Cell Biology: Endoplasmic Reticulum

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Questions and Answers

What is the structure that the endoplasmic reticulum is connected to?

Mitochondria

Peroxisomes

Cytoplasm

Nucleus (correct)

What is the main function of the smooth endoplasmic reticulum?

Lipid synthesis and detoxification (correct)

Nucleic acid synthesis

Carbohydrate breakdown

Protein synthesis

What is the difference between the rough and smooth endoplasmic reticulum?

The rough endoplasmic reticulum has no ribosomes

The smooth endoplasmic reticulum has more ribosomes

The smooth endoplasmic reticulum has no ribosomes (correct)

The rough endoplasmic reticulum has more ribosomes

What is one of the functions of the smooth endoplasmic reticulum in terms of carbohydrates?

Metabolism Signup and view all the answers

What is the site of protein synthesis in the rough endoplasmic reticulum?

Ribosomes Signup and view all the answers

Where do proteins synthesized in the cytoplasm tend to end up?

In the mitochondria, peroxisomes, or cytoplasm Signup and view all the answers

What is one of the functions of the smooth endoplasmic reticulum in terms of steroids?

Synthesis Signup and view all the answers

What is the main difference between proteins synthesized in the cytoplasm and those synthesized in the rough endoplasmic reticulum?

Their location Signup and view all the answers

What is the main reason why the endoplasmic reticulum, Golgi apparatus, lysosomes, and cell membrane are grouped together?

Because they are all part of the secretory pathway Signup and view all the answers

Where is the protein initially made in the cell?

Endoplasmic reticulum Signup and view all the answers

What happens to the vesicle that contains proteins that need to be secreted from the cell?

It merges with the cell membrane Signup and view all the answers

What is the function of the vesicle that contains proteins that need to be embedded in the cell membrane?

To transport proteins to the cell membrane Signup and view all the answers

What happens to the cell membrane after the vesicle merges with it?

It goes back to its original shape Signup and view all the answers

What is the purpose of the secretory pathway?

To transport proteins within the cell Signup and view all the answers

What happens to the protein that was not supposed to go to the lysosome?

It gets secreted from the cell or embedded in the cell membrane Signup and view all the answers

What is the role of the vesicles in the secretory pathway?

To transport proteins between organelles Signup and view all the answers

What is the purpose of post-translational modifications of proteins in the rough endoplasmic reticulum?

To form disulfide bridges and modify proteins Signup and view all the answers

What determines whether a protein follows the secretory pathway or not?

The presence of a signal sequence Signup and view all the answers

What is the primary function of the Golgi apparatus?

To modify, sort, and send proteins to their proper destinations Signup and view all the answers

What happens to a protein that is synthesized in the rough endoplasmic reticulum and needs to be secreted from the cell?

It is transported to the Golgi apparatus for modification and sorting Signup and view all the answers

What is the cis stack of the Golgi apparatus?

The part of the Golgi apparatus closest to the endoplasmic reticulum Signup and view all the answers

What happens to a vesicle that buds off from the trans stack of the Golgi apparatus?

It can take different paths, such as merging with the lysosomes or being secreted from the cell Signup and view all the answers

What is the purpose of the signal sequence in protein synthesis?

To direct the protein to the rough endoplasmic reticulum for synthesis Signup and view all the answers

What is the function of the trans stack of the Golgi apparatus?

To package proteins for secretion or transport to other organelles Signup and view all the answers

What happens to a protein that is destined to become part of the cell membrane?

It follows the secretory pathway Signup and view all the answers

What is the role of the rough endoplasmic reticulum in protein synthesis?

To synthesize proteins that are secreted or become part of the cell membrane Signup and view all the answers

Study Notes

Endoplasmic Reticulum

The endoplasmic reticulum is an organelle that buds off the nucleus and has a continuous space with the nuclear envelope.
The endoplasmic reticulum has two parts: rough endoplasmic reticulum and smooth endoplasmic reticulum.

Smooth Endoplasmic Reticulum

The smooth endoplasmic reticulum synthesizes lipids, including those that are part of the cell membrane and those that are secreted from the cell.
The smooth endoplasmic reticulum also metabolizes carbohydrates and aids in the detoxification of drugs and other toxins.

Rough Endoplasmic Reticulum

The rough endoplasmic reticulum is the site of protein synthesis and has ribosomes attached to it.
Proteins synthesized in the rough endoplasmic reticulum are either secreted into the extracellular environment or become part of the cell membrane.
Post-translational modifications of proteins, such as the formation of disulfide bridges, occur in the rough endoplasmic reticulum.

Protein Synthesis

Proteins synthesized in the cytoplasm can end up in the nucleus, mitochondria, peroxisomes, or remain in the cytoplasm.
Proteins synthesized in the rough endoplasmic reticulum follow the secretory pathway.
The secretory pathway describes the pathway a protein takes from synthesis to being secreted from the cell or becoming part of the cell membrane.

Secretory Pathway

Proteins that follow the secretory pathway have a signal sequence that is detected early in translation, causing the polypeptide to be pushed into the rough endoplasmic reticulum.
The signal sequence determines whether a protein is synthesized in the rough endoplasmic reticulum or the cytoplasm.

Golgi Apparatus

The Golgi apparatus is an organelle found near the endoplasmic reticulum and is composed of stacked sacks.
The Golgi apparatus modifies proteins made in the rough endoplasmic reticulum, sorts and sends proteins to their proper destinations, and synthesizes molecules that need to be secreted from the cell.
The Golgi apparatus has three parts: cis stack, medial stack, and trans stack.

Protein Modification and Transport

Proteins synthesized in the rough endoplasmic reticulum are transported to the Golgi apparatus in vesicles.
In the Golgi apparatus, proteins undergo modifications and are sorted and sent to their proper destinations.
Vesicles from the Golgi apparatus can merge with lysosomes or the cell membrane, releasing proteins into these locations.

Lysosomes and Cell Membrane

The endoplasmic reticulum, Golgi apparatus, lysosomes, and cell membrane are all part of the secretory pathway.
These organelles have ways of transferring proteins between them.
Proteins can be transported to lysosomes or become part of the cell membrane.

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Description

Learn about the endoplasmic reticulum, its structure, and its functions in the cell. Understand how it's connected to the nucleus and its role in cellular processes.