maintaining a balance 1.3

Question 1

explain why the concentration of water in cells should be maintained within a narrow range for optimal function

Answer 1

• solvent for metabolic reactions in living cells
• molecules and ions carried in water for cell life
• metabolic reactions within cells only occur in solution where water is the solvent
• most cells die if water content changes
• absorbs or releases large amounts of heat for a relatively small change in temp

Question 2

explain why the removal of wastes is essential for continued metabolic activity.

Answer 2

metabolic waste: some are poisonous, some take up space, some would create problems for osmoregulation.

nitrogenous waste: change PH of cells which interferes with membrane transport function and may denature enzymes.

organs responsible for excretion in mammals and some fish are the kidneys.

Question 3

identify the role of the kidney in the excretory system of fish and mammals

Answer 3

• the kidneys are the excretory system in both fish and mammals.
• excretion of urine while regulating water and salt concentration in blood is the role of the kidney.

Question 4

what is the effect of different environments on fishes excretion

Answer 4

fresh water:- works continuously copious amounts of diluted urine.

• very low salt concentration
• helps remove excess water gained from hypo-osmotic environments

salt water: - kidneys excrete small quantities of isotonic urine.
-this conserves water and excretes the excess salt they gain their hyperosmotic environment.

Question 5

preform a first- hand investigation of the structure of a mammalian kidney by dissection, use of a model or visual resource and identity the regions involved in the excretion of waste products

Answer 5

the mammalian kidney has different structure associated with filtration to form urine, concentration of the urine and re-absorption of water, glucose and inorganic salts help maintain homeostasis. refer to graph

Question 6

explain why the processes of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes

Answer 6

• diffusion and osmosis both are passive transport.
• both relay on random movement of molecules
• diffusion is slow for body function and is not used for useful solute.
• osmosis deals with movement of water thus only allows water to move out of the body, not nitrogenous waste

Question 7

distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney

Answer 7

passive: filtration in bowmans capsule, water returns via the interstitial fluid from the tubule to the capillary in osmosis. this happens all in the length of the tubule.
active: ions in blood can be transported to cells in the nephron tubules and then secreted by the cells into the tubule. some poisons and drugs are eliminated this way

Question 8

what is active transport

Answer 8

expenditure of energy on the part of the organism, usually because working to move substrate against concentration gradient ie. salt moves to high concentration from low concentration

Question 9

what is passive transport

Answer 9

no expenditure of energy as material follows natural gradient. high concentration to low concentration

Question 10

explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition

Answer 10

filtration of blood occurs in bowmans capsule, this forces -all small molecules out of the blood, protein to large to get through the capsule. there is no selective filtration and components of the blood can be recovered by absorption.

• loop of henle has various reabsorption points
• all glucose molecules, amino acids and most vitamins are recovered. water is also reabsorbed
• chemical composition of the body fluids are precisely regulated by the control of solute reabsorption from the glomerular fitrate.

Question 11

explain how the processes of filtration and re-absorption in the mammalian nephron regulate body fluid composition

Answer 11

filtration of blood occurs in bowmans capsule, this forces -all small molecules out of the blood, protein to large to get through the capsule. there is no selective filtration and components of the blood can be recovered by absorption.

• loop of henle has various re-absorption points
• all glucose molecules, amino acids and most vitamins are recovered. water is also reabsorbed
• chemical composition of the body fluids are precisely regulated by the control of solute re-absorption from the glomerular filtrate.

Question 12

draw a graph explaining filtration and re-absorption in the mammalian nephron .

Answer 12

refer to graph

Question 13

gather, process and analyse information from secondary sources to compare the process of renal dialysis with the function of the kidney

Answer 13

The patient’s blood is pumped from an artery through tubes made of selectively permeable membrane. The artificial tubing allows only water and small solute molecules to pass through it into a dialysing solution that surrounds the tube. This dialysing solution is similar to the interstitial fluid found around nephrons. As the blood circulates through the dialysis tubing, urea and excess salts diffuse out of it instead of leaving by pressure filtration, as in the nephron. Those substances needed by the body, such as bicarbonate ions diffuse from the dialysing solution into the blood

Question 14

outline the role of the hormone, aldosterone in the regulation of water and salt levels in blood

Answer 14

Aldosterone is a steroid hormone secreted by the adrenal gland: Its function is to regulate the transfer of sodium and potassium ions in the kidney. When sodium levels are low, aldosterone is released into the blood causing more sodium to pass from the nephron to the blood. Water then flows from the nephron into the blood by osmosis. balance of blood pressure is thus achieved

Question 15

outline the role of the hormone ADH (anti-diuretic hormone), in the regulation of water and salt levels in blood

Answer 15

Antidiuretic hormone (ADH or vasopressin) controls water reabsorption in the nephron. When levels of fluid in the blood drop, the hypothalamus order the body to release ADH. This increases the permeability of the collecting ducts to water, allowing more water to be absorbed from the urine into the blood. This results in diffrent concentrations of urine depending on if the volume of water need to change ( low water levels or high levels). more water in body the more diluted the urine

Question 16

present information to outline the general use of hormone replacement therapy in people who cannot secrete aldosterone

Answer 16

A replacement hormone, fludrocortisone (Florinef), is used to treat this condition but a careful monitoring must be maintained to avoid fluid retention and high blood pressure.

Question 17

define enantiostasis as the maintenance of metabolic and physiological functions in response to variations in the environment and discuss its importance to estuarine organisms in maintaining appropriate salt concentrations

Answer 17

Enantiostasis is the maintenance of normal metabolic and physiological functioning, in the absence of homeostasis when an organism is experiencing variations in its environment.

as the salt concentration of body fluids in an osmoconformer changes, various body functions are affected, such as the activity of enzymes (denaturing). For normal functioning to be maintained, another body function must be changed in a way that compensates for the change in enzyme activity. changing ph level when overwhelming levels of salt is an example of compensation

Question 18

perform a first-hand investigation to gather information about structures in plants that assist in the conservation of water

Answer 18

these include :

• the location and the number of stomates
  - the arrangement, shape and size of the leaves
• phyllodes or cladodes rather than leaves
• presence of a thick waxy cuticle
• hairy leaves
• leaves reduced to spines
• leaves rolled inwards
• the reflective nature of the leaf surface.

Question 19

Describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss

Answer 19

Australian xerophytes (plants adapted to dry conditions):

• hard leathery, needle-shaped leaves with reduced surface areas
  
  • use of phyllodes for photosynthesis rather than leaves that would lose water by transpiration,
  • some salt bushes, change the reflectiveness of their leaves during leaf development so that they have highly reflective leaves during summer.
• avoid high radiation in the middle of the day by hanging their leaves vertically to present less surface area to sun.
• heat loss is greater for small leaves or highly dissected leaves than it is for larger leaves
  
  • waxy cuticle prevents evaporation

Question 20

what is a osmoconformer

Answer 20

the animal withstand changes in salt concentration to its body’s osmotic pressure and then vary with its environment. Organisms that do this, do not maintain homeostasis, are said to be osmoconformers