ketone bodies] –> Citric acid cycle
- 20 % of basal metabolic rate
- Absolute requirement for glucose
- Will adapt to ketone bodies in starvation
Metabolism in muscle [aerobic]
Glycolysis– > pyruvate [outside liver]
–> Acetyl CoA [synthesis fatty acid] –> Citric acid cycle
Metabolism in muscle [anaerobic]
1 x glucose –> 2 x ATP & 2 x pyruvate –> 2 x Lactate
–> The Cori Cycle
Catabolic reaction
Glycogen –> glucose & ATP & H2O & CO2
Triglyceride –> [glycerol & ATP] & [Fatty acids & ATP] & H2O & CO2
Protein –> Amino acids & ATP & H2O & CO2 & Urea
Anabolic reaction
2 x glucose & ATP –> glycogen
1 x Glycerol & 3x Fatty acids & ATP –> Triglyceride
2 x amino acids & ATP –> protein
Conversion of sugars to fats
Pyruvate –> acetyl CoA –> Fatty acyl CoA –> Triglycerides –> Fatty acid –> Fatty acyl CoA –> acetyl CoA
Fatty acid [+ Insulin / - Epenepherine] –> Fat
Fat [ - Insulin/ + Epenepherine] –> Fatty acid
Metabolism of Fructose in the liver
Fructose metabolism bypasses conversion of glucose to glycerol (storing the energy) and the regulatory activity of phosphofructokinase, lots of acetyl coA produced for fatty acid synthesis
Fructose does not stimulate the secretion of insulin or leptin and does not suppress ghrelin as effectively as glucose or galactose, less satiating (full satisfying)
Control of energy balance
Increasing BMI= increased BMR & increased physical activity energy expenditure
Appestat theory
Hunger Satiety signals energy expenditure
Satiety signals
- Feeding status
- Energy stores
Hunger and appetite
- Gut fill cues, and nutrient sensing in the liver allow neural signalling via the vagal nerve direct to the brainstem, which can then stimulate other components of the brain including the hypothalamus
- Amygada learned behaviours
- Hypothalamus, both satiety and hunger centres influenced by neural stimulation, nutrient sensing, (glucose) insulin and glucagon and hormones
Ghrelin
Ghrelin produced by ghrelin cells (in GI/ stomach) when stomach is empty, signal vagal nerves & hypothalamus to increase hunger, gastric acid secretion and gastrointestinal motility to prepare for the increase food intake.
The hormone also regulatw the distribution and rate of use of energy
Leptin
Leptin is a hormone made by adipose cells. It acts on vagal nerves & hypothalamus to inhibite hunger, helps to regulate energy balance.
Leptin in appetite control
Low/ high level?
Low levels =
Increase appetite
Reduce fecundity
High levels =
Suppress appetite
Increase uncoupling protein expression
Increase lipase activity
Gut fill cues
Cholecystokinin (CCK) in Duodenum
- Glucagon like peptide (GLP1)
- Oxyntomodulin
- Peptide YY
[all 3 in Gut endocrine cells]
Prevalence of Adult obesity in EU
BMI > 30
F 25- 30% in eastern EU
20 - 25% in UK, Germany, Turkey
M 20 - 25% in UK, Finland
15- 20% in Germany
0 -10% in Eastern EU, Turkey
Consequence of increasing BMI
Men have BMI over 30 has greater relative risk of death than women with BMI over 30
Health risks of obesity
Cancer
Cardiovascular disease
- Coronary heart disease
- Stroke
- Hypertension
Respiratory disease
Type 2 diabetes
Metabolic syndrome
Osteoarthritis
Most prevalent cause of the metabolic syndrome
Intra-abdominal (visceral) obesity
Visceral adipose tissue in obesity
Hypoxic (don’t get enough oxygen)
- Glycolytic - Lactate producing
- Necrosis
- Macrophage infiltration
- Chronic inflammation - Inflammatory cytokines / Oxidative stress/ Cortisol
Lipolytic tissue
- Releases NEFAs- Inhibit glucose/ Inhibit the insulin receptor
Suppressed adiponectin release - Stimulates insulin effect
Insulin
A peptide hormone produced by beta cells in the pancreas.
Regulates the metabolism of CHO and fats:
- by promoting the absorption of glucose from the blood to muscles and fat tissue
- by causing fat to be stored rather than used for energy.
Inhibits the production of glucose by the liver
Metabolic syndrome - cluster of disorders linked with Obesity
See energy slide 79
Normal body store
Fats = 141000 cal Protein = 24000 cal CHO = 300 cal
for 80 days fuel store until fatel
World hunger 1998 -2000
> 35 % population in Africa and Asia
20- 35% in India and N. Africa, S. America
5- 20% in S. America, Russia, China, E. Asia
