Nutrition, Diet and Energy Metabolism Flashcards
What four pathways can be classified as Metabolic pathways?
Oxidative Pathways
Detoxification Pathways
Fuel storage and mobilisation pathways
Biosynthetic pathways
What is the role of oxidative pathways?
Convert food into energy
What are the role of detoxification pathways?
To remove toxins. (cytochrome p450 in the liver)
What are the roles of biosynthetic pathways?
Produce basic building blocks for cellls
What are the roles of fuel storage and mobilisation pathways?
Allow fuel to be mobilised when we are not eating or need increased energy
What is a catabolic process?
It is a process that breaks down molecules
What is an anabolic process?
This is a process that uses energy and raw materials to make larger molecules for growth and maintenance.
What do cells require energy for
Biosynthetic work - synthesis of cellular components
Transport work - movement of ions and nutrients across membranes eg NaKATPase
Mechanical work - muscle contraction
Electrical work - nervous conduction
Osmotic work - kidney
In what form do cells use energy?
Cells use chemical bond energy to drive energy requiring activities. Energy exists in many inconvertible forms/.
What is oxidised to produce ATP?
Energy production is by the oxidation of: Lipids Carbohydrates Proteins Alcohol
When ATP is produced, What else is created?
Carbon Dioxide, Water and Heat
What is ATP used for?
Ion Transport Muscle contraction Biosynthesis Thermogenesis Detoxification
What does “a calorie” mean?
I calorie in every day use is actually one kilocalorie. This is the amount of energy needed to raise the temperature of one kilogram of water by one degree Celsius.
How do you convert from SI to units used every day?
Kilojoule (kJ) is the official SI unit of food energy. I kcal = 4.2 Kilojoules so, you times or divide by 4.2.
What different Food groups are in out diet and what are they used for (generally)?
Carbohydrate - to mostly supply energy Protein - energy and amino acids Vitamins and Minerals - essential Water - maintains hydration Fibre - necessary for normal GI function
What are the main dietary carbohydrates?
Starch - Carbohydrate storage molecule in plants. This is a polymer of glucose.
Sucrose - Table sugar, This is a glucose-fructose disaccharide
Lactose - Milk sugar. This is a galacose-glucose disaccharide
Fructose - Fruit sugar. Monosaccharide
Glucose - Predominant sugar in the body
Maltose - glucose-glucose disaccharide
Glycogen - Carbohydrate storage molecule in animals. Polymer of glucose.
Why can’t body break down cellulose?
This is because humans do not have the enzymes needed to break the beta-1,4 linkages in cellulose.
What are proteins made from?
Composed of amino acids joined to form linear chains.
Out of 20 amino acids, how many are essential? Why is this?
9/20 are essential amino acids because they cannot be synthesised and must be obtained form the diet
What are the 9 essential amino acids?
Isoleucine Lycine Threonine Histidine Leucine Methionone Phenylalanine Tryptophan Valine
Why are some amino acids conditionally essential? What does this mean?
This is because they can be synthesised by the body but, specific groups (pregnant women and children) have a high rate of protein synthesis so, they need then in higher quantities. Eg arginine, tyrosine and cysteine.
what does it means when lipid is described as “Triacylglycerol”?
3 fatty acid chains esterified to one glycerol.
What are the difference between unsaturated and satrated?
Unsaturated fatty acids contain double bonds whereas fatty acids do not.
More double bonds, more liquid the fat (eg oil)
What are transfats?
What properties do they give the foods?
What risks give us?
Put double bonds in foods (trans double bonds instead of normal cis)
They give it longer shelf life
But, increased risk of cardiovascular disease. They are banned in some counties but, in the UK manufacturers have mostly stopped putting them in foods.
Why do we need fats in our diet?
For absorption of vitamins ADEK (fat-soluble vitamins) from the gut
To provide essential fatty acids eg linoleum and linolenic (An omega 3 fatty acid as first double bond is on 3rd C) acids which cannot be synthesised by the body.
Why do we need Elecrolytes ?
Electrolytes to establish ion gradients across membranes and to maintain water balance
What amounts of electrolytes (K Na Cl) need if on IV?
1mmol/kg/day +30ml per kg of water (in fluid)
What are calcium and phosphorus essential for?
structure, particularly of Bones and teeth. Calcium is also a very important signalling molecule.
What quantity of vitamins are needed?
All Vitamins are needed in very small quantities usually in the micro or milligram level.
What are vitamins are fat soluble?
ADEK (Any others are water soluble)
What can a deficiency in Niacin cause?
Pellagra. This is characterised by Diarrhoea, Dementia and Dermatitis
What can a deficiency in B1 and B12 cause?
hematopoesis (Patients can develop anaemia as not synthesise RBC)
Main source of fibre?
