Transcript The role of haemoglobin

Lesson starter
• What three elements are common to fats,
carbohydrates and proteins?
• What reaction unites single units of fats,
carbohydrates and proteins?
• What type of bond forms between:
– Fats
– Carbohydrates
– proteins
Title: The role of haemoglobin
29 March 2016
Learning question: Why is haemoglobin integral to our
survival?
Homework:
Globular and fibrous proteins
Fibrous proteins
• Polypeptides join together to form long fibres
or sheets.
• Fibrous proteins are insoluble in water
• Tend to be used for structural functions
– Keratin (human hair)
– Collagen (give skin elasticity amongst other things)
Globular proteins
• These proteins are roughly spherical, or globular in shape
• Usually soluble in water and tend to have biochemical
functions
• Examples include
– Enzymes
– Haemoglobin
• Folded in a particular way so that R groups are on the outside
so that they are soluble in water based liquids e.g. cytoplasm
and blood plasma.
Summary
• Write down the main differences between
fibrous and globular proteins
Denaturation
• Tertiary structure of globular proteins is held together by fairly
weak hydrogen bonds
• High temperatures cause molecules to vibrate more. If
protein molecules vibrate too much, weak hydrogen bonds
will break.
• This changes the conformation of the protein – the protein is
denatured.
• Most proteins denature at about 45oC
Denaturation
• Hydrogen bonds depend on
weak attractions between H+ and
O- in different parts of a protein
molecule.
• Ionic bonds also depend on
small charges like this.
• Because of the nature of these
bonds, pH changes can break
these bonds
Denaturation
• pH measures the concentration of hydrogen ions
(positively charged, H+)
• As the concentration of H+ ions surrounding the
protein increases or decreases, this affects the
charges holding the globular protein together.
• If these bonds break, the protein can become
denatured.
Summary
• What is denaturation?
• What factors can cause denaturation in
proteins?
• Explain how these factors cause denaturation
Carrying oxygen
• Haemoglobin is made of
4 polypeptide chains.
• Each has a haem group
attached.
• The haem group is a
non-protein part of the
protein structure and is
called a prosthetic
group.
Carrying oxygen
• The iron ion in the middle of the
haem groups can associate or
disassociate with oxygen.
• This means that 4 oxygen
molecules can combine with one
RBC.
• When the first haem group
combines with oxygen, it changes
the shape of haemoglobin,
exposing the next haem group.
• This makes it easier to pick up
more oxygen.
Summary
• Describe the structure of haemoglobin
• Describe what happens when more than one
oxygen associates with haemoglobin
When things go wrong
• Beta thalassaemia
– Common in Greek and Italian people
– Haemoglobin beta chains are shorter than normal
– This means that haemoglobin does not carry as
much oxygen as normal haemoglobin
When things go wrong
• Diabetes
– High blood glucose leads to glucose attaching to haemoglobin
in red blood cells
– This forms “glycosylated haemoglobin” which can pick up
oxygen really well
– Issues arise because glycosylated haemoglobin does not give
up oxygen to respiring tissues very easily
– Organs can be damaged by this, including blood vessels in the
eyes, which can lead to blindness (diabetic retinopathy)
When things go wrong
• Sickle Cell Anaemia
– Most common in people of African ancestry
– Suffers of sickle cell anaemia have haemoglobin in which the
alpha chains are normal, but the beta chains have the amino
acid valine instead of glutamic acid (substitution mutation)
– In the arteries and lungs, oxygen associates with this type of
haemoglobin easily
– In respiring tissues however, the molecules tend to stick
together.
When things go wrong
• Sickle Cell Anaemia
– Haemoglobin with the valine substituted for glutamic acid,
changes the formation of the beta chains.
– They become long and stiff, causing the red blood cells to
change shape also
– They become crescent or sickle shaped.
Summary
• Describe what issues arise for sufferers of:
– betathalasemia
– Sickle cell anaemia
– Diabetes
• In relation to oxygen and red blood cells.
Questions
• Complete questions 1-3 on page 15
• Correct your answers in a different coloured
pen.