2.3: Carbohydrates & Lipids

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  • Created by: sofiedb
  • Created on: 19-02-18 08:43
Energy sources
compounds of carbon, hydrogen & oxygen are used to supply & store energy - 2 major categories: carbohydrates & lipids (composed of C, H, O)
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Carbohydrates general formula
Cx(H2O)y
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Monosaccharide
simplest types of carbs & act as monomers (any class of sugars that can be hydrolized to give a simple sugar
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Disaccharide formation
2 monosaccharide monomers are linked by a condensation reaction, which forms a glycosidic bond producing the disaccharide
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Polysaccharide formation
several monomer units form the polysaccharide - polymers (e.g. cellulose, glycogen & starch)
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Condensation reaction
reaction in which 2 smaller organic molecules combine to form a larger molecule & a molecule of water (or another simple molecule)
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glycogen
consists of compact molecules made up of branching chains of glucose
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Glucose
2 isomers: D-glucose & L-glucose
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L-glucose
cannot be used by cells
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D-glucose
biologically active, has 2 forms: alpha-D-glucose & beta-D-glucose - they differ because of the -H and the -OH groups in the structure
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Hydrolysis
opposite of condensation: water is added & used to break up a polymer, disaccharide or dipeptide into smaller monomers
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Disaccharide carbohydrates & monomers
Sucrose (α-D-glucose & fructose), maltose (2 units of α-D-glucose), lactose (β-D-glucose & galactose)
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Polysaccharide carbohydrates & monomers
starch (α-D-glucose ), glycogen (α-D-glucose), cellulose (β-D-glucose)
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Polysaccharides
supply & storage of energy & structural component
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Examples of polysaccharide functions
Plants: cellulose (cell wall strength & protects cell from over-expanding/bursting), starch (mixture of 2 polysaccharides - amylose & amylopectin), animals: glycogen
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Bond between monomers
can involve first carbon of 1 molecule & 4th carbon of the other (1,4 glycosidic bond is formed) // involves first carbon of 1 molecule & 6th of the other (1,6 glycosidic bond is formed)
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Starch
α-D-glucose units, 1,4 bonds (helical shape), 2 forms: amylose (only 1,4 bonds & linear helices), amylopectin (also 1,6 bonds & branching)
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Glycogen
1,4 & 1,6 glycosidic bonds (differs from amylopectin because of the length of the branches formed from 1,6 bonds - amylopectin branches are made up of 24-30 glucose subunits), glycogen made up of 8-12 glucose subunits
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Cellulose
straight chains of β-D-glucose subunits held together by β 1,4 glycosidic bonds with OH groups forming hydrogen bonds between them (formation of strong straight fibers), H-bonds between glucose subunits stabilise structure of polysaccharides
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Monosaccharides examples
glucose, ribose, fructose, galactose - plants: fructose sugar, animals: glucose used as energy source (glycolysis)
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Disaccharides examples
maltose, lactose, sucrose - plants: maltose (glucose + glucose) found in grans (hydrolysis of starch during germination) & sucrose (glucose + fructose) found in cane & sugar beets, animals: lactose (glucose + galactose) found in mammalian milk
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Polysaccharides examples
glycogen, cellulose, amylopectin - plants: cellulose (high tensile strength - structural component tof cell walls to resist cell expansion & natural starches form energy stores), animals: glycogen is storage form of carbohydrate in liver & muscles
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Starch in industry
amylopectin gives starch stickiness, amylopectin in 80% of starch in potatoes (GM potato which predominantly produces amylopectin starches (adhesive making)) - separation of starch components is costly & results in large quantity of waste water
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Fatty acids
carboxylic acids: possess -COOH (functional) group attached to hydrocarbon chain
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Forms of fatty acid
saturated, monounsaturated, polyunsaturated
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Saturated fatty acid
no double bonds between C-atoms in chain
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Monounsaturated fatty acid
single double bond
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Polyunsaturated fatty acid
2+ double bonds
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Unsaturated fatty acids
cis or trans isomers (depends on position of 2 H-atoms around C-C double bond)
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Cis-isomers
commonly occur in nature, 2 H-atoms are attached to the same side of the 2 C-atoms, double bond causes the fatty acid to bend, close packing not possible (bent shape), lipids/triglycerides formed from cis fatty acids have lower melting points
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Trans-isomers
produced when polyunsaturated fatty acids from plants are 'partially hydrogenated' making plant fatty acids more solid, H-atoms are on the opposite side of the 2 C-atoms, no bend in the fatty acid chain, close packing of chains, higher melting points
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Functions of lipids
energy storage, insulation, buoyancy
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Triglycerides
formed by condensation reactions between 1 glycerol & 3 fatty acids - ester bonds- 1 fatty acid is replaced by a phosphate group (phospholipid in membranes)
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Lipids examples
triglycerides, phospholipids, steroids (consist of 4 fused rings but are lipids because they are hydrophobic & insoluble in water e.g. cholesterol)
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'Good' fatty acid
unsaturated fatty acid of the cis type - protect against certain heart diseases
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Glycogen function
carbohydrate used for energy storage in animals, stored in the liver & muscles, can easily be broken down (vs. lipids( to glucose (which can be rapidly transported around the body for use in cellular respiration) - energy more accessible than in fat
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Lipids properties
more energy per gramme (content) than carbs & proteins, less dense (specific gravity) than water, non-polar & will dissolve other non-polar compounds but does not affect water movement, excellent heat insulation
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Lipids & health
high energy content causes obesity, increases risk of type II diabetes, coronary heart disease & types of cancer
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"bad" fats
trans fats & those rich in saturated fatty acids
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Trans fats
formed by hydrogenation of vegetable oils (adding H to unsaturated fats under pressure to increase spreadability & shell life)
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Trans fats & CHD
increased incidence of CHD, as they contribute to the formation of atherosclerotic plaques in arteries leading to heart attack
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BMI
Body Mass Index - weight (kg) / (height (m))^2
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Classification of BMI
underweight (
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Other cards in this set

Card 2

Front

Carbohydrates general formula

Back

Cx(H2O)y

Card 3

Front

Monosaccharide

Back

Preview of the front of card 3

Card 4

Front

Disaccharide formation

Back

Preview of the front of card 4

Card 5

Front

Polysaccharide formation

Back

Preview of the front of card 5
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