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CONTEXT POINT 2:
Plants and animals transport dissolved nutrients and gases in a fluid medium.
•
Identify the form(s) in which each of the following is carried in mammalian
blood:
•
•
•
Carbon dioxide
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70% as hydrogen ________________ ions (HCO3-).
•
7% as CO2 dissolved in plasma.
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23% carried by haemoglobin as ________________________
(carboxyhaemoglobin).
Oxygen
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98% as oxy-haemoglobin (HbO2) in red blood cells.
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2% as oxygen dissolved in plasma.
Water
•
•
Salts
•
•
As lipoproteins, triglycerides and cholesterol.
Nitrogenous waste
•
•
Dissolved in plasma.
Lipids
•
•
Solvent of plasma and comprises about 60% of the volume of blood.
As urea, uric acid and creatinine dissolved in plasma.
Other products of digestion
•
Also dissolved in the plasma are amino acids, sugars, glycerol, nitrogenous
bases, hormones and vitamins.
QUESTION 17
Which of the following correctly responds to the main mode of transport of the named
substances in the blood?
Water
CO2
Salts
A
Plasma
Leucocytes
Red Blood Cells
B
Plasma
Red Blood Cells And Plasma
Plasma
C
Haemoglobin
Haemoglobin
Plasma
D
Leucocytes
Plasma
Kidneys
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 19
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Explain the adaptive advantage of haemoglobin.
HAEMOGLOBIN STRUCTURE
Haemoglobin is a complex molecule made up of t________ main parts; the protein part (the
globin), made of four polypeptide chains, and the haem group (which contains ________)
that is inside each folded polypeptide.
__________ oxygen molecules can be carried by each haemoglobin molecule. Once
4 oxygen molecules have combined, each with an iron ion, the molecule is known as
oxyhaemoglobin. Hb + 4O2  Hb(O2)4.
HAEMOGLOBIN FUNCTION
Haemoglobin transports oxygen from areas of high oxygen concentration (the __________)
to areas of low oxygen concentration (the surface of cells). The ease with which the oxygen
bonds with the haemoglobin molecule depends on the surrounding concentration of oxygen.
In high oxygen concentration levels, it easily picks up oxygen. In low oxygen concentration
areas (such as near cells), the oxygen is easily released from the haemoglobin, and so
enters areas where it is needed.
Haemoglobin can also transport some carbon dioxide – although most travels in the plasma
as a carbonate ion.
HAEMOGLOBIN ADAPTIVE ADVANTAGES
Haemoglobin increases the amount of oxygen that can be carried in the blood, therefore it is
an adaptive advantage for organisms that need a large supply of oxygen.
The structure of haemoglobin is also an adaptive advantage because it l_______________
binds to oxygen at the respiratory surfaces and easily releases oxygen from the capillaries
near the cells of the body that require it.
If oxygen were to be transported in the plasma rather than attached to haemoglobin inside
the red blood cell, it would change the osmotic balance of the blood.
Haemoglobin acts as a buffer in the blood by absorbing hydrogen ions that are left in the
plasma when carbon dioxide reacts with water to form hydrogen carbonate ions. This
prevents dramatic changes in blood pH that would affect normal metabolism.
QUESTION 18
Identify the protein responsible for transporting oxygen in mammalian blood and explain two
advantages it offers. (3 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 20
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Compare the structure of arteries, capillaries and veins in relation to their
function.
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Arteries carry blood __________ from the heart. They have thick walls made of
elastic fibres and muscle. When the heart beats, waves of blood are sent along
the artery, and it is able to stretch (this is the bulging of the artery that you feel
when you take your pulse). The blood in arteries is under very high __________.
It is this pressure that forces the blood through the many branches of the
circulatory system so that is can reach all the tissues of the body. The lumen has
a smooth lining to allow the blood to pass more freely.
•
Capillaries are the _______________ blood vessels, and can be seen only with a
microscope. They have very thin walls, only one cell thick. As blood flows through
a capillary, liquid (“tissue fluid”) leaks through the walls to bathe the surrounding
cells. Cells remove the nutrients they need from the tissue fluid and add any waste
products to it. Some of this fluid drains back into the capillary, in order to maintain
blood volume. It is returned to the heart via the various organs that remove the
excretory products (urea, carbon dioxide etc). Blood leaving a capillary has much
less energy than blood entering one. White blood cells can also squeeze out of
capillaries, to find and kill pathogens.
•
Veins carry blood back to the heart. The pressure of this blood is ________, about
one tenth of what it was when in the artery. To make it easier for the blood to get
through, veins are bigger in diameter than arteries, have thinner walls and a wider
lumen (hole). They have valves to prevent the backflow of blood. Return of blood
to the heart is also helped by the movement of body muscles, which squeeze the
blood along the veins.
Figure 5: Cross-section of three types of blood vessels
(Image taken from: http://www.coolschool.ca/lor/BI12/unit9/U09L01.htm)
QUESTION 19
Using the diagram above, label one structural feature of the artery shown and then relate
this structure to the function of the artery. (3 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 21
QUESTION 20
Blood travels around the body through arteries, veins and capillaries. Which of the following
correctly describes the structure or function of each of these blood vessels?
