Lecture 5 hard

Questions and Answers

What unique role does the smooth ER play in muscle cells?

It generates energy through ATP synthesis.

It produces neurotransmitters for muscle signaling.

It regulates calcium ion concentrations. (correct)

It synthesizes proteins necessary for muscle contraction.

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

Synthesis of lipids and carbohydrates

Detoxification of alcohol

Storage of genetic information (correct)

Production of steroid hormones

In which organ does the smooth ER help to detoxify harmful substances?

Pancreas

Liver (correct)

Heart

Kidney

How does the smooth ER differ structurally from the rough ER?

The smooth ER is more complex in structure. Signup and view all the answers

What precursor substance does the adrenal glands' smooth ER secrete?

Cholesterol Signup and view all the answers

What is the primary function of secondary lysosomes?

To ensure the recycling of damaged cellular components. Signup and view all the answers

Which statement best defines heterophagia?

It is the process of degrading foreign substances absorbed by the cell. Signup and view all the answers

What results from the autolysis process?

Cells undergo self-digestion due to membrane breakdown. Signup and view all the answers

What happens to the products of digestion in secondary lysosomes?

They are reabsorbed into the cytoplasm for reuse. Signup and view all the answers

What characterizes primary lysosomes?

They emerge from the Golgi apparatus filled with inactive enzymes. Signup and view all the answers

Which of the following processes involves the breakdown of own cellular materials?

Autophagy Signup and view all the answers

What best describes the primary function of the endoplasmic reticulum?

It produces, processes, and secretes proteins. Signup and view all the answers

Which statement about the structure of the rough endoplasmic reticulum is true?

It is made up of interconnected flattened sheets and tubules. Signup and view all the answers

What role do ribosomes play in the function of the rough endoplasmic reticulum?

They facilitate the translation of mRNA into proteins. Signup and view all the answers

What distinguishes smooth endoplasmic reticulum from rough endoplasmic reticulum?

Rough ER is involved in protein synthesis while smooth ER is not. Signup and view all the answers

What is a significant consequence of lacking rough endoplasmic reticulum in a cell?

The cell would fail to synthesize proteins. Signup and view all the answers

Which of the following statements accurately describes the lumen of the rough endoplasmic reticulum?

It is smaller in width than the lumen of the smooth endoplasmic reticulum. Signup and view all the answers

What dual role does the smooth endoplasmic reticulum serve in cellular functions?

It synthesizes lipids and stores calcium. Signup and view all the answers

What is the primary role of the Golgi network?

It transports, modifies, and packages proteins and lipids. Signup and view all the answers

Which component of the Golgi is closest to the endoplasmic reticulum (ER)?

Cis Golgi network Signup and view all the answers

What distinguishes the cis and trans faces of the Golgi network?

The cis face is closer to the ER, while the trans is farther away. Signup and view all the answers

What do vesicles carry from the Golgi network?

Lipids, proteins, and other cargo Signup and view all the answers

Which process occurs in the Golgi that involves complex polysaccharides?

Synthesis of complex polysaccharides Signup and view all the answers

What does the lumen of the Golgi contain that is crucial for protein modification?

Important enzymes for modifying proteins Signup and view all the answers

What is the primary function of lysosomes in cellular processes?

To digest waste and recycle cellular components Signup and view all the answers

What type of vesicles leave the Golgi after processing?

Secretory vesicles Signup and view all the answers

What happens to the cargo proteins after they are given to the Golgi?

They are packaged into vesicles for transport. Signup and view all the answers

During autophagy, which process occurs first after the formation of autophagosomes?

Fusion of autophagosomes with lysosomes Signup and view all the answers

Which of the following statements is true regarding the Golgi network and its cisternae?

The Golgi comprises multiple cisternae at both the cis and trans networks. Signup and view all the answers

What occurs during the cellular self-destruction process facilitated by lysosomes?

Lysosomes undergo autolysis releasing digestive enzymes Signup and view all the answers

In addition to breaking down waste, how do lysosomes contribute to the immune response?

By breaking down invading pathogens within the cell Signup and view all the answers

What role do lysosomes play in cellular repair?

They digest damaged organelles and harmful materials Signup and view all the answers

Which of the following best describes the formation of autophagosomes?

An initial step in lysosomal function Signup and view all the answers

What is a consequence of lysosomes exploding during cellular self-destruction?

Leads to the destruction of all cellular components Signup and view all the answers

What substances can lysosomes break down to aid in cellular homeostasis?

Excess cellular material and damaged organelles Signup and view all the answers

What is the primary function of lysosomes within a cell?

Waste degradation and recycling Signup and view all the answers

From which cellular structure do lysosomes primarily originate?

