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Biology A level


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[Front]


Monomer Definition
[Back]


- A single molecule - e.g glucose

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What is osmosis
A process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.
Monomer Definition
- A single molecule - e.g glucose
Whatis osmosis
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What is active transport
The movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration
Polymer Definition
- Many monomers bonded together - e.g starch
Cxzc
Cxzcd
Bdvs
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What is a buffer solution
- Organic substances that maintain a constant pH
Dsfsa
Fdsaf
Why is buffer solution used
- A change in pH will slow the reaction - Buffer solution keeps a constant pH
Fdsf
Fdsfds
Fdsf
Fdsfd
Fdsaf
Fafds
What is a peptide bond
- A chain of amino acids bonded together or just amino acids bonded together
What is hydroxylation
- Introducing hydroxyl into a compound - Oxidation reaction
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Dsad
Hydrolysis reactions
- Breaking bonds by the adding of water
Cdaca
Csacsa
Emulsion test
- Sample is obtained - crushing/grinding - Mixed with ethanol - Water is added - Forms emulsion - Turns cloudy, milky white if lipids are present
What monomer form starch molecules
- Alpha glucose (a - glucose)
What monomers form cellulose molecules
- Beta glucose (b - glucose)
Adaptations of cellulose
- Molecules attach, individual strands of cellulose, together to form rope-like structures - Hydrogen bonds strong in large numbers
Adaptations of starch
- Coils in a spiral shape and is compact so it takes little space in cell - good for storage - Insoluble - does not dissolve in cell
Condensation reactions
- The formation of bonds by the removal of water
How the structure of cellulose is linked to function
- The strength of the cellulose fibres and hydrogen bonds in cell wall maintains shape and rigidity
Hydrogen bonding
- An attraction between the negative and positive region of two polarised molecules
Difference between unsaturated and saturated fatty acids
- Unsaturated fatty acids contain at least one double bond in the fatty acid chain - Saturated fatty acids lack double bonds between carbon atoms
What is a glyosidic bond
- A condensation reaction between two monosaccharides
Monosaccharides
- One sugar
Disaccharides
- Two sugars
Polysaccharides
- Multiple sugars
Rewa
Rewa
What is a reducing sugar
- A sugar that can donate electrons to another molecule e.g. Benedict's reagent
Test for reducing sugars
- Food sample dissolved in water in test tube - Equal volume of Benedict's reagent added - Heated in water bath - If it turns orange-brown sugar is present
What is a non-reducing sugar
- A sugar that cannot donate electrons to another molecule - So it can't be detected with Benedict's reagent
Test for non-reducing sugars
- The non-reducing sugars must be broken down from disaccharides to monosaccharides - Add dilute hydrochloric acid - Heat in water bath - Neutralise it with sodium hydrogen carbonate (Benedict's reagent will not work in acidic conditions) - Heat it again with Benedict's reagent - If sugar is present turns orange-brown
Properties of monosaccharides
- Soluble - Sweet tasting
Examples of monosaccharides
- Glucose - Galactose - Fructose
Examples of disaccharides
- Maltose - Lactose - Sucrose
Properties of disaccharides
- Soluble - Sweet taste
Examples of polysaccharides
- Starch - Cellulose
What monomers make MALTOSE
- Glucose + glucose
Properties of polysaccharides
- Insoluble - Suitable for storage
What monomers make LACTOSE
- Glucose + galactose
What monomers make SUCROSE
- Glucose + fructose
Test for starch
- Add iodine - Turns blue-black if present
Describe the structure of glycogen
- Alpha glucose - Long, branched chains - Its compact - Has 1-4 glyosidic bonds
Adaptations of starch
- Coils in a spiral shape and is compact so it takes little space in cell - good for storage - Insoluble - doesn't affect water potential by osmosis - Chains may be branched or unbranched
Adaptations of cellulose
- Molecules attach together in parallel to form rope-like structures - forming microfibrils (made by fibres) - Hydrogen bonds strong in large numbers - Unbranched chains - Long straight chains
What monomers form cellulose molecules
- Beta glucose (b - glucose)
What monomer form starch molecules
- Alpha glucose (a - glucose)
How the structure of cellulose is linked to function
- The strength of the cellulose fibres and hydrogen bonds in cell wall maintains shape and rigidity
Adaptations of glycogen
- Insoluble - doesn't diffuse out of cells - Compact - suitable for storage - More branched than starch - more rapidly hydrolysed (broken down) by enzymes
Amylose
- a - glucose - Unbranched - 1,4 (carbon atoms) glycosidic bonds
Amylopectin
- a - glucose - Branched - 1,4 and some 1,6 glycosidic bonds
