Chapter 9 -Nutrition Flashcards
Name a non-reducing sugar
Sucrose
Name the reducing sugars
Glucose & multose
Describe the test for reducing sugars
Use 4 cubic centimetres of blue benedict’s solution in a test tube
- shake gently to obtian blue colour
- Crush the food to be tested (larger surface area)
- Shake thoroughly
- Heat the content in a waterbath
- An orange/red precipitate indicates a large amount of glucose/multose
- Greenish yellow indicates a small amount
- If the solution remains blue, no reducing sugar is present
Describe the test for non-reducing sugars
- Crush the food to be tested
- Add a small amount of hydrochloric acid to the food
- Boil it for one minute in a water bath
- Neutralise the solution by adding sodium hydrogen carbonate to the test tube
- Carry out the normal benedict’s test
- Evaluate the same
Describe the test for starch
- Crush the food
- Spread it on a white tile
- Add iodine solution (yellow brown) with a syringe
- If the colour changes to black, starch is present
Describe the test for proteins
- Crush the food and place in a test tube
- Add blue Biuret solution
- Mix with a small amount of distilled water
- Shake gently
- If a purple colour appears, proteins are present
Describe the test for fats
- Crush the food & place in test tube
- Add 10 cubic centimetres of ethanol
- Shake thoroughly and leave for 10 minutes
- Add a few drops of distilled water
- The fat forms tiny globules
- A milky solution forms
- If the solution stays clear, no lipids are present
Describe the test for the PRESENCE of vitamin C
- Put blue DCPIP in a test tube
- Add fruit juice (or liquidised food) with a pipette
- Add the fruit juice drop by drop to the DCPIP
- Count the number of drops until the solution goes clear
- If the solution goes clear, vitamin C is PRESENT
Describe an experiment to investigate the relative concentration of vitamin C in different fruit juices
- Basically repeat the presence test for both juices, recording the amount of drops for each. Shake the solution after each drop. Be sure to use the same amount of DCPIP for both experiments. The solution which required the least drops to go clear indicates a higher concentration of vitamin C.
- obviously moet jy dit nou nie so gaan skryf nie, maar julle is mos slim. Ek hoef regtig nie weer die hele vitamin C ding the gaan herhaal nie, although ek nou al so baie nonsens gepraat het ek kon eintlik maar
Name the four main elements present in organic substances
- Carbon (Most important)
- Oxygen
- Hydrogen
- Nitrogen
Define nutrients
Substances with food value which make up food that can be utilised in the metabolic processes of an organism
Define nutrition
The ability of an organism to obtain organic and inorganic nutrients from the environment, which contain energy and raw materials, for growth and development
Describe autotrophic nutrition
Uses inorganic molecules and an external energy source to build up organic molecules. Occurs in plants during photosynthesis
Describe heterotrophic nutrition
Takes organic molecules into the body during nutrition, which are used as a source of energy and growth. Occurs in animals
Name the chemical elements present in carbohydrates
Carbon
Hydrogen
Oxygen
State the ratio in which hydrogen and oxygen is present in carbohydrates
2:1
Define a saccharide
A single unit of sugar
Outline the structure of true carbohydrates
Polymers assembled from a number of sugar units
Describe monosaccharides
- Single sugars
- Small, sweet tasting molecules
- Basic monomers of complex carbohydrate structures
- Example: Glucose
Describe disaccharides (the double c is important)
- Double sugars: Composed of two monosaccharides
- Formed by condensation
- A glycocidic bond holds the monomers together
- Enzymes are involved in the reaction
- The molecules is split up during HYDROlysis, where a water molecule is added in the process
Desctive polysaccharides
- Many monosaccharide molecules which combine by condensation reactions
- This process is called polymerisation (but you know this from physics)
- A polysaccharide can be reverted to monosaccharides by hydrolysis, which involves a water molecule being added to split the glycocidic bonds
- Polysaccharides are large, insoluble and non-sweet tasting
Describe the function of glucose in living organisms
- Main source of energy
- Building block for larger carbohydrates
- It is the starting molecule for building other molecules, like lipids, fatty acids and vitamins
- Transported in blood
Describe the function of sucrose in plants
- Plants can only transport carbohydrates in the form of sucrose
- This is known as translocation
Describe the function of starch in living organisms
- Energy storage in plants
- Energy source
Why do plants store carbohydrates in starch form?
