Download BC Revision Guide 3

B3 Revision
Monday, 03 April 2017
Starter: Unscramble these anagrams of some
of the key words for B3
-
ioosmss
iyalsisd
fadeoesttionr
ptycoroinme
innulis
tadsoilaionv
B3.1 Movement of molecules
This covers:
- Diffusion
- Osmosis
- Active transport
- Sports drinks
- Specialised exchange surfaces
Diffusion
• Diffusion happens when the particles
are free to move (gases and particles
dissolved in solutions).
• Particles diffuse down a concentration
gradient, from an area of higher
concentration to an area of lower
concentration. No energy is required.
Osmosis
• Osmosis
The movement of water particles from a
concentrated solution to a more dilute solution,
through a partially permeable membrane.
• Osmosis is important to plants. They gain water
by osmosis through their roots.
• In animals water is reabsorbed in the kidney by
osmosis.
• What is a partially permeable membrane?
Some membranes in plant and animal cells allow
certain particles to pass through them but not
others.
Active transport
• Substances are sometimes absorbed against a
concentration gradient. Particles move across a
cell membrane from an area of lower
concentration to an area of higher
concentration.
• This requires energy released from respiration
and protein carriers to move the ions across.
• Active transport occurs in plant roots when
absorbing ions, and also glucose absorption in
the small intestine of animals.
How are these parts of the body
adapted for movement of
molecules?
Sports drinks
http://study.com/academy/lesson/hy
pertonic-solution-definition-effectexample.html
Take notes as you watch
B3.2 Transport of substances
This covers:
- Heart and circulatory system
- Blood vessels
- Components of blood
- Lungs and breathing
- Transport in plants (xylem, phloem,
stomata)
- Transpiration
A double circulatory system
The mammalian
circulatory
system is known
as a double
circulatory
system because
blood passes
through the
heart twice per
one circulation
of the body
lungs
body’s
cells
Two types of blood
The circulatory system carries two types of
blood:
Oxygenated
blood
blood travelling
c to the body cells
 high oxygen content
low carbon dioxide
content
Deoxygenated
blood
 blood travelling
away from the body
cells
 low oxygen content
 high carbon dioxide
content
The arrangement of the circulatory system
means that these two types of blood do not mix.
Components of blood
• The blood is a liquid tissue consisting of:
Blood plasma transports:
 carbon dioxide from the organs to the lungs
 soluble products of digestion from the small intestine to other
organs
 urea from the liver to the kidneys
 hormones
• Red blood cells transport oxygen from the lungs to the organs. Red
blood cells have no nucleus. They are packed with a red pigment
called haemoglobin.
In the lungs oxygen combines with oxygen to form oxyhaemoglobin.
In other organs oxyhaemoglobin splits up into haemoglobin and
oxygen.
• White blood cells ingest and destroy pathogens, produce antibodies
to destroy pathogens, and produce antitoxins that neutralise the
toxins released by pathogens.
• Platelets are irregularly shaped bodies. They help to form clots to
stop bleeding.
Blood vessels
• Arteries: Carry blood away from the heart- largely carry
oxygenated blood under high pressure (except pulmonary
artery). Arteries have a narrow lumen, with layers of
elastic and muscle tissue to allow them to stretch and
recoil.
• Capillaries: Deliver blood to cells. Narrow walls (1 cell
thick) for exchange of nutrients and wastes. Form
capillary beds to increases SA.
• Veins: Carry blood back to the heart- largely
deoxygenated (except pulmonary vein). Large lumen,
contain valves to prevent backflow of blood. Lie close to
muscles to help move blood back to the heart.
How can these treatments
improve circulation?
How are these parts of a plant
involved in transport?
Transpiration
• Transpiration= evaporation
of water from the leaves
through the stomata.
• Rate of transpiration can
be measured using a
potometer.
• Wind, high temperatures
and sunshine increase rate
of transpiration
• Humid conditions reduce
rate of transpiration
B1.3 Homeostasis
This covers:
- Homeostasis, including sugar and
temperature control
- Diabetes
- Kidney function
- Kidney transplant and dialysis
Sugar control
• Pancreas detects glucose levels in the blood.
• Too much glucose: pancreas release insulin- this
causes glucose to be stored as glycogen in the liver,
and some glucose is stored in fat cells.
• Too little glucose: pancreas release glucagon. This
causes glycogen in the liver to be broken down into
glucose and released into the blood.
• Type 1 Diabetes= pancreas does produce/ release
enough insulin. Levels of glucose in the blood remain
high. Injections of insulin given as treatment.
Temperature control
• Thermoregulatory centre in the brain detects
temperature changes.
• Too hot: sweating, evaporates off the skin causing
cooling. Hairs on skin lie flat. Vasodilation- dilation of
blood vessels near the skin means more heat loss
occurs.
• Too cold: shivering, hairs on skin stick up, trapping a
layer of insulating air. Vasoconstriction- constriction of
blood vessels near the skin means less heat is lost.
• Both this, and glucose control are examples of negative
feedback.
Kidney function
Normal kidney function
• Stage 1: Ultrafiltration. Blood is
brought to the kidneys to be
filtered – blood passes through tiny
tubules and water, salt, glucose and
urea are squeezed out.
Stage 2: Selective reabsorption.
The kidneys reabsorb all of the
glucose and as much water and salt
as the body needs into the blood.
This often requires active
transport.
Stage 3: Waste. Water, salt and
urea are left – this is urine. Urine
is sent through the ureter to the
bladder where it is stored before
being excreted.
Dialysis
The patients’ blood flows alongside a partially permeable membrane,
surrounded by dialysis fluid which contains the same concentration
of dissolved ions and glucose as the blood (this ensures that glucose
and useful mineral ions are not lost).
Ions and waste can pass through, but big molecules like blood cells
and proteins can’t pass through (like in the kidneys).
Dialysis removes urea and maintains blood sodium and glucose levels.
Dialysis vs. transplant
Max 6
(b)
any three from:
•
advantages (compared to insulin injections):
• •
(may be) permanent / cure
• •
no / less need for self monitoring
• •
no / less need for insulin / injections
• ignore reference to cost
• •
no / less need for dietary control
•
disadvantages (compared to insulin injections):
• •
low success rate
• •
(may) still need insulin / dietary control
• •
operation hazards
• •
risk of infection from donor
• •
rejection / need for drugs to prevent rejection
• max 2 if only advantages or only disadvantages discussed
can give converse if clear that it relates to insulin injections