Biology Unit 1 - Enzymes and Digestion

  • Created by: FireDwarf
  • Created on: 03-09-13 20:09
Hetrogeneous group of substances
Composed of different types
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A compound which does not contain carbon, or if they do, they do not contain hydrogen
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Molecules with large numbers of atoms
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All the chemical reactions which occur in the cells
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Compound which contains carbon and usually hydrogen
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Molecule consisting of chains of repeating units
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Chemical breakdown of organic molecules with the release of energy
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Equation of Respiration?
Glucose + Oxygen ---> Carbon dioxide + water + energy
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What is photosynesis?
A process of chemical exchange where glucose is produced
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Equation of photosynthesis?
Carbon dioxide + water --> Glucose + oxygen
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What does catabolism mean?
Breakdown of larger molecules into smaller
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What does anabolism mean?
building of smaller molecules into larger?
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What does the Oesophagus do?
Transports food to the stomach, uses a cell wall to push the food down
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What enzymes do the salivary glands produce?
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What does the stomach do?
Churn and grind food via the stomach muscles - contains proteases
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When the food molecules are broken down by the churing of the stomach, what is it called and what is its texture?
chyme- semifluid gloop
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What does the small intestine do?
Absorbs nutrients into the blood stream via the villi
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What do we mean by nutrients?
monosaccharides, amino acids, glycerol and fatty acids
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Large intestine?
Absorbs excess water
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Releases all the enzymes into the small intestine
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Definition of Digestion
Large molecules are broken down (hydrolysed) by enzymes into smaller molecules which are then absorbed and used in the body (assimilated)
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What are the two stages of digestion?
Physical breakdown and chemical breakdown
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What is the scientific term for sugar?
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How does carbon help to form an organic molecule?
Carbons form bonds with each other easily which therefore allows it to act as a backbone and other atoms can be therefore bonded with it to form molecules (such as oxygen or hydrogen)
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What is the general formula for a monosaccharide?
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What number can n be?
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Formula for glucose? What is glucose?
C6h1206 Monosaccharide
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What is special about Monosaccharides and disaccharides?
They are reducing sugars, MONO are always, di are sometimes
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What is reduction?
Reduction is the process where electrons are given by the sugar to the other molecule (such as copper sulfate)
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What is another name for copper sulfate?
Benedicts reagent
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How do we complete the Benedict test?
- Add an amount of the sugar solution with Benedict solution and heat. Will produce a brick red precipitate if the reducing sugar is high in concentration
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What does the test prove?
It proves which sugars are reducing and therefore are either monosaccharides or disaccharides?
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What if it fails the test?
It is either a non-monomer/SOME disaccharide sugar or not a sugar, therefore we need to test if its a sugar
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What is the method for the test you preform on ones which fail the Benedict test?
You add the non-monomer into a test tube. You must first hydrolysis it by heating the solution with 2cm^3 of dilute Hydrochloric acid. This will hydrolyse it and break the bonds. You then have to neutrlise it with hydrogencarbonate solution
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Test with ph paper, then re-test the result using benedict. Because it is now a monomer, then it will be a positive result. This proves its a sugar.
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Summary of tests
Benedict test finds out if it is a monosaccharide or the special disaccharides. If it is neither of these, it will be negative result. You then conduct the acid test to find its a sugar, it becomes hydrolysed which causes it to become a monomer
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What is the process where two monosaccharides join together to form a Disaccharide?
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What is condensation?
Condensation is the act where two monosaccharides join together, causing a water molecule to be removed.
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What is a glcyosidic bond?
A glycosidic bond is a convalent bond which bonds a saccharide with another group ( eg two monosaccharides bonded together to form a disaccharide)
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What is the process where a disaccharide breaks into the two constructing monosaccharides?
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What is Hydrolysis?
Hydrolysis is the act where a water molecule is added to the disaccharide which, under the right conditions, will cause the glycosidic bond to break releasing two monosaccharides
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Glucose + Glucose =
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Gluocose + Fructose =
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Glucose + Galactose =
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Name some properties of polysacchardies
Large, insoluble and good storage molecules
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How can we break them down?
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What can they break down into?
Monosaccharide's and disaccharides
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Name some examples
Cellulose, Starch, glycogen
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Properties of Celluose
B glucose, parallel glucose chains with cross linking between chains, shultz solution (pale blue), Plants, cell wall, microfibres held by hydrogen bonds to form celluose fibres.