Starch is insoluble and has no osmotic effect. Can be hydrolised into glucose when needed
Discuss why fats store twice as much energy per gram compared to carbohydrates
- Both are energy sources
- Both are important for energy storage
- Carbohydrates provide 17 kJ per gram
- Fats provide 38 kJ per gram
- Fats therefore provide twice as much energy as carbohydrates
Name the chamicals found in proteins
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Phosphorus, sulphur and iron may also be present
State the functions of proteins
- Growth and repair of tissue
- Provides 17kJ per gram, making it an energy source
Describe the general structure of a protein
- Polymers made up of monomers called amino acids
- Assembled from 20 different amino acids
- Once molecule may consist of sever hundreds or a few thousand amino acids
- Every amino acid has an AMINO GROUP (NH2) and CARBOXYL GROUP (COOH)
- During condensation, OH is removed from the carboxyl group of the one amino acid, and H is removed from the amino group of the next. A C-N bond forms, (PEPTIDE BOND), and a water molecule is released
- Enzymes catalyse this reaction
Give a name for a molecule consisting out of two amino acids
Dipeptide
Give a name for a molecule which consists out of less than 50 amino acids
Polypeptide
Give a name for a molecule which consists out of numerous polypeptides linked together
Protein
State which process reduces proteins to amino acids
Hydrolysis.
The same principle applies as with carbohydrates, to break a tripeptide, two water molecules is required to break the two peptide bonds, and so forth
Structure of a protein
Primary, secondary and tertiary as studied in Chapter 8 - Enzymes
Describe the role of globular proteins
- Enzymes act as biological catalysts
- Hormones like insulin and glucagon regulates blood sugar levels
- Haemoglobin transports oxygen in red blood cells
- Immunoglobulin (antibodies) form complexes with invading antigens
- Carrier proteins on the cell surface membrane for active transport
State the roles of fibrous proteins
- Keratin forms structural parts like hair and nails
- Fibrin forms fibrinogen to trap red blood cells during blood clotting
- Collagen provides tensile strength to blood vessels and connective tissue
Name the chemical elements found in fats
- Carbon
- Oxygen
- Hydrogen
Describe the structure of fats (triglycerides)
- Ratio of H to O is more than 2:1
- Composed of a glycerol and three fatty acid molecules
- Joined by ester bonds
- Triglyceride molecules are formed when three water molecules are released and the fatty acids bond to the glycerol during condensation
- The same goes for the opposite, hydrolysis
- Fats do not dissolve in water, but in ethanol and ether
- Animal fats are saturated solid fats at room temperature
- Plants fats are unsaturated oils at room temperature
Describe the functions of fats in plants and animals
- Energy source
- Energy storage
- Insulating layer
- Serves as structural component in cell membranes (phospholipids)
- Protection of organs like kidneys
- Forms a waterproof cuticle on leaves
- Insects have a waxy cuticle to prevent evaporation
- Birds have oil spread over their bodies to repel water
Describe the structure of a phospholipid
- Consists of a glycerol molecule combined with only two fatty acids
- The glycerol molecule contains a phosphate group
- The head (glycerol-phosphate part) is hydrophilic
- The tail (fatty acids) is hydrophobic
- Phospholipids form a bilayer
- The tail is a barrier to water-soluble molecules
- The head interacts with water-soluble molecules
- Contribute to the fluidity of the cell surface membrane
Describe the role of water in living organisms
- Transport medium for nutrients
- Transport medium for metabolic waste
- Transport medium for undigested and unabsorbed food
- Major component of blood plasma (99%)
- Acts as a solvent for chemicals
- Reactant in hydrolysis
- Reactant in condensation
- Used when cooling
- Maintains a stable body temperature
- Needed for enzyme reactions
- Used in body fluids
- Part of cytoplasm
- Used in joints for lubrication (synovial fluids)
- Part of mucus
