Cell Biology Quiz on Golgi Apparatus and ER

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Questions and Answers

What is the primary function of the Golgi apparatus?

Synthesize ribosomal RNA

Store genetic information

Modify proteins and lipids (correct)

Generate ATP

Which of the following best describes the structural characteristics of the Golgi apparatus?

A collection of membrane-bound vesicles

A stack of flattened, curved saccules resembling pancakes (correct)

A series of lobed projections

A stack of flat saccules resembling connected tubes

How does the Golgi apparatus participate in vesicular transport?

It transports proteins through the nuclear envelope.

It modifies substances and prepares them for 'shipment' from the outer face. (correct)

It packages proteins into vesicles from the inner face for export.

It directly synthesizes vesicles from the cytoplasm.

What role does the endoplasmic reticulum (ER) play in relation to the Golgi apparatus?

It delivers vesicles containing proteins and lipids to the Golgi. Signup and view all the answers

Which statement about lysosomal enzyme disorders is accurate?

They are caused by mutations that lead to a deficiency of specific enzymes. Signup and view all the answers

What is the primary function of the Golgi apparatus in the endomembrane system?

Modification and packaging of proteins Signup and view all the answers

Which statement accurately describes the role of the rough endoplasmic reticulum (RER)?

Synthesizes and modifies proteins Signup and view all the answers

What is a key characteristic of the smooth endoplasmic reticulum (SER)?

It is involved in lipid synthesis. Signup and view all the answers

What do vesicles primarily do within the endomembrane system?

Transport materials between organelles. Signup and view all the answers

Which of the following is NOT a function of the smooth endoplasmic reticulum?

Protein synthesis Signup and view all the answers

Which of the following correctly describes the function of lysosomal enzymes?

They break down cellular waste and debris. Signup and view all the answers

What is a key feature of the endomembrane system?

It restricts enzymatic reactions to specific compartments. Signup and view all the answers

What type of substances does the smooth endoplasmic reticulum primarily synthesize?

Lipids Signup and view all the answers

What is the primary role of the nucleolus within the cell?

Ribosome assembly Signup and view all the answers

What is a unique characteristic of ribosomes compared to the nucleolus?

Ribosomes are composed of proteins and rRNA. Signup and view all the answers

Ribosomes are classified into two main types based on their location. What are these types?

Membrane-bound and free Signup and view all the answers

What component is essential for ribosome assembly and is produced in the nucleolus?

rRNA Signup and view all the answers

How much of the volume of the nucleus is estimated to be occupied by the nucleolus?

25% Signup and view all the answers

Which component is NOT a function associated with the endoplasmic reticulum?

Energy production Signup and view all the answers

What distinguishes membrane-bound ribosomes from free ribosomes?

Their location Signup and view all the answers

Which best describes the makeup of ribosomes?

Protein and rRNA Signup and view all the answers

Study Notes

Cell Size

Cells range in size from one millimeter to one micrometer.
A cell's volume increases much faster than its surface area as it grows.
This limits cell size.
Materials needed by a cell (nutrients, oxygen) and waste (CO2) must pass into and out of the cell through its surface.

Why are Cells So Small?

If a cell's volume gets too large, it cannot transport enough wastes out or nutrients in.
Surface area limits cell volume/size.

Surface-Area-to-Volume Ratio

The surface-area-to-volume ratio indicates the amount of surface area per unit of volume.
Smaller cells have larger surface-area-to-volume ratios, which allows for efficient exchange of materials.

Strategies for Increasing Surface Area

Cells can have "frilly" edges or be long and narrow to maximize surface area.
Round cells will always be small.

Eukaryotic Cells: Organelles

Eukaryotic cells are compartmentalized
They contain small structures called organelles.
Organelles perform specific functions.
This helps to isolate reactions from others.
Two classes of organelles:
- Endomembrane system:
  - Organelles that communicate with one another via membrane channels and small vesicles.
- Energy-related organelles:
  - Mitochondria and chloroplasts are basically independent and self-sufficient.

Organelles in the Cell

Cytoplasm, Nucleus, Mitochondrion, Chloroplast, Endoplasmic reticulum, Ribosome, Golgi body, Lysosome, Centriole, Cell wall, Cell membrane

Plasma Membrane

A double layer of phospholipid with embedded proteins.
Isolates cell content from the external environment.
Regulates the flow of materials into and out of the cell (e.g., acquiring nutrients and expelling waste).
Allows interaction with other cells.

Cytoplasm/Cytosol

Aqueous medium within the plasma membrane (mostly water- 70%-90%).
Contains:
- Essential ions
- Soluble organic compounds (sugars, amino acids)
- Soluble proteins (enzymes)
- Organelles
- Networks of protein strands (microtubules, microfilaments) forming the cytoskeleton, providing structural support.

The Nucleus

Prominent and characteristic feature of eukaryotic cells.
"Eukaryon" means "true nucleus."
The essence of a eukaryotic membrane-bounded nucleus.
Spherical shape, taking up about 10% of the cell's volume.
Contains the cell's genetic material(DNA).
The control center of the cell regulating gene expression.

