1. Welcome –Happy hump day –
Today a VERY SHORT batch of
Pretty boring (yawn) notes 0n
Enzymes and feedback – dig out
note stuff`

2. Enzymes and feedback
Enzymes= special proteins that
Control all reactions in living
Things.
Enzymes must be present for
Any reaction to occur.

3. Enzymes are catalysts – a
Substance that affects the rate
Of a chemical reaction but
Remains unchanged.

4. Enzymes act only on certain
Substances due to a specific
Shape.

5. Where the enzyme hooks to
The substance it acts on
Is known as the active site.
Active
site

6. Substrate is the substance that
The enzyme is acting on.
substrate

7. Enzymes and all proteins are
Produced in the ribosomes of
The cell.

8. Enzymes control the reaction
Rate based on several factors,
pH, shape and temp.
PH= a measure of the acidity of
Alkalinity of a substance.
0-6 = acid 7= neutral
8-14=base. Enzymes work best
At a pH of 7

9. Optimum temperature = the
Temp. at which the enzyme
Works best. This is body temp.
In humans. (98.6*f or 37*c)

10. Feedback mechanisms – a cycle
Of input and response.
Stimuli – changes in the
Environment that cause a
Response.

11. Negative feedback system
A change (stimuli) causes a
Response in an attempt to
Maintain homeostasis.
Ex. Blood sugar is high,
Pancreas secretes insulin to
Lower Blood sugar
Ex= too hot – you sweat to
Cool body down

12. Negative feedback systems are
The most common.
Positive feedback system = a
Change causes a response
Which leads to a greater change
Ex.= childbirth – contractions,
Then stronger contractions.

13. Dynamic equilibrium = the many
Constant small changes that
Keep the internal environment
At the level needed for survival.
= maintains homeostasis