GRADE 9 NOTES AQA Biology GCSE Topic 2 Organisation

Topic 2: Organisation 12. Large intestine is where water is absorbed out of the food
Principles of Organisation into the bloodstream leaving semi-solid waste material 
 Cells - the basic building blocks of all living organisms faeces
 Tissue - a group of cells with a similar structure and function 13. Egestion  when these faeces pass out of the body
 Organs – a group of tissues performing specific functions through the anus
 Organisms – group of organs which work together to form
organisms Enzymes
Digestive Systems  Used to break down food in the gut into small, soluble
 Breaks down complex food substances molecules –-> so they can be absorbed through gut wall
 Provides the very large surface area for maximum absorption  Biological catalysts (a substance that speeds up reactions
of food without being used up)
 Parts:  Complimentary and specific to substrate
o Glands – salivary glands + pancreas – produces digestive  Protein molecules
juices containing enzymes to break down food  Lock & Key Theory:
o Mouth - Begins the digestion of carbohydrates o Enzyme binds to the substrate because the active
o Oesophagus - This muscular tube connects the mouth to side of the enzyme and the substrate are
the stomach complementary and specific are specific to each
o Stomach - Begins the digestion of protein; small molecules other
such as alcohol absorbed + also has HCl to kill bacteria + o The enzyme breaks down the substrate into its
has 3 tissues: products
o Muscular tissue moves the contents of the o The products are released & enzyme is not changed
stomach around during digestion and goes to bind with another one
o Glandular tissue produces digestive juices that  Conditions:
break down the stomach's contents o Optimum temperature & pH to work best
o Epithelial tissue lines the stomach o Optimum temperature = 37°C (body temperature)
o Duodenum – small intestine - Continues the digestion of  The rate of reaction increases with an
carbohydrate and protein; begins the digestion of lipids increase in temperature up to this
o Ileum – small Intestine - Completes the digestion of optimum
carbohydrates and proteins into single sugars and amino  Too cold  enzymes move to slowly 
acids; absorption of single sugars, amino acids and fatty reactions cannot occur fast enough
acids and glycerol  Too hot  enzymes denature (bonds in
o Large intestine - Absorption of water; egestion of structure break & active site changes
undigested food shape & can’t fit with substrate) 
o Liver – produces bile stored in gall bladder to help digest cannot work anymore
lipids o Optimum pH usually ph7 (neutral for amylase)
 Process  Some that are produced in acidic
1. Food is mechanically digested in the mouth by teeth conditions (like pepsin in stomach pH 1-5-
2. Amylase is released by salivary glands to break down 2) have a lower optimum pH
starch (carbohydrates) into simple sugars in the mouth  If the pH is too high or too low, the forces
(chemical digestion) that hold the amino acid chains that
3. Food is pushed down the oesophagus into the stomach make up the protein will be affected
through waves of muscle contractions – peristalsis  Changes shape of active site  enzyme
4. The food is churned and broken down by the stomach can no longer work
muscles
5. Pepsin is released into the stomach to break down Digestive Enzymes
proteins  Convert food into small soluble molecules that can be
6. Lipase is released into the stomach to break down fats absorbed into the bloodstream
7. Bile is released in the stomach (stored in the gall bladder +  The products of digestion are used to build new
made in the liver) – to neutralise the HCl as bile is alkaline carbohydrates, lipids and proteins. Some glucose is used in
and to emulsify fats respiration
Emulsify fats = breaks down large drops of fat into smaller  Carbohydrates  carbohydrase  simple sugars
ones  larger surface area allows lipase to chemically o E.g. Amylase – a carbohydrase that breaks down
break down the lipid into glycerol and fatty acids faster starch (carbohydrates) into simple sugars
8. Chyme (contents of stomach) emptied into the small o Starch  amylase  glucose
intestine o Found in mouth & small intestine
9. The small intestine is where digested food is absorbed   Protein  Protease  Amino Acids
has a large internal surface area (due to finger-like o E.g. pepsin in stomach
projections called villi) for absorption to happen quickly o Other forms of protease in small intestine
and efficiently o Produced in pancreas
