Metabolic Fuels And Dietary Components Flashcards
What does metabolism mean?
Sum of all the chemical reactions that take place within each cell of a living organism
What is the daily recommended calorie intake for adults?
Females: 2000
Males: 2500
What are the 4 different pathways dietary components are metabolised in cells?
Biosynthetic
Fuel storage
Oxidative processes
Waste disposal
What are anabolic metabolic processes?
Synthesise larger molecules from smaller components, requires energy
What are catabolic metabolic processes?
Breakdown of organic molecules, often yielding energy
Which metabolic processes are anabolic?
Biosynthetic
Fuel storage
Results in formation of macromolecules
Which metabolic processes are catabolic?
Oxidative
Where does the energy for anabolic pathways come from?
Catabolic pathways
From the breakdown of carbohydrates and lipids, energy is released in the form of ATP
What is the krebs cycle also known as?
Citric acid cycle
As the cycle starts with citric acid
What are co-factors?
Macronutrients required for enzymes to function
Give an example of a co-factor in the krebs cycle?
Thiamine
Thiamine pyrophosphate (Vitamin B1)
What is thiamine required for?
The conversion of pyruvate to acetyl-CoA in the Krebs cycle
The conversion of 5-carbon compound to 4-carbon compound in Krebs cycle
What percentage fat is adipose tissue?
85%
In the form of triglyceride molecules
What is the main function of adipose tissue?
Storage of energy rich molecules
Are adipose cells metabolically active?
No
Is the liver metabolically active?
Yes very
What is the function of the liver?
Producing glucose by gluconeogenesis
Removal of toxins
Metabolism of compounds
Give examples of compounds the liver metabolises?
Xenabiotics
What do muscles do?
Use fuels to present kinetic energy
What is a pathway of gluconeogenesis?
The cori cycle
What does gluconeogenesis mean?
Formation of new glucose
What is the concentration of glucose in blood controlled by?
Insulin
What is the main effect of insulin in adipose tissue?
Increase the uptake of glucose and to increase the production of storage compound: triglycerides/tryacelglycerol
What is the effect of insulin in liver and muscle cells?
Increase the uptake of glucose nirvana essence and the uptake of potassiumand phosphate
Increased synthesis of proteins and glycogen
What does insulin stimulate?
Biosynthesis
What effect does insulin have on the liver?
Promotes the synthesis of fatty acids from carbohydrates which are transported to the adipose tissue for storage
What does insulin inhibit?
The hydrolysis of triglycerides
Are the actions of insulin anabolic or catabolic?
Anabolic
What are the 3 main dietary energy sources?
●Carbohydrates
●Lipids
●Proteins
What is used to calculate healthy weight?
BMI, 18-25 is healthy weight
25-30 is overweight
30+ obesity
What is ATP referred as?
The energy currency of the cell
How are energy foods processed?
Undergo oxidation to yield energy, release of ATP
How many times and how much ATP does the human body recycle each day?
Around 1000 times a day
Breakdown approx our own body weight of ATP a day
When does ATP release energy?
When it’s broken down to yield ADP
What happens to organic compounds in aerobic respiration?
Organic compounds are metabolised in the presence of oxygen to Carbon dioxide and water with the release of energy
What is the main carbohydrate?
Glucose
What are glucose fructose and galactose examples of?
Monosaccharides
Formula of C6H12O6
What disaccharide do glucose and fructose form?
Sucrose (C12H22O11)
What is the disaccharide in milk?
Lactose
What structure does starch have?
Long chains of carbohydrates
What structure does glycogen have?
Branched chains of carbohydrates
What are proteins?
Long chains of amino acids
Where are proteins broken down in?
Lumen of the gut
What can the Carbon backbone of aminoacids be used for?
Can be broken down to yield energy
What is an example of gluconeogensis in amino acids?
The conversion of gluconeogenic amino acids such as adenine to glucose
What are constitutes of aminoacids?
Amino group
Carboxyl group
R group
How much protein do we need each day?
0.8 g/kg
How do you convert the protein requirement to nitrogen requirement?
Multiply the protein requirement by 16%
What are lipids?
Fats including triglycerides and cholesterol
What lipids are used as fuel?
Only triglycerides
What is another name for triglycerides?
Triacylglycerol (TAG)
What is a feature of triglycerides?
More reduced than other energy sources
What is a feature of the structure ofanglyceides?
The glycerol backbone can be used as an energy source that can be converted to glucose by gluconeogenesis
How is excess energy stored?
Fat - Adipose tissue (only 15% water)
Carbohydrate – as glycogen in liver and muscles
Protein - Muscle (80% water)
What happens to excess energy intake?
Store as triglycerides in adipose (approx 15kg),
Store as glycogen (up to 200g in liver & 150g in muscle), 80g in the liver after overnight fast,
Store as protein in muscle (approx 6kg).
How much energy per gram of carbohydrates?
4kcal/g
How much energy per gram of protein?
4kcal/g
How much energy per gram of alcohol?
7kcal/g
How much energy per gram of lipid?
9kcal/g
What is the primary source of ATP supplied to the body at rest and during low intensity activities?
The oxidative system (aerobic)
Uses primarily carbohydrates and fats as substrates
What is the Basal Metabolic Rate (BMR)?
