Cell Structure Quiz

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Questions and Answers

What is the diameter range of ribosomes?

40-50 nm

30-40 nm

20-30 nm (correct)

10-20 nm

Which type of ribosome is found in eukaryotes?

70S ribosome

50S ribosome

60S ribosome

80S ribosome (correct)

What is the function of the A site in a ribosome?

Holds the tRNA carrying the growing polypeptide chain

Holds the discharged tRNAs as they exit the ribosome

Holds the tRNA for termination of translation

Holds the tRNA carrying the next amino acid (correct)

How many proteins are in a large ribosomal subunit of a 70S ribosome?

34 proteins Signup and view all the answers

What type of proteins do ribosomes attached to the rough endoplasmic reticulum generally synthesize?

Membrane proteins or proteins for secretion Signup and view all the answers

Which subunit comprises the small ribosomal subunit of a 70S ribosome?

30S subunit Signup and view all the answers

What does the E site of a ribosome do?

Holds discharged tRNAs as they leave the ribosome Signup and view all the answers

What is the primary function of ribosomes?

Protein synthesis Signup and view all the answers

What is the main structural feature of centrioles?

They consist of 9 triplets of microtubules fused together. Signup and view all the answers

During which cellular process do centrioles play a crucial role?

Cell division Signup and view all the answers

Which of the following is NOT a function of the rough endoplasmic reticulum (rER)?

Providing structural support for the nucleus Signup and view all the answers

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

Rough ER has ribosomes; smooth ER does not. Signup and view all the answers

Which characteristic is true for centrioles in animal cells?

They are absent in plant cells. Signup and view all the answers

What is the process by which the rough endoplasmic reticulum is fragmented into microsomes?

Homogenization Signup and view all the answers

What does the presence of ribosomes on the rough endoplasmic reticulum indicate?

It is the site of protein synthesis. Signup and view all the answers

What type of cellular organelle would you find only in animal cells that is involved in organizing spindle fibers?

Centriole Signup and view all the answers

What is the role of the lysosome in the cellular process described?

It hydrolyzes the contents of the phagocytic vesicle. Signup and view all the answers

Where do polypeptide chains undergo folding to achieve their 3D shape?

In the cisternae of the Golgi apparatus. Signup and view all the answers

What occurs after the polypeptides are transported from the RER to the Golgi apparatus?

They undergo modification and sorting. Signup and view all the answers

Which process directly leads to the production of mRNA?

Transcription from the nuclear envelope by RNA polymerase. Signup and view all the answers

What type of modification may occur to polypeptide chains in the Golgi apparatus?

Substituting and deleting sugar residues. Signup and view all the answers

How do mRNA molecules leave the nucleus?

Through pores in the nuclear envelope. Signup and view all the answers

What happens to the products of hydrolysis performed by lysosomal enzymes?

They are released into the cytoplasm. Signup and view all the answers

Which structure buds out from the trans face of the Golgi apparatus?

Transport vesicle carrying synthesized proteins. Signup and view all the answers

What is the primary function of the nuclear pores?

To provide a channel for selective exchange of materials between the nucleus and cytoplasm Signup and view all the answers

What structural feature of mitochondria increases the surface area for energy-producing processes?

Cristae on the inner membrane Signup and view all the answers

What occurs to the nuclear envelope during mitosis and meiosis?

It disintegrates Signup and view all the answers

Which of the following statements about nucleoplasm is true?

It is a semi-fluid matrix that fills the nucleus Signup and view all the answers

Which component of mitochondria is primarily involved in ATP synthesis?

Stalk particles containing ATP synthase Signup and view all the answers

What is the relationship between the mitochondrial matrix and the Krebs cycle?

The mitochondrial matrix contains enzymes required for the Krebs cycle Signup and view all the answers

What distinguishes the double membrane structure of mitochondria?

The outer membrane is smooth and the inner membrane is folded into cristae Signup and view all the answers

How do nuclear pores contribute to maintaining chemical environments within the nucleus?

