biological molecules- nutrients Flashcards
what are nutrients
nutrients are chemical substances that provies energy and materials needed for the body
what are the types of nutrients
- carbohydrates
- proteins
- fats
- vitamins
- dietary fibre
- water
- minerals
why do we need food
- for growth
- for repair or replacement of worn and damaged tissues- replace red blood cells, skin and wounds
- as a source of energy- released and used for: chemical reactions that build complex molecules, activities.
- to maintain health and prevent deficiency dieseases
what are the functions of water in humans
- is the solvent which chemical reactions take place
- is an essential component of cells, tissue fluid, digestive juices and blood
- helps regulate body temperatures
- helps to transport dissolved substances around the body
what are the functions of water in plants
- it is essential for photosythesis
- helps keep plant cells turgid and plant upright
- is needed for the transport of mieral salts up the xylem
- is needed for the transport of fod substances from the leaves to other parts of the plant
how much water do we need
about 70% of the body weight is water. water is lost from the body when we breathe, sweat, urinate. The water that is lost needs to be replaced
the amount of water needed depends on…
- how active the person is
- how healthy the person is
- the environmental conditions
what are carbohydrates
- carbohydrates are organic molecules made up of: carbon, hydrogen, oxygen
- the ratio of hydrogen atoms to the oxygen atoms in carbohydrtes is 2:1
- mainly from plants
monosaccharides (simple sugars)-> glucose, frucose, galactose
disaccharides (double sugars)-> maltose, sucrose, lactose
polysaccharides (complex carbohydrates)-> starch, glycogen, cellulose
- all monosaccharides and disaccharides (except sucrose) are reducing sugars
how are disaccharides formed
a consendation reaction is a chemical reaction in which two simple molecules are joined together to form a larger molecule with the removal of one molecule of water. when two glucose molecules join together via the condensation reaction, maltose is formed.
how can we test for reducing sugars
by carrying out the benedict’s test:
- add 2cm cube of benedict’s solution to 2cm cube of food sample (liquid) in a test tube.
- shake the mixture.
- heat the contents in a boiling water bath for 2-3 minutes.
- a green, yellow or orange- red percipitate is formed after heating if reducing sugars is present in trace, moderate or large amounts, respectively.
observations are recorded as follows:
“ benedict’s solution remained blue”: reducing sugar absent
“ green/yellow precipitate/orange precipitate, orange-red precipitate formed after heating”: reducing sugars present
hydrolysis of disaccharides
hydrolysis is a reaction in which a water molecule is needed to break down a complex molecule into simpler molecules. A double sugar can be split into two single sugar molecule by hydrolysis in the presence of an enzyme
what are the types of complex carbohydrates
- starch:
- > a storage form of carbohydrates in plants
- > found in storage organs in plants
- glycogen:
- > a storage form of carbohydrates in mammals
- > digested to form glucose when needed
- cellulose:
- > cellulose cell wall protects plant cells
- > serve as dietary fibres to prevent constipation
hydrolysis of starch
starch is broken down into maltose molecules by amylase
maltose molecules are broken down into glycose by maltase
how can we test for starch
by carrying out the iodine test:
- add 2cm cube of food sample to a clean test tube
- add a few drops of iodine solution to the test tube
- a blue-black solution is formed if starch is present
observations are recorded as follows:
“iodine solution remainded brown”: starch present
“ iodine solution turns from brown to blue-black”: starch present
why are both glycogen and starch suitable for storage molecules
- they are insoluble in water, so does not affect the water potential in cell
- they are large molecules, so cannot pass through the cell membrane
- they can be hydrolysed to glucose, to release energy
- they have compact shapes, so occupy less space
what are the sources of carbohydrates
potatoes, rice, bread, cereals
what are the functions of carbohydrates
carbohydrates are needed:
- to be broken down to release energy for cell activities
- to form cell componants (e.g. cell wall)
- for conversion into other organic compounds (e.g. amino acids and fats)
- to form nucleic acids (e.g. DNA)
- to synthesise lubricants
- to synthesise nectar in flowers
since both starch and cellulose are made of glucose units joined toether, why then only starch cn be digested in our bodies but not cellulose
humans have amylase but not cellulose
what are fats made up of
- fats are organic compounds made up of: carbon, hydrogen, oxygen
- fats contain much less oxygen in proportion to hydrogen
- the proportions of the elements in fats are not fixed
- a fat molecule is made up of: glycerol, fatty acid chain
hydrolysis of fats
fats an be broken down into simpler compounds by hydrolysis. Hydrolysis of fats produces fatty acids and glycerol
how can we test for fats
by carrying out the ethanol emulsion test:
- add 2cm cube of ethanol to 0.5cm cube of food sample in a clean and dry test tube
- shake the contents of the tube vigorously
- decant the liquid from step 2 into a new test tube
- add 2cm cube of distilled water into the test tube from step 3 and shake the mixture
- a white emulsion is formed if fats are present
observation are recorded as follow:
“solution remained colorless”: fats absent
“white emulsion formed”: fats present
what are the sources of fats
nuts, oils
functions of fats
- a source and store of energy. Fats release about twice the amount of energy as compared to same anount of carbohydrates
- act as an insulating material to prevent exessive heat loss
- are a solvent for fat soluble vitamins and some hormones
- form the main part of cell membrane
- help prevent water loss from skin surface
what are proteins made up off
- proteins are organic compounds made up off: carbon, oxygen, hydrogen, nitrogen
- each protein molecule is made up of smaller basic units called amino acids
what are amino acids made up off
- amino acids are made up off: an amino group, an acid group, a side chain
- peptied bonds link up amino acids to form a polypeptide (condensation reaction)
- two or more polypeptide chains fold to form a 3-D molecule, called protein
- similarly, proteins can be hydrolysed into amino acids
- amino acids are small enough to be absorbed by the body
how can we test for proteins
by carrying out the biuret test:
- add 1cm cube f biuret solution to 2cm cube of food sample
- shake the mixture thoroughly
- a purple or violet solution is formed if proteins are present
observations are recorded as follow:
“biuret solution remained blue”: protein absent
“biuret solution turned from blue to purple”: protein present
what are the sources of proteins
meat, beans, fish, egg
what are the functions of proteins
proteins are needed for the synthesis of:
- new protoplasm for growth and repair of worn-out cells
- enzymes and some hormones
- antibodies
what is a balanced diet
- a balanced diet should contain the right amount of: carbohydrates, fats, proteins, vitamins, dietary fibre, water and mineral to meet the daily requirement of the body
- different food has different energy level which is the different amounts of energy stored in them
- fats store twice as much energy as carbohydrates
- when the body needs energy, carbohydrates is he first to be used, followed by fats. Proteins is the last resort
