Cell Biology: Endoplasmic Reticulum Overview

Questions and Answers

What is the primary function of lysosomes in the cell?

To facilitate the movement of organelles within the cell.

To generate energy for the cell.

To synthesize proteins for cellular functions.

To digest intracellular and extracellular materials. (correct)

What type of ribosome is found in eukaryotic cells and is referred to as 80s ribosomes?

Cytoplasmic ribosomes with a size of 40s and 60s subunits. (correct)

Ribosomes found in prokaryotic cells.

Ribosomes found in mitochondria.

Ribosomes exclusively present in mammalian RBCs.

Which statement correctly describes the structure of a ribosome?

Ribosomes contain no nucleic acids and are solely made of proteins.

Ribosomes consist of two unequal subunits composed of rRNA and protein. (correct)

Each ribosome is made up of three equal subunits.

Ribosomes are membrane-bound organelles.

What role do lysosomes play in the process of autolysis?

They carry out self-digestion of cell tissues or organs. Signup and view all the answers

In which type of cells are 70s ribosomes typically found?

In both prokaryotic and eukaryotic cells. Signup and view all the answers

What is the primary function of the Golgi apparatus?

Modification and packaging of proteins Signup and view all the answers

Which of the following correctly differentiates between rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER)?

RER is covered in ribosomes, whereas SER lacks ribosomes. Signup and view all the answers

What is the role of ribosomes in cellular processes?

Site of protein synthesis Signup and view all the answers

Which statement about lysosomes is incorrect?

They are present in all mammalian cells. Signup and view all the answers

What describes the structure of lysosomes?

Single membrane-bound vesicles containing hydrolytic enzymes. Signup and view all the answers

Which of the following lipids is produced by the smooth endoplasmic reticulum?

Cholesterol Signup and view all the answers

What occurs when a primary lysosome fuses with a food vacuole?

It becomes a secondary lysosome. Signup and view all the answers

Which function is NOT associated with the smooth endoplasmic reticulum?

Protein synthesis Signup and view all the answers

What is one of the primary functions of the Golgi complex?

Collecting, processing, and sorting molecules Signup and view all the answers

Which of the following best describes a unique feature of rough endoplasmic reticulum (RER)?

It has ribosomes on its surface. Signup and view all the answers

What is a key structural component of lysosomes?

Single membrane enclosing digestive enzymes Signup and view all the answers

How do ribosomes participate in protein synthesis?

By translating mRNA into polypeptides Signup and view all the answers

Which statement correctly differentiates between rough and smooth endoplasmic reticulum (SER)?

RER has ribosomes; SER lacks ribosomes. Signup and view all the answers

Which function is NOT associated with the Golgi body?

Generation of ATP Signup and view all the answers

What role do enzymes in the Golgi body play in plants?

They convert sugars into cell wall components. Signup and view all the answers

What structural feature characterizes the dictyosomes found in Golgi complexes?

They are unbranched and interconnected. Signup and view all the answers

Study Notes

Endoplasmic Reticulum (ER)

RER (Rough Endoplasmic Reticulum) has ribosomes on its surface, giving it a rough appearance, and is involved in protein synthesis.
Ribosomes are located both free in the cytoplasm and attached to RER; they synthesize proteins that enter sacs within the RER.
SER (Smooth Endoplasmic Reticulum) lacks ribosomes, resulting in a smooth appearance, primarily consists of cisternae and tubules, and synthesizes lipids and steroids such as cholesterol and reproductive hormones (estrogen and testosterone).
SER is often associated with the cell membrane and has distinct functions from RER, including lipid and steroid synthesis.

Functions of ER

Provides mechanical support and aids in intracellular transportation of substances.
Involved in the synthesis of glycogen, proteins, lipids, and steroids.
Contributes to the formation of cellular structures like the cell wall, cell membrane, and nuclear membrane.
Produces enzymes for primary lysosomes.

Lysosomes

Single membrane-bound vesicles containing hydrolytic enzymes for digestion, often referred to as "suicidal bags" due to their role in cell digestion.
Enzymes are synthesized in the ER and packaged by the Golgi body.
Present in all animal cells except for mammalian red blood cells, and found in protists and fungi.
Lysosomes have a rounded, irregular shape and contain about 40 types of hydrolytic enzymes.

Types of Lysosomes

Primary Lysosomes: Newly formed from the Golgi complex containing hydrolytic enzymes.
Secondary Lysosomes (Digestive Vacuoles): Formed when primary lysosomes fuse with food vacuoles.
Residual Bodies: Contain undigested food residues after digestion.

Golgi Complex

Discovered by Camillo Golgi in 1898, it consists of cisternae and a network of tubules and vesicles (Golgi bodies).
Absent in prokaryotic cells and certain plant structures, it contains unconnected units called dictyosomes.
Dictiosomes can vary in number from one in algae to 15,000 in specialized cells.
Comprises four structures: cisternae (flattened sac-like), tubules (branching network), vesicles (sac-like), and Golgi vacuoles.

Functions of Golgi Complex

Collects, processes, and sorts molecules.
Synthesizes carbohydrates like mucilage and cellulose, contributing to cell wall components.
Produces primary lysosomes and acrosomes in sperm for fertilization.
Mediates hormone production in endocrine glands.

Ribosomes

Non-membranous, sub-spherical organelles known as the "protein factory" of the cell.
Discovered by Robinson and Brown (1953) in plant cells; term coined by Palade (1955) in animal cells.
Present in all cell types except mammalian red blood cells; composed of two unequal subunits (large and small).
Larger subunit is dome-shaped; smaller is ellipsoidal; both subunits are made of rRNA and protein.

Types of Ribosomes

70S Ribosomes: Found in both prokaryotic and eukaryotic cells, comprising 30S and 50S subunits; occur in mitochondria and chloroplasts.
80S Ribosomes: Found in eukaryotic cells, consisting of a 40S smaller subunit and a 60S larger subunit; occur in the cytoplasm.

Functions of Ribosomes

Primary site for protein synthesis, creating enzymes and hormones, including insulin.

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Description

This quiz covers the structure and function of the endoplasmic reticulum, focusing on both the rough and smooth types. Understand the role of ribosomes in protein synthesis and the process of protein transport within the cell. Test your knowledge of cellular organelles and their interconnections.