Download Maintaining a balance

Maintaining a balance
1. Most organisms are active in a limited
temperature range
• identify the role of enzymes in metabolism,
describe their chemical composition and use
a simple model to describe their specificity
on substrates
Keeping things constant
• Living organisms exist in a wide range of
environmental conditions
• Even so, organisms function best within a
narrow range of temperatures
• Organisms have adaptations that help to keep
a relatively constant internal temperature and
balance of chemicals
– Homeostasis
Keeping things constant
• http://www.abc2news.com/sports/how-youcan-die-from-drinking-too-much-waterexplained
Enzymes
• Enzymes are important biological molecules
that help maintain homeostasis
• They also control the metabolic processes
within the body
– Metabolism: chemical reactions in the body
• Catabolic reactions: breaking down of substances
– Usually exergonic reactions (release energy)
– e.g. breaking down of glucose to release energy
• Anabolic reactions: building of larger molecules
– Usually endergonic reactions (require energy)
– e.g. production of proteins from amino acids
Enzymes
• Structure: globular proteins (cf fibrous and
membrane)
– Composed of a chain of
amino acids which fold
to form a 3-dimensional
shape
– (Somewhat) spherical
– Soluble
– Contain an active site
Catalase
Enzymes
• Function: biological catalysts
– Speed up the rate of metabolic reactions but are
unchanged at the end of the reaction
– Can be reused
– Each enzyme can only catalyse one type of
reaction because the active site recognises a
specific molecule (substrate)
Enzyme-substrate complex
Enzymes
• Reactions need activation energy to proceed
• Enzymes function by lowering the activation
energy required  the reaction proceeds
more quickly
Lock and key model
• The active site is fixed in shape
• The shape of the substrate fits exactly into the
active site like a lock and key
• This forms the enzyme-substrate (ES) complex
• When the reaction has taken place, the products
are released from the active site
Induced fit model
• Proteins are not fixed in shape but flexible
• Binding of the substrate at the active site
causes it to bind more tightly
Enzymes
• Cofactors and coenzymes
– Some enzymes need other molecules to function
– Cofactors: inorganic molecules e.g. ions (Zn+, Ca+)
– Coenzymes: organic molecules e.g. vitamins
• identify the pH as a way of describing the
acidity of a substance
Factors affecting enzyme activity
• Activity of enzymes are affected by:
– temperature
– pH
– substrate concentration
Temperature
• Enzymes function best at the
body temperature of the
organism
– Usually up to 40 °C
• Most enzymes completely
stop functioning above 60 °C
because they become
denatured
– Proteins are held together by
hydrogen bonds, these are
disrupted at high temperatures
pH
• pH is a measure of the acidity or alkalinity of a
substance
– Acidity is caused by the presence of hydrogen ions
(H+)
• pH is the –log10[H+]
– Therefore, the higher the concentration of H+, the
lower the pH
pH scale
pH
• As with temperature, enzymes function best
within a narrow range of pH
• Outside of the optimum pH, the enzyme
becomes denatured
• Most enzymes inside cells function around
neutral pH
• Enzymes in the stomach (pepsin) function best in
acidic conditions whereas amylase, the enzyme in
saliva that breaks down starch function in slightly
alkaline conditions
Substrate concentration
• If an enzyme and substrate have a high affinity
for each other, then the rate of an enzyme
controlled reaction is affected by the
concentration of the substrate until all
enzymes are being
used to catalyse
reactions
Substrate concentration
• The saturation point is when all active sites
are occupied by substrate and the reaction is
proceeding at its maximum rate
• In biological systems, the
substrate is usually
slightly in excess
• identify data sources, plan, choose
equipment or resources and perform a firsthand investigation to test the effect of:
– increased temperature
– change in pH
– change in substrate concentrations
on the activity of named enzyme(s)
Enzyme: catalase
• Catalase is found in potato or fresh plant or
animal tissue
• Converts hydrogen peroxide (H2O2) to water
(H2O) and oxygen (O2)
substrate
concentration
Results and discussion questions
• Results:
– Results table
– Graph of concentration of H2O2 v. height of O2 gas
• Discussion:
– Questions from handout
– What substrate concentration would you choose if
you were investigating the effect of pH on
catalase? Explain your choice.
