Excretion and Osmoregulation

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  • Created by: Lotto65
  • Created on: 12-10-17 16:33
What are two types of metabolic pathway?
Chains and cycles
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What do metabolic pathways do?
Build up and break down biochemicals
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Why must the products of metabolic pathways be removed?
They are waste products that would be toxic if they were allowed to accumulate in cells or could damage molecular structures
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What is excretion?
The removal or expulsion of potentially toxic waste products of metabolic pathways from the body cells
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Name three nitrogenous compounds that can be excreted by animals
Ammonia, urea and uric acid
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Which animals excrete ammonia as main nitrogenous waste product?
Freshwater fish and amphibian larvae
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Which animals excrete urea as main nitrogenous waste product?
Marine mammals, terrestrial animals, marine fish, adult amphibians
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Which animals excrete uric acid as main nitrogenous waste product?
Birds and insects
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The type of nitrogenous waste excreted correlates to...
The habitat the animal lives in
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Why is ammonia only excreted in animals where abundant supplies of water are available?
Ammonia is very toxic and must be diluted with a large volume of water so is excreted by animals that can intake the water lost easily
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How can urea be excreted?
In a more concentrated solution with less water required
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What is required to convert ammonia to urea?
Energy
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Why would animals excrete urea if that requires more energy?
That is worthwhile if the animal is able to conserve more water
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Is uric acid toxic?
No
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What state does uric acid form when it is really concentrated?
Semi-solid paste
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What does the conversion of ammonia to uric acid require?
A lot of energy
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Why would animals excrete uric acid?
Good for animals that live in arid countries where water conservation is necessary
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How can uric acid also benefit animals that can fly?
Concentrated paste of uric acid requires less water than dilute urine so reduces body mass during flight
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As well as the habitat, nitrogenous waste is also correlated with...
Evolutionary history
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Give an example of how evolutionary history correlates to nitrogenous waste
Terrestrial mammals excrete urea but aquatic animals like beavers and otters also excrete urea although they could excrete ammonia because they do not need to conserve water
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How does water move in and out of cells?
By osmosis
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What two factors affect movement of water by osmosis?
Hydrostatic pressure and solute concentration
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What is hydrostatic pressure?
The pressure exerted by a fluid at equilibrium at a given point due to the force of gravity
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If the hydrostatic pressures between solutions are equal, where does water move?
From a lower to higher solute concentration
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What is osmoregulation?
Control of the internal solute concentration of a living organism
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How do animals osmoregulate?
Adjust solute concentrations in their cells and body fluids
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What are osmoconformers?
Animals that do not attempt to maintain constant internal solution conditions and they allow their internal solute concentration to fluctuate with the water around them
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Give two examples of osmoconformers
Squids and sea squirts
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What is a disadvantage of osmoconforming?
Body may not contain ideal solute concentrations for bodily processes
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What type of animals are normally osmoregulators?
Terrestrial animals, freshwater animals and some marine organisms like bony fish
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Why are terrestrial animals osmoregulators?
They are able to maintain their internal solute concentration no matter what the external solute concentration is
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Give an example of an osmoregulator?
Humans
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What is a disadvantage of osmoregulators?
Energy has to be used up to keep solute concentrations constant in the body
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In osmoconformers, as external solute concentration increases...
Internal solute concentration increases (directly proportional)
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In osmoregulators, as external solute concentration increases...
Internal solute concentration remains the same
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What does isotonic mean?
When solute concentration is equal to that of normal body fluids
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What does hypotonic mean?
A lower solute concentration than normal body fluids (high dilution so water enters cells, causing them to swell)
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What does hypertonic mean?
Higher solute concentration than normal body fluids (low dilution so water leaves cell, causing it to shrink)
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What is dehydration?
Loss of water from the body but not an equal loss of solutes so body fluids become hypertonic
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What are consequences of dehydration?
Thirst, dark coloured urine, lethargy, increased heart rate, low blood pressure, seizures, brain damage, death
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What is over-hydration?
Excessive intake of water so body fluids become hypotonic
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What are some consequences of over-hydration?
Drowsiness, confusion, behaviour changes, delirium, blurred vision, muscle cramps, nausea, dizziness, seizures, coma, death
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Why must urea be removed from the body?
It breaks weak non-covalent bonds in proteins leading to denaturing
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Give two ways excretion can take place?
Kidneys and malpighian tubule system in insects
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What is water potential?
The tendency for water to move from one place in favour of another
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How does osmosis work in terms of water potential?
Water will move by osmosis from a solution with higher water potential, to a solution of lower water potential
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Higher water potential means...
Lots of water so more likely to move to an area with less water and a higher solute concentration
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Lower water potential means...
Less water and more solutes so more likely to stay where it is
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What is osmotic potential?
The tendency for water molecules to move from a hypotonic solution to a hypertonic solution
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What is the osmotic potential like in osmoregulators?
Different to that of their environment
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What do osmoregulators have to do if they live in freshwater?
Eliminate excess water that flows in by osmosis
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What do osmoregulators have to do if they live in salt water?
Conserve water and eliminate salts
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What do osmoregulators have to do if they live on land?
Conserve water
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Water conservation in the body is controlled by...
A homeostatic mechansism
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What do osmoconformers do in terms of osmotic potential?
Allow their osmotic potential to mirror that of the environment osmotic potential
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How do osmoconformers have the same osmotic potential as the environment?
Active transport to maintain specific ions in their tissue fluid at concentrations different to those in the environment
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What is osmolarity?
The solute concentration of a solution
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What are the four main excretory organs in a human?
Skin, lungs, liver, kidneys
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What does the skin excrete?
Urea, salts and water
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What does the liver excrete?
Bile pigments and cholesterol
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What does an excretory organ do?
Separates the waste products from the blood and discharges them
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What is secretion?
The process where substances are produced and discharged from a cell, gland or organ for a particular function in the organism or for excretion
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What do the lungs excrete?
Carbon dioxide
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What do the kidneys excrete?
Urea, water, ammonium compounds, salts
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What is bilirubin?
Waste product of broken down red blood cells
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Name two other substances that can be excreted?
Hormones and enzymes
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What is egestion?
Removal of waste products never in cells or produced by cells
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What is the importance of excretion?
Maintain same internal body conditions, no obstruction or interference with metabolism which could kill cells, osmoregulation maintenance, build up could be toxic
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Name types of nitrogenous waste...
Proteins, breakdown of nucleic acids and amino acids, ammonia/ ammonium ions
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Why is ammonia toxic?
Basic so alters pH, highly reactive and inhibits enzymes
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What else can ammonia be converted to as some seawater fish do?
Convert ammonia to TMA which means less water to excrete
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Card 2

Front

What do metabolic pathways do?

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Build up and break down biochemicals

Card 3

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Why must the products of metabolic pathways be removed?

Back

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Card 4

Front

What is excretion?

Back

Preview of the front of card 4

Card 5

Front

Name three nitrogenous compounds that can be excreted by animals

Back

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