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 14 March 2016 Learning question: Why is haemoglobin integral to our survival? Homework:

Key words Haemoglobin Oxygen Beta chains Alpha chains Anaemia Red blood cells Fibrous proteins Globular proteins

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 45 o C

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.