1. Cell membrane damage in diabetes mellitus

4. Structure of the cell membrane
The membrane is a phospholipid bi-layer (i.e. two layers of phospholipid molecules.
The phosphate ‘head’ of the phospholipid molecules are hydrophilic (attracted to water), and form the outer and inner boundaries of the membrane.
The lipid ‘tail’ of the phospholipid molecules are hydrophobic (repelled by water), and form the inner layer of the membrane.

5. The phospholipid bi-layer also contains the steroid compound cholesterol, which maintains the stability of the membrane.
A variety of protein and carbohydrate molecules are embedded in the membrane.

7. The cell membrane
Drawing by Mariana Ruiz Villarreal

8. Functions of the cell membrane
Isolates the cell from the surrounding tissue fluid
determines what substances enter and leave the cell
contains a variety of receptors that respond to substances in the cell’s environment e.g. hormones, antigens.

9. What determines the rate of diffusion? There 4 factors:
The steepness of the concentration gradient. The bigger the difference between the two sides of the membrane the quicker the rate of diffusion.
Temperature. Higher temperatures give molecules or ions more kinetic energy. Molecules move around faster, so diffusion is faster.
The surface area. The greater the surface area the faster the diffusion can take place. This is because the more molecules or ions can cross the membrane at any one moment.
The type of molecule or ion diffusing. Large molecules need more energy to get them to move so they tend to diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in the non polar phospholipid tails.
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10. Diffusion through the membrane
Because the cell membrane is fatty, most water soluble substances cannot diffuse through it.
Exceptions include oxygen & carbon dioxide.

11. Membrane proteins A variety of proteins are embedded in the bi-layer.
These serve various functions including the movement of substances in and out of the cell.

13. Membrane transport proteins
Membrane proteins that aid the movement of substances in and out of the cell include:
Channel proteins (ion channels) – open channels that allow simple diffusion.
Carrier proteins that allow facilitated diffusion (e.g. glucose) and active transport (specific membrane pumps).

14. Membrane transport Transport processes are either passive or active.
Passive processes require no cellular energy and include diffusion, osmosis & facilitated diffusion.
Active processes require ATP and include specific membrane pumps and phagocytosis/pinocytosis.

15. Simple diffusion (left) & facilitated diffusion
Diagram created by LadyofHats

16. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell
AS Biology, Cell membranes and Transport

17. Diffusion through a membrane
Cell membrane
diffusion
Outside cell
Inside cell
AS Biology, Cell membranes and Transport

18. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell
EQUILIBRIUM
AS Biology, Cell membranes and Transport

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21. Molecules that diffuse through cell membranes
Oxygen – Non-polar so diffuses very quickly.
Carbon dioxide – Polar but very small so diffuses quickly.
Water – Polar but also very small so diffuses quickly.
AS Biology, Cell membranes and Transport

23. Osmosis
‘The diffusion of water from an area of high concentration of water molecules (high water potential) to an area of low concentration of water (low water potential) across a partially permeable membrane.’
AS Biology, Cell membranes and Transport

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25. Facilitated diffusion
Large polar molecules such as glucose and amino acids, cannot diffuse across the phospholipid bilayer. Also ions such as Na+ or Cl- cannot pass.
These molecules pass through protein channels instead. Diffusion through these channels is called FACILITATED DIFFUSION.
Movement of molecules is still PASSIVE just like ordinary diffusion, the only difference is, the molecules go through a protein channel instead of passing between the phospholipids.
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29. Cell markers and receptors
Various protein and carbohydrate molecules exposed on the surface of the membrane:
act as markers – these indicate to cells of the immune system whether a cell is norm or abnormal (see MHC proteins).
serve as receptors that interact with substance in the cell’s environment and initiate specific cellular responses e.g. receptors sensitive to the hormone insulin alter the rate of glucose intake.

30. WHO estimates that more than 346 million people worldwide have diabetes. This number is likely to more than double by 2030 without intervention.
346 million people worldwide have diabetes1.
In 2004, an estimated 3.4 million people died from consequences of high blood sugar.
More than 80% of diabetes deaths occur in low- and middle-income countries.
WHO projects that diabetes deaths will increase by two thirds between 2008 and 2030.
Healthy diet, regular physical activity, maintaining a normal body weight and avoiding tobacco use can prevent or delay the onset of type 2 diabetes.

31. World Diabetes Day (14 November 2013)[2] World Diabetes Day raises global awareness of diabetes - its escalating rates around the world and how to prevent the illness in most cases. Started by the International Diabetes Federation (IDF) and WHO, the Day is celebrated on 14 November to mark the birthday of Frederick Banting who, along with Charles Best, was instrumental in the discovery of insulin in 1922, a life-saving treatment for diabetes patients

32. Physiology of the Pancreas:- The pancreas is composed of two major types of tissues, (1) the acini, which secrete digestive juices into the duodenum, (2) the islets of Langerhans, which secrete insulin and glucagon directly into the blood

33. I. Type I or IDDM:-Insulin Dependent Diabetes Mellitus II
I.  Type I or IDDM:-Insulin Dependent Diabetes Mellitus II. Type II or NIDDM:-Non-Insulin Dependent   Diabetes Mellitus III. MRDM:-Malnutrition Related Diabetes Mellitus IV. IGT:-Impaired Glucose Tolerance V.  Gestational Diabetes:-Occur during pregnancy

34. Type I or IDDM (Insulin Dependent Diabetes Mellitus):- The cells in the pancreas that make insulin are destroyed, causing a severe lack of insulin.
This is thought to be the result of the body attacking and destroying its own cells in the pancreas - known as an autoimmune reaction.
It is an auto-immune disease where the body's immune system destroys the insulin-producing beta cells in the pancreas. This type of diabetes, also known as juvenile-onset diabetes, accounts for 10-15% of all people with the disease. It can appear at any age, although commonly under 40. People with type 1 diabetes must inject themselves with insulin.

35.  Type II or NIDDM:-Non-Insulin Dependent   Diabetes Mellitus Type 2 diabetes is the most common form of diabetes, affecting 85-90% of all people with the disease. This is characterised by insulin resistance and relative insulin deficiency. The disease is strongly genetic in origin but lifestyle factors such as excess weight, inactivity, high blood pressure and poor diet are major risk factors for its development. Type 2 diabetes may be treated by dietary changes, exercise and/or tablets. Insulin injections may later be required.
The receptors on cells in the body that normally respond to the action of insulin fail to be stimulated by it - this is known as insulin resistance. In response to this more insulin may be produced, and this over-production exhausts the insulin-manufacturing cells in the pancreas; 1. There is simply insufficient insulin available 2.The insulin that is available may be abnormal and therefore doesn't work properly.