Golgi apparatus Signup and view all the answers

What is the optimal internal pH range of lysosomes for enzyme activity?

4.5 to 5.5 Signup and view all the answers

How do lysosomes acquire external materials for degradation?

Endocytosis Signup and view all the answers

What types of enzymes are primarily found within lysosomes?

Hydrolases Signup and view all the answers

What is the role of proteins covering the outer membrane of lysosomes?

Serving as signaling molecules Signup and view all the answers

Which process describes the fusion of a vesicle with a lysosome?

Endocytosis Signup and view all the answers

What are lysosomes often referred to as due to their functions?

Recycling centers Signup and view all the answers

What initiates the activation of enzymes within a newly formed lysosome?

Acidic environment Signup and view all the answers

How many different types of acid hydrolases are present in lysosomes?

60 Signup and view all the answers

Study Notes

Smooth ER

Located near the cell periphery, the smooth endoplasmic reticulum (SER) lacks ribosomes, distinguishing it from rough ER.
Functions include lipid, steroid, and carbohydrate synthesis, along with metabolizing drugs and toxins.
The type of cell influences the specific functions of the SER.
In muscle cells, it's known as the sarcoplasmic reticulum, regulating calcium ion concentrations during muscle contraction and relaxation.
In adrenal glands, SER secretes cholesterol, a precursor to steroid hormones.
In liver cells, SER synthesizes and stores detoxifying enzymes to process harmful substances like alcohol and drugs.

Functions of ER

Rough ER (RER) is primarily responsible for protein production, while SER synthesizes phospholipids and steroids.
The ER detoxifies harmful exogenous molecules and regulates calcium ion sequestration and release.

Lysosomes

Heterophagia involves breaking down foreign substances absorbed via endocytosis.
Autophagy is the process of degrading internal materials, including nutrients and dysfunctional organelles.
Autolysis occurs when lysosomes rupture, digesting the cell due to pathology or aging.
Primary lysosomes form from the Golgi apparatus and contain inactive hydrolases for degrading large molecules.
Secondary lysosomes form when primary lysosomes merge with endocytic vesicles, digesting various materials and recycling products to the cytoplasm.

Endoplasmic Reticulum Structure and Function

The endoplasmic reticulum (ER) produces, processes, and secretes proteins, playing a vital role in every cell of humans and other organisms.
Its structure consists of interconnected flattened sheets (cisternae) and tubules, facilitating efficient function.
Rough ER is studded with ribosomes, while the smooth ER lacks them.

Rough ER

Lumen of rough ER is narrower than that of smooth ER.
Central to protein synthesis as ribosomes translate mRNA into proteins, which are then modified and transported.

Golgi Network

Composed of two networks: cis and trans Golgi networks, each made of multiple cisternae.
The cis Golgi network is adjacent to the ER, while the trans Golgi network is the farthest.
The Golgi modifies proteins and lipids received from the ER, packaging them into vesicles for transport.

Protein Trafficking

Newly synthesized proteins are transported from the ER to the Golgi for modification and sorting to their destinations.
The Golgi creates polysaccharides and packages proteins and lipids within vesicles for secretion or internal use.

Lysosome Functionality

Lysosomes are membrane-bound organelles responsible for cellular waste degradation and recycling.
Their acidic internal environment (pH 4.5-5.5) contains hydrolytic enzymes, facilitating the breakdown of internal and external materials.
They play a role in autophagy, cellular repair, and can trigger autolysis when a cell is irreparably damaged.

Ribosome Structure and Function

Ribosomes are essential for protein synthesis, directing what type of proteins are produced based on location.
Composed of two subunits (large and small), they come together to facilitate protein production when needed.
The ribosomal process involves initiation, elongation, and termination of protein synthesis.

Golgi Apparatus Structure

The Golgi apparatus, made up of stacked pouches called cisternae, operates closely with the ER.
Composed of the cis face (closest to the ER), trans face (farthest from the ER), and medial section, it processes proteins and lipids.
The endoplasmic reticulum-Golgi intermediate compartment (ERGIC) facilitates transport between the ER and Golgi.

Golgi Processing Steps

Proteins or lipids leave the ER as vesicles, enter the Golgi at the cis face, and are modified as they move through its lumen.
Modifications may include sugar replacements or the addition of fatty acids or phosphates.
At the trans face, molecules are sorted and packaged into vesicles for delivery to specific cellular locations.

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Description

This quiz explores the differences and functions of the smooth and rough endoplasmic reticulum (ER) in cells. Learn about their roles in lipid and protein synthesis, detoxification, and muscle contraction regulation. Test your knowledge on lysosomes and cellular processes like heterophagia and autophagy.