DNA/RNA

Macromolecules

Carbohydrate

• Function: Short-term energy storage

• Monomer: Monosaccharide (single sugar)

• Polymer: Polysaccharide (many sugars)

• Elements: Carbon, Hydrogen, Oxygen

Lipid

• Function: Long-term energy storage, insulation, protection

• Monomer: Glycerol (head) + Fatty acid (tail)

• Polymer: Lipids (triglyceride, phospholipids, oils, etc.)

• Elements: Carbon, Hydrogen, Oxygen

Nucleic Acids

• Function: Store genetic info for protein synthesis

• Key Elements: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus (CHONP)

• Monomer: Nucleotide

• Polymer: Nucleic Acid

• Example: DNA, RNA

Proteins

• Function: Control reactions, build bon + muscle, transport substances

• Key Elements: Carbon, Hydrogen, Oxygen, Nitrogen

• Monomer: Amino acids

• Polymer: Proteins- held together by peptide bonds

Example: Enzymes, hemoglobin, cell identifiers, anti bodies

Chemical Reactions

What is a Chemical Reaction?

Interactions between molecules/chemicals where bonds are formed and/or broken

Parts of a Chemical Reaction

• Reactant: What goes “in” or reacts

• Product: What comes “out” or is produced

Energy in Reactions

Endothermic

• Product = more energy than reactants

• Absorbs energy from surroundings

• Building polymers

• Surrounding temperature

• Example: Ice melting

Exothermic

• Product = less energy than reactants

• Releases energy from surroundings

• Digesting polymers

• Surrounding temperature decreases

Example: Burning wood

Activation Energy

• Our bodies require a lot of energy to occur in cells

• The energy needed for a chemical reaction to start

Most of the body’s energy is lost as heat (Exothermic)

Enzymes

What are Enzymes

• Proteins and biological catalysts

• Speed up chemical reactions by lowering activation energy

Enzymes lower activation energy

Anatomy of an Enzyme

Enzyme

Protein that is a biological catalyst

Active Site

Where the enzyme and substrate come together

Substrate

A reactant that the enzyme acts on (there can be more than one)

Enzymes and Substrates

• Enzymes work only with specific substrate (reactants) that fit in the enzyme’s active site

• Enzymes and Substrates have an induced fit together

When the enzyme and substrate have combined, it is called the Enzyme-Substrate Complex

Five Features of an Enzyme

1. Enzymes end in “-ase” (ex. DNA Helicase)

2. Speed up reactions (catalysts)

3. Reactions do not change or use up enzyme molecules

4. The same enzyme can work forward of backward reactions (build + break molecules)

5. Each enzyme has specific shape and binds a specific substrate

DNA Structure

What is DNA?

• DNA is the material that makes up out chromosomes and stores our genetic information. All organisms contain DNA.

  • Instructions for cells

  • DNA= deoxyribonucleic acid

  • double helix structure (twisted ladder)

• Nucleotides are building blocks of DNA

  Nucleotides

• Nucleotides are composed of three main parts:

  • a phosphate group

  • a 5-carbon sugar (deoxyribose in DNA).

a nitrogen-containing base

Purines

• Nitrogen Bases: Adenine and Guanine

• Ring Structure: double rings

Pyrimidines:

• Nitrogen Bases: Cytosine and Thymine

• Ring Structure: single rings

The sequence or order of nitrogenous bases contains the genetic “code”. But since your chromosomes contain millions of nucleotides, there are many different combinations possible with those four letters.

Discovery of DNA

Scientists credited with discovery

1. J. Watson

2. F. Crick

3. Rosalind Franklin

Base Pairing - Chargaff’s Rules

• Complementary base pairs:

  • Adenine (A) - Thymine (T)

  • Cytosine (C) - Guanine (G)

• Base pairs held together by hydrogen bonds

  • 2 bonds between A-T

3 bonds between G-C

DNA Supercoiling

• DNA is found in the nucleus of eukaryotic cells.

• In your cells you have roughly 2 meters (m) of DNA inside the nucleus. You can fit this much DNA into your cells by supercoiling.

