Biology Quiz: Cellular Respiration and Fermentation

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Questions and Answers

What is the primary product of alcoholic fermentation?

Glucose

Lactic acid

Ethanol (correct)

NADH

Which structure is formed during the secondary structure of proteins?

Polypeptide strands

Active sites

Helix and pleated sheets (correct)

Quaternary structures

What is the role of oxygen in the electron transport chain?

It is the final electron acceptor. (correct)

It is converted into glucose.

It acts as an electron donor.

It serves as a substrate for ATP synthesis.

Which process occurs in the cytoplasm and does not require oxygen?

Fermentation Signup and view all the answers

What is the end product of lactic acid fermentation?

Lactic acid Signup and view all the answers

How many ATP are produced in total from one molecule of glucose during aerobic respiration?

38 Signup and view all the answers

What type of fermentation is carried out by Saccharomyces?

Alcoholic fermentation Signup and view all the answers

What is produced during the Krebs Cycle?

NADH and FADH Signup and view all the answers

What occurs during the Lag phase of bacterial growth?

Bacteria are preparing for growth but no increase in population is observed Signup and view all the answers

Which of the following terms describes organisms that require oxygen to grow?

Obligate aerobes Signup and view all the answers

What method is used to determine the number of bacteria per milliliter using colony counts?

Standard Plate Count Signup and view all the answers

Which type of bacteria thrive in extreme acidic environments?

Acidophiles Signup and view all the answers

What is an example of a nutrient source that bacteria commonly require?

Ammonia Signup and view all the answers

Which of the following is true of turbidimetric methods using a spectrophotometer?

It quantifies cloudiness but not specific cell counts. Signup and view all the answers

What is the primary focus of the Most Probable Number (MPN) method?

Estimating the concentration of bacteria in dilute samples Signup and view all the answers

What is the purpose of the streak plate method in bacterial culturing?

To isolate pure cultures of bacteria Signup and view all the answers

What is the role of DNA polymerase in DNA replication?

Synthesizes new complementary DNA Signup and view all the answers

Which statement correctly describes transcription?

It occurs in the nucleus and produces mRNA Signup and view all the answers

What is an Okazaki fragment?

Short DNA fragments synthesized on the lagging strand Signup and view all the answers

What type of mutation results in a premature stop codon during protein synthesis?

Nonsense Mutation Signup and view all the answers

How does RNA polymerase differ from DNA polymerase?

RNA polymerase uses uracil instead of thymine Signup and view all the answers

What is the primary function of transfer RNA (tRNA)?

To carry amino acids to the ribosome Signup and view all the answers

What occurs at the replication fork?

The DNA double helix unwinds Signup and view all the answers

Which type of mutation occurs spontaneously without a mutagen?

Spontaneous Mutation Signup and view all the answers

What do F plasmids primarily facilitate in bacterial cells?

Conjugation between donor and recipient cells Signup and view all the answers

Which of the following statements about F- cells is correct?

F- cells lack F plasmids. Signup and view all the answers

What is a primary function of transposons?

Enable segments of DNA to move within the genome Signup and view all the answers

Which type of plasmid carries genes that provide resistance to antibiotics?

Resistance plasmids Signup and view all the answers

How does an F+ cell contribute to the transformation of an F- cell?

It creates an F pilus to facilitate DNA transfer. Signup and view all the answers

What is the primary function of structural genes?

They encode proteins (enzymes). Signup and view all the answers

What happens to gene expression in the absence of lactose in an inducible operon?

The repressor protein binds to the promoter region. Signup and view all the answers

Which component is required to stop the synthesis of tryptophan in a repressible operon?

Active repressor protein Signup and view all the answers

What role does allolactose play in an inducible operon system?

It functions as an inducer preventing the repressor from binding. Signup and view all the answers

How does the presence of glucose affect the use of lactose as an energy source?

It delays the onset of lactose utilization. Signup and view all the answers

What process occurs when tryptophan levels are too high in the cell?

Tryptophan synthesis is repressed. Signup and view all the answers

What is catabolite repression?

The suppression of lactose metabolism when glucose is present. Signup and view all the answers

What is the effect of feedback inhibition in biochemical pathways?

It prevents substrate binding to the active site. Signup and view all the answers

Study Notes

Fermentation

Occurs in the absence of oxygen
Pyruvic acid is metabolized
Alcoholic Fermentation
- Performed by Saccharomyces (yeast)
- Produces: 2 ethanol + 2 CO2 + 2 ATP
- Used in beer production
Lactic Acid Fermentation
- Performed by Streptococcus, Lactobacillus, and Bacillus
- Produces: 2 lactate + 2 ATP
- Used in yogurt production

Krebs Cycle

Occurs in the presence of oxygen
Also known as the TCA cycle or citric acid cycle
Products:
- Oxygen (waste)
- NADH (electron carriers, major product)
- FADH
- ATP
- It is the pathway that pyruvate enters following glycolysis

