First Five Define and give an example of: – Carbohydrate – Lipid – Protein – Nucleic Acid.
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Transcript of First Five Define and give an example of: – Carbohydrate – Lipid – Protein – Nucleic Acid.
First Five
• Define and give an example of:– Carbohydrate– Lipid– Protein– Nucleic Acid
Enzymes
Major Characteristics of Enzymes
• Enzymes are special proteins present in the cytoplasm of all cells
• They help speed up the chemical reactions in cells
• There are hundreds of different kinds of enzymes, but each enzyme only speeds up one reaction.
Enzymes
For example, glucose and fructose might join up slowly to form sucrose
glucose- -fructose
With the right enzyme present, the reaction happens faster
glucose- -fructose
Enzyme Action
• Enzymes are large proteins– like all proteins, each enzyme molecule has a
certain shape– the shape determines which reaction the enzyme
can speed up• In speeding up the reaction, the enzyme
combines temporarily with a substrate– substrate: any substance an enzyme acts on
enzyme
substrate A
substrate B
The substrate molecules fit the shape of the enzyme
STAG
E 1
two substrates combine temporarily with enzyme
the enzyme joins the two substrates together
STAG
E 2
new compound released by enzyme
enzyme unchangedand ready fornext reaction
STAG
E 3
Different Types of Enzyme Reactions
• Enzymes can–join substrates together–break a substrate apart
A ‘breaking-down’ reactionthe shape of the substrate molecule fits the enzyme shape
this is calledthe active siteof the enzyme
STAG
E 1
substrate combinestemporarily with enzyme
enzyme will breakmolecule here
STAG
E 2
A ‘breaking-down’ reaction
A ‘breaking-down’ reaction
A ‘breaking-down’ reaction
substrate splits andseparates from enzyme
STAG
E 3
Final break-down products
end-products
enzyme ready for next reaction
STAG
E 3
Properties of Enzymes
1. Enzymes can act on only one type of substrate
2. Enzymes always produce the same end-products.
3. Enzymes are not used up in the reaction.– They return to their original state after the
reaction.
Enzymes can act on only one type of substrate
this substrate cannot combine with this enzyme
this substrate cannot combinewith this enzyme
Properties of Enzymes
4. Enzymes – like any protein – are denatured by heat or some chemicals.– Denaturing changes the shape of a protein– For an enzyme, this means that it can no longer
combine with the substrate.
5. Each enzyme works best at a particular temperature and pH (acidity or alkalinity)– These are referred to as the optimal temperature
and optimal pH
Because enzymes are proteins, they are denatured by heat or some chemicals
enzymedenaturedby heat
denatured enzyme cannot combine with substrate
enzyme +substrate
1
glucosemolecules
E
1. A glucose molecule combines with the active site on the enzyme phosphorylase
ENZYME ACTION
E
2 A region of the active site is still available
part of starchmolecule
E
3 One end of a growing starch molecule combines with the glucose molecule at the active site
E
4 The growing starch molecule breaks free from the enzyme phosphorylase which is now free to repeat the reaction
Enzyme action
E
E
E 2
E 3
E 4
part of starchmolecule
1
glucosemolecules
E1
Enzymes Reading
• Read the text individually• Mark the text as you read:• Answer the summary questions in
your journal.–Put all answers into your own words.
• Finish as homework. Due Tuesday