energy, fats, carbs, proteins

how is energy created

cannot be created or destroyed only converted one form to another

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types of energy used by human body

chemical, mechanical, electrical

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mechanical work

muscular contraction

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electrical work

maintaining ionic gradients across membranes

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chemical work

synthesis new macromolecules

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all energy becomes ..... eventually

heat

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standard units of energy

joule

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energy units in nutrition

kilocalories or calories

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energy obtained in humans from

from the oxidation macronutrients provided by food consumed

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1 kcal in mj

4.184MJ

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1MJ in kcal

239kcal

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energy from fat

9kcal / 37kj per gram

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alcohol calories

7 kcal/ 29kj

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energy stored in body in form of

fat glycogen protein

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protein used for energy

rarely, only in severe cases of starvation and other wasting conditions

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3 main components of energy expenditure

10% thermic effect of feeding, 15-30% energy expenditure physical activity, 60-70% basal metabolic rate

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positive energy balance

intake higher than output= weight gain

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negative energy balance

intake lower than output= weight loss

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negative energy balance over a long time

likely to be underweight, health risks of osteoporosis, infertility and heart failure

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positive energy balance over a long time

overweight, risks of cancer, cardiovascular disease, type 2 diabetes

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energy balance maintained by

regulating energy intake, adjusting physical activity levels

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fats at room temperature

solids

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oils at room temperature

liquids

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edible fats are

triglycerides

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solid and liquid state of fats depends on

degree of saturation and length of carbon chain

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is there a difference between energy value of solid and liquid fats

no - always 9kcal

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lipids composed of

carbon, hydrogen and oxygen

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lipids structure

glycerol and fatty acids

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what is glycerol

a poly hydric alcohol containing 3 carbons attached to a hydroxyl group

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fatty acid chain length

usually contain 2-24 carbons

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products of carbohydrate fermentation in the small intestine

acetic acid, propionic acid and butyric acid

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short chain fatty acids

4-8 carbons

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medium chain triglycerides

c10-c14 - well absorbed in small intestine

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medium chain triglycerides for patients

used for patients with bowel problems or recovering from malnutrition as they are absorbed directly into blood

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long chain fatty acids

c16 - c22 - essential fatty acids and marine oils

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degrees of saturation

saturated unsaturated and polyunsaturated

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trans fatty acids

functional groups positioned on opposite sides of the c=c bond

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cis fatty acids

functional groups positioned on same side of the c=c double bond

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full and partial hydrogenation

veg oils which have high proportion unsaturated fatty acids hydrogenated to make solids for use as margarine

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hydrogenation

increases melting point so that fats become solid at room temp

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partially hydrogenated oils

contains trans fats, known to increase risk of cardiovascular disease

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oleic acid

c18:1, n-9

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linoleic acid

c18:2 n-6

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alpha - linoleic acid

c18:3 n-3

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fatty acid rancidity

deterioration of fats and oils leading to unpleasant odours and flavours

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hydrolytic rancidity

affects dairy foods can be caused by enzyme lipase

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oxidative rancidity

can be caused by contact with heat, light, oxygen and metals causes problems with long chain polyunsaturated fatty acids

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3 stages of oxidation

initiation propagation termination

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reactivity of polyunsaturated fatty acids

highly reactive due to double bonds

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what is a free radical

chemical species with an unpaired electron

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free radicals created from

UV, x-rays, catalytic metals

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effect of free radicals

can cause cascade of damage to cell membranes, may cause cancers, atherosclerosis and rheumatoid arthritis

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antioxidants

vitamins C and E can scavenge free radicals

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food spoilage

also caused by free radicals

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visible sources dietary fat

butter margarine meat

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invisible sources dietary fat

cakes, biscuits, pastry, confectionary

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total fat intake

35% total energy intake

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saturated fatty acid intake

10% total energy intake

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polyunsaturated fatty acids intake

no more than 10% total energy intake

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essential fatty acid n-6 intake

more than 1% energy intake

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fatty acid n-3 intake

more than 0.2% energy intake

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trans fat energy intake

2% total energy intake

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fat-soluble nutrients

important for good health- vitamin A,K,E,D

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absorption of fat soluble vitamins

require fat

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fats increase bioavailability of what compounds

phytochemicals: lycopene in tomatoes and beta carotene in carrots

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polyunsaturated fatty acids include

omega-3 and omega-6

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role of mouth in lipid digestion

mechanical digestion: mixing with saliva, limited enzyme action

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role of stomach in lipid digestion

travel down oesophagus, mixing and churning, add gastric lipase, can tolerate low pH

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roll of small intestine in lipid digestion

emulsification with bile, larger droplets to small droplets, pancreatic lipase digests and micelles help absorb

