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Niki's Notes

Transport systems
Simple organisms

Organisms such as Amoeba can rely on simple diffusion to get all of the substances they
need. Nutrients and oxygen can diffuse into the cell and waste can diffuse out. This is because these
organisms have a large surface area to volume ratio. Because…

Page 2

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Niki's Notes

Water in living organisms

Water has the chemical formula HO. Water molecules are described as slightly polarised because
they have a slight positive charge at one end of the molecule and a slight negative charge at the
other end. As a result, individual molecules form hydrogen bonds with…

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Niki's Notes

The Heart (Cardiac cycle)

All arteries (except the pulmonary arteries) take oxygenated blood away from the heart.

The valves close up to stop blood from going back into the heart.

Mammals have a double circulation consisting of a pulmonary (to lungs) and systemic (to the rest of

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Niki's Notes


1. The heart is at rest and the myocardium is relaxed.
2. The atria and ventricles passively fill with blood (AV valves)
3. The aortic and pulmonary artery semilunar valves are closed, bi and tri are open

Atrial Systole:

1. The atria contract and the ventricles relax…

Page 5

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Niki's Notes

SA node ­ pacemaker, because it determines the rate of contraction of the rest of the cardiac
muscle (Where the vena cava enters the right atrium)

Intrinsic rhythmicity ­ In early embryo cells that are destined to become the heart, begin
contracting long before the heart forms.

Page 6

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Niki's Notes

Factors that affect membrane fluidity

1. Temperature ­ at lower temps, lipids have less kinetic energy so are packed more tightly,
decreasing fluidity. High temps = loose lipids, more fluidity.
2. Lipids ­ Long with saturated tails have a high melting point, which decreases fluidity. The
straight unkinked…

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Niki's Notes

Diffusion and gas exchange
Facilitated diffusion ­ proteins in the membrane allow only specific substances to move through
passively down their concentration gradient.


Hypotonic ­ The osmotic concentration of solutes is lower than that in the cytoplasm of the cells.
Water enters the cell.

Isotonic ­ There…

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Niki's Notes

Plasma - mostly water with dissolved nutrients, salts, hormones and proteins

Largely water
Contains fibrinogen, a substance vital for blood clotting
Contains a range of dissolve substances

Platelets ­ cell fragments involved in blood clotting

Tiny fragments of larger cells called megakaryocytes found in bone marrow


Page 9

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Niki's Notes

The vessels

They carry blood away from the heart
(except pulmonary artery)
Arteries near the heart have the most
elastic fibres to withstand high blood
Blood pressure in the arteries
decreases the further away it is from
the heart
The diameter of the lumen changes. It…

Page 10

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Niki's Notes

Gas exchange in the alveoli
Inhalation (active)

The muscles around the diaphragm contract and it is lowered and flattened.
The intercostals muscles between the ribs also contract, raising the rib cage upwards and
The volume of the chest cavity increases, reducing the pressure in the cavity.




Just wanted to say these notes are incredibly helpful as my textbook hasn't arrived so using your notes as a refresher from class. Really recommend them, Thank you!

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