Eukaryotic Cell Structure and Functions

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Questions and Answers

What primarily regulates the movement of substances in and out of the nucleus?

Nuclear envelope

Nuclear lamina

Pore complex (correct)

Nuclear matrix

When do chromatin strands coil into visible chromosomes?

During interphase

During cell division (correct)

When proteins are synthesized

During DNA replication

What is the main function of ribosomes?

Transporting mRNA

Creating ribosomal RNA

Regulating gene expression

Synthesizing proteins (correct)

What feature distinguishes bound ribosomes from free ribosomes?

Association with the ER or nuclear envelope Signup and view all the answers

How is mRNA transported out of the nucleus?

Via nuclear pores Signup and view all the answers

What is the potential significance of the nucleolus during cell division?

It could play a role in cell division processes. Signup and view all the answers

Which component primarily maintains the shape of the nuclear envelope?

Nuclear lamina Signup and view all the answers

What type of RNA is primarily made by the nucleolus?

Ribosomal RNA (rRNA) Signup and view all the answers

What is the primary role of the Golgi apparatus in cellular transport?

Sort, modify, and secrete transport vesicles Signup and view all the answers

How do lysosomes digest macromolecules?

By employing hydrolytic enzymes in acidic conditions Signup and view all the answers

What happens if a large number of lysosomes in a cell break?

The cell can auto digest itself Signup and view all the answers

Which process describes how amoebas ingest food?

Phagocytosis Signup and view all the answers

What is the function of the carbohydrates added to glycoproteins in the Golgi apparatus?

To modify based on cellular needs Signup and view all the answers

Which of the following is NOT a function of vacuoles?

Digestion of macromolecules Signup and view all the answers

What is the significance of adding phosphate groups or sugars to products in the Golgi apparatus?

To serve as zip codes for targeting Signup and view all the answers

How are hydrolytic enzymes and lysosomal membranes produced?

Produced by the rough endoplasmic reticulum and the Golgi apparatus Signup and view all the answers

What is the main function of the plasma membrane?

Regulate the movement of substances in and out of the cell Signup and view all the answers

Which organelle is responsible for the synthesis and modification of proteins?

Golgi apparatus Signup and view all the answers

Which organelle in plants is responsible for photosynthesis?

Chloroplast Signup and view all the answers

What role do ribosomes play in the eukaryotic cell?

Make proteins Signup and view all the answers

What primarily determines the size limitation of a cell?

The surface area to volume ratio Signup and view all the answers

Which of the following structures is exclusively found in plant cells?

Chloroplast Signup and view all the answers

What is the role of the central vacuole in plant cells?

Store waste and maintain turgor pressure Signup and view all the answers

What is found in the region known as the centrosome?

Centrioles Signup and view all the answers

Which of the following is NOT a function of the Golgi apparatus?

Synthesis of proteins Signup and view all the answers

Which component of the cytoskeleton is responsible for reinforcing the shape of the cell?

All of these options Signup and view all the answers

What is the primary function of contractile vacuoles in freshwater protists?

To pump out excess water Signup and view all the answers

Which of the following is NOT a role of plant vacuoles?

Photosynthesis Signup and view all the answers

How many membranes do chloroplasts typically have?

3-4 Signup and view all the answers

Where is ATP produced within mitochondria?

Mitochondrial matrix Signup and view all the answers

What can be found inside mitochondria and chloroplasts that supports their semi-autonomous nature?

DNA that codes for some of their proteins Signup and view all the answers

What structural feature of mitochondria increases their ability to produce ATP?

Folded inner membrane called cristae Signup and view all the answers

Which statement about mitochondria is false?

They primarily engage in photosynthesis. Signup and view all the answers

What pigment found in chloroplasts is essential for photosynthesis?

Chlorophyll Signup and view all the answers

What is the primary function of peroxisomes in the liver?

Detoxifying alcohol by removing hydrogen Signup and view all the answers

What structure within chloroplasts is responsible for converting light energy into chemical energy?

Thylakoids Signup and view all the answers

Which of the following accurately describes the composition of microtubules?

Hollow structures composed of globular tubulin proteins Signup and view all the answers

What role does the cytoskeleton play in cell motility?

It aids in the movement of vesicles along its fibers Signup and view all the answers

What substance is produced as a byproduct of the enzymatic activity in peroxisomes?

Hydrogen Peroxide Signup and view all the answers

Which of the following statements about thylakoids is correct?

They are organized in stacks called granum Signup and view all the answers

How do peroxisomes contribute to cellular metabolism?

By converting stored fats into sugars in plants Signup and view all the answers

What is a key characteristic of the cytoskeleton?

It can be disassembled and reassembled in different locations Signup and view all the answers

Study Notes

Plasma Membrane

Acts as a barrier that allows nutrients, oxygen, and waste to leave the cell.
Only a certain amount of substance can cross the membrane, eventually limiting cell size.
Organisms with multiple cells become larger by increasing their number of cells.