Nucleus: Structure

Largest organelle
Approximately 10-20 µm in diameter.
All cells (except mature red blood cells and outermost skin layer) contain a nucleus.
Composed of proteins, RNA, and DNA (chromosomes).

Nucleus: Function

Stores DNA.
Maintains DNA.
Replicates and repairs DNA.
Controls cell activities by regulating gene expression.

DNA (Deoxyribonucleic acid)

Stores and transmits genetic information.
Instructions about the proteins to make.
DNA—proteins—traits.
Double helix (two single strands of DNA wound around each other).

DNA in the Nucleus

Two forms:
- Chromatin: Unwound DNA (thread-like).
- Chromosomes: Condensed form of DNA.

Anatomy of the Nucleus

Nuclear envelope (two lipid bilayers).
Nuclear pores.
Nucleoplasm.
Nucleolus.

Components of the Nucleus

Nuclear membrane (or nuclear envelope).
Separates nuclear material from cytoplasm.
Consists of two lipid bilayers.
Outer membrane connects to the ER.
Exchange of large molecules (proteins and RNA) occurs between the nucleus and cytoplasm through pores.

Nuclear Pore

Small cylindrical channels.
Direct contact between cytosol and nucleoplasm.
Exchange of polar materials between nucleus and cytoplasm.
Structural complexity controlling transport of key molecules.
Each pore is a ring of 8 proteins with an opening in the center.

Nucleoplasm

Jelly-like substance (mostly water).
Also known as karyoplasm.
Holds materials within the nucleus.
Gives the nucleus its shape and facilitates transportation of molecules.
Enclosed within the nuclear membrane.

Nucleolus

Ribosome factory.
Large, prominent structure.
Does not have a membrane.
Directs rRNA synthesis, essential for ribosome assembly (crucial for protein synthesis)
About 25% of the nucleus' volume.
Made of proteins and RNA.

Ribosomes

First observed in 1953 by the Romanian cell biologist George Emil Palade
Cells' factory; site for protein synthesis:
Non-membranous organelle
Composed of protein and rRNA (ribosomal RNA)
Large and small subunits
Classified by location:
- Membrane-bound ribosomes (on ER).
- Free ribosomes (in cytoplasm).
Some linked to ER, making it "rough"
Some are found freely in the cell. These are called polyribosomes

Endomembrane System (The Endoplasmic Reticulum)

System of intracellular membranes compartmentalizing the cell.
Restricts enzymatic reactions to specific compartments.
Consists of nuclear envelope, membranes of the endoplasmic reticulum, Golgi apparatus, and vesicles.
Transports materials between organelles.

Rough ER

Studded with ribosomes on the cytoplasmic side.
Synthesizes proteins.
Modifies and processes proteins.
Adds sugars to create glycoproteins.

Smooth ER

No ribosomes.
Synthesizes lipids (e.g., steroid hormones, cholesterol).
Detoxifies organic compounds (e.g., in liver cells).
Forms transport vesicles.
Stores calcium.

Golgi Apparatus

Stack of flattened, curved saccules.
Modifies proteins and lipids.
Receives vesicles from the ER on the cis face.
Packages molecules in vesicles for shipment.
Releases vesicles on the trans face inside or outside the cell.

Lysosomes

Spherical vesicles.
Single membrane-bounded, except in plants.
Contains digestive enzymes.
Highly acidic (hydrolytic digestive enzymes).
Digests large molecules, recycles cellular resources, and assists in apoptosis (programmed cell death)

Vacuoles

Membranous sacs larger than vesicles
Store materials
Plants typically have a central vacuole (up to 90 % volume of some cells)
Functions include storing water, nutrients, pigments, and waste products.
Development of turgor pressure
Some functions performed by lysosomes in other eukaryotes

4-10 µm long, 2-3 µm wide, biconvex disc shape.
Only in plants.
Double membrane structure.
Site of photosynthesis. Converts solar energy to chemical energy.

Powerhouse of the cell.
0.5-1.5 µm wide, 3-10 µm long, rod-shaped.
Numerous, contain ribosomes and their own DNA.
Has a double membrane, inner membrane folded into cristae.
Site of aerobic respiration (Glycolysis→ Krebs Cycle→ETC), producing energy stored as ATP.

Endosymbiotic Theory

Explains the origin of chloroplasts and mitochondria, and their double membranes.
These were once free-living prokaryotes that were ingested by eukaryotes.
The prokaryotes became integrated into the eukaryotic cell, becoming organelles.

Cell Wall

Plant cells (and different types of cell walls in bacteria and fungi) have an outermost rigid layer.
Consists of cellulose chains held together by a matrix of other polysaccharides.

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Description

Test your knowledge on the Golgi apparatus, endoplasmic reticulum, and the endomembrane system. This quiz includes questions on their structures, functions, and interactions within the cell. Perfect for students studying cell biology concepts in detail.