Artery
Vein
Capillary
A
Always carries
oxygenated blood
Always carries
oxygenated blood
Always carries waste
products
B
Thick muscular walls
Thin walls with valves
C
Takes blood to the heart
Thick muscular walls
Walls one cell thick
Takes blood to and from
heart
D
Carries blood under
pressure
Carries blood under
variable pressure
Thin muscular walls
QUESTION 21
Construct a table to compare the three main types of blood vessels, relating the structure of
each to its function and providing a diagram of each. (6 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
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_________________________________________________________________________
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_________________________________________________________________________
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_________________________________________________________________________
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_________________________________________________________________________
_________________________________________________________________________
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© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 22
•
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.
The composition of blood changes as the blood moves around the body. Blood collects
some substances from the tissues and releases others into tissues.
•
Urea is a ______________ waste product produced by the liver and removed by
the kidneys. The concentration of urea entering the kidneys is higher than the
blood urea concentration leaving the kidneys.
•
Glucose levels in blood rise after a meal but as glucose is removed by the liver
and muscles (with the aid of hormones), its concentration returns to normal range
of about 70 – 90 mg/100mL of blood.
•
Hormones are produced in endocrine glands and travel to their target organ in the
circulatory system. Most hormones usually involve a response that may take a
long while to complete, so the concentration of some hormones is relatively
stable. One exception is adrenalin, which produces an immediate response to
protect the body. Levels of hormones in a person’s body depend on their gender,
as well as their age, diet, activity and other external stimuli.
•
The gas oxygen is needed by all living cells that respire aerobically. The
concentration of oxygen is highest in the pulmonary vein, which is taking newly
oxygenated blood from the lungs to the heart. From here, oxygen-rich blood is
then transported via the circulatory system to __________ that need it.
Oxygen-depleted blood returns to the heart, via the veins and is then pumped to
the lungs for more oxygen.
•
The gas carbon dioxide is formed as a waste product from cellular __________.
It is excreted from the lungs, in exchange for oxygen. Carbon dioxide needs to be
removed from the blood as it can influence the pH of blood and in turn inhibit
essential metabolic processes. The highest concentration of carbon dioxide is
found in the pulmonary a____________, which connects to capillaries around the
alveoli in the lung. During exercise, carbon dioxide production increases and this
then causes increased breathing and heart rate, so that the excess carbon dioxide
can be removed quickly.
QUESTION 22
Which main body system is responsible for excreting the metabolic wastes carbon dioxide
and water?
A
B
C
D
The stomatal system.
The excretory system.
The endocrine system.
The respiratory system.
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 23
QUESTION 23
Describe two main changes in the chemical composition of the blood as it moves around the
body and identify the tissue(s) in which these changes occur. (3 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 24
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Outline the need for oxygen in living cells and explain why removal of
carbon dioxide from cells is essential.
WHY OXYGEN IS NEEDED
Oxygen is needed by cells for the energy releasing process of respiration. Without energy,
cells cannot function and the organism will die.
glucose +
oxygen
→
water
+
carbon dioxide
+
energy (ATP)
WHY CARBON DIOXIDE NEEDS TO BE REMOVED
Carbon dioxide needs to be removed as it l___________ the blood pH, that is, makes it
more acidic. This is because carbon dioxide reacts with water to produce carbonic _______.
The increased acidity decreases the capacity for haemoglobin to carry oxygen and affects
enzyme functioning (as enzymes work best at a specific pH) which in turn affects metabolic
processes.
QUESTION 24
State why oxygen is essential for all cells and outline why it is necessary for carbon dioxide
to be removed from animal cells. (3 marks)
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 25
•
Perform a first-hand investigation to demonstrate the effect of dissolved
carbon dioxide on the pH of water.
FIRST HAND INVESTIGATION
Make sure you are able to write up all or any part of the experiment you conducted and
discuss features such as accuracy, reliability and validity.
DISSOLVING CARBON DIOXIDE
In class you would have carried out an investigation to dissolve carbon dioxide into water.
You could have done this by either blowing through a straw into water, or reacting two
chemicals such as an acid and a carbonate and bubbling the reactant – carbon dioxide
– through water.
MEASURING THE pH
This would have been done before and after dissolving the carbon dioxide into the water so
that the effect could have been measured. You could have done this qualitatively with
universal indicator or quantitatively (and more accurately) with a pH meter.
QUESTION 25
Describe an investigation that you have carried out to demonstrate the effect of dissolved
carbon dioxide on the pH of water. (3 marks)
_________________________________________________________________________
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_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
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_________________________________________________________________________
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 26
•
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.
FIRST HAND INVESTIGATION
In class you will have examined whole blood on a microscope slide, calculated the scale and
the size of red and white blood cells and drawn scaled diagrams of them. Make sure you can
describe your method and results.
RED BLOOD CELLS
Red blood cells would have appeared round with a pale centre (due to being thinner in the
middle because of the biconcave shape). They are smaller than white blood cells and more
n___________________.
WHITE BLOOD CELLS
There are many different kinds of white blood cells, but they can be identified because they
are often larger than red blood cells and contain one or more purple _____________. There
are not as many white cells as red cells in a normal human blood count.
SCALED DIAGRAMS
To estimate the scale you would have used a grid of known size and estimated the diameter
of the field of view in millimetres. To convert this to μm, x 1000. Using this grid you can
estimate the diameter of a red blood cell and a white blood cell.
© The School For Excellence 2016
Trial Exam Revision Lectures – Biology – Book 1
Page 27