C5 Flashcards
(50 cards)
DNA is…
- Deoxyribonucleic acid
- Double-stranded molecule
Structure of DNA
Nucleotide Structure
Base pairs
Refer to: Student version - DNA Replication, Slides 11 and 12
Why is DNA Replication Considered Semi-Conservative?
Each new DNA molecule is made up of one old ‘conserved’ strand, and one new strand
What are the 4 Enzymes Involved in DNA replication?
Helicase - ‘unzips’ double-stranded DNA by breaking
hydrogen bonds
Primase - Builds starting Primer
DNA Polymerase - Forms new DNA strands
Ligase - connects segments to form one strand
Process of DNA replication + what enzymes: STEP 1
- Double-stranded DNA molecule is ‘unzipped’ into 2 stands
Enzyme: helicase
- breaks hydrogen bonds between base pairs to separate two strands
- There are now 2 template strands
Process of DNA replication + what enzymes: STEP 2
-Primer Binding
Enzyme: Primase
- synthesises a small RNA primer which acts as a kick-start the process
Process of DNA replication + what enzymes: STEP 3
Elongation
Enzyme: DNA polymerase
- attaches new bases to the 2 template strands
- is the enzyme responsible for synthesising the new strands of DNA as well as correcting any errors
Process of DNA replication + what enzymes: STEP 4
No name
Enzyme: Ligase
- Connects the DNA fragments that have been added
- Forms one continuous new strand
- Removes RNA primer
Enzyme Structure Diagram (should include)
Substrate: Molecule that binds to the enzyme’s active site
Active Site: Region on the enzyme where the substrate binds
Enzyme: Biological catalyst that speeds up chemical reactions
Allosteric site: Site on the enzyme where molecules can bind to change its activity
What is the active site?
Induced Fit Model?
The place on the enzyme’s surface that is complementary to its substrate.
Induced Fit Model: The enzyme’s active site slightly conforms to the shape of the substrate
What are Enzymes?
What do they do?
- Biological catalysts
- Requires less energy to start reactions (Activation Energy)
- Rate of reaction speeds up
- Enzyme remains unchanged after the reaction
De-naturing
Denatured proteins lose their shape and function
Denaturing can occur from changes in temperature and pH level
Proteins: 2 types
Globular proteins: proteins used for cellular processes, eg. enzymes
Structural Protein: proteins used for structure, eg. hair, nails
Anabolic vs Catabolic Reactions
Anabolic: building up reactions
- Bonds between substrates are formed to
produce product
Catabolic: Breaking down reactions
- Bonds between substrates are broken to
produce product
2 Types of Inhibitors + what do they do?
Competitive Inhibition: A molecule binds to the enzyme’s active site and prevents substrate from binding
Non-competitive Inhibition: A molecule binds to the allosteric site and causes a conformational change to the enzyme’s active site.
Co-factors and Co-enzymes
- Any non-protein chemical needed for an enzyme reaction to proceed
Organic molecules are called co-enzymes
Inorganic molecules are called co-factors
4 Factors Affecting Rate of Reaction With Enzymes
- Temperature
- pH level
- Enzyme concentration
- Substrate concentration
What is a Protein?
What do they do?
- A protein is a complex structure (polymer) composed
of amino acids, joined together by peptide bonds - They are responsible for virtually all functions in
organisms - The shape of a protein determines it’s function
Added helpful info (not needed for exam):
- The synthesis of proteins is determined by the
sequence of bases in a gene
- Each gene codes for a specific protein
Process of Protein Synthesis: Transcription
post transcription mod
Enzymes bind to DNA and unwind the double helix to expose the gene to be transcribed
- this is the template strand
The RNA polymerase moves along the gene, producing an mRNA strand
- Moves to ribosome for next stage
- Introns removed to create the mature strand
Process of Protein Synthesis: Translation
The mRNA exits the nucleus and docks onto a ribosome in the cytoplasm.
- ribosome contains a unit that reads (translates) each codon
- The translation starts when the ribosome reads the ‘start’ codon
- the tRNA brings the complimentary anticodon
- the tRNA carries the correct amino acids
- The amino acids bond via peptide bonds and form a polypeptide chain
Prokaryotic Gene Expression
What is the Lac Operon
How is it regulated
A group of genes with a single promoter that codes for the breakdown of lactose in E. coli bacteria
- The lac operon is regulated by the presence or absence of lactose
Gene Expression - Lac Operon (2 main components)
Promoter - the region of DNA where the RNA polymerase enzyme binds
- Gene regulation begins at the promoter
Operator - Segment of DNA between promoter and genes. Acts as a switch.
- When the repressor protein (Lac I) binds to the operator, it blocks transcription from occurring.
Genes Involved in Lactose Metabolism (3) + drawing
Lac Z: gene with code to make lactase (breaks down lactose)
Lac Y: increases membrane permeability
Lac A: Codes for a second enzyme that helps with the first enzyme
Refer to: Student Pro Gene expression and regulation - Slide 2 for drawing
Why is it Beneficial To Only Express Genes When They’re Needed?
- It saves energy for the other important cellular functions.
- prevents overproduction