Enzyme: rennin
• Rennin is found in junket tablets
• It is used to set/curdle milk protein
(caseinogen)
temperature
Results and discussion questions
• Results:
– Table of results
– Graph of temperature v. activity (1/clotting time)
• Discussion:
– Questions from handout
– If you place the tubes that didn’t clot into the
waterbath with optimum activity, what would you
expect to see?
• Why would you do this?
• What if the milk doesn’t clot at the optimum
temperature?
Enzyme: amylase
• Amylase is found in saliva (and also
commercially available)
• Breaks down starch into simple sugars
• Starch reacts with iodine
(brown) to form a blue/black
colour
pH
Sample data
pH
Time for complete
breakdown of starch (s)
1
-
4
60
7
210
10
-
14
**iodine went colourless
without enzyme
• describe homeostasis as the process by which
organisms maintain a relatively stable
internal environment
Homeostasis
• Homeostasis = “same state”
• It is “the maintenance by an organism of a
constant or almost constant internal state,
regardless of external environmental change”
• Plants and animals have regulatory systems to
maintain the internal balance of:
– Temperature
– Chemical substances (metabolites aka substrate)
– Water and salt balance
– (Absence of) waste and toxins
Homeostasis
• For example, in humans:
– Blood sugar remains close to 90 mg/100 mL blood
– Body temperature approximates 37°C
– Blood pH must be within the range 7.38–7.42
regardless of external temperature, diet or physical
activity.
• explain why the maintenance of a constant
internal environment is important for
optimal metabolic efficiency
Homeostasis and metabolic efficiency
• Internal environment refers to:
– Cells and their cytoplasm
– Interstitial fluid surrounding the cells
• All chemical reactions within cells must occur
efficiently and be effectively co-ordinated to bring
about optimal metabolic efficiency
All chemical reactions necessary for the cell’s survival
and functioning are controlled by enzymes
Enzymes need a stable internal environment to
function effectively
E.g. Cellular respiration
C6H12O6 + 6O2  6H2O + 6CO2 + energy (ATP)
Importance of temperature and pH
• Enzymes which need a narrow range of
temperature and pH to function optimally
• Outside of the optimal range, metabolic
efficiency decreases
• Low temperatures can freeze the water in cells
which changes solute concentration and
ruptures cells
• High temperatures denature proteins
(enzymes and others), disrupting cell function
Importance of metabolites
• Metabolites are the chemicals of a chemical
reaction in the cell
• Cells need the right amount of reactants
which come from the outside environment or
are products of other metabolic pathways
– E.g. ATP is the energy produced from cellular
respiration  many reactions need ATP to
proceed
Importance of water and salt
concentrations
• Reactants are dissolved in water (in solution)
so the amount of water affects the
concentration of solutes
• Salt concentrations affect the osmotic balance
Osmotic balance
• http://www.youtube.com/watch?v=t1nwSuW
r_q8
Importance of absence of toxins
• Build up of wastes (e.g. carbon dioxide) can be
toxic to cells
• They can interfere with enzymes by blocking
the active site or change the condition of the
environment (e.g. dissolved carbon dioxide
decreases pH)
• Therefore wastes must be removed to ensure
optimal metabolic efficiency
• explain that homeostasis consists of two
stages:
– detecting changes from the stable state
– counteracting changes from the stable state
Maintaining homeostasis
• Enzyme activity depends on
substrate concentration until
saturation point is reached
• Ideally the substrate
concentration should be at a
level where the enzyme is
close to maximum capacity
• Metabolic pathways use
feedback mechanisms to
regulate enzyme activity
Homeostasis
• In order to maintain homeostasis, an organism
needs to:
– Detect changes (stimulus)
• Sensory cells or receptor cells detect changes in
temperature or chemical composition
– Counteract changes (response)
• Effector organs (muscles or glands) work to reverse the
change
– The ideal or normal value is known as the set
point
• outline the role of the nervous system in
detecting and responding to environmental
changes
Nervous system
• A negative feedback system ensures
homeostasis even when
external conditions are
changing
– Coordinated by the
nervous system:
1. Detects information
2. Transmits information
to the control centre
3. Information is processed
and response is generated
Nervous system
• Parts of the nervous system:
– Receptors: sensory cells/organs
– Control centre: central nervous system
– Effectors: muscles/glands
– Nerves: relay message
• Stimulus-response pathway
Thermoregulation in humans
• What are some causes of temperature change
in the body?
