biological molecules

• monosaccharides

  -monomers of larger carbohydrate molecules

  alpha glucose= OH group on bottom

  beta=OH group on top
• Disaccharides

  -carbohydrates formed of two monosaccharides

  glucose+glucose= maltose

  glucose+fructose=sucrose

  glucose+glactose=lactose
• polysaccharides

  -carbohydrates formed from two or more monosaccharides
• starch

  • energy store in plants
  • polymer of alpha glucose
  • consists of amylose and amylopectin
• cellulose

  • formed from beta glucose
  • hydrogen bonds form between molecules (microfibrils)
  • unable to coil or form branches
  • forms strong insoluble fibres
• amylose

  • alpha glucose joined by 1,4 glycosidic bonds
  • compact, less stable than alpha glucose
  • twists to form a helix with hydrogen bonds
• glycogen

  • energy store in animals and fungi
  • built up/broken down easily
• amylopectin

  • 1,6 glycosidic bonds
  • more branches makes it compact
  • insoluble in water
• esterification

  glycerol+3 fatty acids=triglycerides+3H2O

  • condensation forms ester bond
  • glycerol contains hydroxyl group (OH)
  • fatty acids contain carboxyl group (-COOH)
• phospholipids

  • contains 1 phosphate head attached to a glycerol molecule with 2 fatty acid tails
  • tail- hydrophobic
  • head- hydrophilic
• sterols

  • complex alcohol molecule based on 4 carbon ring structure with OH group at one end

  cholesterol- adds to stability and regulates fluidity (keep at low temp)
• roles of lipids

  • membrane formation
  • hormone production
  • thermal insulation
  • buoyancy
  • protects organs
• saturated triglycerides

  -no double bonds between carbon atoms
• monounsaturated- one double bond between carbon atoms

  polyunsaturated- more than one double bond between carbon atoms

  • the presence of a double bond causes the molecule to kink
  • they therefore cannot pack together as tightly making them a liquid at room temperature (oils)
• characteristics of water

  • high boiling point
  • ice less dense than water
  • ice floats (bonds far apart)
  • moves as one mass (cohesive)
  • adhesive
• importance of water

  • adhesion and cohesion allow capillary action to take place
  • buffers temperature change- prevents enzymes denaturing
  • acts as a solvent- transports dissolved compounds in and out of cells
  • water freezes over lakes- creates an insulating layer for organisms
• proteins

  two amino acids- dipeptide

  two or more amino acids- polypeptides
• primary structure

  • sequence of amino acids determined by DNA
  • held together by DNA
• secondary structure

  • hydrogen bonds form between NH and CO groups
  • hydrogen bonds form within the amino acid chain, pulling it into a coil shape (alpha helix)
  • or
  • polypeptide chains can lie parallel to one another (joined by hydrogen bonds) to form beta pleated sheets
• tertiary structure

  -interactions can form between R-groups

  • hydrophilic and hydrophobic
  • hydrogen bonds
  • ionic bonds
  • disulfide bonds
• quaternary structure

  • hydrophobic and hydrophilic
  • ionic bonds
  • disulfide bonds
  • hydrogen bonds
• globular proteins

  • compact
  • water soluble
  • roughly spherical in shape

  insulin

  • hormone transported in the blood stream (must be soluble)
• conjugated proteins

  • contains prosthetic group

  haemoglobin

  • contains prosthetic haem group

  catalase

  • contains 4 haem prosthetic groups
• fibrous proteins

  • formed from long insoluble molecules due to presence of amino acids with R-groups
  • organised structures

  keratin

  • few strong disulfide bonds so that hair is flexible

  elastin

  • found in elastic fibers to allow flexibility in vessels

  collagen

  • allows flexibility in tendons and ligaments
• testing for starch

  chemical used- iodine

  positive result

  • blue/black
  • iodine ion fits into helix molecule of amylose
• testing for lipids (emulsion test)

  1. sample suspended in alcohol
  2. liquid decanted into water
  3. ethanol falls out the solution giving a cloudy white emulsion
• testing for reducing sugars

  chemical used- benedicts reagent

  positive result

  • reducing sugars donates electrons to cu2+ ions
  • precipitate left behind
• testing for non-reducing sugars

  chemical used- heat with hydrochloric acid then add benedicts reagent

  positive result

  • brick red
  • hydrolysed in reducing reducing sugar
  • electron donation can occur so precipitate forms
• condensation reaction

  1. water molecule released
  2. new covalent bond formed
  3. polymer formed
• hydrolysis reaction

  1. water molecule added
  2. covalent bond broken
  3. monomer formed
• nucleotides

  • joined together by condensation reaction
  • 5th carbon reacts with OH group of 3rd carbon
  • phosphodiester bond formed
  • long strong sugar phosphate backbone is formed
  • contains a phosphate, nitrogenous base, deoxyribose sugar
• double helix

  • two coiled polynucleotides
  • held together by hydrogen bonds between bases
  • each strand has a phosphate group one end and a hydroxyll group at the other end
• pyrimidies

  • thymine
  • cytosine
  • smaller
  • single carbon rings

  purines

  • adenine
  • guanine
  • larger
  • double carbon rings
  • uracil (RNA)
  • pyrimidies always bond with a purine as it maintains a constant distance between the DNA backbone
• bases

  adenine and thymine (2 hydrogen bonds)

  cytosine and guanine (3 hydrogen bonds)
• DNA replication and the genetic code

  DNA helicase- enzyme breaks hydrogen bonds between complimentary base pairs

  DNA polymerase- enzyme catalyses the formation of phosphodiester bonds between nucleotides

  semi conservative- half new DNA, half original DNA
• protein synthesis

  transcription- copying sections of DNA and transporting it to the ribosome

  translation- complimentary code is decoded into amino acid sequences
• types of RNA

  mRNA- carries the instructions from the nucleus to the ribosome

  rRNA- located in the ribosome, maintains the structural stability during the synthesis process

  tRNA- forms the anticodon (ensures the correct amino acids are brought together in a sequence)
• ATP uses

  • synthesis
  • transport
  • movement
• RNA

  • phosphate, ribose sugar and nitrogenous base

  bases

  • adenine and uracil (2 hydrogen bonds)
  • cytosine and guanine (3 hydrogen bonds)

  ribonucleic acid

  single short strand of RNA, able to leave the nucleus of the cell and travel to the ribosome

  • information is then used for protein synthesis
• replication errors

  • incorrect sequence may occur in the newly copied sense strand
  • this leads to a change in sequence (mutation)