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Shape of starch molecule
chain in a tight coil with amylose and amylopetin, amylose (linear unbranched 80%) amylopetin (Branched structure)
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A glucose, Potassium iodide in iodine - blue/black, plants, starch grains in cytoplasm and chloroplasts, energy source
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A glucose, 1,6 bonded chain, animals, granuelles in cytoplasm, energy store
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What breaks down starch? What does this leave us with? What is broken?
Amylases- Disaccharides (Maltose) - Glycosidic bonds
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What hydrolyses Maltose? What into?
Maltase- Monosaccharide (alpha glucose)
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Where are the enzymes produced?
Amy lases- Pancrease and Salivary glands, Maltases- Lining of the intestine.
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What are proteins made of?
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Another term for amimo-acids?
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Describe the composition of the peptide
Made up of a carbolyxic group and an amino group.
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How do we form dipeptides?
The joining of two monopeptides via condensation (making of a seperate water molecule) therefore bonding the Carbon and Nitrogen atoms together from the seperate peptides forming a peptide bond and therefore a dipeptide
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Lots of peptides together?
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And therefore what are protiens made of?
Chains of polypeptides
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whats special about the monopeptide cysteine?
It contains a sulfur atom
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Why are there so many protiens?
a) There are 21 diffrent types of amino acids and therefore there are lots of combinations of amino acids we can put togther b) The order we put them in will change the shape and therefore the function and therefore make a diffrent protien.
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Conclusion of the post before
Therefore changing the order and the amino acids used will cause the sequenece to change and therefore change the shape and therefore the function. This is important becuse the shape of a protien is very important in its function
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What happens if a proteins shape changes?
It will preform its function less well, if at all.
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What is lactose?
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What digests Lactose?Where is it found?
Lactase ( an enzyme)- small intestine
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What does the enzyme do?
It hydrolyses the glycosidic bond and therefore breaks lactose into its constructing monosaccharides (glucose and galactose)
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What happens to lactase as we get older?
The enzyme quantity decreases as we get older because we rely less on milk
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What is lactose intolerance?
A condition where the sufferer does not produce enough lactase to hydrolyse all the disaccharide lactose into its monosaccharides therefore resulting in a gas build up in the large intestine.
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Flatulance, vommiting, bloating
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What do they lack? Alternatives?
Calcium, Vitamin D, Broccoli and vitamin D supplements
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What makes each protein unique?
The order of amino acids, the lengh of the chain and the amino acids used
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What makes each amino acids unique?
The "R" group
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What are the 4 diffrent structures of a protien?
Primary, secondary, Tertiary, quaternay
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What is the Primary based upon?
The sequence of amino acids in the polypeptide chain
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Why is there so many diffrent primary structures?
Due to there being a 20 naturally occuring amino acids and there being a almost limitness combination between them
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How is the primary structure determined?
By the genetic sequence of our DNA. (DNA and mRNA)
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What happens if our DNA changes?
if our DNA mutates or is changed, then the amino acid sequence may change, therefore affecting the primary structure, therefore effecting the shape, therefore stopping/liming its function
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How many chains of polypeptides make up a protein?
Any number, normally a large number of chains
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What does the secondary structure consist of?
C-O group negatively charge, H-N positively charged. This postive and negative charges cause them to be attracted to each other therefore causing it to fold into shapes such as alpha helixes or beta sheets
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How is an alpha helix formed?
When these attractions cause the chain to be pulled and twisted into a spiral shape
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How is a beta sheet formed?
When two chains run parallel to each other and then are linked via hydrogen bonds
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What determines which one it forms?
The sequence of amino acids decide this. Usually a mixture.
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Tertiary Structure- What is it?
The tertiary structure is the globular (3D) structure of a protien. It is formed when the alpha helixs and beta sheets fold even further.
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What bonds are formed to cause it to fold?
Disulphate, Ionic and hydrogen
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Strong and formed between sulphur atoms (eg:Cystiene)
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Formed between any of the -C=O and the +NH which are not involved in the pepside bonds. These are weaker then disulphate and can be broken via changes in PH
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Numerous by easilly broken
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Why is the teritary structure important?
Because the 3d shape makes each of the protiens unique. Because of this they can be easilly reconised and therefore can complete their unique function.
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Quaternary Stucture- How are they formed?
When a protien contains numerous individual polypeptide chains and also assosiated non-protien groups (prosthetic).