3
2
Thermoregulation in humans
1
1
3
2
• gather, process and analyse information from
secondary sources and use available evidence
to develop a model of a feedback mechanism
Homeostasis analogy
• Temperature of a refrigerator or waterbath
• identify the broad range of temperatures
over which life is found compared with the
narrow limits for individual species
Temperature ranges
• Temperature is a limiting factor for the
presence of living things
• Temperatures on Earth:
– Land: –89 to 60°C
– Ocean: –2 to 30°C
– Hydrothermal vents:
>350°C
Temperature ranges
• Most living things live at temperatures
between 10-35°C
– Some organisms have evolved to
live at extreme temperatures (extremophiles)
Hydrothermal vents
• http://www.deepseaphotography.com/vent_a
nimals.html
Narrow temperature limits for
individual species
• Optimal range – temperature range that a
species can live comfortably
• Tolerance range – range of temperatures for
survival
– The most temperature tolerant organism
known is the Pompeii worm
(22-80°C)
• compare responses of named Australian
ectothermic and endothermic organisms to
changes in the ambient temperature and
explain how these responses assist
temperature regulation
Ecto/endotherms
• Ectothermic organisms depend on an external
source for heat energy
– E.g. Fish, amphibians, reptiles
• Endotherms rely on internal sources such as
metabolic activity for heat energy
– E.g. Birds and mammals
Ectothermic organisms
• Internal temperature of these organisms are
largely influenced by the ambient temperature
• They have a limited ability to regulate their
body temperature, instead they adapt their
behaviour
Eastern brown snake
• Found in open grassland and desert scrub
• Usually diurnal (awake during the day)
– Can be active at night and seek shelter during day
if day is too hot
– If ambient temperature is too low, it will bask in
sun to gain heat
– When it is very cold, metabolism
will slow down and use fat stores
or snake will hibernate
Endothermic organisms
• They have the ability to control their body
temperature and maintain it at a stable level
• They adjust their metabolic rate to control
heat loss
– Small animals lose heat faster so they usually have
a high metabolic rate
Bentwing bat
• Produce brown fat during the summer
months when food is abundant
• During colder months the brown fat can be
quickly metabolised to produce heat and
increase body temperature
Fairy penguin
• Their feathers trap heat around their body to
reduce heat loss
– In cold ambient temperatures, the feathers are
lifted to increase the air layer and increase the
insulation
– In hot weather, their
feathers lie flat
• Behavioural mechanisms:
– Swimming when hot
– Huddling when cold
• identify some responses of plants to
temperature change
Homeostasis in plants
• Homeostasis in plants is also important for
their metabolism
– Light
– Water availability
– Temperature
Responses to high temperatures
• Evaporative cooling (transpiration)
– Stomata open, leading to loss of water
– BUT risk of dehydration
Responses to high temperatures
• Turgor response – wilting
– Transpiration leads to water loss and leaves lose
turgor
– Wilted leaves have less surface area exposed to
the sun
Responses to high temperatures
• Leaf orientation
– Eucalypt leaves can hang vertically downwards in
hot weather
• Leaf fall
– Eucalypt leaves can drop
off to reduce exposure to
the sun
Responses to high temperatures
• Reseeding and resprouting in fire
– Bottle brush, tea trees and eucalypts, have
epicormic buds or lignotubers which resprout after
fire
Responses to cold temperatures
• Organic antifreeze
– Reduces freezing temperature of cell cytoplasm or
sap
• Dormancy
– Deciduous trees lose their leaves in winter and
become dormant, sometimes seeds or spores are
produced
• Vernalisation
