Most organisms are active in a limited temperature range

Question 1

What are enzymes?

Answer 1

• Proteins; catalyse chemical reactions in living organisms

- Increase the rate of reaction (otherwise reactions would be too slow to maintain life)

Question 2

Chemical composition of enzymes

Answer 2

• Protein molecules (made from amino acid chain)
• Folded in specific shape
• Enzyme acts on substrate (reactant molecules)
• Fits with substrate at specific locations on surface of enzyme molecules (active site)

Question 3

Enzymes: Acceleration of chemical reactions

Answer 3

• Speed up or slow down reactions without changing temp (important–> heat damages tissues)
• Lower activation energy needed to start

Question 4

Enzymes; Lowering of activation energy

Answer 4

• Don’t produce activation energy; just reduce amount needed

- Brings specific molecules together, instead of relying on them colliding randomly

Question 5

Enzymes: Action on specific substrates

Answer 5

• Only one particular enzyme can work on only one particular molecule (active site is shaped to bind with only that molecule)
• Enzyme isn’t chemically changed in reaction (can be used again)
• Reactions are always reversible

Question 6

Enzyme characteristics: Temperature sensitive

Answer 6

• Function best at body temp of organism in which they occur (humans 37 degrees)
• Any temp above 60 degrees–> enzymes stop functioning
• Heat causes hydrogen bonds to break–> alters shape and structure so won’t fit active site
• Temp to high or low; will denature

Question 7

Enzyme characteristics: pH sensitive

Answer 7

• Has own narrow range of pH within it functions efficiently
• Levels of pH outside optimum–> alters shape and stops functioning
• Most function at or near neutral

Question 8

Enzyme characteristics: Substrate specific

Answer 8

• Molecules are specific–> act on only one type of substrate

E.g. Renin acts on protein in milk, causes it to curdle

Question 9

Induced fit explanation

Answer 9

• When substrate binds to active site, binding induces temporary changes to shape of enzyme
• Chemical reaction occurs, substrate is changed, product is released
• Enzyme returns to original form and can be used again

Question 10

Induced fit model

Answer 10

• Molecules changes shape as substrate molecules get close
• Change in shape is induced by approaching substrate molecule
• Model relies on molecules are flexible
• E.g. gloved hand changing to catch a ball. Active site is palm and it closes around the ball when it gets closer

Question 11

Lock and key explanation

Answer 11

• The active site on the enzyme has a surface groove which fits the substrate perfectly
• This brings the active site of both chemicals into alignment so reaction occurs quickly

Question 12

Lock and key model

Answer 12

• Substrate fits into active site to form immediate reaction’
• Enzyme active doesn’t change (not considered great explanation of enzyme action)
• Model depends on unlikely random event of random collisions of enzyme and substrate

E.g. Like trying to get a key in a lock by throwing it with your eyes closed.

Question 13

First hand investigation: Increased temp

Answer 13

• Milk with rennin curdled quickly at temp of 37 degrees
• Temperatures higher or lower; the milk won’t curdle
• Temps higher or lower than optimum; rennin didn’t react and curdle milk

Question 14

First hand investigation: Change in pH

Answer 14

• pH affects activity of catalase in potato tissue; has an optimum pH
• Measured height of foam produced when catalase is put in hydrogen peroxide
• pH of 9; optimum, as average bubble height was higher

Question 15

Identify pH as a way of describing acidity of a substance

Answer 15

• pH scale; higher value= alkaline,
• Lower value=acidic
• Neutral= 7

Question 16

Explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency

Answer 16

• Must be kept stable; so enzymes can function effectively and metabolic efficiency is maintained
• enzymes are sensitive to changes in temp, pH, substrate concentration etc
• Enzymes only function within narrow range of pH and temp; variations cause decreases in activity

Question 17

Develop a model of a feedback mechanism (Temperature regulation; high)

Answer 17

Stimuli: Increased body temp (exercising or hot surroundings)

Co-coordinating centre: Hypothalamus control centre detects change and activates cooling mechanism

Effectors: Skin blood vessels dilate, sweat glands activate

Negative feedback loop: Body temp decreases, hypothalamus shuts off cooling mechanism

Question 18

Develop a model of a feedback mechanism (Temperature regulation; low)

Answer 18

Stimuli: Decreased body temp (cold surroundings)

Coordinating centre: Hypothalamus control centre detects change and activates warming mechanism

Effectors: Skin blood vessels constrict, skeletal muscles activate (shivering)

Negative feedback loop: Body temp increases, hypothalamus shuts off warming mechanism

Question 19

Homeostasis definition

Answer 19

The maintenance by an organism of a constant or almost constant internal state, regardless of external environmental change

Question 20

Homeostasis as process by which organisms maintain a relatively stable internal environment

Answer 20

• Various body systems act to maintain homeostasis through hormonal and nervous mechanisms
• Body must regulate respiratory gases, protect itself from disease, maintain salt and fluid balance, maintain constant temp

Question 21

What is kept at a constant internal level regardless of external environmental change?

Answer 21

• Core body temp
• Blood pH
• Oxygen and carbon dioxide concentration
• Blood glucose concentration
• Water/solute balance
• Blood pressure

Question 22

Homeostasis consists of 2 stages

Answer 22

S1: Detecting the change from a stable state; Sensory cells or receptors within the body detect a change; E.g. thermoreceptors in the skin

S2: Counteracting the change: An effector receives the message that undesirable change must be counteracted. A response is initiated to reverse the change. E.g. body temp low, muscles will shiver to generate heat (muscles are effector organs)

Question 23

Negative feedback

Answer 23

• Fluctuations in any organism need to be monitored and countermeasures put into place
• If variation is large/exceeds normal range; Negative feedback mechanism operates in response to change
• It counteracts change and therefore returns body to normal range, state of homeostasis

Question 24

Adaptations and responses that have occurred in Australian organisms to assist temp regulation (Heat the body)

Answer 24

Raised hairs (retain heat) Aims to trap layer of warm air around the body to reduce heat lost

Shivering (generate heat) rapid muscle contractions

Increased metabolism (Generates heat) Heat gain centre stimulates activity of thyroid gland, speeds up metabolism

Constriction (narrowing) of arterioles to skin (retain heat) Muscular walls of small blood vessels constrict so most blood flow is redirected to the core of the body

Question 25

Adaptations and responses that have occurred in Australian organisms to assist temp regulation (Cool the body)

Answer 25

Expansion of arterioles to skin (releases heat) Blood carrying heat is directed towards surface, heat is lost

Sweating (releases heat) Liquid sweat secreted, heat is removed from body to evaporate liquid

Decreased metabolism (Releases heat) Heat loss centre causes thyroid gland to lower rate of metabolism, generates less heat

Flattened hairs (releases heat) Hairs lay flat by tiny muscles, increases heat loss

Question 26

Stimulus

Answer 26

Any change in the environment that can be detected by receptors and triggers a response (e.g. extreme heat)

Question 27

Receptors

Answer 27

Thermoreceptors in the skin and in the hypothalamus of the brain detect the stimulus (change in temperature)
Convert this into a ‘message’ in the form of nerve impulses, which travel along nerves towards the central nervous system (brain and spinal cord).

Question 28

Darling make your own study notes

Answer 28

Don’t use mine