Biochemistry: Cellular Respiration and Metabolism

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Questions and Answers

What is the primary function of transaminases in amino acid biosynthesis?

To transport amino acids across membranes

To synthesize glucose from amino acids

To remove amino groups from amino acids

To move amino groups between molecules (correct)

In which type of medium are the exact nutrient compositions known?

Complex medium

Defined medium (correct)

Differential medium

Selective medium

Why are animal pathogens often cultured in complex media?

They do not utilize simple carbon sources

They grow better in solid media than in liquid media

They require specific purified chemicals for growth

They have minimal biosynthetic capacity and need numerous nutrients (correct)

What is the role of ACP in fatty acid biosynthesis?

To serve as a carrier for building fatty acids Signup and view all the answers

What does selective media do?

Inhibits the growth of certain organisms while allowing others to thrive Signup and view all the answers

During binary fission, how is cell division characterized?

It leads to replication of DNA before division Signup and view all the answers

What characteristic is associated with liquid media?

Facilitates rapid and constant mixing for uniform conditions Signup and view all the answers

What is one advantage of using solid media for microbial growth?

It facilitates the counting of colony forming units (CFU) Signup and view all the answers

What is the primary product of glycolysis?

2 pyruvate Signup and view all the answers

What happens to NADH produced during glycolysis?

It is recycled through fermentation or respiration. Signup and view all the answers

In aerobic conditions, how much ATP is generated from one glucose molecule?

36-38 ATP Signup and view all the answers

Which molecule serves as the terminal electron acceptor in aerobic respiration?

Oxygen Signup and view all the answers

What is produced during fermentation under anaerobic conditions?

Ethanol and Lactate Signup and view all the answers

What is the role of ATP Synthase in cells?

To synthesize ATP using energy from proton movement Signup and view all the answers

Which of the following does NOT occur during glycolysis?

Formation of six carbon dioxide Signup and view all the answers

What mechanism allows cells that do not require oxygen to generate a proton motor force?

Reverse ATP synthesis Signup and view all the answers

What is the role of the divisome during cytokinesis?

It facilitates the formation of the septum. Signup and view all the answers

Which of the following is a disadvantage of direct count using a Petroff-Hausser counting chamber?

It cannot differentiate between live and dead cells. Signup and view all the answers

What is the statistical significance range for counting colonies on a plate?

30-300 colonies Signup and view all the answers

What does TMTC stand for in the context of colony counting?

Too Many To Count Signup and view all the answers

Which method allows for counting in lower concentrations of cells?

Viable Count Signup and view all the answers

What is a primary feature of the pour plate method?

It involves mixing the sample with agar before solidifying. Signup and view all the answers

Which of the following statements about cytokinesis is incorrect?

It does not involve the cell wall synthesis. Signup and view all the answers

What is the calculated concentration of bacteria if 159 colonies are counted from a total dilution of $10^{-3}$?

1.59 x $10^{6}$ CFU/mL Signup and view all the answers

How many cells will there be after 60 minutes if the initial population (N0) is 2 cells and the generation time (g) is 20 minutes?

16 cells Signup and view all the answers

In which phase does microbial growth occur at its maximum rate due to an abundance of nutrients?

Exponential Phase Signup and view all the answers

What method allows for continuous growth of cultures while mimicking low nutrient environments?

Chemostat Signup and view all the answers

What is the maximum temperature range for mesophiles?

15°C - 45°C Signup and view all the answers

Which type of organism can grow optimally at temperatures exceeding 80°C?

Hyperthermophile Signup and view all the answers

Which group of microorganisms can grow in environments with salt concentrations below 1%?

Nonhalophile Signup and view all the answers

What pH range do neutrophiles thrive in?

Between pH 6-8 Signup and view all the answers

What happens to bacterial growth when there is too little fresh media in a continuous culture?

Bacteria enters stationary or death phase Signup and view all the answers

What is the function of buffers in artificial mediums?

To maintain a constant pH Signup and view all the answers

Which of the following characteristics is typical of acidophiles?

Growth below pH 5 Signup and view all the answers

What is the primary function of the bacterial cell wall?

To protect cells from osmotic pressure Signup and view all the answers

Which component is not involved in the synthesis of peptidoglycan?

Ribosomes Signup and view all the answers

Which characteristic is unique to Gram-negative bacteria compared to Gram-positive bacteria?

Presence of two membranes Signup and view all the answers

What energy sources drive the active transport system for large proteins across the membrane?

ATP and PMF Signup and view all the answers

Which structure is specifically referred to as the peptidoglycan layer?

Cell wall Signup and view all the answers

What role do Penicillin-Binding Proteins (PBPs) play in bacterial cell wall synthesis?

Catalyzes glycosyl transferase and transpeptidase activities Signup and view all the answers

What links the peptide side chains in the peptidoglycan layer of Gram-negative bacteria?

