Cell Biology: Centrosomes and Centrioles

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Questions and Answers

What is the main function of microtubules in the cell?

To aid in cell movement and shape the cell (correct)

To provide mechanical support to the cell membrane

To participate in muscle contraction

To synthesize proteins

What is the main function of rough endoplasmic reticulum (RER)?

Cell division

Protein synthesis (correct)

Lipids synthesis

Carbohydrate synthesis

What is the arrangement of microtubules in centrioles?

10+2

10+3

9+3 (correct)

9+2

What type of filaments provide support for microfilaments and microtubules?

Intermediate filaments Signup and view all the answers

What provides the amino acid during protein synthesis?

Transfer RNA (tRNA) Signup and view all the answers

What is the main function of centrioles in animal cells?

To form cilia and flagella structure Signup and view all the answers

What is the function of the Golgi apparatus in the cell?

Storage and modification of proteins and other macromolecules Signup and view all the answers

What is responsible for translating encoded messages from messenger RNA molecules to synthesize proteins from amino acids?

Ribosome Signup and view all the answers

What is the main component of microtubules?

Tubulin protein Signup and view all the answers

What type of ribosomes do eukaryotes have?

80S Signup and view all the answers

What is the main function of mitochondria in eukaryotic cells?

Generation of metabolic energy Signup and view all the answers

What is the subunit composition of eukaryotic ribosomes?

Small (40S) and large (60S) subunit Signup and view all the answers

What is the function of intermediate filaments in epithelial cells?

To form keratin structures Signup and view all the answers

What is the name of the fluid inside the mitochondria?

Matrix Signup and view all the answers

What is the shape of mitochondria?

Rod-shaped Signup and view all the answers

What is the role of centrosomes in cell division?

To control the formation of mitotic spindle fibers Signup and view all the answers

What is the role of smooth endoplasmic reticulum (SER)?

Lipid synthesis Signup and view all the answers

What happens to the modified products in the Golgi apparatus?

They are stored in vesicles for later use or transported to the plasma membrane for excretion Signup and view all the answers

What is the main function of microfilaments in the cell?

To participate in muscle contraction Signup and view all the answers

What is the function of cristae in mitochondria?

Increase the surface area for energy production Signup and view all the answers

What is the name of the process by which mitochondria generate energy?

Aerobic respiration Signup and view all the answers

What is the function of the endoplasmic reticulum (ER)?

Synthesis, folding, modification, and transport of proteins and lipids Signup and view all the answers

What is the name of the part of the cytoplasm that does not contain membranes, organelles, or the nucleus?

Cytosol Signup and view all the answers

Which type of cells lack mitochondria?

Mature mammalian red blood cells Signup and view all the answers

What is the main function of lysosomes in a cell?

To degrade and recycle cellular waste and foreign substances Signup and view all the answers

Where are lysosomal enzymes synthesized?

Endoplasmic reticulum Signup and view all the answers

What is the byproduct of oxidation reactions in peroxisomes?

Hydrogen peroxide Signup and view all the answers

What is the purpose of catalase in peroxisomes?

To convert hydrogen peroxide to water and oxygen Signup and view all the answers

Which organelles contain at least 50 different enzymes?

Peroxisomes Signup and view all the answers

What is the function of peroxisomes in the liver and kidneys?

To detoxify drugs, alcohol, and other potential toxins Signup and view all the answers

What is the location of centrosomes in a cell?

Close to the nucleus Signup and view all the answers

How are lysosomes formed?

By budding from the Golgi complex Signup and view all the answers

Study Notes

Centrosomes and Centrioles

Centrosomes are made up of two barrel-shaped clusters of microtubules called centrioles and a complex of proteins that help in microtubules formation.
These proteins allow centrosomes to start and stop the formation of microtubule proteins, controlling the formation of mitotic spindle fibers during metaphase of mitosis.

Centrioles

Centrioles are two cellular organelles that are cylindrical in shape and found in most eukaryotic cells.
They are made up of groups of microtubules arranged in a pattern of 9+3 and are located near the nucleus.
In animal cells, centrioles play a major role in cell division (mitosis and meiosis) and formation of cilia and flagella structure.