– Some plants flower in response to low
temperatures e.g. Tulips
• analyse information from secondary sources
to describe adaptations and responses that
have occurred in Australian organisms to
assist temperature regulation
2. Plants and animals transport dissolved
nutrients and gases in a fluid medium
• analyse information from secondary sources
to identify the products extracted from
donated blood and discuss the uses of these
products
• analyse and present information from
secondary sources to report on progress in
the production of artificial blood and use
available evidence to propose reasons why
such research is needed
Blood products report
• Weighting: 15%
• Due: Week 8, Tuesday 25th November
• Part A: Table of blood products
• Part B: Development of artificial blood
• identify the form(s) in which each of the
following is carried in mammalian blood:
– carbon dioxide
– oxygen
– water
– salts
– lipids
– nitrogenous waste
– other products of digestion
Transport systems
• Unicellular organisms rely on diffusion and
osmosis
• Multicellular organisms need a specialised
transport system to distribute nutrients and
remove wastes
• Transport systems involve:
1. A transport medium
2. Vessels
3. A driving mechanism
Mammalian transport
• Cardiovascular system:
– Heart
– Blood vessels
– Blood (medium of transport)
Blood
• Human adult has ~5L blood
• pH of 7.35, 38°C
• Blood consists
of:
– Blood cells (45%)
– Plasma (55%)
• Important role in homeostasis
Blood composition
• Blood cells
– Red blood cells
– White blood
cells
– Platelets
– All blood cells
are produced in
the bone
marrow
Blood composition
• Red blood cells
– Aka erythrocytes
– 4-6 million/mL blood
– Transport oxygen
– Initially have a nucleus but
disappears as the cell
matures
– Contains haemoglobin, a
red pigment
– Lifespan of 4 months
Blood composition
• White blood cells
– Aka leucocytes
– 4000-11000/mL blood
– Part of the immune
system and help
protect body from
invading organisms
Blood composition
• Platelets
– Aka thromobocytes
– Disc shaped cell fragments,
half size of RBCs
– 400 000/mL blood
– Help to clot blood by
releasing the enzyme
thromboplastin
• perform a first-hand investigation using the
light microscope and prepared slides to
gather information to estimate the size of red
and white blood cells and draw scaled
diagrams of each
Blood composition
• Plasma
– Yellow, watery fluid
– 90% water, 10% proteins and
solutes
– Contains:
• Proteins (clotting proteins, immunoglobulins, albumin,
enzymes)
• Nutrients
• Gases
• Excretory waste products
• Ions
• Regulatory substances (hormones)
• Other (vitamins)
Blood composition
1. Blood gases
– Cellular respiration:
• C6H12O6 + 6O2  6H2O + 6CO2 + energy (ATP)
• http://ed.ted.com/lessons/what-do-the-lungsdo-emma-bryce
• outline the need for oxygen in living cells and
explain why removal of carbon dioxide from
cells is essential
Blood composition
1. Blood gases
– Oxygen
• Needed for respiration
• Oxygen diffuses across the
lung into the blood
• 98.5% of the oxygen binds to
haemoglobin (transport
protein)  oxyhaemoglobin
(bright red)
• 1.5% dissolved in plasma
Blood composition
1. Blood gases
– Carbon dioxide
• Waste product of respiration
• CO2 + H2O → H2CO3 → HCO3– + H+
• 70 % transported in blood as
hydrogen carbonate ions (HCO3-)
in plasma
• 7% CO2 dissolved in plasma
(carbonic acid, H2CO3)
• 23% carried by haemoglobin 
carbaminohaemoglobin
• perform a first-hand investigation to
demonstrate the effect of dissolved carbon
dioxide on the pH of water
The effect of carbon dioxide on the pH
of water
• Results:
a)
b)
c)
Record the initial pH of the distilled water.
Record the pH of the water after it contained dissolved carbon
dioxide.
State whether each is indicative of a strong or weak acidic or
basic solution.
• Discussion:
1.
