Medical Biology: chapter 3

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Questions and Answers

What are the primary functions of the nucleolus within the nucleus?

Production of proteins using messenger RNA

Regulation of nuclear pore activity

Synthesis of ribosomal RNA (correct)

Packaging DNA for cell division

What is primarily responsible for the rigidity and shape of plant cells?

Cell membrane

Cellulose (correct)

Plasma proteins

Cytoplasm

What is the main structural feature shared by the inner and outer nuclear membranes?

They are fused at nuclear pore sites

They are both composed of a double phospholipid bilayer (correct)

They both contain ribosomal RNA

They are both made up of a single phospholipid layer

Which of the following structures is known for protecting cells from lysing in hypotonic solutions?

Cell wall Signup and view all the answers

Which statement accurately describes mitochondria in relation to cytoplasmic volume?

Mitochondria can account for up to 25% of the cytoplasmic volume Signup and view all the answers

What role does NADPH play in the context of oxidative stress in red blood cells?

Is essential for the activity of glutathione reductase Signup and view all the answers

Which characteristic distinguishes the nucleolus from other components in the nucleus?

It synthesizes ribosomal RNA Signup and view all the answers

Which pathway involves the transport of whole cells to lysosomes?

Phagocytic pathway Signup and view all the answers

What is the primary role of endosomes in cellular processes?

Sorting and delivering proteins Signup and view all the answers

Which type of endoplasmic reticulum is primarily involved in lipid synthesis?

Smooth endoplasmic reticulum Signup and view all the answers

What role does the nuclear envelope play in cellular function?

It encloses the nucleus and regulates material exchange Signup and view all the answers

What consequence may arise due to the peroxidation of membrane lipids in erythrocytes?

Weakened membrane leading to hemolysis Signup and view all the answers

What is the primary energy production process that occurs in mitochondria?

Oxidation of glucose and fatty acids Signup and view all the answers

Which protein is specifically associated with the endocytic pathway during membrane invagination?

Clathrin Signup and view all the answers

What is the primary function of ribosomes in a cell?

Conduct protein synthesis Signup and view all the answers

Which enzyme compartment is responsible for degrading proteins and nucleic acids?

Lysosomes Signup and view all the answers

Which feature of the nucleus is responsible for defining its structure?

The inner nuclear membrane Signup and view all the answers

How does the endoplasmic reticulum function analogously to a road system?

It transports synthesized proteins to various parts of the cell Signup and view all the answers

How do mitochondria relate to chloroplasts in terms of their functions?

Both organelles synthesize ATP Signup and view all the answers

What characterizes the autophagic pathway in cells?

Delivers worn-out organelles for degradation Signup and view all the answers

Which of these can trigger a hemolytic crisis in susceptible individuals?

Ingestion of certain medications Signup and view all the answers

How do cell membranes contribute to cellular functions apart from surrounding the cell?

Involved in cell signaling and adhesion Signup and view all the answers

Which component of the nucleus primarily contains regions of heterochromatin?

The area outside the nucleolus within the nucleus Signup and view all the answers

What components make up ribosomes?

RNA and proteins Signup and view all the answers

What is the role of a coated pit in endocytosis?

Initiates membrane invagination Signup and view all the answers

What distinguishes the late endosomes from early endosomes in cellular trafficking?

Stage in processing of engulfed materials Signup and view all the answers

What is the impact of glutathione peroxidase in red blood cells?

Destroys peroxides to prevent oxidative damage Signup and view all the answers

In cases of hemolytic anemia, what is a likely contributing factor?

Membrane lipid peroxidation Signup and view all the answers

Which of the following conditions is most frequently associated with hemolysis crisis?

Diabetic ketoacidosis Signup and view all the answers

What is the primary characteristic that differentiates the outer membrane of a mitochondrion from the inner membrane?

The outer membrane is more permeable than the inner membrane. Signup and view all the answers

During the process of apoptosis, what role does cytochrome c play?

It stimulates a biochemical cascade leading to cell death. Signup and view all the answers

What process do mitochondria utilize for self-replication?

Binary fission. Signup and view all the answers

Which of the following statements about mitochondrial DNA (mtDNA) is true?

mtDNA is more susceptible to mutations than nuclear DNA. Signup and view all the answers

What is a significant structural feature of the inner mitochondrial membrane that contributes to its function?

Extensive infoldings known as cristae. Signup and view all the answers

What is the major function of acetyl-CoA in relation to mitochondrial processes?

To deliver the acetyl group to the citric acid cycle. Signup and view all the answers

What is a primary mechanism for directing proteins synthesized on bound ribosomes to the endoplasmic reticulum (ER)?

Signal peptide recognition by the signal recognition particle (SRP) Signup and view all the answers

Which of the following statements about proteins synthesized on free ribosomes is accurate?

They remain in the cytosol unless tagged for specific organelles. Signup and view all the answers

In the process of glycosylation, which structure modifies proteins after they leave the ER?

Golgi complex Signup and view all the answers

Which type of secretion describes proteins that are constantly released from the cell?

Constitutive secretion Signup and view all the answers

For lysosomal enzymes, which modification occurs when they reach the Golgi complex?

Phosphorylation of mannose residues Signup and view all the answers

What is critical for a protein synthesized on a free ribosome to be directed to the mitochondria?

