Organisms Respond to their Internal and External Environment - Homeostasis Flashcards
(47 cards)
Define the term homeostasis
Homeostasis is maintaining the constant internal environment within resricted limits
Explain the importance of maintaining body temperature close to normal (If body temperature is to high)
- Hydrogen bonds break within enzymes, changing their tertiary structure and the shape of the active site
- Less enzyme - substrate complexes
Explain the importance of maintaining body temperature close to normal (If body temperature is to low)
- Enzymes have too low kinetic energy
- Less enzyme substrate complexes
- Therefore metabolic rate is reduced
Explain the importance of maintaining blood pH close to normal
Hydrogen bonds break between proteins, changing their tertiary structure
Explain the importance of maintaining blood glucose close to normal (If blood glucuse is too high)
- Blood has a lower water potential than cells, water leaves the cell by osmisis
- Cells lack water for hydrolysis reactions and as a solvent
Explain the importance of maintaining blood glucose close to normal (If blood glucuse is too low)
Glucose is not provided to cells fast enough for a high enough rate of respiration
Define negative feedback
Negative fedback reverses the direction of change back to its original level
Give an example of negative feedback in biology
Regulation of body temperature
In negative feedback why is it important to have separate mechanisms for increasing and decreasing the factor
It gives a greater degree of control
Define positive feedback
Positive feedback is where a change in direction is amplified
In positive feedback why is it important to have separate mechanisms for increasing and decreasing the factor
Binding of oxygen to haemoglobin
What are hormones
Chemical messengers
Where are hormones produced and secreted from
Glands
How are hormones transported around the body
Through the blood
Where do specific hormones act
Act on target cells with receptors
Describe the effect of hormomes
Effects are widespread and long term
In which cells is insulin produced
Beta cells
In which cells is glucagon produced
Alpha cells
Explain how insulin lowers blood glucose when it binds to its receptors
- Insulin binds to receptors on the cell membrane of liver and muscle cells
- This inserts more glucose channel proteins into the cell membrane and glucose enters cell by facilitated diffusion
- This activates enzymes to convert glucose to glycogen for storage
Exolain how glucagon increases blood glucose when it binds to its receptor
- Glucagon binds to receptors on the cell membrane of liver cells
- This activates enzymes to hydrolyse glygogen to glucose
- This also activates enzymes to convert glycerol and amino acids to glucose
How does adrenaline increase blood glucose
- Adrenaline is released from adrenal glands
- It binds receptors on liver cell membranes
- Enzymes are activated which hydrolyse glycogen to glucose
Describe the second messenger model of adrenaline and glucagon action
- Glucagon is released fron alpha cells and adrelanine is released from adrenal glands
- They bing to receptors and activate adenylate cyclase
- Adenylate cyclase converts ATP to cAMP
- This activates protein kinase
- This activates enzymes for glycogenolysis
Define glycogenesis
Activation of enzymes to convert glucose to glycogen
Define glycogenolysis
Activation of enzymes to hydrolyse glycogen to glucose
