AS biology unit 1

Everything you need to know in a small space :D


Causes of disease

Pathogens-Single-celled organisms that cause disease

To be classed as a pathgoen they:

  • Gain entry to the host,
  • colonise the tissues of the host,
  • resist the defences of the host
  • Cause damage to the host tissue

They enter by:

  • Gas exchange system- e.g tuberculosis, influenza.
  • Digestive system- e.g cholera, typhoid.

Data and disease- correlations- effect of one variable on the other (causal relationships)

Lifestyle and health- smoking- lung cancer and emphysemia

Lifestyle choices effecting health- smoking, diet (low fat/high fat), obesity, physical activity and sunlight (skin cancer)

Coronary heart disease (CHC)- reduce risk by: not smoking, ovoid obesity, reducing salt intake, reduce saturated fats and cholesterol, excercise, minimise acohol consumptions.

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Enzymes and the digestive system


Disgestive system summarised-

  • oesophagus- food-stomach, made of thick muscular wall
  • stomach- muscular sac- inner layer produces enzymes- digests food especiall enymes- mucusto stop digestion of self.
  • Small intestine- enzymes produced in walls- (contains villi for large surface area-faster obsorbtion)
  • Large intestine- asorbs water-food becomes drier
  • rectum- faeces stored, then comes out :D
  • salivary glands- mouth- enymes amylase (starch into maltose)
  • Pancreas- secretes protease, lipase and amylase.

Two type of digestion chemical and physical.

Large molecules- each seperate molecule is called a monomer, repeating chain polymer. (monosaccharide and dissacharide)

CHEMICAL TESTS!!!!! i personally have difficulty remebering this.

Reducing sugars- Benedicts test- (good way to remeber this is by shouting to yourself "DAM BENEDICT REDUCED MY SUGAR!!!") this test involves: 2cm3 food sample (liquid form)- equal volume of benedicts-heat. Results-different colours (red high)


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Enzymes and the digestive system continued

Carbohydrates- dissacharides examples are as follows:

  • Glucose+Glucose= Maltose
  • Glucose+Fructose= Sucrose
  • Glucose+Galactose=Lactose

Join by condensation reaction, loses water (think of condensation as inside car windcreen and it fogs up (water) if you catch my drift) This forms a GLYCOSIDIC BOND!!

Hydrolisis is the oppisite of condensation as it uses water to break it :D

Test for non-reducing sugars- benedicts tests

TEST FOR STARCH!!!! iodine- if it turns back it contains starch :D



  • food taken into mouth-chewed by teeth
  • `saliva containing amylase-hydrolysis starch into maltose
  • swallowed and enters stomach-acidic-denatured the amylase and further hyrolysises starch.
  • enters small intestine-gets mixed with the pancreatic juice that hydrolysises any starch into maltose.
  • muscles in intestine wall push food along- epithelial lining produces maltase (hydrolysises the maltose)

DISACCHARIDE DIGESTION- sucrose-sucrase, lactose-lactase.

Lactose intolerance- dont produce lactase-stays in large intestine-produces diarrhoea.

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Enzymes and the digestive system continued


AMINO ACIDS- structure-amino groups, carboxyl group, hydrogen atom and an r-group

peptide bond- created from condensation reaction

Primary structure of proteins- condensation reactions- amino acid monomers join together (polymerisation).

Sendonary structure- possess both -NH and -C=O groups which have different charges, this forms a weak bond called a hydrogen bond, This causes it to be twisted into a double helix shape.

Tertiary structure:

  • disulfide bonds- strong
  • ionic bonds- weaker than above, easily broken by changes in PH
  • Hydrogen bonds- numerous and easily broken

Test for proteins! biuret test detects peptide links.

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Enzymes action

Biological catalysts

Enzymes have active sites- from this substrate is able to make an enzyme substrate complex.

lock and key model- specific shape that operates as a single lock.

limitation is that it suggests that an enzyme is a rigid model but enymes have been shown to adapt to fit the substrate in able to make the enzyme substrate complex.

Induced fit model-modified version of the lock and key modelas it explains how other molecules can effect enzyme activity and how the activation energy is lowered.

Factors effecting enzyme action

  • temperature-deforms active site lowers enzyme action
  • PH break hydrogen bonds in enzyme deforms active site substrate can no longer fit (denatured)
  • substrate concentration- more substare the quicker the reaction until the amount of enzyme becomes the limiting factor.

