Cellular Physiology and Communication

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Questions and Answers

What is produced during alcoholic fermentation?

Pyruvate and NADH

Ethanol and carbon dioxide (correct)

Ethanol and glucose

Lactic acid and oxygen

What is the primary function of fermentation?

To convert glucose into oxygen

To produce energy from sunlight

To reoxidize NADH for glycolysis to continue (correct)

To generate ATP at a higher rate than respiration

Where does photosynthesis occur in eukaryotic cells?

Chloroplasts (correct)

Nucleus

Cytoplasm

Mitochondria

What is produced during the light phase of photosynthesis?

ATP and NADPH Signup and view all the answers

Which pigment is primarily responsible for capturing light energy during photosynthesis?

Chlorophyll Signup and view all the answers

In the Calvin cycle, carbon dioxide is converted into which substance?

Glucose Signup and view all the answers

What type of enzymes play a crucial role in regulating metabolic activities?

Allosteric enzymes Signup and view all the answers

What byproduct is released during photosynthesis?

Oxygen Signup and view all the answers

What is the primary function of Na+ and K+ gradients in cells?

To maintain membrane potential and excitability Signup and view all the answers

Which type of junction is specifically designed to prevent the passage of materials between adjacent cells?

Tight junctions Signup and view all the answers

What type of reaction is characterized by the synthesis of complex molecules from simpler substances?

Anabolism Signup and view all the answers

Which of the following statements about cellular metabolism is accurate?

Catabolic reactions release energy and support anabolic processes. Signup and view all the answers

What is the primary role of gap junctions in cell communication?

To allow ion and small molecule transit Signup and view all the answers

Which component is essential for the formation of ATP?

Adenosine and three phosphate groups Signup and view all the answers

What is the connection found in plant cells that allows communication through cell walls?

Plasmodesmata Signup and view all the answers

Which of the following is characteristic of desmosomes?

They consist of a dense plaque connected to keratin fibers. Signup and view all the answers

What is the total number of ATP required to produce one molecule of glucose by fixing 6 CO₂?

18 ATP Signup and view all the answers

Which type of organisms utilize solar energy for organic production?

Photoautotrophs Signup and view all the answers

What process allows a prokaryotic cell to divide?

Binary fission Signup and view all the answers

What is the purpose of mitosis in eukaryotic cells?

Growth and renewal of tissues Signup and view all the answers

What do heterotrophic organisms require from their environment?

Organic molecules Signup and view all the answers

How does cell division differ between prokaryotes and eukaryotes?

Eukaryotes have complex division involving chromosomes Signup and view all the answers

What is the form of DNA found in prokaryotic cells?

Circular DNA Signup and view all the answers

What is produced through the process of meiosis in eukaryotes?

Reproductive cells Signup and view all the answers

What is the mode of inheritance for colour blindness?

X-linked recessive Signup and view all the answers

Which of the following disorders is inherited in an autosomal dominant pattern?

Huntington's disease Signup and view all the answers

Individuals with which genetic disorder are considered healthy carriers?

Albinism Signup and view all the answers

What characterizes achondroplasia?

Shortened bones leading to dwarfism Signup and view all the answers

Which of the following conditions results from the accumulation of phenylalanine in the bloodstream?

Phenylketonuria (PKU) Signup and view all the answers

What is the primary cause of alkaptonuria?

Disorder affecting the metabolism of tyrosine Signup and view all the answers

Which genetic disorder primarily affects skin, hair, and iris pigmentation?

Albinism Signup and view all the answers

What is unique about the leading strand during DNA replication?

It is synthesised continuously using a single primer. Signup and view all the answers

Which of the following is a likely symptom of galactosemia?

Lack of an enzyme converting galactose to glucose Signup and view all the answers

What are Okazaki fragments associated with during DNA replication?

Synthesis of the lagging strand. Signup and view all the answers

What function does DNA polymerase serve when it encounters an incorrect nucleotide?

It reverses direction to remove incorrect nucleotides. Signup and view all the answers

Which hypothesis was originally formulated by Beadle and Tatum?

One gene – one enzyme hypothesis. Signup and view all the answers

What modification was made to the 'one gene – one enzyme' hypothesis?

One gene – one protein. Signup and view all the answers

Which term is used to describe changes in genetic information of an organism?

Mutations. Signup and view all the answers

What do DNA repair nucleases do after DNA replication?

Identify and replace incorrect nucleotides. Signup and view all the answers

How are proteins related to genes according to the most current hypothesis?