Presence of an N-terminal signal sequence Signup and view all the answers

Where do proteins synthesized on bound ribosomes first travel after leaving the ER?

Transport vesicles to Golgi complex Signup and view all the answers

What role does the signal receptor protein play in the targeting of proteins to the ER?

It recognizes and binds to the signal peptide. Signup and view all the answers

Which cellular process relies on transport vesicles for movement from the ER?

Trafficking to the Golgi complex Signup and view all the answers

What is the function of the trans Golgi network?

Sorting and dispatching proteins to their destinations Signup and view all the answers

Study Notes

The Nucleus

The nucleus is the largest organelle in animal cells.
It is surrounded by a double membrane called the nuclear envelope.
The nuclear envelope is composed of two phospholipid bilayers that contain different types of proteins.
The inner and outer nuclear membranes are fused at nuclear pores, which allow materials to pass between the nucleus and the cytosol.
The inner nuclear membrane defines the nucleus.
The outer nuclear membrane is continuous with the rough endoplasmic reticulum.

The Nucleolus

The nucleolus is a nuclear subcompartment where most of the cell's rRNA is synthesized.
It is not surrounded by a membrane.

Chromosomes

The nucleus is filled with chromatin, which is composed of DNA and proteins.
In dividing cells, the nucleus is the site of mRNA and tRNA synthesis.

Mitochondria

Mitochondria are surrounded by a double membrane and are responsible for generating ATP through the oxidation of glucose and fatty acids
Mitochondria are found in both plant and animal cells and are the site of cellular respiration.
Most eukaryotic cells contain many mitochondria, which can make up to 25% of the cell's cytoplasm.
Mitochondria are among the largest organelles, second only to the nucleus, vacuoles, and chloroplasts.
Mitochondria contain their own DNA.
The inner membrane of mitochondria is extensively folded to provide a large surface area for ATP synthesis.
Enzymes in the inner mitochondrial membrane and matrix carry out the terminal stages of sugar and lipid oxidation, which is coupled to ATP synthesis.

Cell Walls

Cell walls are mainly built of cellulose.
They determine cell shape and provide rigidity to cells.
Cell walls are much stronger than cell membranes and protect cells from lysing (exploding) in hypotonic solutions.

Membranes

Cell membranes surround cells and regulate the entrance and exit of substances, maintaining internal balance and contributing to cell signaling and adhesion.
Cell membranes protect the internal cell from external forces.

Endosomes

Endosomes internalize plasma-membrane proteins and soluble materials from the extracellular medium and sort them back to the membranes or to lysosomes for degradation.

The Endoplasmic Reticulum (ER)

There are two types of ER: smooth ER and rough ER.
Smooth ER synthesizes lipids and detoxifies certain hydrophobic compounds.
Rough ER functions in the synthesis, processing, and sorting of secreted proteins, lysosomal proteins, and certain membranes.
The ER makes up approximately half of all the membranous tissue of the cell and is the site of membrane and protein synthesis.

Ribosomes

Ribosomes are the site of protein synthesis.
They can be found free in the cytoplasm, attached to the rough endoplasmic reticulum, or associated with the nucleus.
They are not membrane-bound and are made of RNA and protein.
Ribosomes bring together RNA and amino acids to assemble proteins.

Trafficking of Proteins Synthesized on Bound or Free Ribosomes

Proteins synthesized on bound ribosomes are trafficked to the ER, Golgi complex, lysosomes, and can be secreted from the cell.
Proteins synthesized on free ribosomes remain in the cytosol, unless they contain a specific tag that directs them to the nucleus, mitochondria, or peroxisomes.

Lysosomal Enzymes

Lysosomal enzymes are glycosylated and modified in a specific way.
Mannose residues in their oligosaccharide chains are phosphorylated.

Mitochondria Membranes

Mitochondria have two membranes: an outer membrane and an inner membrane.
The outer membrane is highly permeable and composed of half lipid and half protein.
The inner membrane is much less permeable, composed of 20% lipid and 80% protein, and is extensively folded.

ATP

ATP is created in the mitochondria and used for energy by the cell.
It is the universal "currency" of chemical energy.
In animal and plant cells, most ATP is produced by large molecular machines located in mitochondria and chloroplasts.

Apoptosis

When apoptosis is stimulated, proapoptotic proteins insert into the mitochondrial membrane, forming pores.
Cytochrome c can then leave the intermembrane space of the mitochondria and enter the cytosol.
Cytochrome c in the cytosol stimulates a cascade of biochemical events that result in apoptotic death of the cell.

Mitochondria and Disease

Mutations or errors in mitochondrial genes can result in disease.
Most mitochondrial proteins are encoded by the genomic DNA of the cell's nucleus.

Mitochondria Replication

Mitochondria replicate or divide by fission, similar to bacteria.
Mitochondria are believed to have originated from bacteria that were engulfed by ancestral eukaryotic cells.
In most multicellular organisms, mitochondrial DNA (mtDNA) is maternally inherited.

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Description

Explore the intricate functions and structures of the nucleus and other cell organelles in this quiz. Discover the role of the nucleolus, chromatin, and mitochondria in cellular processes. Test your knowledge on cell biology and the essentials of cellular components.