Nutrition, Body Weight And Homeostasis Flashcards
Units of energy
- kilojoule (kJ)
- an everyday calorie is actually a kilocalorie (1000 calories = 1kcal)
- 1kcal = 4.2kJ
Carbohydrates
17kJ.g / 4Kcal.g
Starch - polymer of glucose (can be digested by humans unlike cellulose) Sucrose - glucose-fructose disaccharide Lactose - galactose-glucose disaccharide Fructose - monosaccharide Glucose - main sugar in human blood
Protein
16kJ.g / 4Kcal.g
- amino acids joined to form linear chains
- 20 different amino acids used for protein synthesis in the body
- 9 essential amino acids cannot be synthesised by must be obtained from the diet
Energy
- Biosynthetic Work - synthesis of cellular components
- Transport Work - movement of ions & nutrients across membranes. brain cells use 50% of their energy on ion transport.
- Mechanical Work - muscle contraction.
- Electrical Work - nervous conduction.
- Osmotic Work - kidney.
9 essential amino acids
If - Isoleucine Learned - Lysine This - Threonine Huge - Histidine List - Leucine May - Methionine Prove - Phenylalanine Truly - Tryptophan Valuable - Valine
Fat
37kJ.g / 9Kcal.g
Triacylglycerols - 3 fatty acids esterified
Contain much less oxygen that carbohydrates or protein - yield more energy when oxidised
Required for the absorption of the fat-soluble vitamins (ADEK) from the gut
Essential fatty acids needed for linoleic and linolenic acids
Minerals
- electrolytes establish ion gradients across membranes and maintain water balance
- calcium and phosphorus essential for structure (bones and teeth)
- calcium is an important signalling molecule
- enzyme co-factors (Fe, Mg, Mn, Co, Cu, Zn)
- Fe is an essential component of Haemoglobin
Vitamins
- essential for life
- required in micro- or milligram quantities
- fat or water soluble
- deficiency diseases if inadequate intake (also possible to overdose)
B12 - anaemia, B6 - dermatitis, C - scurvy
Dietary Fibre
Cellulose, Lignin, Pectins, Gums
- humans do not produce the enzymes required to break the beta-1,4 linkages in cellulose
- average requirement is 18g
- low fibre is associated. With constipation and bowel cancer
- high fibre reduces cholesterol and risk of diabetes
Liver makes bile salt from cholesterol, fibre absorbs this so it can not be reabsorbed so the liver has to make more bile salt
Dietary Reference Values
DRVs
Reference Nutrient Intake RNI - protein - enough to ensure that needs of 97.5%
Estimated Average Requirement EAR - used for energy - adequate for ~50% of the group (50% will need more)
Lower Reference Nutrient Intake - LRNI - enough for only a small number of people who have low requirements
- values depend on age, gender and levels of physical activity
Daily Energy Expenditure
- vary - age, sex, body composition and physical activity Is the sum of: Basal Metabolic Rate - BMR Diet-Induced Thermogenesis - DIT Physical Activity Level - PAL
BMR
Maintains the resting activity of the body
-biochemical reactions
- functions of organs
Affected by size, gender, environmental temperature, endocrine status, body temperature
Voluntary Physical Activity
- energy required depends on intensity and duration
- reflects energy demands of skeletal, heart and respiratory muscle
Energy stores
- muscles have a few seconds worth
- carbohydrate stores for immediate use
- long term stores of adipose ~ 40 days worth
- muscle protein can be converted to carbohydrates under extreme conditions
Obesity
Excessive fat accumulation - adipose tissue
BMI > 30
Associated with an increase risk of developing some cancers, cardiovascular disease and type 2 diabetes
