Cell Biology Quiz: Transport and Organelles

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Questions and Answers

What is the specific marker for proteins targeted to lysosomes?

Clathrin-like proteins

COP-1 coat proteins

Mannose-6-phosphate (correct)

KDEL sequence

Which secretion method involves storing proteins until they are stimulated for release?

Regulated secretion (correct)

Vesicle budding

Lysosomal secretion

Constitutive secretion

What role does vesicular transport play in the cell?

It prevents the fusion of membranes.

It is limited to exocytosis processes only.

It maintains plasma membrane integrity and transfers molecules. (correct)

It exclusively transports ions across membranes.

Which process is primarily responsible for the uptake of large molecules into the cell?

Endocytosis Signup and view all the answers

What sequence is recognized by receptors in the rough endoplasmic reticulum (rER) for protein import?

Lys-Asp-Glu-Leu Signup and view all the answers

Which component of vesicles is used for continuous secretion of proteins?

COPs Signup and view all the answers

In cytology, which function is attributed to the Golgi apparatus?

Modification and sorting of proteins Signup and view all the answers

Which process describes the formation of vesicles from the plasma membrane?

Vesicle budding Signup and view all the answers

What type of proteins are associated with the nuclear lamina?

Nuclear lamins Signup and view all the answers

What is the significance of the nucleoplasmic ring complex in nuclear pores?

It anchors the nuclear basket. Signup and view all the answers

Which cell type is known to have multiple nuclei?

Osteoclasts Signup and view all the answers

How does the structure of the nuclear envelope relate to the rough-surfaced endoplasmic reticulum?

The outer membrane of the nuclear envelope is continuous with the rough ER. Signup and view all the answers

Which part of the nucleus is primarily responsible for ribosomal production?

Nucleolus Signup and view all the answers

What role do nuclear pores play in cellular function?

They serve as channels for the transport of small molecules. Signup and view all the answers

What type of chromatin is associated with transcriptionally active genes?

Euchromatin Signup and view all the answers

What additional feature do nuclear pores possess to facilitate molecular transport?

Water-filled channels Signup and view all the answers

What role does the smooth endoplasmic reticulum (sER) NOT play in cellular function?

Modification of proteins Signup and view all the answers

Which phase of the Golgi apparatus is closest to the rough endoplasmic reticulum (rER)?

Cis-Golgi Network (CGN) Signup and view all the answers

Which of the following enzymes is associated with the smooth endoplasmic reticulum (sER)?

Lipid oxidase Signup and view all the answers

What is a primary function of the Golgi apparatus?

Modification of proteins and lipids Signup and view all the answers

Which structure serves as a network for transporting vesicles in the Golgi apparatus?

Microtubule-organising centre Signup and view all the answers

In which phase of the Golgi apparatus are proteins typically modified?

Medial-Golgi Network Signup and view all the answers

Which component is NOT a recognized function of the smooth endoplasmic reticulum (sER)?

Exocytosis of proteins Signup and view all the answers

What characterizes the Golgi apparatus in terms of its structural organization?

It forms a series of stacked, flattened sacs. Signup and view all the answers

Study Notes

Plasma Membrane

The plasma membrane is a lipid bilayer structure, visible under transmission electron microscopy.
It has a thickness of 8 to 10 nm.
Molecules are arranged asymmetrically.
- Complex sugars are on the outer portion.
- 40-50% are proteins.
- 30-40% are phospholipids (with different residues).
- Cholesterol is present.
The plasma membrane is a selective barrier regulating cell-to-cell adhesion.
The fluid mosaic model describes the membrane's amphipathic lipid bilayer with embedded integral membrane proteins and peripheral proteins attached to its surfaces.
Phospholipids and proteins move within the bilayer, making it fluid.
Temperature is directly proportional to fluidity; fatty acid chain length, protein number, and unsaturated fatty acid amount are inversely proportional to fluidity. Cholesterol makes the bilayer less deformable, decreasing its permeability and preventing fatty acid crystallization.
Lipids can move laterally and rarely flip-flop between layers.
Lipid rafts are localised regions containing high concentrations of cholesterol and glycosphingolipids, offering distinct structural and functional properties.
Lipid rafts are dynamic platforms for cell signaling, with close proximity of interacting proteins enabling rapid and efficient signal transduction.
Rafts act as platforms separating specific signaling molecules.

Rough Endoplasmic Reticulum (RER)

RER is a network of interconnected tubules delimited by a membrane.
Its membrane is continuous with the nuclear envelope, which is important for mRNA exit.
RER is abundant in cells with high protein synthesis needs.
Ribosomes on the RER membrane synthesize proteins destined for the lumen of the RER, beginning translation there.
RER is involved in post-translational modifications of proteins (proteolysis, glycosylation, phosphorylation).

Smooth Endoplasmic Reticulum (SER)

SER is a network of interconnected tubules.
It lacks ribosomes.
SER plays roles in lipid metabolism, synthesizing and secreting steroids, particularly in hepatocytes (where it detoxifies ingested alcohol).
SER functions in lipid and steroid metabolism, glycogen metabolism, membrane formation, and recycling activities.
SER contains enzymes involved in detoxification and conjugation of noxious substances.

