Edexcel AS Biology unit 1 notes

writing in black is topic 1 and writing in blue is topic 2

this is very summarised and some things may not make sense, but readable and useful

If I have good feedback, I can do the same for AS chemistry and Statistics (S1)

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  • Created by: Cymbeline
  • Created on: 29-11-11 20:21
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Biology Notes
Surface area to volume ratio
Mass transport systems: have branching vessels, make sure of ideal substance direction and movement and have a medium.
Dipole: slight separation of charge between oxygen and hydrogen atoms.
There are weak bonds between many molecules, this gives water high surface tension
Water is amphoteric: can mop up h+ and oh- to maintain PH
Water can dissolve: ionic substances, polar substances (covalent) and non-polar to form colloids.
Emulsions: L+L, Suspensions: S+L
Cardiovascular system: carrying hormones, defence, even temp, carries away waste food, delivers food to cells.
Blood takes food from intestines to store and from storage to cells, carries excretion, carries hormones, acts as a buffer, maintains temp
Leucocytes either produce antibodies and antitoxins or engulf pathogens by phagocytosis
O2 from lungs diffuses in RBC, the cytoplasm keeping the gradient stable, some O2 is then diffused into tissue, this process of oxygen
disassociation gives a sigmoid curve.
Carbon dioxide diffuses into plasma, reacts with water with the catalyst carbonic anhydrase, forms carbonic acid which separates into hydrogen
and hydrogencarbonate ions. The haemoglobin acts as buffer, and with the hydrogen makes haemoglobinic acid, while the hydrogencarbonate
ions move out the plasma to allow chloride ions in, making the chloride shift
Serotonin minimises blood flow by contracting vessels while thromboplastin is an enzyme that converts fibrinogen into fibrin, forming a mesh and
prothrombin into thrombin with the help of calcium ions.
Double circulation system:

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Systemic: carries oxygenated blood from heart to cells, takes cell's deoxygenated blood back to heart
o pulmonary: carries deoxygenated blood from heart to lungs, takes lungs oxygenated blood to heart
The mass and pressure of blood is suited to the type of tube it is carried by, similar to roads.
Angiogenesis is formation of blood vessels, cancer cells stimulate this to produce activator molecules, this spreads the cancer to surrounding
epithelial cells, by stopping this and blocking blood supply it combats cancer.
Dr.…read more

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Veins oxygenated when -inferior and
Venules -pulmonary carries superior vena cava
Carries blood back from lungs to heart are the veins that
to heart from the -umbilical cord carries blood to
cells carries from heart.…read more

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The right side of the heart receives blood from the body and pumps it to the lungs. The left side is larger because it has to receive the blood form
the lungs and pump it around the whole body.
The blood from each side of the heart never mixes and the heart is made or unique non-fatiguing cardiac muscle.
The tricuspid valve has three flaps while the bicuspid valve has 2 flaps.
`LubDub' heartbeat sound, separation of 0.8s.…read more

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Atrial systole: when atria contracts together forcing blood into the ventricle
Ventricular systole: when the ventricle contracts and forces blood into the aorta and pulmonary artery
Diastole: between contractions when the heart relaxes and fills with blood
During diastole the semilunar valves are closed and the atrioventricular valves are open, the opposite goes for systole.…read more

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Blood pressure falls due to greater distance from pulsing heart, increased friction of narrow vessels and loss of fluid into the tissues.
Temporary changes in blood pressure such as exercise, cause arteries to constrict (narrow) or dilate (widen), but permanent changes in pressure
or flow rate can cause health issues.…read more



please do the same for as chem unit 1!

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