Lipids ATP And Proteins Flashcards
Triglycerides structure and function
Three fatty acids molecules and a glycerol
Ester bonds formed between fatty acids and glycerol molecules in a condensation reaction (releasing molecule of water)
Difference in properties of fats acids and oils comes from variation of fatty acids (can be saturated or unsaturated)
High ratio of energy storing hydrocarbons to carbon atoms- good energy source
Low mass to energy ratio- useful for animals as more energy stored in less volume
Insoluble in water doesn’t affect osmosis and water potential
High ratio of hydrogen to oxygen molecules meaning water can be released.
Phospholipids structure and function
One of the fatty acid molecules in a triglyceride replaced with a phosphate molecule. Hydrophobic tail- fatty acid molecule
Hydrophillic head- phosphate group
Place themselves in a position where head is as close to water as possible visa versa
Polar meaning can form bilayer in membranes
Heads help hold surface of cell membranes
Phospholipid structure allows them to form glycolipids by combining with carbs which are needed for cell recognition
Role of lipids
Energy source
Waterproofing (insoluble in water)
Insulation slow conductors of heat
Protection (fat stored around delicate organs)
ATP function
Cells cannot get energy directly from glucose so energy released from glucose is used to make ATP.
ATP diffuses to the part of the cell that needs energy, the energy in ATP is stored in high energy bonds between the phosphate groups.
Energy is released in hydrolysis reactions
When energy is needed by a cell ATP is broken down into ADP and Pi (inorganic phosphate) and energy is released reaction is catalysed by ATP hydrolase
ATP structure
Adenine molecule, ribose molecule and a triphosphate. Nucleotide derivative (modified form of a nucleotide)
ATP hydrolysis and condensation reactions
ATP hydrolysis can be coupled to energy requiring reactions within the cells this means energy released can be used directly to make the coupled reaction happen rather than being lost as heat the inorganic phosphate during hydrolysis can be added to another compound known as phosphorylation which it often makes the compound more reactive. ATP is resynthesised in a condensation reaction between ADP and PI this happens in photosynthesis and respiration and is catalysed by the enzyme ATP synthase.
Amino acids structure and function
Small monomer units used to form polypeptides which are joined to form proteins. 20 amino acids in body provide evidence for evolution.
Each amino acid has a Central carbon atom attached to 4 different groups these groups are an amine group (NH3) a carboxyl group (COOH) a hydrogen atom (H) and a variable side group (R) each amino acid differs by their variable group.
Peptide bond formation- condensation reaction to form dipeptide, OH removed from carboxyl and H from the other amino acid from hydrogen group. Water molecule lost and peptide bond formed between the nitrogen group of one amino acid and the carbon group of another.
Primary structure proteins
Polypeptide chain of amino acids by polymerisation.
Primary structure determines its ultimate shape and function.
Secondary protein structure
The hydrogen from the NH group is positively charged therefore bonds with the carbon C=O atom from the COOH group as the O has an overall negative charge. This causes the long polypeptide chain to twist into a 3-D shape such as the alpha helix coil or the beta pleated sheet.
Tertiary protein structure
The secondary structures can be twisted even more to produce specific and more complex 3-D structures which are the final stage for some small proteins. The structure is maintained by three types of bonds the placement of these bonds depends on the primary structure.
Disulphide bridges fairly strong not easily broken
Hydrogen bonds easily broken
Ionic bonds formed in any amino and carboxyl groups which are not involved in the formation of peptide bonds easily broken by changes in pH
Quaternary structure
Large complex proteins often make more complex structure combining many more polypeptide chains. There may also be prosthetic groups involved such as the haem group in haemoglobin.
Emulsion test for lipids
1) take a dry and grease free test tube
2) to 2 cm³ of the solution being tested at 5 cm³ of ethanol
3) shake the tube thoroughly in order to dissolve any lipid in the sample
4) A milky white emulsion indicates the presence of any lipid
5) as a control repeat the process using water the result should be clear
Biuret test for proteins
1) placed the sample being tested in a test tube and add an equal amount of sodium hydroxide to the solution at room temperature
2) add a few drops of very dilute copper sulphate solution and mix very gently
3)If turns purple then peptide bonds are present therefore protein is present if stays blue no protein present
Lipid absorption
Digested lipids in the form of monoglycerides and fatty acids associate with them bile salts called micelles
The bile has emulsified the fat into tiny droplets
As the contents of digestion passed through the ileum the micelles come into contact with epithelial cells in the wall this helps maintain a high concentration of fatty acids near to the epithelial cell membrane where they will be absorbed
The micelles breakdown releasing monoglycerides and fatty acids because these molecules are nonpolar they’re able to diffuse across the cell membrane no specific transport proteins needed
Once transported into the cell the molecules are transported into the endoplasmic reticulum where they’ll be combined into a triglycerides
The triglycerides then combined with cholesterol and lipoproteins to form a chylomicron
The chylomicrons move out of the epithelial by exocytosis an enter the lacteal in the centre of each villus. The lacteal is a lymphatic capillary
The chylomicrons into the bloodstream where the endothelial cells hydrolyse the triglycerides allowing fatty acids to diffuse into cells 
