Biological molecules - Nutrients

• Nutrients

  • Cells, tissues and organs are all composed of chemicals
• Organic nutrients

  1. Carbohydrates
  2. Fats
  3. Proteins
  4. Vitamins
• Inorganic nutrients

  • Water
  • Mineral salts
• Biological molecules of life

  • All living things are composed of four classes of large molecules
  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acid
• Polymers

  • Long molecules consisting of similar building blocks linked together by covalent bonds
• Synthesis and breakdown of polymers

  • Need enzymes
  • Condensation
  • Two monomers joined together through the loss of one water molecule
  • Hydrolysis
  • Disassembly of polymers to monomers
• Monosaccharides

  • Single sugars
  • Formula: C6H12O6
  • Consists of glucose, fructose, galactose
  • Hexagonal
  • Glucose + Galactose
  • Pentose
  • Fructose + ribose + deoxyribose
• Disaccharides

  • Formed when a dehydration process joins with two monosaccharides
  • Sucrose
  • Non-reducing sugar
  • Glucose + Fructose
  • Maltose
  • Reducing sugar
  • Glucose + Glucose
  • Lactose
  • Reducing sugar
  • Glucose + Galactose
• Polymers

  • Storage + structural roles
  • Starch
  • Long straight chains of amino acids
  • Few side branches
  • Energy storage for plant cells
  • Glycogen
  • Highly branched polymer of glucose molecules
  • Carbohydrate storage for animals
  • Found in liver + muscles
• Polymers

  • Cellulose
  • Straight chain of glucose molecules
  • Structural carbohydrate in plant cells
  • Chitin
  • Polymer of glucose with amino acids attached
  • Primary constituent of exoskeleton
• Functions of carbohydrates

  1. Energy
  2. Converted to amino acids and fats
  3. Nectar in flowers
  4. Nucleic acid
  5. Lubricants
  6. Cellulose cell wall in plant cells
• Hydrolysis of starch

  1. Starch broken down by amylase
  2. Amylase breaks bonds, releasing maltose
  3. Maltose cannot be broken down by amylase
  4. Maltose broken down by maltase
  5. Further bond breaking by maltase releases glucose
• Hydrolysis of fats

  • Fats broken down into fatty acids and glycerol
  • Needs the involvement of water
  • Occurs readily with enzyme
• Why fats separates from water

  • Water form hydrogen bonds with each other, excluding the fats
• Functions of fats

  1. Source + stored form of energy
  2. Insulation
  3. Absorption + transportation
  4. Part of all cell membranes
  5. Reduces water loss from skin surface
  6. Cushion organs
  7. Forms hormones
  8. Satiety + flavour to foods
• Amino acids

  • Building blocks of protein molecules in polypeptides synthesized on ribosomes
  • Contains an amine group, a functional R group and a carboxyl group
  • Difference in R group is what makes each protein unique
• Proteins

  • Polymer of amino acids held together by peptide bonds
  • Amine end of one amino acid join together with carboxyl end of another amino acid
  • Order in which amino acids are arranged determines the function of the protein
• Protein formation

  • Amino acids link up to form polypeptides
  • Held in place by strong peptide bonds
  • Polypeptides can link up to form even longer chains of amino acids
  • Coils are held in place by weak bonds
  • Protein is formed when one or more long chains of amino acids is folded together
• Primary structure of proteins

  • Linear sequence of amino acids composing the polypeptide chain

  Secondary structure of proteins

  • Alpha helix/beta pleated sheets
  • Example is DNA
• Tertiary structure of proteins

  • Superimposed folding of secondary structures, producing a ball-shape molecule
  • Example is Subunit of hemoglobin

  Quaternary structure of proteins

  • Polypeptides chain linked together in a specific manner
  • Example is hemoglobin
• Protein denaturation

  • Weak bonds easily broken by heat and chemicals
  • Protein is denatured when it unfolds and loses its 3 dimensional shape
  • Depending on severity, denaturation can be irreversible
• Functions of protein

  1. Synthesis of new protoplasm for growth
  2. Repair of worn out body cells
  3. Forms enzymes, some hormones and antibodies
  4. Fluid and pH balance
  5. Should not be used for energy
  6. Protein deficiency disease in children = kwashiorkor
• Why must proteins be broken down in body

  1. Protein molecules too large to pass through cell surface membrane
  2. Must be broken down by enzymes during digestion
  3. Proteins hydrolysed into polypeptides then amino acids
  4. Amino acids are simpler and smaller structures
  5. Amino acids are soluble and small enough to diffuse through cell surface membrane
  6. Easily absorbed into body cells
  7. Once absorbed they link up again to form proteins
• Reducing sugar

  • Any sugar that is able to act as an reducing agent due to its free ketone group
• Iodine tests

  • Blue-black = starch present
  • Yellowish-brown = starch absent

  Benedict's solution tests

  • Light blue to green = reducing sugar absent
  • Yellow to orange = reducing sugar present
  • Brick red = reducing sugar very present
• Ethanol emulsion test

  • Clear solution = fats absent
  • Chalky white emulsion = fat present

  Biuret test

  • Violet colour = proteins present
• Starch

  
• Cellulose

  
• Glycogen

  
• Primary structure

  
• Secondary structure - Beta pleated sheets

  
• Tertiary structure

  
• Quaternary structure

  
• Secondary structure - Alpha helix