bio e2

What goes into and comes out of PSII?

IN: H₂O + light.

OUT: O₂, electrons, H⁺.

What does Photosystem I (PSI) help produce?

NADPH by transferring electrons to NADP⁺.

How does ATP synthase make ATP?

Uses the H⁺ gradient to turn ADP + Pi into ATP.

What does the Calvin cycle use and produce?

USES: CO₂, ATP, NADPH.

MAKES: G3P (sugar precursor), ADP + Pi, NADP⁺.

How much ATP and NADPH are needed for 1 net G3P?

9 ATP + 6 NADPH + 3 CO₂. Two net G3P can make one glucose.

If NADPH decreases but ATP stays normal, why does sugar decrease?

The Calvin cycle needs NADPH to make G3P. Think PSI/NADPH production.

Where does O₂ come from, and what happens to CO₂?

O₂ comes from H₂O. CO₂ carbon gains electrons (is reduced) to make sugar.

What happens if H⁺ pumping decreases but electron transport continues?

ATP decreases, but NADPH can stay normal.

What happens when acetyl-CoA enters the citric acid cycle?

2C acetyl group + 4C oxaloacetate = 6C citrate.

What is the difference between mRNA, tRNA, and ribosomes?

mRNA = codons.

tRNA = anticodons + amino acids.

Ribosome = makes peptide bonds.

What starts and stops translation?

START = AUG.

STOP = UAA, UAG, UGA.

How do you identify a defective enzyme in a metabolic pathway?

Find the earliest compound that restores growth. The blocked step comes before it.

What is an operon?

Multiple genes controlled together by shared regulatory sequences.

What's the difference between exons and introns?

Exons = kept in mature RNA. Introns = removed.

What are the four main mutation types?

Silent =

Missense =

Nonsense =

Frameshift =

Silent = same amino acid.

Missense = different amino acid.

Nonsense = early STOP → shortened protein

Frameshift = insertion/deletion shifts the reading frame

What's the difference between leading and lagging strands?

Leading = continuous, toward fork. Lagging = short pieces, away from fork.

What does telomerase do?

Extends chromosome ends to help prevent shortening during DNA replication.

What are the three steps of PCR in order?

Heat to separate DNA → Cool so primers bind → DNA polymerase extends.

Which direction must PCR primers point?

Their 3′ ends must point TOWARD each other on opposite strands.

How do you design forward and reverse PCR primers?

Forward = copy the beginning of the target

Reverse = reverse complement of its end.

How do you calculate PCR product length?

Count from the outer edge of one primer to the outer edge of the other, INCLUDING primers.

How do you calculate DNA copies after PCR?

Final = starting copies × 2ⁿ. To find starting copies, divide final by 2ⁿ.

What does a fluorescent ddNTP do in Sanger sequencing?

Stops DNA synthesis and labels the final added base.

If ONLY fluorescent ddGTP is used, which bands appear?

One for each possible G added AFTER the primer (opposite C on the template).

How do you read a traditional Sanger gel, and what makes a good primer?

Read bottom → top (5′ → 3′). Primer binds uniquely outside the target and extends toward it.

How do you calculate the number of possible codons?

Number of bases raised to the number of positions.

Example: 3 bases and 4 positions = 3⁴ = 81.

What happens if a mutation prevents transcription proteins from recognizing a promoter?

Transcription decreases → less mRNA → fewer proteins.

How do you convert coding vs. template DNA into mRNA?

CODING = COPY (just change T → U)

TEMPLATE = COMPLEMENT (A→U, T→A, C→G, G→C)

During transcription, RNA forms base-pairs with the _________ strand. The new RNA has the same polarity and nucleotide sequence (with Us instead of Ts) as the __________ strand.

During transcription, RNA forms base-pairs with the non-template (coding) strand. The new RNA has the same polarity and nucleotide sequence (with Us instead of Ts) as the template strand.

Which DNA strand does RNA polymerase read, and in what direction is RNA made?

Template DNA: Read 3′ → 5′

mRNA: Made 5′ → 3′

Coding DNA: Matches mRNA (except T → U).