10. Carbohydrase breaks down starch into sugar molecules +  Lipids  Lipase  3 fatty acids + 1 glycerol (molecule)
protease breaks down protein into amino acids + lipase o Produced in pancreas
breaks down lipids into fatty acids & glycerol in the small o Found in small intestine
intestine  Bile is not an enzyme – it is an emulsifier
11. Water + bacteria (living and dead) + cells from the lining of o Made in the liver
the gut + indigestible substances - such as cellulose from o Stored in the gall bladder
plant cell walls  left in the small intestine after nutrients o Alkaline to neutralise hydrochloric acid from the
are removed are moved into the large intestine stomach
o Emulsifies fat to form small droplets  increases
the surface area

, o The alkaline conditions and large surface area  o Oxygenated blood enters pulmonary vein  left atrium
increase the rate of fat breakdown by lipase  (through valve)  left ventricle  up through aorta
 Afterwards:  to body
o Soluble glucose, amino acids, fatty acids and  Structure
glycerol pass into the bloodstream to be carried to o Cardiac muscle walls – strong heartbeat
all the cells around the body o Muscular wall of the left ventricle is thicker blood
o Used to build new carbohydrates, lipids and needs to be pumped all around the body rather than just
proteins, with some glucose being used in to the lung like the right ventricle  more force needed
respiration o 4 chambers to separate deoxygenated + oxygenated
blood
Required practical activity 4: use qualitative reagents to test for o Valves ensure that blood does not flow backwards
a range of carbohydrates, lipids and proteins. (FOOD TESTS) o Coronary arteries cover the heart to provide its own
Required practical activity 5: investigate the effect of pH on the oxygenated blood supply
rate of reaction of amylase enzyme.  Heart Rate
Circulatory System o Resting = around 70bpm
 Double circulatory system: Passes through the heart twice o Controlled by a group of cells found in the right atrium
o Blood gets oxygenated at lungs and goes to heart that act as a pacemaker
(pulmonary veinaorta) & then to body o Provide stimulation through small electrical impulses
o Used in body and becomes deoxygenated which pass as a wave across the heart muscle  causing
o Deoxygenated blood goes to heart and back to lungs to it to contract
become oxygenated o Without this, the heart would not pump fast enough to
o E.g. humans deliver the required amount of oxygen to the whole body
o If not working correctly  artificial pacemaker can be
used = electrical devices used to correct irregularities in
the heart rate
 Blood vessels
o Arteries
 Carry blood away from the heart (oxygenated blood
apart from pulmonary artery)
 Helps vessels withstand high pressure blood created
by pumping of heart
 Have thick muscular and elastic walls (with fibres to
let it stretch) to withstand high pressure pumping
 Narrow lumen (The channel in the blood vessel that
carries blood)
 A type of supporting tissue called connective tissue
provides strength
o Veins
 Single circulatory system: - Passes through the heart once  Carry blood towards the heart (deoxygenated blood,
o Blood gets oxygenated at lungs except for the pulmonary vein)
o Goes straight to body and is used and become  Lumen is wide – allows low pressure blood to flow
deoxygenated through
o Goes through heart to gills to lungs to become  Valves  ensure blood flows in the right direction
oxygenated again  Have thin walls - have less muscular tissue than
o E.g. fish arteries
Heart  Have less connective tissue than arteries
 Organ in circulatory system o Capillaries
 Carry blood close to the cells
 Allow blood to flow very close to cells  enable
substances to move between them (diffusion)
 One cell thick walls  short diffusion path
 Permeable wall  substances can move across
 Very small, only allows blood to pass through one cell
at a time
 Functions:
 Oxygen diffuses through the capillary wall  into
the tissue fluid  the cells
 Carbon dioxide diffuses from the cells  into the
tissue fluid  across the capillary walls  into
the blood plasma
 Glucose diffuses from the blood plasma  across
the capillary walls to the tissue fluid then to the
cells
 The waste product urea diffuses from the cells of
 Process: the liver  to the tissue fluid across the capillary
o Deoxygenated blood enters vena cava  right atrium  walls into the blood plasma
atrium contracts forcing blood into ventricles  (through  The rate of blood flow is = volume of blood/number of
valve)  right ventricle  up through pulmonary artery minutes
 lungs to get oxygenation