Cytoskeleton of Cells

The cytoskeleton is a network of fibers consisting of a complex mesh of protein filaments and motor proteins that aid in cell movement and stabilize the cell.
It is composed of at least three different types of fibers: microtubules, microfilaments, and intermediate filaments.

Microtubules

Microtubules are hollow rods that help support and shape the cell and act as routes for organelle movement.
They are composed of tubulin protein and vary in length and measure.

Microfilaments

Microfilaments (or actin filaments) are thin, solid rods that are active in muscle contraction and consist of globular actin protein.
They also participate in organelle movement.

Intermediate Filaments

Intermediate filaments provide support for microfilaments and microtubules by holding them in place.
They form keratins found in epithelial cells and neurofilaments in neurons.

Cytoplasm and Cytoplasmic Organelles

Cytoplasm is the space inside the cell membrane but outside the nucleus, containing water, salts, proteins, and other organic particles.
Cytosol is part of the cytoplasm but does not contain membranes, organelles, or the nucleus.

Mitochondria

Mitochondria play a critical role in the generation of metabolic energy in eukaryotic cells.
They are responsible for most of the useful energy derived from the breakdown of carbohydrates and fatty acids, converted to ATP by aerobic respiration.
Mitochondria are rod-shaped organelles bounded by double membranes, with the outer membrane being smooth and derived from the endoplasmic reticulum, and the inner membrane being folded into many folds called cristae.
The protein that carries out oxidative metabolism is submerged within the membranes or located on the surfaces of these membranes.
Mitochondria have their own genome (DNA) that carries several genes producing proteins essential for respiration.
Mitochondria can divide by simple fission, similar to bacteria, but with participation of DNA.
Cells have 100-300 mitochondria, depending on the activity of the cell in producing energy.

Endoplasmic Reticulum (ER)

The endoplasmic reticulum is a continuous membrane system that forms a series of flattened sacs within the cytoplasm of eukaryotic cells.
It serves as a site for synthesis, folding, modification, and transport of proteins and lipids.
There are two types of ER: rough ER and smooth ER.
Rough ER is coated with ribosomes and is the site of protein synthesis.
Smooth ER lacks ribosomes and is the site of lipids synthesis.

Ribosomes

Ribosomes are complex molecules made of ribosomal RNA molecules and proteins that form a factory for protein synthesis in cells.
They translate encoded messages from messenger RNA molecules to synthesize proteins from amino acids.
Each codon of the mRNA template is matched with the appropriate amino acid in a process called translation.
The amino acid is provided by a transfer RNA (tRNA) molecule.
Eukaryotes have 80S ribosomes, each consisting of a small (40S) and large (60S) subunit.

Golgi Apparatus (Golgi Complex)

The Golgi apparatus is a collection of stacked, flattened, cup-shaped sacs situated in the cytoplasm of cells near the nucleus.
It stores and modifies proteins and other macromolecules, then transports them within the cell (by vesicles) or excretes them from the cell.
The modified products are stored in vesicles (such as lysosomes) for later use or transported by vesicles to the plasma membrane, where they are excreted from the cell.

Lysosomes

Lysosomes are membrane-bound organelles found in nearly all animal cells.
They contain hydrolytic enzymes that can break down many kinds of biomolecules like proteins, nucleic acids, carbohydrates, and lipids.
Lysosomes function as the digestive system of the cell, serving to degrade material taken up from outside the cell (heterophagy) and to digest obsolete components of the cell itself (autophagy).
Lysosome enzymes are made by proteins from the endoplasmic reticulum and enclosed within vesicles by the Golgi apparatus.
Lysosomes are formed by budding from the Golgi complex.

Peroxisomes

Peroxisomes or microbodies are membrane-bound organelles similar in structure to lysosomes but smaller.
They contain at least 50 different enzymes that oxidize certain molecules normally found in the cell.
Peroxisomes contain enzymes that convert hydrogen peroxide to water and oxygen.
They also contain enzymes that function to detoxify drugs, alcohol, and other potential toxins.
The liver and kidneys contain large numbers of peroxisomes because these organs help to cleanse the blood.

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Description

Learn about the structure and function of centrosomes and centrioles in cell biology, including their role in microtubule formation and mitosis.