2.
3.
4.
Comment on the accuracy of the pH measurements that you
have taken, and any difficulties that you had.
Describe the effect of carbon dioxide on the pH of the water.
Explain in chemical terms, what caused the change in the pH
of the water in your experiment.
Mammals try to maintain a blood pH of 7.4. Outline why they
need to get rid of carbon dioxide from their cells as soon as
possible
Blood composition
2. Water and salts
– Water is essential for transport of substances in:
•
•
•
Cytoplasm
Interstitial fluid
Blood
– Salts are transported as ions
•
•
E.g. NaCl is transported as Na+ and Cl- ions
Aka electrolytes: Na+, K+, Cl-, HCO3-
Blood composition
3. Lipids and other products of digestion
– Digestion involves breaking down large molecules
into smaller molecules:
• Carbohydrates  glucose
• Lipids  fatty acids and
glycerol
• Proteins  amino acids
• Nucleic acids 
nucleotides
Blood composition
3. Lipids and other products of digestion
– Soluble compounds (glucose, amino acids, glycerol
and nucleotides) are dissolved in plasma and
transported in the bloodstream
– Lipids and end products are insoluble in water and
need to be packaged for transport
• “Chylomicrons” are carried by the lymphatic system
Blood composition
4. Nitrogenous wastes
– Produced from breakdown of proteins
– Ammonia, urea, uric acid and creatinine
– Dissolved in plasma (very dilute) and excreted
from the body
• explain the adaptive advantage of
haemoglobin
Haemoglobin (Hb)
• Is a protein in RBCs which
contains iron (Fe)
• Adaptation of RBCs
– No nucleus, more space for
haemoglobin (250 million
molecules/RBC)  carry lots
of oxygen
– Biconcave shape of RBC
increases surface area for
oxygen diffusion
Haemoglobin (Hb)
• Each Hb binds to 4 oxygen molecules 
oxyhaemoglobin
1. Haemoglobin increases the oxygen carrying
capacity of blood
More oxygen can be transported than if dissolved in
plasma
2. The ability to bind oxygen increases once the
first oxygen molecule binds to it
3. Its capacity to release oxygen increases when
carbon dioxide is present
– Hb binds less strongly to O2 in acidic pH
• compare the structure of arteries, capillaries
and veins in relation to their function
Transport systems
1. A transport medium (blood)
2. Vessels
3. A driving mechanism (heart)
Cardiovascular system
• Arteries
• Veins
• Capillaries
How the heart pumps blood
• http://ed.ted.com/lessons/how-the-heartactually-pumps-blood-edmond-hui
Arteries
• Function: transport blood away from the
heart, towards the tissues
• Structure:
– Artery walls have 3 layers:
1. A thin inner layer of endothelial cells
2. A middle layer of smooth muscle and elastic fibres
3. An outer layer of connective tissue
• Artery walls are thick due to the
high pressure of the blood
pumping through
Veins
• Function: transport blood towards the heart,
away from the tissues
• Structure: Same basic structure as arteries
• Walls of veins are thinner than
arteries because the blood travels
under lower pressure
• Fewer elastic fibres
• Wider lumen
Veins
• Backflow is prevented in veins by:
– Contraction of surrounding muscles
– Valves in the endothelium lining
Capillaries
• Function: Tiny, thin-walled blood vessels in the
tissues of the body, linking arteries and veins
– Allow for exchange of chemical substances
between cells and the bloodstream
• Structure:
– Capillary walls have an endothelium layer which is
one cell thick
– Allows one RBC through at a time
• describe the main changes in the chemical
composition of the blood as it moves around
the body and identify tissues in which these
changes occur
Change in carbon dioxide and oxygen
• Lungs:
– External gas exchange
– Deoxygenated blood arrives
at the lungs, releases carbon
dioxide and picks up oxygen
– Most of the oxygen binds to haemoglobin to form
oxyhaemoglobin. A small amount is dissolved in
plasma.