Direct cross-linking Signup and view all the answers

In the context of microbial cell structure, the term 'cell envelope' encompasses which of the following?

All layers surrounding the cell including membranes Signup and view all the answers

Study Notes

Glycolysis Pathway

Glucose is broken down in a catabolic pathway that does not require oxygen
2 ATP are produced from substrate phosphorylation
Glucose is converted to pyruvate, NADH is produced

Recycling Reduced Coenzymes: Fermentation

Fermentation occurs in the absence of oxygen
Fermentation recycles reduced coenzymes: NADH
This process produces ethanol and lactate

Recycling Reduced Coenzymes: Respiration

Respiration requires oxygen.
2 Pyruvate are converted using cofactors to produce carbon dioxide, NADH, FADH, and GTP
The Citric Acid/Krebs/TCA cycle is part of respiration

Electron Transport Chain (ETC)

Oxidizes electron carriers NADH and FADH2
Protons are pumped across the membrane generating a proton motor force
Oxygen acts as the terminal electron acceptor

ATP Synthase

ATP is synthesized by the movement of protons down the gradient
This enzyme is called ATP Synthase
ATP Synthase is reversible

Anabolic Metabolism

Organisms can synthesize sugars, polysaccharides, amino acids, proteins, nucleotides, nucleic acids, fatty acids, and lipids
Gluconeogenesis produces glucose when it is not available
Transaminases move amino groups between molecules
ACP is a carrier for fatty acids

Microbial Division and Growth

Culture media is used to grow microbes

Defined Medium

Contains minimum nutrients for growth and is made with purified chemicals
The exact composition is known
Good for studying metabolism and physiology

Complex Medium

Composed of animal digests or plant products
Needed for microbes with unknown growth requirements

Growth Media

Selective media inhibits the growth of certain organisms while allowing others to grow
Differential media provides different visual appearances of colonies

Liquid Medium

Provides consistent conditions for microbes

Solid Medium

Used for isolating individual colonies

Bacterial Cell Division

Binary fission is the division of a cell

Binary Fission

Occurs in three steps: DNA replication and segregation, cytokinesis, synthesis of a new cell wall

Measuring Population Growth

Direct Count is done using a Petroff-Hausser counting chamber to count cells rapidly
Viable Count determines living cells by counting colonies after serially diluting a sample of cells

Growth Phases in Batch Culture

Lag Phase: The bacteria adapt to new conditions
Logarithmic (Log) Phase: Rapid growth and nutrient use
Stationary Phase: Growth slows down due to limited nutrients
Death Phase: Cells die due to lack of energy for maintenance

Growth in a Continuous Culture

Continuous cultures are used to grow microbes for an extended period of time
It is important to maintain adequate nutrient levels and control the growth rate

Factors Affecting Microbial Growth

Temperature
pH
Osmotic strength
Oxygen levels

Factors Affecting Microbial Growth: Temperature

Psychrophile: Growth in cold temperatures
Mesophile: Growth in moderate temperatures
Thermophile: Growth in hot temperatures
Hyperthermophile: Growth in very hot temperatures

Factors Affecting Microbial Growth: pH

Acidophile: Growth in acidic environments
Neutrophile: Growth in neutral pH environments
Alkalophile: Growth in alkaline environments

Factors Affecting Microbial Growth: Osmotic Strength

Nonhalophile: Cannot tolerate high salt concentrations
Halotolerant: Tolerate some salt concentrations
Halophile: Requires high salt concentrations
Extreme Halophile: Requires very high salt concentrations

Factors Affecting Microbial Growth: Oxygen Levels

Obligate Aerobe: Requires oxygen for growth
Facultative Anaerobe: Can grow with or without oxygen
Aerotolerant Anaerobe: Can tolerate oxygen but does not use it for growth
Obligate Anaerobe: Cannot tolerate oxygen
Microaerophile: Requires low oxygen levels

Cell Structure and Function Part 2

Transglycosylase: Forms glycan chains
Transpeptidase: Cross-links peptide side chains
Autolysins: Cut glycan chains for cell wall expansion
Bactoprenol: Lipid carrier for cell wall precursors
PBPs: Penicillin Binding Proteins catalyze the glycosyl transferase and transpeptidase activities

Bacterial Cell Wall Structures

Gram-positive bacteria: Have a thick peptidoglycan layer
Gram-negative bacteria: Have a thin layer of pepotidoglycan

Cell Wall Structures: Peptidoglycan

The cell wall is made up of interconnected glycan chains
The cell wall prevents the cell from lysing.
The cell wall provides the cell with a shape.
The cell wall is also called murein.

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Description

This quiz covers key concepts related to glycolysis, fermentation, respiration, the electron transport chain, and ATP synthesis. You will be tested on your understanding of these metabolic processes and their roles in energy production. Perfect for students studying biochemistry or cellular biology.