ms topic 1

• amylose has a helical structure and 1-4 glycosidic bonds
• cellulose molecules are

  ~ straight

  ~ have many hydrogen bonds that hold molecules together

  ~ strong to prevent cell lysis / resist turgor pressure

  ~ polar nature of glucose allows water/minerals to diffuse through
• calcium pectate is found in the middle lamellae and holds together cell walls, and does not prevent the movement of water
• glycogen structure

  ~ joined by 1-4 glycosidic bonds and 1-6 glycosidic bonds -> branched for rapid hydrolysis

  ~ compact for energy storage

  ~ large insoluble molecule -> does not affect osmosis
• glycogen releases energy slower than glucose as it is a polysaccharide which needs the glycosidic bonds to be broken first
• phospholipids in a membrane are

  ~ arranged in a bilayer

  ~ with hydrophilic/polar heads along the outside as they can interact with the aqueous environment

  ~ and hydrophobic/non - polar tails within the membrane as the phospholipids repel water/water repels phospholipids
• fibrous vs globular

  ~ fibrous proteins has little tertiary structure unlike globular

  ~ fibrous proteins are insoluble in water whilst globular proteins are semi - soluble ( as they form colloids)

  ~ fibrous proteins are made of long polypeptide chains whereas globular proteins are folded into a globular shape
• a tertiary structure is the 3 dimensional folding of a protein, held together by bonds between r- groups
• translation process /4

  ~ mRNA attached to ribosome

  ~ tRNA is attached to specific amino acid

  ~ tRNA anticodon binds to mRNA codon

  ~ peptide bond between the amino acids

  ~ continues until stop codon
• three enzymes involved in DNA replication

  ~ DNA polymerase -> forms phosphodiester bonds to connect the complementary free nucleotides

  ~ DNA ligase -> joins fragments of DNA via phosphodiester bonds

  ~ DNA helicase -> separates the two strands of DNA
• why would different DNA sequences be more different than the amino acid sequence

  ~ more tripelet codes than there are amino acids

  ~ therefore code is degenerate

  ~ the same amino acids might have different codes

  ~ this helps maintain the same structure of the protein
• DNA ligase joins sections of DNA together/repairs breaks in the phosphodiester backbone by forming phosphodiester bonds between a phosphate group and a deoxyribose
• a ribosome is composed of protein and RNA, made of two sub units
• role of ribosomes in protein synthesis

  ~ in translation

  ~ holds the tRNA onto the mRNA

  ~ whilst peptide bonds form to join adjacent amino acids together
• transcription process /2

  ~ DNA strands separates by DNA helicase

  ~ antisense/template strand used as template

  ~ RNA polymerase synthesises mRNA