Energy needed to stay alive at rest
A measure of the energy required to maintain non-exercise bodily functions such as;
●respiration,
●contraction of the heart muscle,
●biosynthetic processes,
●repairing & regenerating tissues,
●ion gradients across cell membranes
What are the conditions essential for measuring BMR?
• Post-absorptive (12 hour fast)
• Lying still at physical and mental rest
• Thermo-neutral environment (27 – 29oC)
• No tea/coffee/nicotine/alcohol in previous 12 hours
• No heavy physical activity previous day
• Establish steady-state (~ 30 minutes)
What factors decrease BMR?
●Age
●Gender
●Dieting/Starvation
●Hypothyroidism
●Decreased muscle mass
What factors increase BMR?
●Body weight (BMI)
●Hyperthyroidism
●Low ambient temp.
●Fever/infection/chronic disease
What do thyroid hormones do?
Thyroid hormones regulate metabolic rate, core body temperature, appetite, sympathetic activity and more
Why do people with a higher muscle to fat ratio tend to have a higher BMR?
Muscle cells require more energy to maintain than fat cells
What is hypothyroidism?
Medical condition with reduced thyroid hormone section
Why does BMR tend to decrease with age?
As we get older, we tend to gain fat and lose muscle
What is hyperthyroidism?
When the body secretes too much thyroid hormone
How is BMR assessed?
• Harris Benedict Equations (1919)
• Schofield Equations (1985)
• Henry equations (2005)
Rough estimate: ~1kcal/kg body mass/hour
Example of Henry equation?
Equation for estimating basal metabolic rate from gender, age and weight; (formulae & examples are for interest);
Example: (70 kg X 16) + 545 = 1665 kcal/day (BMR)
Why does the Henry equation not use weight?
In the clinical setting height can be difficult to obtain or include in calculations, & other variables may negate the advantage of including height
When should the Henry equation be adjusted?
●Adjust for metabolic stress
●Adjust for activity and maybe diet-induced thermogenesis (DIT)
What is the NHS Nutrition guideline for patients who are not severely ill or injured, nor at risk of re-feeding syndrome?
25-35 kCal/kg/day
How much glucose does the brain require a day?
Around 150g
How much glycogen does the liver have after an overnight fast?
80g
How is glucose formed during a longer period of fasting/starvation?
Formed from non-carbohydrate sources - gluconeogenesis
What happens to secretion of insulin after an overnight fast?
Switched off/decreased
Glycogenolysis
What does gluconeogenesis use?
●Lactate
●Amino acids
Muscle
Intestine
Skin
●Glycerol
Fat breakdown
What is the hormonal response to starvation
Insulin production switched off
Cortisol being produced
What does the hormonal response to starvation facilitate?
Lipolysis
Proteolysis
What are the metabolic changes of prolonged fasting?
Liver produces ketones from fatty acids
Brain adapts to using ketones instead of glucose as a fuel
Reduction to BMR
What is malnutrition?
A state of nutrition with a deficiency, excess or imbalance of energy, protein or other nutrients,
causing measurable adverse effects
What are effects of malnutrition?
Adverse effects are on tissue/body form (shape, size, composition), body function and clinical outcome
What is re-feeding syndrome?
Clinical condition caused by re-feeding too quickly after a period of undernutrition
●Re-distribution of phosphate, potassium, magnesium etc due to insulin,
●Switch back to carbohydrates as the main fuel which requires phosphate and thiamine.
What are essential amino acids?
They can’t be synthesised in the human body so need to be supplemented by food
What are essential fatty acids?
Human body can’t synthesise so have to be present in the diet or occasionally as supplements
What are macronutrients?
Trace elements and vitamins
●Co-factors in metabolism
●Gene expression
●Structural components
●Antioxidants
What does vitamin C do?
Facilitates collagen synthesis
Improves iron absorption
Antioxidant
Where can vitamin C be found?
Fruit and veg
Ascorbic acid
What is Vitamin B12?
Co-factor in synthetic processes such as:
Formation of DNA
Protein synthesis
Regenerate folate (and therefore – cell division)
Fatty acid synthesis
Energy production
What does vitamin B1 (Thiamine) do?
Helps with energy production in body
What does Vitamin D do?
Increases amount of calcium and phosphorus your body absorbs from foods
Deposits calcium and phosphorus in bones and teeth, making them stronger and healthier
Protects against infections by keeping immune system healthy
What are the 4 main fat soluble vitamins?
Vitamins A, D, E and K
What does Vitamin A do?
Helps you to see in the day and at night.
Protects you from infections by keeping
skin and other body parts healthy.
Promotes normal growth and development
What does Vitamin E do?
Helps to maintain a healthy immune system and other body processes.
Acts as an antioxidant and protects cells from damage
What does Vitamin K do?
Makes proteins that cause our blood to clot, when you are bleeding
Involved in making body proteins for your blood, kidney and bones
What is the prudent diet?
5+ servings fruit/veg
Base your meals around starchy carbohydrate foods
No more than 5% of the energy we consume should come from free sugars
0.8g/kg/day protein
The average man should have no more than 30g saturated fat a day, & women 20g.
Adults should have no more than 2.4g of sodium per day, which is equal to 6g of salt.
Men and women are advised not to regularly drink more than 14 units of alcohol a week (over >3 days).
Avoid excess dietary supplementation
Adequate Calcium