Enzyme inhibition

competitive inhibitors-occupy the active site of the enzyme in COMPETITION with the substrate for the active site. (imagine two different teams the substrates and the competitive inhibitors fighting for the same spot of the active site)

NON- competitive inhibitors deform the active site by attaching to the enymes other site that isnt the active site so the substrate cant combine with the enyme and form the enzyme substrate complex. (so the substrate is like ahhh i cant get in)

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Cells and movement in andout of them!!!!!!

magnification=size of image/size of object

and size of object=size of image/maginification

This can all be put into a triangle of... image

object maginifaction

So object is image/manginification...image=object*magnification...maginifcation=image/object

CELL FRACTIONATION- cells broken up into different organelles


  • cold-reduce enzyme activity
  • isotonic- to prevent organelles bursting or shrinking
  • buffer-maintains PH

Homogenation-cells broken up by blender (honmogeniser) and is then filteredto remove any whole cells

Ultercentrifugation- put in a spinny thing and the heavy stuff goesw to the end and lighter stuff at the top,organelles weigh different and so are seperated into different groups.

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Electron microscopes!!!

light microscopes poor resolution, but has colour.

Electron smaller wavelength and so higher rosultion

The transmission electron microscope (TEM)- must be in vacuum and so living organisms cant be used- staining process so image is only black and white- must be extrememly thing (like a cell thick which is incredably thin) and can only do a 2-D image

The scanning electron microscope (the better one) 3D image produced as electrons go on surface of specimen- lower resolution than TEM but ten times better than light microscope.

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Structure of the epithelial cell

The nucleus:

  • nucler enevlope- double membrane surrounding the nucleus- endoplasmic rectilium on outer layer- it control the entry and exits of material and contains the reacrtions taking place (i think of this like im sending a letter and the letter is the nucleus and the envelope is selfexplanitary and you contain what goes in your letter as its what your sending :P)
  • Nuclear pores: allows passges of large molecules
  • Nucleoplasm- jelly stuff makes up bulk of nucleus
  • Chromatin- DNA found in the nucleoplasm
  • Nucleolous- manfactures ribosomal RNA and assembles ribosomes


  • double membrane surrounds it- outer one cntrols the entry and exit of material- inner one is the cristae
  • Cristae- increases the surface area in the cell- provide area for enymes to attach to carryout respiration
  • Matrix- matertial containing protein, lipids and traces of DNA thsat allows mitochondrian to controlthe production of their own enzymes.

Endoplasmic rectilium (weird weird word biologists never comeup with simple stuff)

  • RER Rough endoplasmic (weird word) has ribosomes. Function are: to provide a large surface area for synthesis of proteins and to transport materials.
  • SER Smooth endoplasmic (weird word) so ribosomes and is therefore smooooooth. Its fuctions areto sythesise, store and transport lipids and carbohydrates.
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Structure of the epithelial cell continued...

Golgi appartus: transports and modifies proteinsm, is basically transport system.

Lysosomes: these: breakdown material like whiteblood cells and cells after they have died; release enymes to destroy things outside of the cell.

Ribosomes: carry out protein sythesis

Microvilli: increase the surface area to increase the rate of absorbtion.

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LIPIDS!!!! good ol' fat

lipids: contain carbon hydrogen and oxygen, insoluble in water but soluble in organic solvents.

Role: energy source, waterproofing, insulation, protection.

saturated-no double bonds between carbons

Mono-unsaturated- one double bond between carbons

Polyunsaturated- more than one double bonds between carbon atoms

Phospholipids- hydrophilic head-iinteracts with water hates fat, hydrophilic tail hates the water loves the fat

test for lipids- emulsion test- ethanol added to dissove the fat (think woo drink is a weight loss program) and if the solution becomes foggy then it contains fat

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everything for unit 1 on one page?! thanks but is there any more to this? :)

Ashley Rogers


little more added im doing it bit by bit :P just pacing myself :P



fair enough :) they're quite good so thanks,
ps. the exam is next tuesday ;) hehe

Ashley Rogers


ill get right to it :P

Ashley Rogers


dam i just typed up loads sand forgot to save it ahhhh!!!



your doing so well!! :D

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