Cellular & Molecular Bioscience - Nutrition. macro-nutrients Flashcards
Nutrition
Nutrient
Science of foods and their actions within the body. This includes: Relationship between health and disease (malnutrition)
any substance that is absorbed into the bloodstream from the diet and used to promote the various functions of the body.
Diet
selection of foods and beverages that an individual eats and drinks
balanced diet - appropriate intake of nutrients for health
What are the 6 nutrient classes?
Macronutrients
carbohydrates
proteins
lipids
water
Micronutrients
vitamins
mineral salts
Macronutrients - energy-yielding nutrients:
Organic nutrients that are broken down to provide energy
energy released from nutrients can be measured in;
calories
or
kcal
1000 cals in 1 kcal
daily calorie intake
2,000 Kcal - women
2,500 Kcal - men
Excessive prolonged lower calories intake – weight loss
Nutrient/energy deficiencies
Consistent higher calories intake
weight gain - Obesity/risk of chronic diseases
what are carbohydrates made up of?
Monosaccharides – simple sugars –
Smallest sugar Unit
General formula (CH2O)n, where n is 3 to 6.
Disaccharides
two linked monosaccharide units
Polysaccharides
composed of between a few and thousands of monosaccharides linked together.
E.g. cellulose, glycogen, starches, chitin (fungal cell wall component)
examples of monosaccharides
1) Glucose – enters the cells via an active transport
source of immediate energy (via cellular respiration, generating ATP – Lecture 6). 1g produces 4 Kcal
Excess are stored as glycogen (by condensation reactions) by hepatic (liver) and muscle cells
Blood glucose regulation by insulin and glucagon
2) Fructose
3) Galactose
examples of Disaccharides (units of 2 monosaccharides)
1) Sucrose - composed of a glucose + fructose
2) Lactose - composed of a galactose + glucose
3) Maltose – composed of 2 glucose units
Key structural motif of starch. It is released during starch breaking down (digestion)
examples of Polysaccharides – chains of monosaccharides
1) Glycogen - multibranched polysaccharide of glucose
in meats (in a limited extent)
Storage form of glucose, mainly in hepatic and skeletal muscle cells
If glycogen is abundant, glucose excess can be used to make fats
2) Starch - long, branched or unbranched glucose chains
in grains, rice, wheat (storage form of glucose in plants)
Broken down during digestion, by salivary and pancreatic amylases into disaccharides (maltose), then hydrolysed into monosaccharides (glucose) energy source
Polysaccharides in nutrition (Dietary fibres)
Vegetables, fruits, whole grains, and legumes
Digestion - undigested until the large intestine, where some are broken down by bacteria
Trap/get rid of bile ( cholesterol levels) and molecules in the gut regulate bowel activity
Prevention of heart diseases, obesity, as they help lower cholesterol
What are the risks of low fibre intake diets?
Constipation and haemorrhoids
Increased risk of heart diseases and some types of tumours
E.g. colon cancer
Glycaemic Index (GI)
Degree to which a food increases blood sugars and elicit insulin response
(diff carbo. digested and absorbed at different rates)
High GI (processed carbs, white bread, potatoes, watermelon) > raise blood sugar high and rapidly
Low GI (fruit, legumes, whole wheat) raise blood sugar slowly and to a lesser extent
Why has unhealthy foods such as crisps and chocolates have low GI
contains a lot of fat so the lipophilic effect means less carbohydrates absorption
what type of food should type 2 diabetes consume?
low GI foods
Help stabilise long-term blood glucose levels
(contains a lot of fat)
What are the Recommended intake of free sugar in the UK:
Limit the intake of free sugars (either added to food/drink or naturally present in fruit/vegetables, e.g. honey/smoothies) to 5% of the overall energy daily intake (30g of free sugars a day)
Sugar Deficiency
hypoglycaemia
Energy deficit > CNS suffering, dizziness, mental and physical weakness
Protein breaking down to produce energy kidney stress, digestive problems
High free sugar intake effects on health
Obesity > weight gain and obesity
Increased chronic diseases risk (type 2 diabetes, cancers, hypertension, heart diseases)
Dental Caries bacterial fermentation of added sugars producing acids, contributing to tooth decay
how many different types of amino acids?
20 with unique R group
Non essential amino acids
can be synthesised by the body
Essential amino acids
CANNOT be synthesised by the body
MUST be provided in the diet
*Conditionally Essential Amino Acid.
In some cases, some nonessential amino acids become essential (e.g. in newborns)
Complete proteins
containing all the essential amino acids in the required proportions
meat, fish, soya beans, milk, and eggs.
Incomplete proteins
do NOT contain all the essential amino acids in the correct proportions.
mainly of vegetable origin (cereals, peas, beans, and lentils).
a diet based on a wide variety of incomplete proteins can avoid amino acid deficiencies. Essential consideration for strict vegetarian or vegan diets.