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gall bladder

stores and secretes bile

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bile dispersed

watery parts of small intestine

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bile in small intestine

larger surface area for emulsification of lipids

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journey of micelles

through microvilli, enter epithelial

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fatty acids in lipid digestion

form triglycerides

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fatty globules combine with proteins to form

chylomicrons

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chylomicrons inside where

Golgi apparatus

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chylomicrons extruded from

epithelial cell, enter lymph capillary

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lymph

transports chylomicrons away from intestine

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what are chylomicrons

type of lipoprotein, transports lipids from small intestine to blood stream

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structure of chylomicrons

triglycerides, embedded a-lipoproteins, phospholipids

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glycemic

relating to presence of glucose in blood

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glycemic index

indication of how blood glucose levels change after ingesting different carbohydrate

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monosaccharides

simple sugars, not broken down any further, glucose, fructose, galactose

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disaccharides

two monosaccharides

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sucrose

disaccharide found in table sugar - glucose + fructose

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lactose

disaccharide found in milk - glucose + galactose

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maltose

disaccharide from breakdown of starch - glucose + glucose

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complex carbs

polysaccharides - over 1000 glucose units

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complex carbs in animals

glycogen stored in muscle and liver

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complex carbs in plants

starches and fibres

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starches

digestible by humans - amylopectin and amylose

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amylose

straight chain starch in humans

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amylopectin

branched chain starch in humans

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fibres

indigestible by humans, pectins and cellulose

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energy from carbs

3.75kcal/16grams

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functions of carbs

glucose/ insulin response, prevent high fat intakes, reduce risk of cardiovascular disease, prevent ketosis, carbohydrate foods are filling so have high satiety

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types of sugars

intrinsic, extrinsic, milk sugar

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intrinsic sugars

those which are an integral part of cell structure

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extrinsic sugars

not an integral part of cell structure, added to foods by manufacturer, cook, consumer

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milk sugar

not intrinsic

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non-milk sugar

can cause health problems, aka free sugars, also includes honey and syrups

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main sources free sugars

cakes, biscuits, puddings, breakfast cereals

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digestion of carbs in mouth

starch to maltose by salivary amylase

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carb digestion in stomach

amylase denatured by stomach acid no further digestion

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pancreas in carb digestion

pancreatic amylase breaks down starch to maltose in small intestine

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small intestine in carb digestion

enzymes in wall of small intestine break down disaccharides to monosaccharides

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absorption of glucose, fructose and galactose

into blood, taken to liver via portal vein

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large intestine role in carb digestion

viscous fibre is fermented into acid and gases by bacteria

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role of rectum and anus during digestion of carbs

non fermentable fibres escapes digestion and is excreted in the faeces

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high blood glucose

pancreas releases insulin, glucose transported into cells, conversion of glucose into glycogen

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low blood glucose

pancreas releases glucagon, breakdown glycogen into glucose, increase gluconeogenesis

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free sugar intake

should not exceed 5%

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glycemic index

overall effect of carbs on blood glucose levels

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low GI

absorbed more slowly

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low GI foods

0-55, high satiety, maintain blood glucose levels

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moderate GI foods

56-69

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high GI foods

70 and above - does not travel through entire GI tract, low satiety

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dietary fibre

edible parts of plants that are not broken down or absorbed by small intestine

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non-starch polysaccharides

cellulose, pectins, gums, mucilage, chitin

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insoluble non starch polysaccharides

chitin and cellulose

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soluble non starch polysaccharides

pectins gums mucilages

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cellulose

widely distributed in cereals and all plant foods

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pectins

mainly fruit and veg

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gums

plants used as food additives

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mucillages

ispaghula - seed, psyllium husk

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chitin

mushrooms and fungi

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NSPs have 4 major effects on gastrointestinal activity

1. slow gastrointestinal absorption, 2. affect reabsorption/plasma cholesterol levels, 3. undergo fermentation in the colon, 4. increase faecal weight

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rate of intestinal absorption

high fibre foods encourage mastication and stimulate secretion of digestive juices

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soluble non-starch polysaccharides

cause increase in viscosity of stomach contents, delaying gastric emptying

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some non starch polysaccharides

eg pectin can bind to fe, ca, zn, mg, leading to decreased bioavailability

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non starch polysaccharides affect the reabsorption of bile acids and therefore plasma cholesterol levels

fibre can slow the reabsorption of bile acids in the ileum as they are bound and trapped by dietary fibre, leads to a decrease in the enterohepatic circulation of bile acids as they are lost in the faeces. lowers plasma cholesterol as cholesterol used to

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bile produced

produced from breakdown of cholesterol in the liver

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bile stored

in gall bladder and secreted into intestine when food ingested

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bile in the faeces

small amount of bile excreted

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bile absorbed

normally most bile absorbed by intestines and returned to liver for recycling

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fermentation in the colon

fibre enters colon, fermented by bacteria, carbohydrate enters, short chain fatty absorbed, bacterial matter and unfermented carbohydrate to faeces: heat, ch2, h2 and co2

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wheat bran on faecal weight

increases faecal weight due to its unfermented residue bound to water

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oat bran affect on faecal weight

increases faecal weight due to increase in bacterial bulk following fermentation

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high fibre diet recommended

decreases exposure to carcinogens from microbial decomposition, bile salts decrease constipation, decrease intra colon pressure during defaecation