  Steps of Supercoiling

1. DNA wraps around proteins called histone to make a nucleosome

2. Nucleosomes coil together

Coiled strands of chromatin fiber coil together to create chromosomes. (Condensed DNA)

DNA Replication

DNA Replication Steps

1. The enzyme DNA helicase breaks the hydrogen bonds between the nitrogenous bases to unwind the DNA helix.

2. Using the single DNA strands as a template, DNA polymerase reads the original strands and builds a new strand by adding complementary base pairs.

The new sets of nucleotides join to form 2 new DNA molecules, each with one old and one new strand

Accuracy of Replication

Only about 1 in a billion base pairs are paired incorrectly.

What usually happens when mistakes are made during replication?

• DNA molecule can correct itself

Mutations= mistakes that cannot be corrected.

Mutations

Types

• Beneficial: help survival

• Harmful: harm organism

Silent/ Neutral: No effect; most common

Categories of Mutations: Genes

• Gene mutations affect only one gene in a DNA sequence

Point mutations occur at a single nucleotide (base) poing in the DNA

Types of Point Mutation

• Substitution: One base changes to another base

• Insertion: Base added, bases shift down the line

Deletion: Base removed, bases shift up the line

Categories of Mutations: Chromosomal

• Chromosomal mutations affect entire sections of DNA.

Causes more changes than a point mutation

Types of Chromosomal Mutation

• Deletion: A segment is removed

• Duplication: A gene segment is repeated

• Inversion: One segment is inverted/reversed

• Translocation: DNA segments are swapped between chromosomes

RNA

What is RNA?

• RNA is a type of nucleic acid that is used to produce proteins for the cell.

  • Ribonucleic acid

  • Monomer= nucleotide

    • phosphate group

    • sugar= ribose

  • nitrogen base

Comparing DNA vs RNA

DNA

• Double strand

• Sugar: deoxyribose

• Contains thymine

• Stays in nucleus

• One type

RNA

• Single strand

• Sugar: ribose

• Contains uracil

• Leaves nucleus

• Types: mRNA, tRNA, rRNA

Types of RNA

• There are 3 different types of RNA.

• Each type serves a different purpose in the production of proteins

Messenger RNA (mRNA)

• Location: Nucleus, Cytoplasm, and Ribosome

• Single, uncoiled strand

• Makes a copy of a DNA

Transfer RNA (tRNA)

• Location: Cytoplasm and Ribosome

• A single strand, in “t” shape

• Carries amino acids to the ribosome

Ribosomal RNA (rRNA)

• Location: Ribosome

• Globular form with a large and small subunit (top and bottom)

Builds proteins

Protein Synthesis

• Protein synthesis is the process of creating a protein from the instructions found in a DNA molecule

• There are 2 major processes: transcription and translation

Transcription

What is transcription?

• Process of making an mRNA copy of a strand of DNA

• Location: Nucleus

• RNA base pairs: Adenine-Uracil and Guanine-Cytosine

• Uracil replaces Thymine in mRNA

Steps in Transcription

1. The enzyme RNA polymerase unzips/unwinds the complementary strands of DNA into two strands

2. RNA nucleotides bond to the strand of DNA. Pairing up with complementary bases.

3. The finished mRNA strand is released and the two DNA strands rezip. The mRNA leaves the nucleus

mRNA Processing

• Before mRNA goes on to the next step in making a protein, it is processed; Enzymes remove unnecessary sections of mRNA.

• Introns are removes

• Exons are sections that stay and will be translated as proteins

Translation

What is translation?

• The process of using RNA to assemble amino acids into proteins or polypeptide chains

• Location: Ribosome

Steps in Translation

1. mRNA attaches to the ribosome (rRNA)

2. rRNA (ribosome) reads off the codon one at a time

3. tRNA transports amino acids to the ribosome based on codon

   This is called the anticodon: the bases on the tRNA that line up with the codon on the mRNA

4. Amino acids form peptide bonds and form a strand called a polypeptide (this is also called a protein)

5. rRNA continues to read codons on mRNA until stop codon is reached and ends the process. The finished protein is then released.