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Iron in the hame group in hameoglobin
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Test for protien?
Biuret test- add a equal amount of sodium hydroxide - add few drops of copper sulphate- should turn purple if positive, and remain blue if not
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What are enzymes made up of? What are they?
Amino acids therefore a protien
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What makes the enzyme specific to a catalyzing one reaction?
It is a protien and therefore has a specific tertiary structure which therefore creates a specific shaped active site which only fits one substrate (either via lock and key or induced fit) theories.
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Two theories?
Lock and key theory and the induced fit theory
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What is the lock and key theory?
The theory is in essence based upon the idea that the active site of the enzyme is the exact shape of the substrate. The subtract then fits into the active site, where the reaction occurs, and the substrat leaves the active site as the products
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What happens to the enzyme after it catalyzes a reaction?
The enzyme remains the same as it can be re-used
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Equation for the Lock and Key enzyme action?
Enzyme + Substrate ---> Enzyme-substrate complex ----> Enzyme + Products
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Support for this theory?
accounts for the enzyme being specific to a reaction (shape of active site), Substrate shape fits exaclly into the active site
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It suggests that the enzymes active site is fixed and rigid, like a lock. However, they found that when other molecules bound to the enzyme in places other then the active sites, it altered the enzymes shape via the molecule bonding and therefore
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What is a better model based on this?
The Induced fit model
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Why is it better?
Because it explains for when other molecules attach to the protien, not on the active site, that the enzyme activity can be effected and it also accounts that changes in the enzymes shape via these bindings may cause the AE to be lower
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What is the model about?
It agrees with the majority of what is stated in the lock and key. The enzyme is specific to a reaction and therefore its active site is specific to an enzyme. It states that the shape is more flexible and not 100% the same as the substract, but it
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molds around the substrat for the catayst process. So while its shape is close enough to cause the binding between the substrate and the enzyme, it must mold (like a glove)
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What factors effect the rate of enzyme controlled reactions?
Enzyme Conc, substrate Conc, Ph, Temperture, Presence of inhibitors, presence of cofactors
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How to measure the rate of enzyme related reactions?
Either via the amount of product produced or the removal of reactants/substrate
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What happens when the temp is increased on the reaction?
-Gives molecules more heat energy which makes them move around more. More likely to collide, more likely to form s-e complex. They also will colldie harder and increase likelyhood of a reaction
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BUT, increases in temperture will cause the atoms to vibrate more which will cause the hydrogen bonds to break in the terdiary structure to break and denature protien
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What happens in a normal reaction?
-More molecules of substrate- more collisions- more binding in the active sites- more product formed, less substrates. Hwoever, the rate decreases as its harder for the
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substrates to bind to the active sites as products get in the way. Theres also less substrate to bind and therefore slower rate of reaction. Eventually all S to P and therefore the rate declines.
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What is Ph?
Ph is the measurement of hydrogen ion concentration
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why does the ph effect the rate of enzyme action?
Can effect the charges of the amimo acids active sites. If the charges both become postive by the H+ ions then it can repel the substrate and vice versa with the Oh-
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In addition, changes in Ph can cause the hydrogen bonds to break and therefore effect the secondary and tertiary structure. which effects the structure and therefore the shape of the protien therefore changing the shape of the active site
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What are the two diffrent types of inhibitors?
Reverible and unreversible
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Examples of reversible inhibitors
Non-competitive and competitive
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What is a non-competitive inhibitor?
An inhibitor which does not bind to the active site but binds to the enzyme molecule in other areas.
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Due to the induced fit theory, this will cause the enzyme shape to change (as it is not rigid) which will cause the substrate to be unable to fit (incorrect shape) and therefore prevent substrate-enzyme complexs from being formed.
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Competitive Inhibitor
A molecule which competes with the substrate to bind to the active site. They occupy the AC and therefore prevent the ESC being formed. This decreases the rate of the enzyme. Increasing the conc of the enzyme or substrate will overcome this issue.
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Non-reversible inhibitor?
heavy metal ions (eg: Ag+ or Hg+) will cause the disulphate bonds to break and therefore effect the tertiary structure of the enzyme. This changes the tert sturct therefore the globular structure and therefore active sites shape.
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what is the benedicts test described as?
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Diffrent colours?
None, blue, very low, green, low yellow, medium brown, high red.
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What is the test for starch?
changes iodine in potassium-iodide from yellow to blue/black.
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