Cellulose
Lignin
Pectins
Gums
Recommended amount per day?
18g / day
However, the average intake is below this. In UK women only have 12.8g and men only have 14.8g.
Why fibre good?
Dietary Fibre can lower plasma cholesterol. This is because fibre sequestered bile salts so, bile salts cannot be reabsorbed (as passed out in faeces) so, Liver has to make more cholesterol.
What is low fibre intake associated with?
Constipation
Bowel cancer
What is RNI?
Reference Nutrient Intake- used for proteins. vitamins and minerals. This is 2SDs above EAR
What is LRNI?
Lower reference nutrient intake -This is the number which, if you have less. you are considered unhealthy. It is 2SDs below EAR
What is EAR?
Estimated average requirement (used for energy). This is avg, so top of curve.
What is safe intake?
This is used when there is insufficient data to calculate the other values (LRNI, EAR, RNI)
What are there reference values based on?
Sex, Age Group and Level of physical activity.
Why does daily energy epediture vary?
Sex, Age, Body composition, Physical Activity
Why are energy requirement of men higher than that of women?
This is because males have a higher percentage of muscle in their body.
How is average daily intake worked out?
Basal Metabolic Rate (BMR) + Diet Induced Thermogenesis (DIT) (energy required to process food) + Physical Activity Level (PAL)
What is the Basal metabolic rate?
This is the amount of energy required to maintain resting activites of the body. Eg: Maintenance of cells: -Ion transport across membranes -Biochemical reactions Function of organs -Skeletal Muscle (30% of BMR) -Liver (20% of BMR) -Brain (20% of BMR) -Heart (10% of BMR) -Other (20% of BMR) Maintaining body temperature
What factors effect BMR?
Body size (Surface Area) Gender (males higher than females as males higher muscle mass) Environmental temperature (more in cold) Endocrine status (increased in hyperthyroidism) Body temperate (12% increase per degree)
How does Voluntary Physical Activity affect the amount energy required?
Energy required depends in intensity and duration of activity.
Reflects energy demands of -Skeletal Muscle
-Heart Muscle
-Respiratory Muscles
roughly:
Sedentary person = 30kJ/Kg/day
Moderate activity = 65kJ/Kg/day
Very active = 100 kJ/Kg/day
Main sources of energy in british diet?
Grains (bread, pasta ect..) Meat Drinks Milk and Produces Crisps and snacks
What is the theoretical energy content of food components?
- Fat (37 KJ/g)
- Alcohol (29KG/g)
- Proteins (17KJ/g)
- Carbs (17KJ/g)
When does your body begin to break down muscle?
Starvation
What energy stores does the body have?
- The body has very hurt term stores of energy rich molecules (phosphocreatine) in muscle. This is a few seconds worth.
- Carbohydrate stores (Glycogen ect.) for immediate use -These can last for minutes or hours depending on the level of physical activity,
- Long term stores in adipose. We have about 40 days worth
- In extreme conditions (starvation) the muscle proteins .can also be converted into energy.
How much glycogen can the body store?
100g liver and 300g in muscle. Stored in granules and cells. These is only a finite amount we can store
How much fat can the body store?
Storage is not limited. Keep laying down adipose tissue. Difference between 70kg and 100kg man is almost entirely a difference in the amount of Lipids (adipose tissue)
What is obesity?
Excessive fat accumulation in adipose tissue which impairs health.
BMI is over 30.
It results in energy intake exceeding energy expenditure over a period of years.
It is associated with an increased risk of developing some cancers, cardiovascular disease and type 2 diabetes.
How do you calculate BMI?
BMi = Weight (kg) / Height squared (m squared)
How do you measure BMI? What is it for?
BMI is used to clinically evaluate a patients weight. The hight is measured without clothes and the weight is measured with minimal clothing. It shows a good correlation with body fat measurements.
What is the problem with BMI? What is the alternative?
Muscular people may be wrongly classified as Obese so, you can use a waist to hip ratio instead.
How is the distribution of fat clinically important?
Evidence that distribution of fat is clinically important. Greater proportion of fat in upper body (especially abdomen) compared with that on hips is associated with increased risk of: Insulin resistant Hyperinsulinism Type 2 diabetes Hypertension Hyperlipidaemia Stroke Premature death
What is Sterlings Law of the capillary?
Net flow = (hydrostatic pressure of capillary - hydrostatic pressure of interstitial fluid) - (Oncotic pressure of capillary - Oncotic pressure of intersticial fluid)
What can low protein intake lead to?
Kwashiorkor.
Low protein intake can result in insufficient blood protein synthesis leading ti a decrease in plasma oncotic pressure and oedema. This is seen in Kwashiorkor.
