DNA and RNA Comparison Quiz

DNA vs RNA

• DNA is found in the cell nucleus and stores/transfers genetic info
• RNA is found in all parts of a cell and is involved in protein synthesis
• DNA is double-stranded, has deoxyribose sugar, bases C, G, A, T, and self-replicates
• RNA is single-stranded, has ribose sugar, bases C, G, A, U, and can't self-replicate

Purines vs Pyrimidines

• There are five nitrogenous bases in total
• Purines are double-ring structures (Guanine, Adenine)
• Pyrimidines are single-ring structures (Cytosine, Thymine, Uracil)
• Purines pair with pyrimidines (e.g., Guanine with Cytosine)

Nucleoside Formation

• The nitrogenous base is connected to the sugar at C1
• The sugar is differentiated from H and OH at C2
• The phosphate group attaches at C5

Structural Characteristics of DNA

• DNA is comprised of two anti-parallel polynucleotides
• One strand runs 5' to 3', the other 3' to 5'
• The sugar-phosphate backbone is on the outside
• The hydrophobic bases are on the inside

Base Pairing

• A pyrimidine always pairs with a purine
• A pairs with T (2 H-bonds), and G pairs with C (3 H-bonds)
• These base pairings are called Watson-Crick base pairs

Central Dogma

• Replication: identical copies of DNA are made
• Transcription: genetic messages are read and carried out of the nucleus to the ribosomes for protein synthesis
• Translation: genetic messages are decoded to make proteins

DNA Replication Steps

• Helicase unwinds and separates the DNA strands
• Primase adds RNA primers
• Polymerase III copies each strand
• Polymerase I replaces primers with DNA nucleotides
• Ligase seals up the DNA segments

RNA and Protein Synthesis

• Ribosomal RNA (rRNA) is part of the ribosome
• Transfer RNA (tRNA) carries amino acids to the ribosome
• Messenger RNA (mRNA) carries genetic info from DNA to the ribosome

Translation

• mRNA is translated to protein
• Codons (3 mRNA nucleotides) code for specific amino acids
• The order of codons determines the order of amino acids in a polypeptide chain
• Start codon (AUG) and stop codons (UAA, UAG, UGA)

Mutations

• Changes in DNA sequence at a particular gene locus
• Can be harmful, beneficial, or neutral
• Types include point mutations (silent, missense, nonsense) and frameshift mutations (deletion, duplication, inversion, translocation)

Lipids

• Organic compounds that are insoluble in water but soluble in non-polar solvents.
• Classified based on solubility not functional groups
• Contain fatty acids
• Examples of lipid classes include
  • fatty acids
  • triglycerides (triacylglycerols)
  • phospholipids
  • sphingolipids
  • steroids
  • waxes

Fatty Acids

• Members of carboxylic acids
• Hydrocarbon chain with one terminal carboxyl group (COOH).
• Saturated vs Unsaturated:
  • saturated: solid at room temperature, no double bonds
  • unsaturated: liquid at room temperature, one or more double bonds

Prostaglandins

• c20 fatty acid derivative
• Cyclopentane ring with oxygen-containing functional groups
• Involved in raising body temperature, inhibiting gastric secretions, increasing mucus secretion in stomach, altering water & electrolyte balance, and intensifying pain/inflammation responses.

Eicosanoids

• 20-carbon fatty acids
• Precursors are prostaglandins
• Include prostaglandins and leukotrienes

Essential fatty acids (EFAs)

• Animals cannot synthesize these on their own and it's crucial to consume them in their diet.

Cholesterol

• Major steroid in the body.
• Important component of cell membranes and precursor for other steroids (e.g., hormones and bile acids)
• Includes:
  • bile acids
  • hormones (sex hormones, adrenal cortical hormones)

Protein Structural Organization

• Primary, secondary, tertiary, and quaternary structures are levels of protein structure organisation.
• Proteins are formed from a chain of amino acids.

Amino Acids & Protein Organization

• Building blocks of proteins
• Vary by their side chains (R groups).
• Also categorized based on the polarity of the R group (neutral, acidic, basic) and whether they are essential (must consume them) or non-essential (body can synthesize).

Amino Acid Properties

• Amino acids are typically zwitterions (dipolar ions) at physiological pH, having both a positively charged amino group and a negatively charged carboxyl group.
• The side chain (R group) determines the specific chemical properties of each amino acid.

Isoelectric Point (pI)

• pH at which an amino acid solution has no net charge.

Sterochemistry of Amino Acids

• Amino acids have chiral (asymmetric) carbon centers, leading to stereoisomers.
• L-amino acids are predominant in proteins.

Models of Substrate-Enzyme Binding

• Lock and key, induced-fit (enzyme shape changes on substrate binding)

Enzyme Kinetics

• Measure the rate of enzyme-catalyzed reactions
• Km (Michaelis-Menten constant) reflects the enzyme's affinity for the substrate.

Enzyme Inhibition

• Competitive, non-competitive, and uncompetitive inhibition are all types of enzyme inhibition in which an enzyme is bound to its inhibitor.