Each gene codes for one polypeptide chain. Signup and view all the answers

Study Notes

Na+ and K+ Gradients
- The gradients of Na+ and K+ play a crucial role in maintaining cell membrane potential, regulating cell volume, and contributing to nerve and muscle cell excitability.
- These gradients are also involved in the transport of essential nutrients like sugars and amino acids.
Cell Communication
- Distant cells communicate indirectly through chemical messengers transported in the bloodstream.
Cells in close proximity can communicate directly through junctions.
Plant cells use plasmodesmata, channels connecting the cytoplasm of adjacent cells.
Animal cells have various types of junctions.
- Desmosomes: Anchoring junctions that provide tissue continuity and strength.
- Tight junctions: Seal spaces between cells, preventing material passage.
- Gap junctions: Contain protein complexes forming channels that allow the passage of ions and small molecules between cells.

Cellular Metabolism

Cellular metabolism encompasses reactions transforming matter and energy within cells.
Catabolism: Breakdown of complex molecules into simpler substances.
Anabolism: Synthesis of cellular components from simple compounds.
Catabolic reactions release energy, fueling cellular processes.
Anabolic reactions require energy, supplied by catabolic reactions through ATP.

ATP: The Energy Carrier

ATP is formed from adenosine linked to three phosphate groups.

Fermentation

In the absence of oxygen, cells undergo fermentation, a process using NADH to reduce pyruvate.
Alcoholic Fermentation: Pyruvate is transformed into ethanol and CO2.
Lactic Fermentation: Pyruvate is transformed into lactic acid.

Regulation of Metabolism

Allosteric enzymes play a critical role in regulating metabolic activities by binding to molecules at specific sites, acting as activators or inhibitors.

Photosynthesis

Plants and some prokaryotes perform photosynthesis, converting solar energy into chemical energy in the form of glucose.
Light energy is used for carbon fixation, the transformation of CO2 into glucose.
Photosynthesis involves the absorption of CO2 and H2O, producing glucose and releasing O2.
The key equation representing this process is: 6CO2 + 6H2O + energy → C6H12O6 + 6O2.
In eukaryotes, photosynthesis occurs in chloroplasts.
Chlorophyll and carotenoids capture light energy embedded in thylakoid membranes.
Two phases of photosynthesis:
- Light Phase: Occurs in thylakoids; light energy is converted into chemical energy (ATP and NADPH).
- Dark Phase: Occurs in the stroma; ATP and NADPH energy reduce CO2 to produce glucose via the Calvin cycle.

Autotrophic and Heterotrophic Organisms

Autotrophs: Produce organic substances from inorganic substances.
- Photoautotrophs: Use solar light as an energy source.
- Chemoautotrophs: Utilize energy from redox reactions.
Heterotrophs: Obtain organic molecules from the environment by feeding on autotrophs, heterotrophs, or organic substances.

Cell Division and Chromosomes

Cell division is the process of a cell giving rise to two daughter cells.
DNA duplicates before cell division, ensuring each daughter cell receives identical genetic information.
Cell division ensures equitable distribution of DNA, cytoplasm, and organelles.
Prokaryotes have a single DNA molecule, undergoing simple binary fission.
Eukaryotes have multiple DNA molecules in the form of chromosomes.
- Mitosis: Cell division ensuring the fair distribution of genetic material.
- Cytokinesis: Cell division ensuring the fair distribution of cytoplasmic material.
- Meiosis: Specialized cell division occurring in germ cells to form reproductive cells.

Cell Division in Prokaryotes

Prokaryotic cells contain a single circular DNA molecule located in the cytoplasm, associated with the plasma membrane at the mesosoma.
They divide by binary fission:
- DNA duplicates while the cell grows.
- The cell elongates, and the duplicated DNA molecules separate.
- The cell divides into two daughter cells, each containing a complete copy of the DNA molecule.

Chromosomes in Eukaryotes

Eukaryotic cells have multiple linear DNA molecules that are packaged into chromosomes during cell division.
Chromosomes consist of DNA tightly wound around proteins called histones.

DNA Replication

DNA replication occurs prior to cell division to ensure each daughter cell receives a complete copy of the genome.
The process is semi-conservative; each new DNA molecule consists of one original strand and one newly synthesized strand.
Replication proceeds in the 5' to 3' direction; one strand is synthesized continuously (leading strand), while the other is synthesized discontinuously in fragments (lagging strand).
DNA polymerase adds nucleotides to the growing chain and proofreads for errors.
DNA repair nucleases scan for and correct remaining errors.

The One Gene – One Enzyme Hypothesis

Beadle and Tatum demonstrated that mutations in genes result in the corresponding enzyme functioning abnormally.
They proposed the "one gene – one enzyme" hypothesis, stating that a specific gene is responsible for the synthesis of a specific enzyme.
Later modified to "one gene – one protein" and then "one gene – one polypeptide chain".

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Description

This quiz covers essential concepts in cellular physiology, focusing on Na+ and K+ gradients, cell communication methods, and cellular metabolism. Understand how these elements contribute to cell function and intercellular interactions. Test your knowledge on the mechanisms that sustain cellular health and communication.