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BIOMOLECULES AND CELLS > Osmoregulation > Flashcards

Osmoregulation Flashcards

1
Q

What are the main functions of excretory organs?

A
  1. maintain osmotic concentrations
  2. maintain body fluid volume
  3. maintain proper concentration of ions
  4. remove metabolic end products
  5. remove foreign substances/toxins/anything that is in excess
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2
Q

What is osmolarity?

A

The concentration of moles of active solutes per litre of solvent

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3
Q

What is osmotic pressure?

A

Force associated with the movement of water

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4
Q

What are osmolality and tonicity?

A

Osmolality - conc. of solutes per KG of solvent

Tonicity - conc. of IMPERMEABLE solutes per litre of solvent

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5
Q

How do excretory organs control the osmolarity and volume of extracellular fluids?

A
  • By excreting water and solutes that are in excess

* By conserving water and solutes in short supply

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6
Q

In what different ways are Nitrogen excreted?

A

Different animals deal with nitrogen in different ways
• converted to ammonia - most toxic and need a lot of water to get rid of it
• converted to urea (human)
• converted to uric acid - least toxic and requires least amount of water to excrete

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7
Q

How is urea synthesised?

A 
Urea is synthesised from 
- carbon dioxide
- water aspartate  
- ammonia
• in a metabolic pathway called the UREA CYCLE
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8
Q

Where is urea synthesised?

A

Liver

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9
Q

Excretory function for marine animals

A

Have to conserve water and excrete excess salts

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10
Q

Excretory function for freshwater animals

A

Have to excrete excess water and conserve salts

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11
Q

Excretory function of terrestrial animals

A

Must conserve water and salts

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12
Q

What is an osmoconformer

A
  • Marine organisms that maintain an internal environment which is osmotic to their external environment.
  • Osmotic pressure of their cell and the surrounding environment is equal
  • do no have physiological systems to perform osmoregulation
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13
Q

What is an osmoregulator?

A
  • Organism who actively regulate their osmotic pressure in different environments
  • Can survive in varied environments by maintaining the osmolarity of their body
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14
Q

What are teleost fish?

A

Most bony fish that can be in either salt or fresh water (osmoregulators)
- They are cartilaginous - have cartilage instead of bone

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15
Q

What happens when the teleost fish internal environment is hypo-osmotic to the external environment?

A
  • Higher salt concentration in the surrounding en/v
  • water lost via osmosis, and salts gained
  • fish drink seawater to replace the water lost to the en/v
  • produce little, more concentrated urine (kidney)
  • eliminate the salts ingested fro salt water
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16
Q

What is the principle nitrogenous waste in aquatic invertebrates and bony fish?

A
  • Ammonia
  • easily removed because very soluble in water
  • Excreted by diffusion across the gill membranes directly into water
17
Q

What are the different ways terrestrial animals obtain water and get rid of it?

A 
In:
1. drinking
2. water in food
3. metabolic
Out:
1. evaporation
2. urine
3. faeces
18
Q

What are the behavioural strategies of desert animals to minimise water loss?

A
  • Avoid the daytime heat and emerge at night

* Aestivation: low metabolic activity so low H20 Turnover (similar to hibernation - stay burrowed during dry seasons)

19
Q

What are some structural/physiological changes in desert animals to minimise water loss?

A
  • Have a thick keratinised cuticle - high lipid content

* Have efficient kidneys and excrete highly concentrated urine (long loops of Henle)

20
Q

Nephron

A

functional unit of the vertebrate kidney, and consists of a glomerulus and renal tubule

21
Q

Glomerulus

A
  • Dense ball of capillaries which filters blood plasma to produce a fluid lacking cells, proteins and other large molecules
  • Where blood is filtered across the walls of a mesh of capillaries
22
Q

Renal tubule

A

Processes the filtrate into urine

23
Q

Bowman’s capsule

A

Receives renal filtrate from glomerulus, mainly water and small molecules such as glucose, amino acids and ions (salts).

24
Q

Why is the rate of filtration high in the glomerulus?

A
  • high glomerulus blood pressure
  • high permeability of glomerulus capillaries and their podocytes (which wrap around capillaries and leave slits between them)
25
Q

What happens in tubular reabsorption?

A
  • Glomerular filtrate flows into the renal tubule

* here it is modified by reabsorption of water and ions

26
Q

Why do you not produce 200L of urine even though it is amount of water filtered by the glomerulus?

A

Most of the water and solutes filtered out of the glomerulus are reabsorbed and do not appear in urine

27
Q

Where does most of the water reabsorption take place?

A
  • 75% in the proximal convoluted tubule - resulting in a filtrate that is iso-osmotic to blood
  • remainder occurs in the rest of the renal tubule resulting in the filtrate that is more concentrated than blood
28
Q

Describe the structural features of the proximal convoluted tubule and each of their functions

A
  1. PCT cells are cuboidal with increased surface area due to microvilli
  2. large numbers of mitochondria near the apical surface - PCT cells are highly metabolically active
  3. the PCT cells actively transport Na+, glucose and amino acids out of the filtrate & back into tissue fluid
    • This causes water to follow by osmosis (water & solutes are taken up by peri-tubular capillaries )
29
Q

What are aquaporins?

A

Water channel molecules which assist osmosis

30
Q

What is the function of aquaporin 1?

A

AQP1 regulates the movement of water molecules in the proximal convoluted tubule (PCT).

31
Q

What happens in mice who have AQP-1 that does not properly function?

A

Mice cannot concentrate their urine because there is no movement of water from renal filtrate in the PCT.

32
Q

What 3 components make up the loop of Henle?

A
  • thick ascending limb
  • thin ascending limb
  • descending limb

BIOMOLECULES AND CELLS (32 decks)

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