Difference in the structure of the starch molecule and the cellulose molecule
- Starch formed from α-glucose but cellulose formed from β-glucose - Position of hydrogen and hydroxyl groups on carbon atom 1 inverted
Describe how the molecules of cellulose are similar to molecules of starch
- Both insoluble - Both made up of glucose - Both contain glyosidic bonds
Hydrogen bonds are important in cellulose molecules. Explain why
- Holds chains together - Forms microfibrils, providing strength - Hydrogen bonds strong in large numbers
Describe the structure of glycogen
- a - glucose - Long, branched chains - Its compact - Has 1-4 glyosidic bonds
Difference between unsaturated and saturated fatty acids
- Unsaturated fatty acids contain at least one double bond in the hydrocarbon chain - Saturated fatty acids lack double bonds between carbon atoms - Saturated FA unable to accept more hydrogen
Emulsion test
- Sample is obtained - crushing/grinding - Mixed with ethanol - Water is added - Forms emulsion - Turns cloudy, milky white if lipids are present
Roles of lipids
- Energy - Insoluble - waterproofing - Insulation - fats are low conductors of heat - Protection - often stored
What is a triglyceride
- A group of lipids - They have three fatty acids combined with glycerol - Contains unsaturated fatty acid tails which are hydrophobic and insoluble
Mono-unsaturated meaning
- One double bond between carbon atoms
Poly-unsaturated meaning
- More than one double bond between carbon atoms
What are phospholipids
- A group of lipids - Made up of two fatty acids, a phosphate and a molecule of glyercol
Structure of a phospholipid
- The fatty acid molecules repel water (hydrophobic) - non polar tail - The phosphate molecules attract water (hydrophilic) - polar head
Fatty acids
- Carboxyl group - Attached to a long non-polar hydrocarbon chain (hydrophobic)
Structure of a triglyceride related to its function
- Lots of C-H bonds (stores energy) - Non-polar and insoluble (does not affect water potential)
Structure of phospholipids related to function
- Polar heads forms a bilayer in water - Water holds phospholipids in place - Can form glycolipids
Triglycerides have a hydrophobic tail. Explain how this feature of a lipid is important for its function.
- Hydrophobic tails force them to clump together as insoluble droplets - So they can be stored, as a source of energy - Without affecting water potential by osmosis
What is a peptide bond
- A condensation reaction between amino acids - bonding them together
What is a dipeptide
- Two amino acids bonded together
What is a polypeptide
- Multiple amino acids bonded together
What chemical groups are the central carbon atom in an amino acid attached to
- Amino group - Carboxyl - an acidic group - Hydrogen atom - R group
Polymerisation of amino acids meaning
- Many amino acids monomers joined together in a series of condensation reactions - Forming a polypeptide
The primary structure of proteins
- The sequence of amino acids in the polypeptide chain
The secondary structure of proteins
- Hydrogen bonds form between the amino acids in the chain - It either coils into an alpha helix or folds into a beta pleated sheet
Different bonds in the tertiary structure
- Disulfide bridges - strong not easily broken (sulfur-sulfur, covalent bonds), binds chains together - Ionic bonds - not involved in peptide bonds - weak - Hydrogen bonds - numerous but easily broken
The tertiary structure of proteins
- The chains are coiled or folded even further - More bonds form - Single polypeptide chained proteins form their final 3D structure at this point
The quaternary structure of proteins
- Some proteins are made of many polypeptide chains - These chains are assembled again - Forming their final 3D structure
Test for proteins
- Add sodium hydroxide solution - solution needs to be alkaline - Add copper sulfate solution - Turns purple if protein is present
Functions of proteins
- Enzymes - Antibodies - Transport proteins - Structural proteins
Types of proteins
- Fibrous proteins - Globular proteins
Fibrous proteins
- Insoluble - Structural - Many disulfide bridges - e.g collagen
Globular proteins
- Soluble - SPECIFIC 3D shape - Metabolism - e.g enzymes
How disulfide bridges provide strength
- Chemical bonds formed between sulphur-containing groups - Form stronger disulphide bonds - Binds chain to each other
Explain why differences in primary structure result in proteins with different properties
- Different sequences of amino acids - Means bonds in different places which gives a different tertiary structure (shape)
What are enzymes
- Biological catalysts - Speed up an reaction without changing themselves - can be reused - Globular proteins
Conditions that must be satisfied for reaction to take place
- Molecules must collide with sufficient energy to alter arrangement of atoms - activation energy - The free energy of the products must be less than the substrates
Activation energy meaning
- The minimum amount of energy required for reactions to take place