MAB 1 Flashcards
What are enzymes
Organic catalysts
Protein molecules that are produced within living cells and have a specific shape
Role of enzymes
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
Explain the lock and key model
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.
Why use “lock and key”
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
Induced fit model?
- proteins are not rigid
The active site is more flexible and is changed by the substrate binding to it.
Types of metabolism and explain
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)
How does temperature affect enzyme activity
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
How does pH affect enzyme activity
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
How does substrate concentration after enzymes
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
Identify pH as a way of describing the acidity of a substance
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
What’s metabolism?
All chemical reactions occurring within a living organism & are controlled by enzymes
Why is the maintenance of a constant internal environment important for optimal metabolic efficiency
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
What is homeostasis
The process where an organism maintains a relatively stable internal environment despite external conditions
How can a stable internal environment be maintained within an organism
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)
What stages that homeostasis consist of
- Detecting change
2. Counteracting change
What is detecting change?
Sensory cells / receptors present within the body detect change in the temperature and chemical composition of the body.
What is counteracting change
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
What are the parts of a homeostasis system
Receptors
Control centre
Effectors
What is the receptor and how does it work
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
What is the control centre and what does it do
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
What is the effector
They bring out the responses to stimuli
Eg muscles, glands
What is the change in the environment called
Stimulus
What is the mechanism that brings about the homeostatic change
Negative feedback mechanism
What does the negative feedback mechanism do
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
Example of negative feedback mechanism and explain
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.
What are some temperature control responses to keeping warm
Shiver Hair muscles erect Increased appetite Vasoconstriction - less blood flow, less heat loss Increase in metabolism
What are some temperature control responses to keeping cool
Sweating Evaporation loses heat Vasodilation - increased blood supply, more heat lost Hair relaxes Less exercise Decrease in metabolism
What is the nervous system
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
Role of the nervous system
The role is to regulate and maintain an organisms internal environment.
How does the nervous system detect and counteract changes
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
Identify the broad range of temperature over which life is found
-40 to 120 for extremes
But majority is -2 to 40
Why can’t life forms exist few degrees below 0
The cytoplasmic fluid of cells freezes
Therefore metabolic activity is unable to continue
Why can’t life forms exist above 50
Proteins being to denature
What is an endotherm
And the pros and cons
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
What is ectotherms
Pros and cons
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
What is an example of an endotherm and its response to temperature regulation
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
Example of an ectotherms and its response to temp regulation
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
Problems with plants in temperature changes
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
Plants responses to high temperatures
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
Plant responses to cold temperature
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