– Oxygenated blood is returned to the heart before
it is pumped to the other tissues of the body
Change in carbon dioxide and oxygen
• Body tissues
– Oxygenated blood arrives at the body tissues
where oxygen is released and used for cellular
respiration
– Carbon dioxide is produced as a waste product of
cellular respiration and is transported back to the
lungs as bicarbonate ions, bound to haemoglobin
or dissolved in plasma
Other chemical changes
• Products of digestion are increased in blood
around the small intestines
• Products of digestion decrease in blood which
has passed through the liver (where food is
metabolised)
• Nitrogenous wastes increase in blood after it
has passed through the liver
• Nitrogenous wasted decrease in blood that
has passed through the kidneys
• analyse information from secondary sources
to identify current technologies that allow
measurement of oxygen saturation and
carbon dioxide concentrations in blood and
describe and explain the conditions under
which these technologies are used
• describe current theories about processes
responsible for the movement of materials
through plants in xylem and phloem tissue
Transport in plants
• Small plants use diffusion
• Larger plants have specialised vascular tissue
– Xylem and phloem
– Movement of materials is called translocation
• Needed for the translocation of substances for
photosynthesis
Xylem
• Consists of:
– Vessel structures
tracheids and xylem
vessels
– Parenchyma cells
– Fibres
• Transport water,
minerals and ions from
roots to leaves for
photosynthesis
(unidirectional)
Phloem
• Consists of:
– Sieve tube elements (alive)
– Companion cells which help
keep sieve tubes alive
– Phloem fibres
– Phloem parenchyma
• Transport nutrients (sugars,
amino acids, hormones) to
all parts of the plant
• Transport is bidirectional
• choose equipment or resources to perform a
first-hand investigation to gather first-hand
data to draw transverse and longitudinal
sections of phloem and xylem tissue
Xylem and phloem in root cross
section
Xylem and phloem in stem cross
section
Xylem: transpiration stream theory
(cohesion-adhesion-tension)
1. As the sun warms the leaves,
stomata open and water evaporates
through the openings (transpiration)
2. Evaporation at the leaf surface
creates a pull at the upper end of
the water column (tension)
3. The pulling force is extended to the
water column and creates a force
that pulls water upwards—the
transpiration stream
4. This creates a force that pulls water
into the roots
Phloem: pressure flow theory
(source-path-sink)
• This is an active process
which requires energy
1. Loading at the source
– Amino acids, sucrose and
other nutrients are
loaded into the phloem
in the leaves using ATP.
– The solute concentration
in the phloem increases
and water moves into the
phloem from the xylem
by osmosis.
Phloem: pressure flow theory
(source-path-sink)
2. Offloading at the sink
– Sugars and materials are
removed from the phloem
by active transport.
– As a result, water is drawn
out by osmosis.
3. Pressure flow along the
‘path’
– The movement of water
creates an osmotic
pressure gradient which
drives the movement of
phloem sap
3. Plants and animals regulate the
concentration of gases, water and waste
products of metabolism in cells and in
interstitial fluid
• explain why the concentration of water in
cells should be maintained within a narrow
range for optimal function
Excretion
• The process by which waste products are
removed from the body
• Waste products need to be removed because
they affect the internal environment of the
cell
• Organs of the excretory systems in mammals
include:
– Lungs (CO2)
– Kidneys (nitrogenous wastes)
– Skin (salt)
Why is water important?
• Water makes up 2/3 of the composition of
most living organisms
• Water is a solvent
• Makes up the cytoplasm and body
fluids
– Carries ions, organic solutes and wastes
• Transport medium in plants
– Carries ions and sugars
Why is water important?
• Changes in concentration
of water:
– Changes the osmotic
balance
• Leads to a change in solute
concentration
• Or cells can burst
• Needed for structural
support
Why is water important?
• All chemical reactions of metabolism take
place in water
• Reactants and products are dissolved in water
– E.g. CO2  affect pH
• Water sometimes
take place in reactions
e.g. photosynthesis
• explain why the removal of wastes is
essential for continued metabolic activity
Accumulation of wastes
• Wastes may be toxic to cells and must be
removed from the body to maintain
homeostasis.
