Unit 1- Molecules, Blood and Gas Exchange

Molecules and Blood

  • Created by: Rebecca
  • Created on: 19-09-12 10:59

Blood Tests

1. Torniquet to make the vein stand out and easy to target the needle

2. Clean area with alcohol based solution

3. Push sterile needle attached to sterile syringe

4. Cotton ball over the wound

5.Press for 1-2 mins and apply dressing

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Blood Smear

1. Put small drop of blood near end of clean microscopic slide

2. Place end of slide on sample to "catch" blood

3. Hold spreader @ 30deg angle & slide to smear

4. Label slide with patients details

5. Allow slide to dry in the air so cells stick 

6. Fix slides with alcohol to preserve the cells

7. Stain slide using Romanowsky Stain 

8. Pour over and leave for 2 mins to be washed off w/ water

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  • Bi concave disks
  • Large surface area- to - volume ratio to speed gas exchange
  • Cytoplasm packed with haemoglobin
  • Small and flexible so they can flatten against capillary wall which reduces distance and speeds gas exchange

Mature red blood cells

  • No nucleus
  • More room for haemoglobin
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  • Type of leucocyte
  • Small granules in the cytoplasm
  • Engulf microorganisms by phagocytosis

NeutRO -> ROugh granules -> phaGOcytosis

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  • Type of leucocyte
  • Large dark nucleus
  • Thin layer of clear cytoplasm 

Two types of Lymphocyte

  • Both are cells of the immune system

B Lymphocyte- Produces antiBodies

T Lymphocyte- Several functions including cell destruction

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  • Largest of the leucocytes
  • Large bean shaped nucleus and clear cytoplasm

Spend 2-3 days in circulatory System

-Then move to the tissues

 - Then become macrophages

   - Then engulf microorganisms and other foreign material

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Cell membranes are mainly made up of two kinds of  molecule:

  • Phospholipids (which form the bulk of the membrane)
  • Proteins (which are scattered around in the membrane)

Some molecules of carbohydrate and cholesterol may also be present

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  • Special kind of lipid molecule
  • Made of a glycerol molecule with a phosphate group and 2 fatty acid chains

Phosphate group:

  • Hydrophilic (water loving) because it has a charge
  • Soluble in water

Fatty acid chains:

  • Made up of hydrocarbons
  • Hydrophobic (water hating)
  • No charge and insoluble in water
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Phospholipid (2)

Phospholipids pack together in a membrane

They form a double layer called a bilayer

There is water inside and outside of a cell so:

  • The fatty acid tails pack AWAY from water because they don't like water
  • They hydrophilic heads arrange themselves on the outside of the membrane, facing TOWARDS the water
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  • In a membrane there are different sorts of protein with complex shapes
  • Proteins are scattered around the membrane and change position

Intrinsic Proteins- Large proteins span the whole bilayer

Extrinsic Proteins- Smaller proteins on just one side of the bilayer

Glycoproteins- Some proteins have carbohydrate chains attached on the outside of the cell. In the plasma membrane, these proteins are involved in cell recognition. Therefore, other molecules may attach to them, Some of the carbohydrate chains join to other carbohydrate chains in the glycoproteins of cells which are next to them.This causes the cells to join together -Cell adhesion.

Glycolipids- Sometimes carbohydrate chains attach to phospholipids

Cholesterol- Present in many membranes to keep the membrane stable.

  • Lipid like substance called a steroid
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The Fluid Mosaic Model of Membrane Structure


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Membranes around and within cells

  • The membrane separates the cell from its environment (plasma/tissue fluid) and from other cells. 
  • Glycoproteins are also important in cell to cell signalling
  • The binding of ions or other chemicals to these receptors can trigger reactions inside the cell, including the switching on or off of genes in the nucleus
  • Blocking these receptors is one way that drugs can have an effect

Membranes are also found inside cells to separate cells into 'compartments'. The membranes allow complex processes within the cell to be seperated

E.g. Enzymes involved in respiration are found in the mitochondria.

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Membrane Bound Structures

Plasma Membrane

  • Partially permeable. Retains cell contents

Rough Endoplasmic Reticulum

  • Ribosomes synthesise proteins. Membranes package them for distribution around the cell

Smooth Endoplasmic Reticulum

  • Synthesis of lipids including steroids

Golgi Apparatus

  • Synthesis of glycoproteins, polysaccharides and hormones. Production of lysosomes

Nuclear Envelope

  • Regulates exchange between cytoplasm and nucleus
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Membrane Bound Structures- Organelles


  • Contain enzymes for intracellular digestion


  • Contains DNA and regulates cell activity


  • Aerobic respiration and production of ATP


  • Absorbance of light energy and production of carbohydrates in photosynthesis
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