A-level Biology - 3.4.6 Homeostasis and Negative Feedback
Homeostasis is the process by which an organism maintains a stable internal environment despite external changes. It involves regulating factors like temperature, pH, and blood glucose to keep conditions optimal for enzyme activity and cell function.
What is meant by homeostasis?
Maintenance of a stable internal environment
Key Terms
What is meant by homeostasis?
Maintenance of a stable internal environment
Explain what happens when the body temperature is too high (i.e. to enzymes)
Enzymes denature
Enzyme’s molecules vibrate too much = breaks H-bonds holding them in their 3D shape
Shape of enzyme’s active site chan...
Explain what happens when the body temperature is too low (i.e. to enzymes)
Enzyme activity is reduced = slows rate of metabolic reactions
Explain what happens when the pH is too high/low (i.e. to enzymes)
H-bonds holding them in their 3D shape break ∴ shape of enzyme’s active site changes & no longer works as catalyst
Metabolic reactions ar...
Explain what happens when the blood glucose levels are too high
Ψw is reduced to point where water molecules diffuse out cells into blood by osmosis
Causes cells to shrivel up and die
Explain what happens when the blood glucose levels are too low
Cells unable to carry out normal activities ∵ isn’t enough glucose for respiration to provide energy
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| Term | Definition |
|---|---|
What is meant by homeostasis? | Maintenance of a stable internal environment |
Explain what happens when the body temperature is too high (i.e. to enzymes) | Enzymes denature Enzyme’s molecules vibrate too much = breaks H-bonds holding them in their 3D shape Shape of enzyme’s active site changes = no longer works as catalyst Mean metabolic reactions are less efficient |
Explain what happens when the body temperature is too low (i.e. to enzymes) | Enzyme activity is reduced = slows rate of metabolic reactions |
Explain what happens when the pH is too high/low (i.e. to enzymes) | H-bonds holding them in their 3D shape break ∴ shape of enzyme’s active site changes & no longer works as catalyst Metabolic reactions are less efficient |
Explain what happens when the blood glucose levels are too high | Ψw is reduced to point where water molecules diffuse out cells into blood by osmosis Causes cells to shrivel up and die |
Explain what happens when the blood glucose levels are too low | Cells unable to carry out normal activities ∵ isn’t enough glucose for respiration to provide energy |
What is negative feedback? | Mechanisms that restore the level to normal (to the set point) |
Negative feedback only works within certain ___ | limits If change is too big = effectors may not be able to counteract it |
Homeostasis involves _____ negative feedback mechanisms | multiple |
Why does homeostasis involve multiple negative feedback mechanisms? | ∵ gives more control & allows you to actively increase or decrease a level so it returns to normal |
1 negative feedback mechanism means ___ ____ and ___ ____ | slower response and less control |
What does postive feedback do? | Amplifies a change from the normal level |
What does postive feedback cause effectors to do? | Effectors respond to further increase the level away from normal level |
What is postive feedback useful for? | Useful to rapidly activate something e.g. blood clot after injury |
Positive feedback is ___ involved in homeostasis | NOT |
When does positive feedback also occur? | When homeostatic system breaks down e.g. of you’re too cold for too long |
Hypothermia involves ____ feedback | postive |
When does hypothermia occur? | Happens when heat’s lost from body quicker than it can be produced |
As body temp. ↓, brain…. | doesn’t work properly & shivering stops Makes body temp. ↓ even more |
Describe the role of positive feedback in hypothermia | Positive feedback takes body temperature further away from normal level & continues to decrease unless action is taken |