MAB 1

Question 1

What are enzymes

Answer 1

Organic catalysts

Protein molecules that are produced within living cells and have a specific shape

Question 2

Role of enzymes

Answer 2

Control all chemical processes of living things. They enable reactions to occur. Used over and over and remain unchanged.
An efficient rate of metabolism is necessary for life processes to continue

Question 3

Explain the lock and key model

Answer 3

An enzyme fits together with its substrate molecule on its active site. It’s active site is very specific meaning only one compound can react with a particular enzyme.

Question 4

Why use “lock and key”

Answer 4

The key has a specific shape for the lock. Like the substrate has a specific shape for the active site.

The active site = lock
Substrate = key

Question 5

Induced fit model?

Answer 5

• proteins are not rigid

The active site is more flexible and is changed by the substrate binding to it.

Question 6

Types of metabolism and explain

Answer 6

Anabolic - reactions that involve building up large organic molecules form simpler molecules

Catabolic- reactions that involve breaking down complex organic compounds to simpler ones. (Amylase in saliva)

Question 7

How does temperature affect enzyme activity

Answer 7

As temperature rises, the rate increases because molecules move faster. However, beyond the optimum temperature (37), the active site begins to be distorted. The substrate no longer fits the active site and so reaction slows down. At extremes, the enzyme will denature

Question 8

How does pH affect enzyme activity

Answer 8

The optimum pH for enzymes is 7. The enzyme works best as at the optimum, it is ideal for attracting the substrate. At any pH higher or lower than optimum, reaction rate declines as the substrate no longer fits perfectly and at extremes on both sides, enzyme will denature

Question 9

How does substrate concentration after enzymes

Answer 9

The rate of reaction will go up until a cartoon point when the enzymes are saturated with substrate and can no longer work any faster. If you add more enzymes then the same thing would happen again

Question 10

Identify pH as a way of describing the acidity of a substance

Answer 10

PH is a way of describing the acidity of a substance. The pH scale measures alkalinity/acidity

Under 7 = acidic
Over 7 = alkaline

Measure pH using a probe/data logger to increase accuracy and universal indicator

Question 11

What’s metabolism?

Answer 11

All chemical reactions occurring within a living organism & are controlled by enzymes

Question 12

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

Answer 12

Enzymes control all the metabolic processes in the body. For optimum metabolic efficiency, the reaction in cells must be occurring at the optimum rate. Enzymes can only act within a limited temperature and pH range. If enzymes are not working at the optimum range then reactions cannot be maintained at a stable rate then metabolic efficiency cannot be maintained

Question 13

What is homeostasis

Answer 13

The process where an organism maintains a relatively stable internal environment despite external conditions

Question 14

How can a stable internal environment be maintained within an organism

Answer 14

Through adaptation:
Structural - physical characteristics ( body size, limbs )

Physiological - organisms function. The way an animal operates ( sweating, production of enzymes)

Behavioural - how an organism acts in response (seeking shelter)

Question 15

What stages that homeostasis consist of

Answer 15

1. Detecting change

2. Counteracting change

Question 16

What is detecting change?

Answer 16

Sensory cells / receptors present within the body detect change in the temperature and chemical composition of the body.

Question 17

What is counteracting change

Answer 17

Effector organs such as muscles or glands then work to reverse the change. A response that successfully reverses the change will return the body to homeostasis

Question 18

What are the parts of a homeostasis system

Answer 18

Receptors
Control centre
Effectors

Question 19

What is the receptor and how does it work

Answer 19

Monitors changes in the internal and external environment and initiates a response to them. They do this by sending a message to the control centre

Question 20

What is the control centre and what does it do

Answer 20

Is programmed to maintain the set value, analyses the message from receptors and determines the appropriate response. The control centre causes a response to be sent out via an effector that restores the set value

Question 21

What is the effector

Answer 21

They bring out the responses to stimuli

Eg muscles, glands

Question 22

What is the change in the environment called

Answer 22

Stimulus

Question 23

What is the mechanism that brings about the homeostatic change

Answer 23

Negative feedback mechanism

Question 24

What does the negative feedback mechanism do

Answer 24

During the second stage (response), if a set value deviates then negative feedback instructs the system to restore the correct value, meaning negative feedback counteracts the change

Question 25

Example of negative feedback mechanism and explain

Answer 25

Control of body temperature

When receptors in the skin detect a low temperature, a negative feedback mechanism is activated to stop the original action. The temp in the control centre is hypothalamus in mammals. It is a gland that detects change. It initiates a response to increase/decrease temp until it goes back to set value

Eg. If receptors in the skin detect heat, they replay information via the nerves to the hypothalamus. This triggers the nervous system to dilate skin capillaries and activate sweat glands.