Electron Transport Chain (ETC) in Bacteria

Occurs in the cell membrane
Oxygen is the final electron acceptor
Oxygen combines with hydrogen to form H2O (waste product)
Large amounts of ATP are produced (38-40 ATP)

Calculation of ATP Production

From 1 glucose molecule: 10 NADH + 2 FADH2 = 30 ATP + 4 ATP = 34 ATP

Oxidative Phosphorylation

The transfer of electrons from high energy to low energy states
With each transfer, energy in the form of ATP is captured
High energy states release energy, which is captured as ATP

Chemiosmosis

Conversion of ADP to ATP using the ATPase enzyme complex
Occurs in the cell membrane

Glycolosis

Occurs in the cytoplasm
Glucose is converted to pyruvate
Does not require oxygen
Produces 2 ATP
Breakdown of glucose and requires 2 ATP to start

Krebs Cycle

Occurs in the cytoplasm
Requires oxygen
Pyruvate is converted to NADH and FADH2 (electron carriers)
Produces 2 ATP

Electron Transport Chain

Occurs in the cell membrane
Requires oxygen
Produces ATP
Produces 34 ATP

Fermentation

Occurs in the cytoplasm and does not require oxygen
Lactic Acid Fermentation
- Pyruvate is converted into lactic acid
- Performed by Streptococcus, Lactobacillus, and Bacillus
Alcoholic Fermentation
- Pyruvate is converted into ethanol and CO2
- Performed by Saccharomyces (yeast)

Protein Structures

Peptide linkage: The formation of a peptide bond by removing H2O.
Primary Structure: A polypeptide strand consisting of a sequence of amino acids.
Secondary Structure: Alpha helix and pleated sheets.
Tertiary Structure: A folded structure that combines alpha helixes and pleated sheets.
Quarternary Structure: The combination of two or more polypeptide chains in folded states.

Binary Fission

Cell elongation and DNA replication occurs
Cell wall and plasma membrane begin to constrict
A cross-wall forms, separating the DNA copies
Cells separate
Mother cell produces two daughter cells
Daughter cells are exact replicas of the mother cell
Budding is another form of cell division where a small new cell develops at the surface of the parent cell.

4 Phases of Bacterial Growth

Lag: Preparing for growth, but no growth occurs yet
Log: Exponential growth, increasing population
Stationary: Growth and death of cells are equal
Death: No more nutrients, population declines

Measuring Bacterial Growth (Pure culture only)

Serial Dilution Method:
- A concentrated solution of bacteria culture is diluted by a series of 10 folds
- Colonies in the medium are counted.
- Example: Diluting a glass of juice with water.
Standard Plate Count:
- Culture is added to a medium and allowed to grow
- Colonies are counted

Other Methods

Direct Microscopic Counts: Use a counting chamber and can not distinguish dead from alive bacteria
**Most Probable Number (MPN): ** Used for measuring small amounts of microbes in water quality studies and can't do standard plate counts
Turbidity: A spectrophotometer is used to measure the cloudiness of a sample.

Factors Affecting Growth

pH
- Acidophiles: Extremophiles (not pathogenic), prefer acidic environments
- Neutrophiles: Prefer neutral pH
- Alkaliphiles: Prefer alkaline environments
Temperature
- Psychrophiles: -10-20°C
- Psychrotrophs: 0-30°C
- Mesophiles: 10-50°C (most active, our body temperature)
- Thermophiles: 40-71°C
- Hyperthermophiles: 65-110°C
Oxygen
- Obligate aerobe: Requires oxygen
- Facultative anaerobe: Can grow with or without oxygen
- Obligate anaerobe: Requires the absence of oxygen
Salinity/Salt:
Nutrients:
- Carbon: Ex) glucose
- Nitrogen: Ex) ammonia, amino acids
- Sulfur: Ex) sulfur amino acids
- Phosphorus: Ex) inorganic phosphate
- Trace elements: Very small amount, used as cofactors for enzymes (micronutrients)
- Vitamins: Small amounts, used as coenzymes

Culturing Bacteria

Streak Plate Method: Used to isolate a pure culture
Types of Media:

In DNA

Mutations cannot be fixed - permanent
Mutations will be copied repeatedly
Large mutations can be fatal

Transfer of Information

DNA -> RNA -> Protein
Replication: DNA polymerase: ATGC -> TACA (DNA to DNA)
Transcription: RNA polymerase: ATGC -> UACG (DNA to RNA)
Translation: mRNA, tRNA, rRNA: AUG/GCU/UAC/UGA = Met/Ala/Tyr/(stop) (RNA to protein)

Replication (DNA to DNA)

Leading Strand: Synthesized continuously
Lagging Strand: Synthesized discontinuously
Key enzymes:
- DNA polymerase: Synthesizes complementary DNA
- RNA polymerase: Synthesizes RNA primers
- Okazaki fragments: Short DNA fragments
- DNA ligase: Seals nicks in DNA during synthesis and repair
- Helicase: Unwinds the double strand of DNA
- Origin of replication: Location on the chromosome where DNA synthesis starts

Transcription: DNA to RNA

RNA polymerase is key enzyme
Uracil replaces Thymine: ATGC -> UACG

Transcription of RNA:

RNA polymerase binds with the promoter sequence and opens the DNA double helix.
Ribonucleotides (ATP, GTP, CTP, UTP) are assembled into RNA.
Ribonucleotides are inserted according to base pairing: G, C, A, U.
RNA synthesis proceeds in the 5' to 3’ direction until it reaches the termination sequence, releasing the RNA.