Proteins are the only source of _______
nitrogen
Protein Deficiency
Diet consistently suppling too little protein or lacks essential amino acids
E.g. Marasmus and kwashiorkor (swollen abdomen), clinical syndromes in children/infants
It can cause severe weight loss, slowed growth, impaired brain functions, etc
Eating disorders, cancer, difficults to absorb nutrients
Excess of Proteins
Diet consistently suppling too much protein (especially from animal sources). A risk factor for:
Cardiovascular diseases
Cancer (processed & red meat as carcinogens),
Osteoporosis - calcium excretion increases, depleting the bone
Kidney stones
Digestion of stomach - describe process
starts in stomach; pepsin and acid > shorter polypeptides
In pancreas, enzyme peptidases break down the polypeptides in the cells of small intestine to a.a
Amino acid absorption (crucial for the essential ones)
Intestinal cells uptake amino acids and:
released into the bloodstream
used to make proteins
converted to glucose, if needed
broken down to provide energy via deamination producing ammonia (NH3) that is then converted to urea
how much lipid should be in a daily intake?
20 - 35 %
why are lipid important for diet?
Major fuel source during light/moderate exercise
more energy per gram than carbohydrates (9 vs 4 kCal/g)
Major store of energy from food (Triglycerides)
Adipose cells uptake lipids and expand in size.
advantages of lipid
Primary component of cell membranes and nerve sheaths (myelin)
Cushioning and thermal insulation for the organs
Required for the synthesis of steroid hormones
Serve as a vehicle for the absorption of lipid soluble vitamins
Types of fatty acids (3)
1) triglycerides - Primary lipid in food and in body
GLYCEROL BACKBONE + 3 fatty acids
2) Phospholipids - Amphipathic molecule
Cell membrane component
HEAD GROUP
PHOSPHATE
GLYCEROL BACKBONE
2 FATTY ACID CHAINS
3) Sterols (cholestrol)
Components of vitamins, hormones, cell membrane
STEROID NUCLEUS
HYDROXYL GROUP
Fatty acids
Aliphatic building blocks of triglycerides, phospholipid and glycolipids. They differ by:
Chain Length - 4 to 24 carbons long (even numbers) – Short (<6 C), medium (6-12 C), long (>12 C)
Degree of saturation
presence & No. of double bonds in the chain
Saturated – No double bonds
Monounsaturated – having one double bond
Polyunsaturated – having two or more double bonds
Locations of Double Bonds
position of the double bond closest to the methyl (omega No.)
Omega-3
Omega-6
Omega-9
What are the properties of fatty acids?
firmness
stability
food sources
health effects
SATURATED
- more solid at room temp
- more stable / resistant to oxidation
- animal-based food (milk, cheese, butter, eggs, fatty meat)
- factor risk for heart diseases
UNSATURATED
- the more unsaturated points has, the more liquid it is (at room temp.)
- more unsaturated points, the less stable/resistant to oxidation
- plant-based food (avocados, olives, vegetable oils, etc), seafood
- protective against chronic diseases (heart disease, stroke, cancer, etc)
Essential fatty acids - The body can make fatty acids, except for:
Linolenic acid (an omega-3) and linoleic acid (an omega-6)
These essential fatty acids MUST be provided by the diet (vegetable oils, seeds, nuts, fish, seafoods)
Fatty Acid Deficiencies (infants)
Impaired growth, reproductive failure, skin lesions, kidney and liver disorders
Trans-fatty acids
Hydrogenation of unsaturated fatty acids - some unsaturation points are saturated by adding hydrogen molecules, (reducing the double bonds in the structure)
Partially hydrogenation in food industry, to prevent oxidation, and ensure a longer shelf life
some double bonds that remain after processing change their configuration from cis to trans
Trans unsaturated fatty acids - in which the H are located on opposite sides of a double bond
What os the health effect when LDL cholesterol in blood is increased??
^ risk of heart diseases
Describe the process of Lipids digestion:
1) Mouth - lingual lipases released by salivary glands
Important in infants - minor role in adults
2) Stomach - little lipid digestion by gastric lipases
3) Small Intestine – lipids activates the cholecystokinin (CCK) that release bile from the gallbladder
Bile emulsifies fat for digestion - promotes the dispersal of fats in watery fluids, so that
pancreatic & intestinal lipases can degrade triglycerides
What are emulsifiers/
required to make lipids accessible to lipases
water & oil > emulsification (micelles) > emulsified oil
Describe the process of Absorption of lipids
1) Long chain fatty acids and monoglycerides combine with the bile, forming micelles, diffuse into intestinal cells and are reassembled into triglycerides
2) Triglycerides and phospholipids are packaged with proteins as chylomicrons
3) Chylomicrons are transport vehicles released into lymph vessels and reach the bloodstream (thoracic duct)
Where are lipids (triglycerides) stored
adipose tissue
energy deficit, triglycerides are hydrolysed to release energy
