Biology SL Unit 1 - Biological Processes

Chemical equation of Photosynthesis

Chemical equation of Photosynthesis

6CO₂ + 6H₂O → C₆H₁₆O₆ + 6O₂

Chemical equation for Photolysis

2H₂O + photons → 4H⁺ + O₂ + 4e^–

What is the wavelength of green light

550-650 nm

absorption spectrum

At which wavelengths does photosynthesis occur the most?

400nm and 700nm

Where does light dependent reactions occur?

Thylakoids

Where does light independent reactions occur?

Stroma

Describe light dependent reaction

1. photolysis → split water to produce hydrogen ions and electrons (oxygen waste product)

2. chemiosmosis → h-ions go through ATP synthase to product ATP

3. electrons from photolysis used to pump h-ions against electrochemical gradient

Describe light independent reaction

Producing glucose from ATP and CO₂

1. carbon fixation

2. reduction of GP

3. regeneration of RuBP

What is the retention factor used for?

in chromatography to determine pigments present in sample

glucose + oxygen → carbon dioxide + water (+ATP)

aerobic respiration

glucose → lactate (+ATP)

anaerobic respiration

Where does aerobic respiration occur?

Cytoplasm and mitochondria

Where does anaerobic fermentation occur?

Cytoplasm

Describe aerobic respiration

can use all respiratory substrates, high ATP yield, CO2 and water waste products

What is respiratory substrate?

Any molecule that can be broken down in respiration to release energy

Describe anaerobic fermentation

carbohydrates only, low ATP yield, lactic acid waste product (ethanol in plants)

What is the respirometer experiment?

measuring oxygen consumption as indicator of respiration

State the stages of DNA Replication

1. Helicase breaks H-bonds between nitrogenous bases of DNA to unwind the double helix (forming a replication fork)

2. Primase starts the copy by adding DNA primers

3. DNA polymerase III binds to the primer and copies via complementary base pairing in the 5’ to 3’ direction. (Lagging strand needs many primers due to direction, creates okazaki fragments)

4. DNA polymerase I removes primers and replaces with new DNA

5. Ligase connects the fragments to form one DNA strand

Describe what ‘semi-conservative’ means:

The 2 new DNA strands created from replication each have one original strand (parent strand) and a copied one (daughter strand)

Describe the process of Transcription

1. RNA polymerase binds to DNA’s promoter and separates the two strands by breaking the h-bonds

2. RNA polymerase builds a strand of mRNA on the antisense strand via complementary base pairing (the mRNA strand is thus a copy of the sense strand)

3. Terminator sequence of DNA strand is reached and mRNA strand is released. RNA polymerase detaches, DNA winds back up

What is the importance of complimentary base pairing?

assures correct placement of bases to form correct code and message in DNA replication, transcription, and translation

Describe the process of Translation

1. Small ribosome subunit binds to mRNA at the start codon AUG

2. tRNA with complementary codons (anticodons) attaches to the start codon with amino acid methionine

3. Big ribosome subunit attaches to complex, has 3 binding sites A-P-E

4. Next tRNA attaches at A site, and peptide bond forms between the two amino acids. tRNA in P site then becomes uncharged, moving to E site

5. Polypeptide strand forms. Multiple ribosomes can read the mRNA at once

6. When stop codon reached, release factor binds to A site and releases the polypeptide chain. Ribosome subunits detach from mRNA. Polypeptide chain folds into 3D protein strucuture.

Somatic mutations are:

body cell mutations, are not inherited

Germline mutations are:

sex cell mutations, can be inherited

Name the three mutagen types and examples

Physical: UV, X-ray
Chemical: Cleaning products, processed food
Biological: Viruses, bacteria

What are mutagens?

agent that changes genetic material

What is a silent/neutral mutation?

no significant impact on an organism, same amino acid is still translated

What is a missense mutation?

a single amino acid change (substitution mutation)

What is a nonsense mutation?

a stop codon is created, and the whole protein stops being translated

What are frameshift mutations?

insertions and deletions

What is the effect of a frameshift mutation?

changes in the genetic code of ALL triplets following the mutation

What is polymerase chain reaction used for?

Amplify fragments of DNA and DNA replication

Describe the steps of PCR

1. Denaturation: DNA is heated to break H-bonds of double strands (98 deg)

2. Annealing: sample is then cooled down (60 deg) and short primers are bonded to complementary sequences in DNA sample

3. Extension: at 72 deg, Taq polymerase replicates DNA using primers as starting point

4. DNA is replicated, sample is heated, and process starts again.

Why is PCR used?

Each time a cycle occurs, the amount of DNA replicas doubles. This leads to exponential growth for gel electrophoresis

What is gel electrophoresis?

method used to separate DNA fragments by size

Describe the process of gel electrophoresis

1. DNA samples loaded into depressions start at the negative pole

2. an electrical current is used to move molecules through semisolid fluid (gel)

3. DNA molecules have negative charge and will move to the positive electrodes in the field

4. restriction endonucleases cuts the backbone of DNA at specific points to create shorter fragments

What is the application of DNA profiling?

• paternity tests

• forensic investigation

Examines portions of DNA to create a profile unique to the individual