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23 Cards in this Set
- Front
- Back
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Most physiologically important sugars are D/L isomers
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D
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What is a dextrin?
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A group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose
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What are polysaccharides divided into?
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Start and non-starch polysaccharides
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What are oligosaccharides divided into?
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Dextrins and trisaccharides/tetrasaccharides
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What are mono/di sugars divided into?
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Extrinsic and intrinsic sugars
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What does an aldehyde group on a sugar indicate?
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That it is a reducing sugar
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What does a ketone group on a sugar indicate?
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That it is non-reducing
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What is the glycaemic index?
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The extent to which a test dose of a carbohydrate increases blood glucose compared with an equivalent amount of glucose from a reference carbohydrate
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What are 'conjugated double bonds'?
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Ones which alternate (db, sb, db, sb etc.)
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What are the nutritionally and metabolically important monosaccharides?
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Glucose, galactose and fructose
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In what way can human enzymes manipulate fatty acids?
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They can add two carbons to the alpha carbon
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How are sugar alcohols formed?
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Reduction of the aldehyde or keto group of a sugar to a hydroxyl group, and therefore are often called polyols
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What are the major dietary disaccharides? M SLIT
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sucrose, lactose, trehalose, maltose and isomaltose
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What are the two forms of starch? Which is branched?
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Amylose and amylopectin (branched)
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What is the fate of non-digested starch?
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Excretion or metabolised by bacteria in the gut
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What are the benefits of non-starch polysaccharides in the diet? (5)
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Bacterial fermentation in the colon
Soluble ones increase the viscosity of the intestinal contents, and so slow the absorption of the products of digestion. A modest amount of soluble non-starch polysaccharide before or with a meal lowers the post-prandial rise in blood glucose, and improves glycaemic control in people with diabetes mellitus. Soluble ones also bind bile salts and potential carcinogens, preventing their absorption. Insoluble non-starch polysaccharides increase the bulk of the intestinal contents, so aiding peristalsis - this is valuable in the prevention or treatment of diverticular disease of the colon |
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What is the befit of having bacteria ferment sugars in the colon? (3)
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They yield short-chain fatty acids, carbon dioxide and small amounts of hydrogen and methane.
Encourage the growth and proliferation of beneficial bacteria at the expense of pathogens. The butyrate produced may also provide protection against colorectal cancer |
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Why do we need fat in the diet? (5)
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On a very low fat diet, providing less than about 10% of energy intake, it is difficult to eat a large enough bulk of food to meet energy requirements. Fat provides 37 kJ /gram, compared with 16 kJ /gram from carbohydrate and 17 kJ /gram from protein
Carbohydrates and proteins in foods are associated with a considerable amount of water, while high-fat foods contain much less (easier to consume more of a high-fat food due to less bulk --> Obesity), and many carbohydrate-rich foods are also sources of non-starch polysaccharides, which add to the bulk of the food without providing a significant amount of energy. Vitamins A, D, E and K, as well as carotenes and other lipid-soluble compounds are absorbed dissolved in dietary fat, and indeed fatty foods are the main sources of these nutrients Lubricates the food in the mouth, and makes chewing and swallowing easier Two families of polyunsaturated fatty acids cannot be synthesised in the body, and are required as precursors for the synthesis of prostaglandins and related compounds |
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What are the four physiologically, nutritionally and metabolically important lipids?
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Triacylglycerols (triglycerides)
Phospholipids Cholesterol Vitamins |
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What is the importance of one of the tails on the phospholipid bilayer being a polyunsaturated fatty acid? (2)
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It permits more space for lipids such as cholesterol and vitamin E to fit in the inner part of the membrane
Also permits greater fluidity of the cell membrane, which is important for normal membrane function. |
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There are desaturases in human tissues that can introduce carbon-carbon double bonds between an existing double bond and the carboxyl group, but not between an existing double bond and the terminal methyl group
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.
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Compared with mono-unsaturated fatty acids:
saturated fatty acids increase serum cholesterol proportionally to Y x the intake polyunsaturated fatty acids decrease serum cholesterol proportionally to X x the intake |
Y = 2
X = 1 |
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Which kind of molecule can easily move through the cell membrane?
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HydroPHOBIC
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