Organisms Respond to their Internal and External Environment - Homeostasis Flashcards
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
Define glyconeogenesis
Activation of enzymes to convert glycerol and amino acids to glucose
Describe the difference between Type I and Type II diabetes
- Type I - Individuals can’t produce insulin because pancreatic beta cells have been destroyed
- Type II - Insulin is produced from pancreatic beta cells but insulin receptors do not respond to insulin
Explain how Type I diabetes can be controlled
- Inject insulin since individuals with Type I can’t produce insulin. Insulin cannot be injected orally as insulin would be digested
- Complex carbohydrates should be eaten rather than sugar because this prevents rapid increase in blood glucose. It also takes time to be absorbed as glycosidic bonds need to be hydrolysed
Explain how Type II diabetes can be controlled
- Regular exercise since more glucose will be taken to muscle tissue for respiration to produce ATP
Define osmoregulation
The control of blood water potential
Name each part of the nephron
- Glomerulus
- Basement membrane
- Bowman’s capsule
- Podocytes
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
Explain the function of the Bowman’s capsule
It is where ultrafiltration takes place
Explain the function of the Proximal convoluted tubule
Selective reabsorption takes place here
Explain the function of the Loop of Henle
Regulates blood water potential
Explain the function of the Distal convoluted tubule
Reabsorption takes place here
Explain the function of the Collecting duct
This is the final place for reabsorption
During ultrafiltration what layers do the substances pass through
- Pores in the capillary endothelium
- Basement membrane
- Bowman’s capsule epithelium
During ultrafiiltration what is filtered
Water and glucose
During ultrafiiltration what not is filtered
Cells and proteins
What is the name of the filtrate formed in ultrafiltration
Glomeruar Filtrate
How are the cells of the proximal convuluted tubule adapted for selective reabsorption
- Microvilli - Provides a large surface area for diffusion
- Micrivilli - Many carrier proteins for facilitated diffusion and active transport
- Many mitochondria - Produce ATP for active transport
- Many ribosomes - To produce carrier proteins
How are glucose and water reabsorbed at the proximal convoluted tubule
- Water is reabsorbed by osmosis
- Glucose is reabsorbed via co-transport with Na+ using the same method as the small intestine
Describe the steps for water reabsorption at the Loop of Henle (Descending Limb)
- Na+ is actively transported in
- Water moves out of tubule by osmosis as walls are permiable to water
- Glomerular filtrate becomes more concentrated
Describe the steps for water reabsorption at the Loop of Henle (Ascending Limb)
- Na+ is actively transpported out into the medulla
- Water stays in the tubule as walls are imppermeable to water
- Filtrate becomes less concentrated
Describe the steps for water reabsorption at the Loop of Henle (Collecting Duct)
- Na+ concentration increases deeper into the medulla
- Water potential gradient is maintained across whole length of the collecting duct
- Water moves from the collecting duct and the distal convoluted tubule into medulla by osmosis along the whole length
Which part of the brain detects water potential in blood
The hypothalamus
Which part of the brain secretes ADH
Posterior Pituitary Gland
Give the process for osmoregulation by ADH when dehydrated
- There is a decrease in blood water potential
- Water moves out of osmoreceptors into the blood by osmosis in the hypothalamus in the brain
- Posterior pituitary gland releases MORE ADH into the blood
- ADH causes collecting duct membrane to become MORE permeable to water, more aquaporins are present in the membrane
- More water reabsorbed into the blood by osmosis
- Urine volume becomes LESS and is More concentrated
