Cell Biology: Nucleus and Endoplasmic Reticulum

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Questions and Answers

What is the main function of the smooth ER?

DNA replication

Cell division

Protein synthesis

Lipid synthesis (correct)

Which of the following is NOT a function of the rough ER?

Protein folding

Protein synthesis

Lipid synthesis (correct)

Glycosylation

What is the role of the nuclear envelope's inner layer?

Protein folding

Interaction with chromatin (correct)

Ribosome synthesis

DNA replication

Which type of chromatin is more active in transcription?

Euchromatin (B) Signup and view all the answers

What is the primary role of the Golgi apparatus?

Packaging and modification of molecules (C) Signup and view all the answers

What is the function of CYP450 enzymes found in the smooth ER?

Detoxification (D) Signup and view all the answers

Which of these is a type of glycosylation that occurs exclusively in the Golgi apparatus?

O-type glycosylation (A) Signup and view all the answers

What is the function of nuclear pores?

Transport of molecules in and out of the nucleus (C) Signup and view all the answers

Which of the following organelles is responsible for breaking down worn-out cellular components?

Lysosomes (A) Signup and view all the answers

Which of the following statements accurately describes the role of cholesterol in the cell membrane?

Cholesterol increases the fluidity of the membrane at low temperatures. (B), Cholesterol helps to maintain the rigidity of the membrane. (C) Signup and view all the answers

Which of the following structures is involved in the movement of cilia and flagella?

Microtubules (A) Signup and view all the answers

Which of the following is NOT a function of ribosomes?

Synthesis of lipids (D) Signup and view all the answers

Which of the following organelles is involved in the breakdown of fatty acids and the production of acetyl-CoA?

Peroxisomes (C) Signup and view all the answers

Which of the following statements accurately describes the role of the mitochondrial matrix?

It is the site of the Krebs cycle and other metabolic reactions. (A) Signup and view all the answers

What is the primary function of the cell membrane?

To regulate the passage of molecules into and out of the cell. (C) Signup and view all the answers

Which of the following statements about the structure of the cell membrane is CORRECT?

The phospholipid bilayer has hydrophilic heads facing inward. (C) Signup and view all the answers

Which of the following types of filaments is involved in muscle contraction?

Actin filaments (A), Microfilaments (B) Signup and view all the answers

Which of the following statements about peroxisomes is TRUE?

Peroxisomes contain enzymes that break down hydrogen peroxide. (A) Signup and view all the answers

Study Notes

Nucleus

The nucleus is the "brain" of the cell, controlling cell activities.
The nuclear envelope is a double-layered membrane surrounding the nucleus, separating it from the cytoplasm.
The outer layer of the nuclear envelope is studded with ribosomes, sites of protein synthesis.
The inner layer of the nuclear envelope is lined with lamins, proteins crucial for cell division and interaction with chromatin.
Nuclear pores are protein complexes allowing transport of ions, proteins, nucleotides, and other molecules between the nucleus and cytoplasm.
The nucleolus is a structure within the nucleus where ribosome subunits are assembled.
Chromatin is DNA complexed with histone proteins, appearing as euchromatin (loose, actively transcribed) or heterochromatin (tight, less active).
The nucleus is responsible for DNA replication, transcription (DNA to RNA), and the synthesis of various RNA types, including tRNA, mRNA, and rRNA.

Endoplasmic Reticulum (ER)

The rough ER is a network of membranes with ribosomes attached, facilitating protein synthesis.
The smooth ER is a network of membranes lacking ribosomes, involved in lipid synthesis, detoxification, and calcium storage.
The rough ER synthesizes proteins destined for lysosomes, membranes, or secretion.
Rough ER processes proteins through folding and glycosylation (addition of sugars).
The smooth ER synthesizes lipids, including fatty acids, phospholipids, and cholesterol.
The smooth ER contains enzymes like CYP450 for detoxification.
The smooth ER regulates calcium levels critical for various cellular processes and muscle contraction.
The ER plays a key role in protein and lipid synthesis and processing, transporting these substances throughout the cell.

Golgi Apparatus

The Golgi apparatus is a membrane-bound organelle that modifies, sorts, and packages proteins and lipids received from the ER.
The cis Golgi is the receiving region, and the trans Golgi is the shipping region.
The Golgi modifies proteins and lipids through glycosylation (addition of sugars), phosphorylation, and other post-translational modifications.
N-type and O-type glycosylation modify proteins. O-type glycosylation occurs exclusively in the Golgi.
The Golgi packages molecules into vesicles, directing them to their final destinations, such as lysosomes, cell membranes, or for secretion.

Cell Membrane

The cell membrane is a selectively permeable barrier defining the boundary of the cell.
The cell membrane is composed of a phospholipid bilayer, cholesterol, and proteins.
The phospholipid bilayer has hydrophilic heads (water-loving) and hydrophobic tails (water-fearing).
Cholesterol regulates membrane fluidity.
Membrane proteins perform diverse functions, including transport, enzymatic reactions, and cell-cell recognition.

Lysosomes

Lysosomes are membrane-bound organelles containing hydrolytic enzymes for breaking down macromolecules (proteins, nucleic acids, lipids, carbohydrates).
Lysosomes degrade materials ingested by the cell via phagocytosis and endocytosis.
Lysosomes contribute to autophagy (breakdown of cellular components) and autolysis (breakdown of damaged cells).

Peroxisomes

Peroxisomes are organelles containing enzymes, like catalase and oxidase, crucial for breaking down harmful substances, including hydrogen peroxide.
Peroxisomes participate in fatty acid metabolism, producing acetyl-CoA.
Peroxisomes synthesize lipids, like plasmalogen, playing a vital role in brain tissue.
Peroxisomes contribute to ethanol metabolism (to a lesser extent).

Mitochondria

Mitochondria are the "powerhouses" of the cell, generating ATP through oxidative phosphorylation.
Mitochondria have an outer membrane and an inner membrane folded into cristae.
The mitochondrial matrix houses enzymes for crucial metabolic processes like the Krebs cycle, heme synthesis, urea cycle, and others.
Mitochondria contain their own DNA (mtDNA), inherited maternally.

Ribosomes

Ribosomes, composed of rRNA and proteins, are sites of protein synthesis (translation).
Ribosomes can be free in the cytoplasm or bound to the rough ER.
Free ribosomes synthesize proteins utilised within the cytosol.
Bound ribosomes synthesize proteins destined for secretion or incorporation into membranes.

Cytoskeleton

The cytoskeleton is a network of filaments maintaining cell shape and enabling movement.
The cytoskeleton includes microfilaments (actin), intermediate filaments, and microtubules.
Microfilaments participate in muscle contraction, cytokinesis, and cell movement.
Intermediate filaments provide structural support.
Microtubules facilitate intracellular transport via motor proteins like kinesin and dynein, and form cilia and flagella.
Cilia and flagella enable cellular movement..

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Description

Explore the essential functions and structures of the nucleus and endoplasmic reticulum in this quiz. Understand the role of nuclear components in DNA replication and RNA synthesis, as well as the importance of the rough ER in cellular processes. Test your knowledge of cell biology principles and concepts.