F4 Chapter 4 (SPM Questions)

SPM 2007 Paper 1

carbohydrates - carbon, hydrogen,oxygen (CHO)
proteins - carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus (CHONSP)
lipids - carbon, hydrogen, oxygen (CHO)
nucleic acids - carbon, hydrogen, oxygen, phosphorus, nitrogen (CHONP)
water- hydrogen, oxygen (HO)

SPM 2007 Paper 1

Hydrolysis - chemical reaction that involves the breaking up of large molecules by adding water to them

SPM 2008 Paper 1

maltose + water --> glucose + glucose ( hydrolysis )
sucrose + water --> glucose + fructose ( hydrolysis )
lactose + water --> glucose + galactose ( hydrolysis )

SPM Clone 2006

Vitamin B functions as a coenzyme in cellular respiration

SPM 2005 Paper 2

The production of extracellular enzymes

-The nucleus contains DNA which carries the information for the synthesis of enzymes
- Proteins that are symthesised at the ribosomes are transported through the space within the rough endoplasmic reticulum (RER)
- Proteins depart from the RER wrapped in vesicles that bud off from the membranes of the RER
- These transport vesicles then fuse with the membranes of the Golgi apparatus and empty their contents into the membranous space
- The proteins are further modified during their transport in the Golgi apparatus
- Secretory vesicles containing these modified proteins bud off from the Golgi apparatus and travel to the plasma membrane
- These vesicles will then fuse with the plasma membrane before releasing the proteins outside the cell as enzymes

SPM 2004 Paper 1 & Paper 2, SPM 2005 Paper 1 & Paper 2, SPM 2007 Paper 1, SPM 2008 Paper 1

"lock and key" hypothesis - substrate molecule -"key"
                                        - enzyme molecule - "lock"

substrate molecule binds to the active site - enzyme-substrate complex

- a specific substrate molecule arrives at the active site of the enzyme molecule
- the substrate molecule binds to the active site to form enzyme-substrate complex which is very unstable
- the enzyme is free to take another substrate molecule into its active site to catalyse another reaction
- product molecules leave the active site of the enzyme

SPM 2005 Paper 1 & SPM 2007 Paper 1 

SPM 2008 Paper 2 

- most enzyme do not function in a highly acidic environment.
- vinegar is an excellent preservative used to pickle many types of food such as cucumbers and onions
- the acetic acid in vinegar destroys enzymes and bacteria in food
- the bacteria are unable to break down nutrients in the food
- the pickled food will have a longer shelf life

SPM 2008 Paper 1 

The effects of substrate concentration on the activity of enzymes

- at low substrate concentrations, few substrate molecules are present.
- there are many active sites which are available
- the rate of reaction increases in direct proportion to the substrate concentration
- an increase in substrate concentration means more substrate molecules are available 
- this means there are more chances of collision between the substrate molecules and enzyme molecules for a catalytic reaction to take place. 
- as more substrate molecules fill the active sites, more products are formed per unit time
- at a certain substrate concentration, the rate of reaction will not increase further and become constant
- all active sites are filled and said to be saturated
- at high concentration, there are more substrate molecules than enzymes molecules
- the excess substrate molecules will have to compete with one another for the active sites 
- the rate of reaction becomes constant
- the enzyme concentration becomes a limiting factor

SPM 2004 Paper 2 & SPM 2005 Paper 2 

- enzymes used is protease for meat products to tenderise meat
- enzymes used is cellulase for seaweed products to extract agar from seaweed
- enzymes used is zymase for alcoholic drinks to convert sugar into ethanol