1.1.1 Blood

Sylabus guided notes for AS OCR Biology (Human) 1.1.1 Blood

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1.1.1 Blood
(a) Blood Samples
Sterile equipment and disposable gloves are used. Skin is swabbed with alcohol.
Tourniquet is put on upper arm to make the veins stand out more. The needle is inserted
into a vein and blood is slowly drawn. Place a swab over wound as soon as needle is
removed.Cover with a sterile dressing once bleeding has stopped.
(b) Blood Smears
Place a very small drop of blood near the end of a clean microscope slide, Place the end
of another slide on the sample slide and hold it at about 30o and push it along the slide,
spreading the blood. Allow the slide to dry in the air and fix with alcohol. Stain the slide
using Romanowsky stain, such as Wright's or Leishman's stain. Pour over and leave for 2
minutes and wash off with water.
(c) Haemocytometer
A haemocytometer is a chamber designed for counting blood cells. The cells have to be
diluted using Dacie's fluid. Red blood cells are diluted 1:200 and white blood cells 1:20.
Place the diluted cells on the lined squares and count using the northwest rule discount the
cells lying on the east or south boundary of the squares.
(d) Different Cell Types
Lymphocyte Large nucleus, small rim of cytoplasm, makes antibodies
Neutrophil Granular toxins, multilobed nucleus, engulfs cells by phagocytosis
Monocyte Horseshoe nucleus, used in immunity
Lymphocyte Single round nucleus in the lymphatic system
(e) Platelets
Platelets are fragments of giant cells called megakaryocytes which are a very important
part of blood clotting.
(f) Cell Organelles
Golgi modify and repackage vesicles.
RER is where proteins are made.
SER is where lipids are synthesised.
Lysosomes are vesicles with enzymes in.
Vesicles are small membrane sacks.
Mitochondria are where ATP is made.
Chloroplasts are involved in photosynthesis.

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Cytoskeleton provide stability to the cell.
Nucleus controls cell functions.
Nucleolus is a concentrated part of the nucleus.
(g) Magnification
Magnification = size of structure in picture
real size of the structure
(h) Fluid Mosaic Model
(i) Membranes
The cell surface membrane separates the cell from its environment. Membranes are also
found inside the cell in the form of membrane bound organelles. These membranes allow
complex processes to happen separately from others. Such as, only the enzymes needed
for respiration are found in mitochondria.…read more


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