Golgi Apparatus

The Golgi apparatus is a stack of flattened, membrane-limited sacs (cisternae) and tubular extensions near the microtubule-organising center.
Two faces are cis-Golgi network (CGN) (closer to RER), and trans-Golgi network (TGN) (further from RER).
Golgi functions include protein and lipid modification (glycosylation), activation of peptides, complex carbohydrate synthesis (glycosaminoglycans), and selection of enzymes for lysosomes.
Golgi produces micro-vesicles.

Vesicular Transport

Vesicular transport maintains plasma membrane integrity and helps in transferring molecules between cellular compartments.
This involves vesicle budding (formation) and fusion with other membranes.
Endocytosis brings substances into the cell, playing a role in nutrient uptake, cell signalling, and shape changes.
Exocytosis carries substances out of the cell.
Different kinds of vesicles are characterized by specific coatings (COPs), used for moving substances from RER to Golgi and vice versa, and clathrin, for transporting materials in cell.
Rab-GTPases provide specific addressing for vesicle transport, directing vesicles to their target destinations.
SNARE proteins (v-SNARE and t-SNARE) ensure accurate fusion.

Receptor-mediated Endocytosis

Allows entry of specific molecules (cargo) via receptors accumulating in specific regions of the membrane (lipid rafts).
Cargo receptors bind specific molecules.
Clathrin molecules build a basket-like cage around them, triggering membrane invagination to form a vesicle.
Adaptin aids in selecting cargo.
Dynamin, a mechanoenzyme GTPase, mediates vesicle formation.

Pinocytosis

A non-specific process engulfing fluid and small proteins by small vesicles (below 150 nm).
Continuously happens in most cells.
Often associated with caveolin and flotillin proteins in lipid rafts (not clathrin).

Phagocytosis

Ingestion of large particles (cell debris, bacteria) by large vesicles (phagosomes).
Generally involves receptor-mediated recognition and is triggered by pathogen-associated molecular patterns (PAMPs).

Lysosomes

Digesting organelles containing hydrolytic enzymes.
Involved in degradation of macromolecules and organelles
Acidic internal environment protects the cell
Contain transport proteins to release digested products.
Lysosomal disorders arise from abnormal accumulation of substances.

Peroxisomes

Small organelles with oxidative enzymes (catalase).
Important for detoxification (especially in liver cells).
Involved in beta-oxidation of fatty acids.

Mitochondria

Double-membrane organelles with an outer membrane (lipid-rich) and inner membrane (with cristae).
Contain their own DNA, ribosomes, and tRNAs (maternally inherited).
Site of ATP synthesis (cellular respiration).
Involved in lipid and steroid synthesis, ion storage, and heat production.

Cell Cycle

Sequence of events from one cell division to the next.
Consists of phases: G1, S, G2, and M (mitosis).
G1 and G2 are growth and preparation phases, respectively.
S phase stands for DNA synthesis.
Mitosis involves division and separation of replicated genetic material.
Prophase, Metaphase, Anaphase, Telophase are the four steps of mitosis

Meiosis

Two sequential nuclear divisions producing gametes with half the chromosome number.
Two cell divisions (meiosis I, II).
Meiosis I is characterised by homologous chromosomes pairing up, crossing over, and separation.
Meiosis II is similar to mitosis, resulting in four haploid gametes.

Apoptosis

Programmed cell death.
Active process involving DNA fragmentation, cytoplasmic shrinkage, and membrane blebbing.
Apoptotic bodies are engulfed to avoid inflammation/damage.

Necrosis

Accidental cell death triggered by various physical or chemical stressors
Process characterized by cellular swelling, membrane rupture, and release of harmful cellular content, which leads to inflammation at the surrounding tissue.

Cytoskeleton

A network of protein filaments in the cytoplasm.
Maintains cell structure, provides support, drives vesicle movement, allows for cell movement, allows for chromosome separation during cell division and allowing neurones to maintain shape and spatial conformation;

Centrosomes

The microtubule organizing centre (MTOC) of animal cells.
Composed of two centrioles, orthogonally arranged.
Involved in spindle formation during cell division.
Centrioles are responsible for forming basal bodies for cilia and flagella.

Nucleus

Membrane-bound organelle containing the genetic material (chromatin).
Site of DNA replication and RNA transcription.
The nucleus is enveloped by a double membrane (nuclear envelope).
The inner and outer membrane touch at points called nuclear pores allowing for material flow in and out.
The nucleolus is a structure within the nucleus involved in rRNA synthesis.

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Description

Test your knowledge on cell biology, focusing on vesicular transport, lysosomal targeting, and the functions of various organelles. This quiz covers critical concepts related to protein secretion, cellular uptake, and nuclear structures. Challenge yourself with questions that dive into the specifics of cellular mechanisms and their significance.