Biological molecules

Chemical elements present in carbohydrates

Chemical elements present in carbohydrates

Carbon, Oxygen, Hydrogen

Chemical elements present in protein

Carbon, Oxygen, Hydrogen, Nitrogen

Chemical elements present in lipids (fats and oils)

Carbon, Oxygen, Hydrogen

Structure of carbohydrates

starch made from monosaccharides (simple sugars) like glucose and fructose

Structure of protein

amino acids

Structure of lipids

fatty acids and glycerol

Structure of glucose

• monosaccharide

• 6 carbon atoms

Structure of maltose

• disaccharide

• 2 glucose molecules joined together

Structure of sucrose

• disaccharide

• glucose and fructose molecule joined together

Structure of starch and glycogen

• polysaccharides

• made of many glucose units

Test for glucose

• add several drops of benedicts solution to sample of glucose

• place in beaker of boiling water for 5 minutes

  pale blue = no glucose

  yellow → red = glucose

test for starch

• add several drops of iodine solution to starch sample

  yellow = no starch

  blue/black = starch

test for protein

• add several drops of biuret reagent (NaOH) to protein sample

  blue = no protein

  pink/violet = protein

test for lipids

• grind food particles and add level teaspoon to test tube

• add ethanol to test tube, put bung on and shake well

• once the lipids have dissolved into the ethanol, pour into test tube containing distilled water

  clear/no colour = no lipids

  milky/white emulsion = lipids

metabolic reaction

reactions inside living organisms

what is an enzyme?

• A biological catalyst that speeds up a reaction, without being used up itself.

• effective in small quantities

structure of an enzyme

• enzymes a proteins.

• specific shape derived from their unique amino acid sequence

how do enzymes/catalysts speed up metabolic reactions?

enzymes lower the activation energy

substrate

molecules that bind to an active site.

resulting structure is called an enzyme-substrate complex

explain enzyme function at low temperatures

• reaction rate slows because molecules have less kinetic energy.

• therefore, it takes longer for substrate molecules to travel to the active site.

explain enzyme function at optimum temperature

• 37 degrees Celsius (in humans)

• enzymes working most efficiently

explain enzyme function at high temperatures

• enzyme denatures and substrate no longer fits the active site

• enzyme can no longer catalyse reaction

Describe an experiment to investigate how enzyme activity can be affected by changes in temperature

1. starch solution heated to a set temperature to ensure enzyme works quickly enough.

2. iodine added to spotting tile (orange → blue/black = starch)

3. amylase added to spotting tile.

4. as starch is broken down, iodine returns to its original colour.

   NOTE: amylase will work at different rates depending on the temperature of starch solution.

explain how enzyme function can be affected by different pH

• optimum pH 7

• if pH is not at optimum, the pH causes peptide bonds between amino acids to break.

• therefore, the enzyme denatures and active site no longer fits with substrate.

Describe an experiment to investigate how enzyme activity changes with pH

1. 5 test tubes containing milk.

2. add a few drops of HCl to 2 test tubes (acidic.)

3. add a few drops of dilute KOH to 2 test tube (alkaline.)

4. add nothing to the 5th test tube (neutral - pH7)

5. place all test tubes in a water bath to equilibrate.

6. add 1 cm3 of renet to each test tube and time how long it takes for milk to solidify.