Types of RNA

Messenger RNA (mRNA): Translates to form a polypeptide
Transfer RNA (tRNA): Carries amino acids to the growing polypeptide
Ribosomal RNA (rRNA): Used in building ribosomes (machinery for synthesizing proteins)

Types of Mutations

Spontaneous Mutation: Occurs naturally in the absence of a mutagen
Mutagen: An agent that causes mutations
Base Substitution: A change in one base (point mutation)
Missense Mutation: Results in a change in the affected amino acid.
Nonsense Mutation: Results in a stop codon, shortening the protein coded by the gene.

Structural Genes

Code for proteins (enzymes)
Example: Represent the output (product) that is created.

Operon

Control region for structural genes: I P O Z Y A
Contains regulatory elements: promoter, operator, and genes

Constitutive Genes

Expressed at a fixed rate
Always "on"

Inducible Genes

Increase transcription of genes
"Turned up" when needed

Repressible Genes

Decrease transcription of genes
"Turned off" it there is too much product

Gene Expression - Inducible Operon: Lactose Metabolism

Example: lactose metabolism
Key elements:
- I - P - O - Z - Y - A
- I: Repressor gene
- P: Promoter
- O: Operator
- Z: β-galactosidase gene
- Y: Permease gene
- A: Transacetylase gene

Absence of Lactose

Repressor protein binds to the promoter region, blocking it
Prevents the enzyme needed for lactose metabolism from being produced

Presence of Lactose

Allolactose (inducer) binds to the repressor protein, inactivating it.
The repressor protein can no longer bind to the promoter region.
Allows for the production of the enzymes needed for lactose metabolism

Catabolite Repression

When all glucose is consumed, the microbe will start to use lactose as an energy source.

Gene Expression - Repressible Operon: Tryptophan Synthesis

Example: tryptophan synthesis.
Key elements:
- I - P - O - E - D - C - B - A
- I: Repressor gene
- P: Promoter
- O: Operator
- E, D, C, B, A: Genes for the enzymes in tryptophan synthesis.

Tryptophan Synthesis - Explanation

Tryptophan synthesis is on because the cell needs tryptophan to function.
When there is too much tryptophan it could be detrimental, therefore, the system needs to stop it.
An active repressor protein is used to repress the synthesis of tryptophan.

Feedback Inhibition

A type of non-competitive inhibition
The end product inhibits the first enzyme in the biosynthetic pathway
End product binds to the enzyme, distorting the active site and preventing it from binding to the substrate.
This stops the entire pathway.

Bacterial Conjugation

The transfer of genetic material from one cell to another.
It requires contact between the donor and recipient cells.
It transfers much larger quantities of DNA than transformation.
The transfer occurs in the form of plasmids (extra DNA) that provide benefits like antibiotic resistance.

F Plasmids (Fertility Plasmids)

Circular, double-stranded DNA molecules.
Types:
- F+ cells: Contain F plasmids and make an F pilus (sex pilus).
- F- cells: Lack F plasmids.
- F pilus: A conjugation pilus that bridges the donor and recipient cell.
  - The donor cell has the F plasmid (F+)
  - The recipient cell does not (F-)
  - F+ creates and attaches to the F pilus
  - F+ creates a copy of itself
  - The copy is sent to F-
  - F- becomes F+ because it now has the blueprint of the F plasmid

Types of Plasmids:

**F plasmids/ Fertility plasmids **
Resistance plasmids: Carry genes that provide resistance to antibiotics
Virulence plasmids: Carry genes that cause disease (toxin genes)
Tumor-inducing plasmids: Cause tumor formation in plants.
Some plasmids contain genes for catabolic enzymes.

Transposons

Jumping genes
Mobile genetic sequences
Can move from one location to another (transposition)
Contain transposase: An enzyme that allows the transposon to jump and often carries genes like antibiotic resistance.
Segments of DNA that can move within or between DNA molecules.
Contain insertion sequences used for cutting and resealing DNA (transposase).
Complex transposons carry other genes besides the transposase.

Transposon Example:

- ACTTACTG ATCAGTAAGT AT
- TGAATGACTA TA GTCATTCA
- Transposase gene
 - ACTTACTGAT ATCAGTAAGT 
- TGAATGACTA TAGTCATTCA
     - Inverted repeat, Tn5, kanamycin resistance, IS1, IS1

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Description

Test your knowledge on cellular respiration and fermentation processes with this quiz. Explore key concepts such as alcoholic fermentation, the Krebs Cycle, and the role of oxygen in energy production. Perfect for biology students looking to reinforce their understanding of these fundamental topics.