Cell Organelles: Ribosomes, ER, Golgi, Mitochondria

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Questions and Answers

Which organelle is primarily responsible for the oxidative metabolism of carbohydrates, lipids, and amino acids?

Ribosomes
Mitochondria (correct)
Endoplasmic Reticulum
Golgi Apparatus

The endoplasmic reticulum's primary function is protein synthesis.

False (B)

Which organelle acts as the sorting center for proteins and membranes within the cell?

Golgi apparatus

__________ are the protein-synthesizing organelles present in all cells.

Ribosomes Signup and view all the answers

Which of the following supports the endosymbiont theory regarding the origin of certain organelles?

Mitochondria contain ribosomes. (B) Signup and view all the answers

Which of the following is the primary function of mitochondria within a cell?

ATP generation through oxidative metabolism (D) Signup and view all the answers

The outer mitochondrial membrane, unlike the inner membrane, is characterized by being rich in cardiolipin.

False (B) Signup and view all the answers

What is the significance of the mitochondrial matrix?

site of oxidative metabolism Signup and view all the answers

Mitochondrial DNA is inherited exclusively from the ______.

mother Signup and view all the answers

Match the mitochondrial component with its primary function:

Outer Membrane = Contains porins for transport Inner Membrane = Electron transport chain location Intermembrane Space = Contains cytochrome c and apoptosis regulators Matrix = Site of oxidative metabolism Signup and view all the answers

The concept of 'mitochondrial Eve' suggests that:

All current living humans share a common female ancestor in Africa about 140-200,000 years ago. (C) Signup and view all the answers

Ribosomes are enclosed by a membrane.

False (B) Signup and view all the answers

What are ribosomes made of?

protein and RNA Signup and view all the answers

Which of the following is a primary function of the smooth endoplasmic reticulum (ER)?

Lipid synthesis and detoxification (B) Signup and view all the answers

The endoplasmic reticulum lumen is completely separate and isolated from the nuclear intermembrane space.

False (B) Signup and view all the answers

What modification is made to most rough ER-synthesized proteins?

N-linked glycosylation Signup and view all the answers

The Golgi apparatus consists of flattened discs called ______ arranged in a stack.

cisternae Signup and view all the answers

Match the following cellular locations with their primary function:

Rough ER = Synthesis of secreted proteins Smooth ER = Lipid synthesis Golgi apparatus = Protein sorting and modification ER Lumen = Calcium storage Signup and view all the answers

What is the attachment site for N-linked glycosylation?

–NH2 group of asparagine (A) Signup and view all the answers

The trans face of the Golgi apparatus is closest to the endoplasmic reticulum.

False (B) Signup and view all the answers

Besides protein sorting, what is another major function of the Golgi apparatus?

Carbohydrate synthesis Signup and view all the answers

Which of the following protein modifications occurs in the Golgi apparatus?

Both N-linked and O-linked glycosylation (A) Signup and view all the answers

The rough ER appears 'rough' due to the presence of ______ on its surface.

ribosomes Signup and view all the answers

A researcher treats cells with a drug that disrupts the function of the Golgi apparatus. How might this affect protein secretion from the cell?

Protein secretion would be reduced or halted. The Golgi is responsible for sorting, modifying, and packaging proteins for secretion. Signup and view all the answers

Describe how the structure of the endoplasmic reticulum (ER) supports its function in protein and lipid synthesis.

The ER's large surface area, created by its network of interconnected tubules and flattened sacs (cisternae), provides ample space for the many enzymes and ribosomes involved in these processes. The compartmentalization also allows for specialized environments. Signup and view all the answers

If a cell's mitochondria were damaged, what immediate effect would this have on cellular metabolism, and why?

ATP production would decrease, because the mitochondria are responsible for oxidative phosphorylation, the main process that generates ATP. Signup and view all the answers

A mutation impairs the ability of ribosomes to properly translate mRNA. How would this broadly impact cellular function?

The production of new proteins and enzymes would be impaired, impacting cellular processes due to lack of resources. Signup and view all the answers

Explain how the endosymbiotic theory relates to the function and features of mitochondria.

The endosymbiotic theory suggests that mitochondria were once free-living bacteria engulfed by a eukaryotic cell. This explains why mitochondria have their own ribosomes and DNA, and a double membrane. Signup and view all the answers

How does the unique lipid composition of the mitochondrial inner membrane, specifically its richness in cardiolipin, contribute to its function in energy production?

Cardiolipin enhances the efficiency of the electron transport chain by tightly binding respiratory protein complexes and creating localized proton gradients, which are essential for ATP synthesis. Signup and view all the answers

Explain how the physical separation of the electron transport chain (in the inner membrane) from the enzymes of the citric acid cycle (in the matrix) within mitochondria is crucial for efficient energy production.

Separating the processes allows for efficient generation and maintenance of a proton gradient across the inner membrane. This gradient is critical for ATP synthase to function optimally, converting the proton-motive force into chemical energy. Signup and view all the answers

Describe the significance of the intermembrane space in mitochondria. What role do its contents, such as cytochrome c, play in cellular processes beyond ATP production?