• If their levels increase, the internal
environment will change
 ??
• distinguish between active and passive
transport and relate these to processes
occurring in the mammalian kidney
Kidneys
• Organs responsible for removing nitrogenous
waste from the body by filtering blood
• The renal artery carries oxygenated blood to the
kidneys
• The kidneys filter out
nitrogenous wastes,
water and other solutes
• Urine drains via the
ureters to the bladder
• The renal vein carries
purified blood back into
circulation
active vs passive transport?
diffusion vs osmosis?
Passive transport in the kidney
• Nitrogenous wastes (ammonia
and urea) and water move by
diffusion and osmosis from the
blood to the kidney tubules
• Salts (active) and water (passive)
can be reabsorbed depending on
the need to maintain
homeostasis.
Active transport in the kidney
• Active transport requires energy and involves
the movement from low concentration to high
concentration
• Involves carrier proteins which actively move:
– All glucose and amino acids back into the blood
– Ions (salts) back into the blood
– Additional nitrogenous wastes and hydrogen ions
into the urine
• explain why the processes of diffusion and
osmosis are inadequate in removing
dissolved nitrogenous wastes in some
organisms
Diffusion and osmosis: inadequate
• Diffusion and osmosis are passive so they are
slow
• Diffusion relies on concentration gradient but
net movement stops when equilibrium is
reached
not all wastes will be removed
even small amounts of wastes can be toxic
• Diffusion of wastes into urine will also draw
water into the urine by osmosis  lots of
water loss
• gather, process and analyse information from
secondary sources to compare the process of
renal dialysis with the function of the kidney
• perform a first-hand investigation of the
structure of a mammalian kidney by
dissection, use of a model or visual resource
and identify the regions involved in the
excretion of waste products
• explain how the processes of filtration and
reabsorption in the mammalian nephron
regulate body fluid composition
Nephron structure
Function of nephron
• Carries out 3 processes:
– Filtration
– Reabsorption
– Secretion
1. Filtration
• Renal artery branches out into many capillaries
which end at the glomerulus
• Blood is filtered by high pressure across the
surface of the glomerulus and the inner lining of
the Bowman’s capsule, removing:
–
–
–
–
–
–
Water
Amino acids
Glucose
Salts
Nitrogenous wastes
Other toxic molecules
 glomerular filtrate
2. Reabsorption
• Regulates chemical composition of body fluids
• Active transport
• Membrane permeability is regulated by
hormones to control what is reabsorbed
• 99% of filtrate is reabsorbed
• Reabsorption of water is passive as it follows
the movement of the solutes
2. Reabsorption
• Reabsorption of certain molecules occur at
different parts of the nephron:
– All organic nutrients (amino acids and glucose)
Proximal tubule
– Some ions (Na+, K+, Cl-, Ca2+, HCO3-)
Proximal tubule
– Water
Descending limb of loop of Henle
All parts of tubule except the ascending limb of loop of
Henle
– Na+
Collecting tubules
3. Secretion
• Active secretion of toxic substances into the
nephron:
– Metabolic wastes (urea, uric acid, ammonia, H+)
• H+  proximal tubule
• Urea  Descending limb of loop of Henle
– Drugs (penicillin, saccharine, morphine)
Proximal tubule
• outline the role of the hormones,
aldosterone and ADH (anti-diuretic hormone)
in the regulation of water and salt levels in
blood
Stop drinking water
• http://www.youtube.com/watch?v=zCheAcpF
kL8
Hormone regulation of excretion
• Hormones are secreted by endocrine glands
and travel through the blood stream
• Adjustments to water and salt in the urine are
controlled at the distal tubules and collecting
tubules by changing the permeability of the
membrane
• Aldosterone: conserves salts in the body
• ADH (anti-diuretic hormone): conserves water
in the body
Aldosterone
• ↓[Na+] (sodium ion concentration)
↓blood volume
Stimulates adrenal gland (above kidney)
Aldosterone is secreted
At the kidney, the nephron becomes more
permeable to sodium, especially at the ascending
limb
↑reabsorption of sodium ions