Question 26

What are some temperature control responses to keeping warm

Answer 26

Shiver
Hair muscles erect
Increased appetite
Vasoconstriction - less blood flow, less heat loss
Increase in metabolism

Question 27

What are some temperature control responses to keeping cool

Answer 27

Sweating
Evaporation loses heat
Vasodilation - increased blood supply, more heat lost
Hair relaxes
Less exercise
Decrease in metabolism

Question 28

What is the nervous system

Answer 28

The nervous system consists of the central and peripheral nervous system

It’s a network of nerve cells that send and receives information about what is happening around the body

Question 29

Role of the nervous system

Answer 29

The role is to regulate and maintain an organisms internal environment.

Question 30

How does the nervous system detect and counteract changes

Answer 30

The CNS receives information and initiates a response. It consists of the brain and spinal cord ( control centre ). If temperature exceeds, temperature sensors in the skin detect the temperature change and a sensory neuron conducts a nervous impulse to the hypothalamus. Nerve impulses pass this information to effector neutrons then to effectors like blood vessels, sweat glands.

The peripheral nervous system connects receptors and effectors. It transmits messages from the CNS and back

Question 31

Identify the broad range of temperature over which life is found

Answer 31

-40 to 120 for extremes

But majority is -2 to 40

Question 32

Why can’t life forms exist few degrees below 0

Answer 32

The cytoplasmic fluid of cells freezes

Therefore metabolic activity is unable to continue

Question 33

Why can’t life forms exist above 50

Answer 33

Proteins being to denature

Question 34

What is an endotherm

And the pros and cons

Answer 34

An animal in which its internal temperature is constant despite changes in ambient temperature

Pros - can do everyday life activities, be anywhere
Cons - they use a lot of energy

Question 35

What is ectotherms

Pros and cons

Answer 35

Animals in which their internal temperature changes as the ambient temperature changes

Pros - don’t use much energy
Cons - unable to move around much and explore life, they are slow

Question 36

What is an example of an endotherm and its response to temperature regulation

Answer 36

Red kangaroo
Hot temps
- blood vessels dilate
- lick the insides of their paws where skin is thinner and blood supply is close so that heat can be easily dumped outside
- sweating and panting
Seeks shade and sits in a position where it is shaded
- evaporative cooling method

Cold temps

• vasoconstriction to prevent blood going near skins surface where heat would be lost
• huddle in groups
• increases metabolism by 25% to generate greater internal heat
• shiver

Question 37

Example of an ectotherms and its response to temp regulation

Answer 37

Central netted dragon
Hot temps
- retreats to shade of rocks and vegetations or into a burrow
- hints at night when temp is lower

Cold temps
- lies in the sun and shelters from cold winds to increase core body temperature

Question 38

Problems with plants in temperature changes

Answer 38

For photosynthesis to occur, stomata must open. Stomata open in conditions of light and heat. When this occurs, water leaves the plants so therefore plants must possess adaptations to minimise transpiration while maximising photosynthesis

Question 39

Plants responses to high temperatures

Answer 39

Evaporative cooling (transpiration)
- the exposure to heat causes the stomata to open, leading to a loss of water by transpiration

Turgid response ( wilting)

• plants transpire and lose turgid in the palisade cells of their leaves.
• the wilting enables them to reduce surface area exposed to heat and light

Leaf orientation
- hang downwards to limit water loss and overcome problems of overheating

Leaf falls

Question 40

Plant responses to cold temperature

Answer 40

Anti freeze

• water between plant cells freeze
• some plants produce organic compounds that act as anti freeze which reduces the temperature at which the cytoplasm freezes

Dormancy

• deciduous trees lose their leaves and undergo a period of dormancy
• this allows them to survive extremely low temperatures and water shortages

Vernalisation

• some plants flower in response to low temperature
• eg tulips must be exposed to between 6 weeks and 3 months of intense cold before they flower