Lipids and proteins

• what would happens without lipids?.

  we would have no cell membranes.
• What is a triglyceride?

  a lipid made of one glycerol and three fatty acids

  
• what is the structure of a fatty acid molecule?

  -They have long tails made of hydrocarbons.

  -The tails are hydrophobic so repel water.

  -The tails cause it to be insoluble in water.

  -All fatty acids have the same basic structure but the hydrocarbon tail varies.
• how are triglycerides formed?

  by condensation reactions.
• describe how a triglyceride is formed?

  - a fatty acid joins to a glycerol molecule.

  - an ester bond forms and a water molecule is released.

  - this happens 3 times to form a triglyceride.
• what are the 2 types of fatty acids?

  saturated and unsaturated.
• what is the difference between saturated and unsaturated fatty acids?

  - saturated acids dont have any double bonds between their carbon atoms. The fatty acid is saturated with hydrogen.

  - unsaturated fatty acids have at least one double bond between carbon atoms causing the chain to kink.
• what are similar to triglycerides?

  phospholipids.
• the lipids found in cell membranes aren't triglycerides they are..?

  phospholipids.
• how do phospholipids differ to triglycerides?

  in a phospholipid, one of the fatty acid molecules is replaced by a phosphate group.
• what is the phosphate group and the fatty acid tails like in a phospholipid?

  - the phosphate group is hydrophilic (attracts water).

  - the fatty acid tails are hydrophobic (repel water).
• how are triglycerides mainly used?

  as energy storage molecules.
• why are triglycerides good for energy?

  - the long hydrocarbon tails of the fatty acids contain lots of chemical energy because of the tails, lipids contain twice as much energy per gram as carbohydrates.

  - they're insoluble, they dont affect water potential of the cell. Because the tails are hydrophobic the tails face inwards and shield from water with their glycerol heads.
• how are phospholipids good at controlling what enters and leaves a cell?

  - the heads are hydrophilic and their tails are hydrophobic so they form a double layer with heads facing out towards the water on each side.

  - the centre of the layer is hydrophobic so water-soluble substances can't easily pass through. The membrane acts as a barrier to those substances.
• what test would you use to find out if there was any fat in a particular good?

  an emulsion test.
• what are the steps to an Emulsion Test?

  1) shake the test substance with ethanol for a minute so it dissolves, then pour solution into water.

  2) any lipid will show up as a milky emulsion.

  3) the more lipid there is, the more noticeable the milky colour will be.
• what are proteins made of?

  long chains of amino acids.
• what are the monies of proteins?

  amino acids.
• how does a dipeptide form?

  when 2 amino acids join together.
• how does a polypeptide form?

  when more than 2 amino acids join together.
• how many polypeptides are proteins made of?

  more than one polypeptide.
• different amino acids have?

  different variable groups.
• what is the same general structure that all amino acids have?

  a carboxyl group, an amine or amino group and an R group.
• what is an R group also known as?

  a variable side group.
• all living things share a bank of?

  20 amino acids.
• what is the difference in the banks of 20 amino acids that all living things have?

  what makes up their R group.
• how does glycine differ to other amino acids?

  doesnt have carbon in its side group. Its R group only has 1 hydrogen atom.
• how are polypeptides formed?


  by condensation reactions.
• what is linked together by condensation reactions to form polypeptides?


  amino acids.
• what is released in a condensation reaction?


  water.
• what are the bonds called that re formed between amino acids?


  peptide bonds.
• what is the equation to form a dipeptide?


  amino acid 1 + amino acid 2 —> dipeptide.
• is the dipeptide reaction a reverse reaction or single?

  reverse reaction.
• when does the reverse reaction of the deceptive reaction occur?

  in digestion.
• proteins are _________ _______ molecules?

  big, complicated.
• how many structural layers do proteins have?

  4
• what are the names of the 4 layers proteins have?


  primary, secondary, tertiary and quaternary.
• what is the primary structure for proteins?

  the sequence of amino acids in the polypeptide chain.
• what is the secondary structure for proteins?

  the polypeptide chain doesn't remain flat and straight, hydrogen bonds form between the amino acids within the chain. This makes it coil into an alpha helix or fold into a beta pleated sheet.
• what is the tertiary structure for proteins?

  the coiled or folded chain of amino acids is often coiled and folded further. More bonds form between different parts of the polypeptide chain, including hydrogen bonds and ionic bonds.