Less salt is lost in urine, and salt is retained by the
body
ADH
• Dehydration
↓blood volume
Detected by hypothalamus
Stimulates pituitary gland
ADH is released
At the kidney, the nephron becomes more
permeable to water at the distal tubules and
collecting tubules
↑ reabsorption of water
Water is retained in the body
• present information to outline the general
use of hormone replacement therapy in
people who cannot secrete aldosterone
• identify the role of the kidney in the
excretory system of fish and mammals
Role of kidney in fish and mammals
• Excretory and osmoregulatory organs
• Mammals:
– Conserve water and salts (when required)
– Excrete excess water and
salts
– Excrete nitrogenous wastes
Role of kidney in fish and mammals
• Freshwater fish:
– Excrete excess water
– Excrete nitrogenous wastes
– Conserve salt
• Excess salt is excreted via
gills (when needed)
Role of kidney in fish and mammals
• Marine fish:
– Conserve water
– Excrete excess salt via gills
– Excrete nitrogenous wastes
• analyse information from secondary sources
to compare and explain the differences in
urine concentration of terrestrial mammals,
marine fish and freshwater fish
• use available evidence to explain the
relationship between the conservation of
water and the production and excretion of
concentrated nitrogenous wastes in a range
of Australian insects and terrestrial mammals
• 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
Enantiostasis – estuarine organisms
• Tides change the salinity of estuaries from day
to day
– High tide  high salt in water
– Low tide  low salt in water
Enantiostasis – estuarine organisms
• Osmoregulation is maintained by 2 different
strategies:
1. Osmoconformers:
•
Alter internal concentrations of solutes to match
external environment
2. Osmoregulators:
•
Change internal environment to maintain solutes at
an optimal level
Enantiostasis – estuarine organisms
Osmoconformers
• Fiddler crab
– Accumulates solutes in
tissues in saltwater
– Excretes salt through gills in
freshwater
Osmoregulators
• Mussels
– Close their valves in
freshwater to keep internal
conditions same as seawater
• describe adaptations of a range of terrestrial
Australian plants that assist in minimising
water loss
Balance in Australian plants
• Australian plants need to maintain a balance
between:
– Water loss by transpiration (98%) and evaporative
cooling to maintain optimal temperature
– Surface area exposed to the sun and surface area
needed for photosynthesis
– Closing stomata to conserve water and opening
stomata for gas exchange
• Xerophytes are a species of plant adapted to
hot, dry conditions
Adaptations
1. Reducing internal
temperature
– Waxy leaves reflect light
and heat
•
E.g. saltbush
– Coarse, leathery leaves
with thick cuticle
provides insulation from
sunlight
•
E.g. sclerophylls such as
eucalypts and banksias
Adaptations
2. Reducing exposure to sunlight
– Reduce surface area of organs that
have a lot of stomata (leaves)
•
•
E.g. Wattles have reduced leaves
Leaves are so reduced in some plants that
photosynthesis is carried out by the stem (cladodes)
or leaf stalks (phyllodes)
– Change orientation of leaves
•
E.g. Eucalypts
Adaptations
2. Reducing exposure to sunlight
– Absence of transpiring organs
•
•
Reduced flowers or no petals
E.g. Wattles (acacias)
– Shedding leaves
•
E.g. River gum
Adaptations
3. Reducing the water potential
– Water potential is the difference in water
concentration between the plant and the
environment
– Plants create microclimates, trapping moisture
around the leaves to reduce the water potential:
•
Sunken stomata: E.g. Hakea
Adaptations
3. Reducing the water
potential
• Epidermal hairs: E.g. Coastal
banksia
• Curled or rolled leaves: E.g.
porcupine grass
Adaptations
4. Water storage
– Plants such as succulents have fleshy leaves or
stems that can hold water which can be used
during dry periods
•
E.g. Calandrinia
(parakeelya)
• process and analyse information from
secondary sources and use available evidence
to discuss processes used by different plants
for salt regulation in saline environments
• perform a first-hand investigation to gather
information about structures in plants that
assist in the conservation of water