The intermembrane space contains proteins like cytochrome c that are involved in apoptosis. Release of cytochrome c from the intermembrane space into the cytoplasm signals the activation of programmed cell death pathways. Signup and view all the answers

If a mutation occurred in a mitochondrial porin, affecting its ability to transport molecules across the outer membrane, how might this impact the overall function of the mitochondria and the cell?

Reduced transport of essential metabolites like pyruvate or ADP into the mitochondria or the export of ATP could impair ATP production, disrupting cellular energy balance and potentially leading to cell dysfunction or death. Signup and view all the answers

Explain why mitochondrial DNA (mtDNA) is useful for tracing maternal lineage and what unique characteristics of mtDNA make this possible.

mtDNA is inherited solely from the mother, and it has a relatively high mutation rate. These two factors make it ideal to trace maternal lineage and build evolutionary trees. Signup and view all the answers

Describe the potential impact on a cell if the ribosomes within its mitochondria were dysfunctional.

Dysfunctional mitochondrial ribosomes would impair the synthesis of essential proteins encoded by mtDNA. This would disrupt the electron transport chain and oxidative phosphorylation, leading to reduced ATP production and mitochondrial dysfunction. Signup and view all the answers

How does the endosymbiotic theory explain the presence of ribosomes within mitochondria, and what characteristics of these ribosomes support this theory?

The endosymbiotic theory posits that mitochondria were once free-living bacteria. The ribosomes within mitochondria are similar in size and structure to bacterial ribosomes, supporting this theory. Signup and view all the answers

Explain why, despite the 'Mitochondrial Eve' theory pointing to a single common female ancestor, it is inaccurate to assume that no other women from her time have current descendants.

The 'Mitochondrial Eve' theory traces only the unbroken maternal lineage through mtDNA. Other women from her time could have descendants, but their mitochondrial DNA lineage may have been interrupted by male offspring. Signup and view all the answers

How does the continuity between the endoplasmic reticulum (ER) and the nuclear membrane benefit the cell?

The continuity between the ER and the nuclear membrane allows for a direct pathway for the exchange of molecules and signals between the nucleus and the cytoplasm. This facilitates rapid communication and coordination of cellular processes. Signup and view all the answers

Compare and contrast the roles of the rough ER and the smooth ER in a eukaryotic cell.

The rough ER is primarily involved in protein synthesis and modification, particularly for transmembrane and secreted proteins, while the smooth ER is mainly responsible for lipid synthesis, calcium storage, and detoxification. Both contribute to the overall cellular function but specialize in different biochemical pathways. Signup and view all the answers

Explain why N-linked glycosylation occurs in the ER rather than the cytoplasm.

N-linked glycosylation is catalyzed by enzymes present in the ER lumen, and the proper folding and quality control mechanisms associated with glycosylation are also localized to the ER. The cytoplasm lacks the necessary machinery and environment for this process. Signup and view all the answers

Describe the significance of calcium ions (Ca++) storage in the endoplasmic reticulum.

The ER acts as a major reservoir for Ca++ ions, which are essential for various cellular signaling pathways. Controlled release of Ca++ from the ER can trigger diverse responses such as muscle contraction, neurotransmitter release, and enzyme activation. Signup and view all the answers

Outline the steps a transmembrane protein takes as it moves from the ER to its final destination at the plasma membrane.

A transmembrane protein is synthesized and inserted into the ER membrane, undergoes N-linked glycosylation and folding, then is transported to the Golgi for further modification and sorting, and finally, it is delivered to the plasma membrane via transport vesicles. Signup and view all the answers

Explain how the structure of the Golgi apparatus, with its cis and trans faces, contributes to its function in protein sorting and modification.

The cis face receives vesicles from the ER, allowing proteins to enter the Golgi, while the trans face is the exit point, where proteins are sorted and packaged into vesicles for their final destinations. This organization ensures a directional flow of proteins through the Golgi for proper processing. Signup and view all the answers

What is the purpose of modifying the initial N-linked oligosaccharide added in the ER as the protein passes through the Golgi apparatus?

Modifying the N-linked oligosaccharide in the Golgi allows for greater diversity in glycosylation, which can influence protein folding, stability, and interactions. Specific sugar additions also serve as signals for protein sorting and trafficking to different cellular locations. Signup and view all the answers

How does the Golgi apparatus contribute to the synthesis of complex carbohydrates in the cell?

The Golgi contains enzymes that synthesize various carbohydrates and modify existing oligosaccharides on proteins and lipids. It is responsible for the formation of complex polysaccharides used in the extracellular matrix and cell walls. Signup and view all the answers

Describe the role of the ER in detoxification, and explain why this function is primarily associated with the smooth ER.

The smooth ER contains enzymes that detoxify lipid-soluble compounds, including drugs and metabolic waste products. The high concentration of these enzymes in the smooth ER makes it the primary site for this process, protecting the cell from harmful substances. Signup and view all the answers

Why might N-linked glycosylation use a pre-formed common carbohydrate that is later modified for each protein?

Using a pre-formed common carbohydrate and then modifying it allows for efficiency and standardization in the initial glycosylation step, while providing the flexibility to create diverse glycan structures tailored to the specific needs of each protein later on. Signup and view all the answers

Flashcards

Mitochondria

Energy production organelle responsible for oxidative metabolism.

Ribosomes

Protein-synthesizing organelles in all cells.