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resistant starch

resists digestion to its component sugar glucose in small intestine, passes unchanged to large intestine

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4 types resistant starch

R1,R2,R3,R4

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resistant starch 1

contained within cell walls , wholegrain, legumes

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resistant starch 2

resistant starch granules present in raw foods

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resistant starch 3

retrograded starch in food modified by processing eg bread

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resistant starch 4

manufactured modified starch

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function of resistant starch

fermented in colon, release short chain fatty acids, increase faecal weight, also reduces glycemic index of foods

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fibre delays gastric emptying

increase satiety, short term reduction in hunger, decrease obesity and overweight

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fibre less energy dense

can reduce total energy intake

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soluble NSPs decrease absorption bile acids

lower plasma cholesterol reduce risk coronary heart disease

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fermentation in the colon

short chain fatty acids effects faecal pH levels and proliferation of colonic cells, lowers risk colorectal cancer

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slowed intestinal absorption

resistant starch not broken down, lower blood glucose and insulin response, lowers risk of type 2 diabetes

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dietary fibre

too bulky for children, increase gas production decrease availability of minerals

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recommended fibre intake

30g/day

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essential amino acids

valine, leucine, isoleucine, phenylalanine, tryptophan, lysine, histidine, methionine, threonine

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two amino acids joined by

a peptide bond, loss of water

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primary structure of proteins

sequence of chain of amino acids

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secondly structure proteins

hydrogen bonding of the peptide backbone, causes amino acids to fold into a repeating pattern

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tertiary protein structure

3D folding pattern of a protein due to side chain interactions

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quaternary structure

protein consisting of more than one polypeptide chain

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protein required for

normal growth and maintenance of good health

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protein

second most abundant chemical compound in the body after water

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proportion of protein in man

approx 16% of man weighing 70kg= 11kg

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protein in muscle

43%

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protein in skin

15%

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protein in blood

16%

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50% of body proteins comprised of 4 proteins

collagen, haemoglobin, myosin and actin

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functions of proteins

required for growth, repair, transport, immune system, enzymes, hormones, antibodies, receptors, neurotransmitters, transport carriers

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structural function of proteins

approx 50% of bodys proteins, eg skin, muscle

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transport proteins

transport carriers in blood and body fluids eg haemoglobin and lipoproteins

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hormonal proteins

some hormones are proteins or contain peptide or amino acid chains

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enzymes are proteins

regulate biochemical mechanisms in cells and tissues, intracellular and extracellular

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immune functions

antibodies involved with inflammation

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animal protein types

fibrous and globular

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animal fibrous type proteins

insoluble, elastic proteins forming structural part of tissues

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animal fibrous protein samples and sources

keratin in hair, collagen in connective tissue, elastin in tendons and arteries, myosin in muscles

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globular animal proteins

relatively soluble, many food proteins, also part of fluids of all body cells

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examples and sources of globular proteins

enzymes, protein hormones, albumins and globulins in the blood, casein in milk, albumin in egg white

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types of proteins in plants

glutelins and prolamines

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glutelin plant proteins

insoluble in neutral conditions, soluble in acids and alkalis, storage proteins

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glutelines plant proteins examples and sources

glutenin in wheat, oryzenin in rice

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prolamines plant proteins

insoluble in water, soluble in alcohol, storage proteins

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prolamines plant protein examples and sources

gliadin in wheat and zein in maize

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amino acids in eukaryotes

20 are found

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amino acids

regulate all cellular processes and virtually all chemical reactions in living organisms

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essential amino acids

histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

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what is a peptide

2-50 amino acids joined together by a peptide link

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a peptide link

is formed when the amino group of one amino acid reacts with acidic group of an adjacent amino acid

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peptide bond

formed by a condensation, molecule of water is eliminated during the formation of the link

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sources of muscle proteins

actin and myosin

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sources of connective tissue proteins

collage, elastin, gelatin

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protein in eggs

ovalbumin

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protein in milk

casein

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good plant sources of protein

lentils tofu nuts beans

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animal proteins

high biological value contains all essential amino acids

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low biological value proteins

proteins that have a limiting amino acid

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limiting amino acids

amino acids present at a low concentration

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proteins in wheat/ rice

deficient in lysine but rich in methionine

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beans and pulses

deficient in methionine

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new born infants

can absorb some proteins from their mothers milk, including antibodies which provide protection from infection

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diseases associated with protein energy malnutrition

marasmus and kwashiorkor

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marasmus

severe wasting due to chronic deprivation of energy intake to meet requirements

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kwashiorkor

characterised by oedema affects only young children

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catabolic illness

burn injuries, cancer, trauma, sepsis, major injury , muscle protein catabolised to provide amino acids for synthesis of new cells and proteins for an immune response as well as energy

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males 19-50 protein RNI

55.5 grams per day

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females 19-50 yrs protein RNI

45 grams per day

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Get Revising

energy, fats, carbs, proteins

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