Nutrients Flashcards
what are carbohydrates?
organic molecules made up of elements carbon, hydrogen and oxygen
why is water important? (6 points)
1) solvent in which chemical reactions take place
2) essential for photosynthesis
3) keeps cells turgid/firm
4) helps in transport of dissolved mineral salts in plants
5) regulates body temperature
6) helps transport dissolved substances around body
what is the general formula of carbohydrates?
CₙH₂ₘOₘ
*hydrogen-to-oxygen ratio — 2:1
what are is difference between the 2 single sugars?
glucose: found in plants and animals
fructose: common in plants, rare in animals
*single sugars can fit through cell membranes and are basic units of carbohydrates
*both chemical compositions are C₆H₁₂O₆, but atoms are arranged differently
what is maltose (malt sugar) made of and what is its enzyme?
glucose + glucose, maltase
what is sucrose (cane sugar) made of and what is its enzyme?
glucose + fructose, sucrase
*sucrose is a non-reducing sugar
what are 4 sources of carbohydrates?
1) bread
2) rice
3) noodles
4) cereal
describe Benedict’s test and its results
steps:
1) add 2cm³ of Benedict’s solution to 2cm³ of food sample in test-tube
2) shake the mixture
3) heat contents in boiling water bath for 2-3min
results:
green precipitate — traces
yellow/orange precipitate — moderate amount
brick-red precipitate — large amount
remained blue — no reducing sugars
what are the 4 functions of carbohydrates?
1) provide energy for cell activities
2) form supporting structures (e.g. cell wall)/nucleic acid (e.g. DNA)
3) for conversion into other organic compounds (e.g. amino acids/fats)
4) synthesis of lubricants/nectar in flowers
what are the structure, role and occurrence of starch?
several thousand glucose molecules joined together
storage form of carbohydrates in plants, found in storage organs of plants (e.g. potato/tubers/tapioca)
*starch broken down by amylase into maltose, maltose broken down by maltase into glucose
what are the structure and role of cellulose?
many glucose molecules joined together but bonded differently from starch
makes up cellulose cell walls to protect plant cells/serves as dietary fibres preventing constipation
what are the structure, role and occurrence of glycogen?
branched molecule of many glucose molecules
storage form of carbohydrates in animals, stored in liver/muscles of mammals
why are starch and glycogen suitable stores of energy? (4 points)
1) insoluble in water (do not change w.p. in cells)
2) large molecules cannot diffuse through cell membranes (won’t be lost from cells)
3) easily hydrolysed to glucose if needed (for tissue respiration)
4) made of molecules that have compact shapes, occupying lesser space
describe the iodine test and its results
steps:
add a few drops of iodine solution to food sample
results:
starch present — iodine solution turns blue-black
starch absent — iodine solution remains brown
what are fats?
organic molecules made up of elements carbon, hydrogen and oxygen
*contain less much oxygen than hydrogen, has more than 2 times more energy than carbohydrates
what compounds are fats made of?
1 glycerol molecule + 3 fatty acid molecules
*fats broken down by lipase
what are 3 sources of fats?
1) butter
2) corn oil
3) olives/nuts and their oils
what are the 5 functions of fats?
1) source and store of energy
2) act as insulating material to prevent excessive heat loss
3) solvent for fat-soluble vitamins and some hormones
4) form main parts of cell membranes
5) reduces water loss from skin surfaces
describe the ethanol emulsion test and its results
steps:
1) add 2cm³ of ethanol to 2cm³ of food sample in clean test-tube
2) shake contents of test-tube vigorously
3) add 2cm³ of water into test-tube and shake mixture
results:
cloudy white emulsion formed — fats present
remains clear — fats absent
what are proteins?
organic molecules made up of elements carbon, hydrogen, exygen, nitrogen and sometimes sulfur
*basic sub-units of proteins are amino acids
what are the 3 building blocks of protein?
1) amino group
2) acidic group
3) side chain
what is the structure of proteins?
peptide bonds link up amino acids to form polypeptides
two or more polypeptide chains fold to form a specific 3-D molecule called protein
what are the 8 sources of proteins?
1) red meat
2) seafood
3) egg whites
4) cheese
5) milk
6) nuts
7) beans
8) lentils
what are the 3 functions of proteins?
for the synthesis of:
1) new protoplasm for growth and repair of worn-out cells
2) enzymes and some hormones
3) antibodies
describe biuret test and its results
steps:
1) add 2cm³ of sodium hydroxide to 2cm³ of food sample in clean test-tube and shake
2) add 1% copper(II) sulfate drop by drop and shake after each drop
results:
violet solution — proteins present
remained blue — proteins absent
what if the food sample for Benedict’s and biuret tests are solids?
add water to crushed food to dissolve nutrients, shake and decant mixture into new test-tube before adding reagent
what if the food sample for iodine test is solid?
add the iodine solution directly to the crushed food
what if the food sample for ethanol emulsion test is solid?
add ethanol to crushed food to dissolve nutrients, shake and decant mixture into new test-tube before adding water