By regulating the passage of specific molecules between the two compartments Signup and view all the answers

What is the primary function of the enzymes in the Golgi body related to proteins and lipids?

To attach short carbohydrate chains to proteins and lipids Signup and view all the answers

Which process occurs first during the modification of glycoproteins in the cell?

Carbohydrates are added during rough ER synthesis Signup and view all the answers

What happens to hydrolytic enzymes within lysosomes?

They are stored to prevent cell degradation Signup and view all the answers

Which of the following accurately describes how proteins are sorted in the Golgi body?

Proteins are specifically packaged and transported to their targets Signup and view all the answers

What characteristic of lysosomal contents helps to maintain its function?

They are kept in an acidic environment Signup and view all the answers

What is NOT a type of protein sorting that occurs in the Golgi body?

Directing proteins to be degraded by proteasomes Signup and view all the answers

What role does pectin play in plant cells?

It is a non-cellulose polysaccharide synthesized for the cell wall Signup and view all the answers

How are glycoproteins modified after initial carbohydrate addition?

They undergo further chemical modifications in the Golgi body Signup and view all the answers

Study Notes

Ribosomes

Organelles composed of ribosomal RNA and proteins, measuring 20-30 nm in diameter.
Consist of two subunits: small (30S in prokaryotes; 40S in eukaryotes) and large (50S in prokaryotes; 60S in eukaryotes).
Two types: 70S found in prokaryotes, mitochondria, and chloroplasts; 80S found in eukaryotes.
Have three binding sites for tRNA: A site (aminoacyl), P site (peptidyl), E site (exit).
Main function is protein synthesis, with bound ribosomes (on rough ER) creating proteins for membranes and organelles, while free ribosomes synthesize cytosolic proteins.

Centrioles

Measure approximately 0.2 µm in diameter and 0.3 to 0.5 nm in length.
Composed of 9 triplets of microtubules, forming a rod-like structure positioned at 90° to each other.
Exclusively found in animal cells.
Function to organize spindle fibers during cell division and serve as anchorage for cilia and flagella.

Endoplasmic Reticulum (ER)

Composed of membrane-bound sacs called cisternae, serving different roles in synthesis and packaging.
Types: Rough Endoplasmic Reticulum (rER) and Smooth Endoplasmic Reticulum (sER).

Rough Endoplasmic Reticulum (rER)

Flattened cisternae interconnected with the outer nuclear membrane; ribosomes on the surface contribute to a rough appearance.
Ribosomes facilitate protein synthesis and initial glycoprotein formation.
Modifies proteins and lipids chemically; enzymes add carbohydrates to proteins, forming glycoproteins and glycolipids.
Sorts and packages molecules for transport to other organelles or cell secretion, including lysosomal enzymes and membrane proteins.

Lysosomes

Spherical sacs measuring 0.2 - 0.5 µm in diameter, containing hydrolytic enzymes (proteases, lipases).
Store enzymes separately to prevent cellular damage, maintaining an acidic environment for optimal enzyme activity.

Nucleus and Nuclear Envelope

Nuclear pores enable selective exchange of molecules (e.g., mRNA) between the nucleus and cytoplasm.
The nuclear envelope disintegrates during cell division (mitosis and meiosis), maintaining a distinct internal chemical environment.

Mitochondria

Organelles responsible for ATP synthesis via glucose metabolism, measuring 1.5 – 10 µm in length and 0.25 - 1.00 µm in width.
Feature a double membrane: outer membrane smooth, inner membrane folded into cristae to increase surface area for ETC and oxidative phosphorylation.
Contains mitochondrial DNA, 70S ribosomes, RNAs, and enzymes for the Krebs cycle.
Primary function is energy (ATP) production through catabolic respiratory activities within the cell.

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Description

Test your knowledge on the structure and function of ribosomes. This quiz covers the composition, types, and characteristics of ribosomes found in prokaryotes and eukaryotes. Perfect for biology students looking to enhance their understanding of cellular components.