Eukaryotic Cell Organelles

Animal Cells:
- Flagellum: Used for locomotion, made of microtubules.
- Centrosome: Region where microtubules are initiated; contains centrioles.
- Cytoskeleton: Provides cell shape and function through the microfilaments, intermediate filaments, and microtubules.
- Microvilli: Projections that increase surface area.
- Peroxisome: Produces hydrogen peroxide, then converts it into water.
- Mitochondria: Carries out cellular respiration and ATP production.
- ER: Network of sacs and tubes responsible for protein and membrane synthesis.
- Nuclear Envelope: Double membrane surrounding the nucleus with pores connecting to the ER.
- Nucleolus: Produces ribosomes.
- Chromatin: Genetic material consisting of DNA and proteins.
- Plasma Membrane: Membrane enclosing the cell.
- Ribosomes: Produce proteins.
- Golgi Apparatus: Organelle that synthesizes, modifies, sorts, secretes, and tags cell products.
- Lysosome: Hydrolyzes macromolecules.
- Animal Cells: Contain lysosomes, centrosomes, and flagella.
Plant Cells:
- Nuclear Envelope: Double membrane surrounding the nucleus, with pores connecting to the ER.
- Nucleolus: Produces ribosomes.
- Chromatin: Genetic material consisting of DNA and proteins.
- ER: Network of sacs and tubes responsible for protein and membrane synthesis.
- Ribosomes: Produce proteins.
- Central Vacuole: Storage space for waste products; breaks down macromolecules.
- Cytoskeleton: Provides cell shape and function through the microfilaments, intermediate filaments, and microtubules.
- Chloroplast: Photosynthetic organelle that converts sunlight into chemical energy.
- Plasmodesmata: Channels through cell walls that connect the cytoplasm of cells.
- Cell Wall: Provides structural support, made of cellulose, polysaccharides and proteins.
- Plasma Membrane: Membrane enclosing the cell.
- Peroxisome: Produces hydrogen peroxide, then converts it into water.
- Mitochondria: Carries out cellular respiration and ATP production.
- Golgi Apparatus: Organelle that synthesizes, modifies, sorts, secretes, and tags cell products.
- Plant Cells: Contain chloroplasts, central vacuoles, cell walls, and plasmodesmata.

The Nucleus

Contains most of the cell's genes, except for some found in mitochondria and chloroplasts.
Average nucleus is 5 micrometers in diameter.
Nuclear Envelope: Double membrane surrounding the nucleus, with pores that regulate the movement of molecules, mainly proteins and RNA.
Nuclear Lamina: A net of proteins that maintains the shape of the nuclear envelope.
Chromosomes: Carry genetic information; chromatin strands coil into visible chromosomes during cell division.
Nucleolus: Produces ribosomal RNA (rRNA) and small and large ribosomal subunits.
Directs protein synthesis by creating mRNA from DNA, which is then transported to the cytoplasm for protein synthesis.
mRNA is transported through pores in the nuclear envelope.

Ribosomes

Consist of rRNA and protein.
Synthesize proteins.
There are two types of ribosomes:
- Free ribosomes: Found in the cytoplasm (synthesize proteins for use within the cell).
- Bound ribosomes: Attached to the ER or the outer nuclear envelope (synthesize proteins destined for the membrane, export, and other organelles).
Polypeptides destined for the membrane are inserted into the ER via hydrophobic properties.
Phospholipids are also made by the cytosol for the ER.

Golgi Apparatus

Receives transport vesicles from the ER.
Sorts, modifies, and packages proteins.
Modifies carbohydrates of glycoproteins.
Contains cisternae: stacks of flattened sacs.
Cis side: receives vesicles from the ER.
Trans side: releases mature and tagged vesicles to other locations.
Modifies some phospholipids.
Synthesizes certain macromolecules, including pectin and non-cellulose polysaccharides.
Adds phosphate groups or sugars as zip codes for product delivery.

Lysosomes

Membrane-bound sacs containing hydrolytic enzymes.
Digest macromolecules in acidic environments.
Enzymes and lysosomal membrane are produced by the rough ER and bud off from the trans side of the Golgi apparatus.
Involved in digestion of intracellular material: phagocytosis (engulfing of smaller organisms) and autophagy (degradation of damaged organelles).

Vacuoles

Membrane-bound vesicles with varied functions.
Food vacuoles: store food during phagocytosis.
Contractile vacuoles: pump out excess water in freshwater protists.
Plant and fungal vacuoles: carry out hydrolysis.
Central vacuole: found in large plants, stores organic compounds, waste products, and ions.
Contribute to water absorption and plant growth.

Mitochondria and Chloroplasts

Energy conversion organelles.
Mitochondria: Site of cellular respiration, producing ATP from sugars, fats, and fuels.
Chloroplasts: Convert solar energy into chemical energy (photosynthesis) to create sugars.
Both have multiple membranes.
Mitochondria: 2 membranes, outer and inner, with the inner membrane folded to increase surface area, creating cristae.
Chloroplasts: 3-4 membranes, including thylakoids (coiled membranes) forming granum, surrounded by stroma.
Both contain their own DNA and ribosomes, allowing them to synthesize some proteins internally.
Are semiautonomous: capable of reproducing independently.

Mitochondria: Chemical Energy Conversion

Found in all eukaryotic cells.
Can exist as single large mitochondria or numerous smaller ones.
Size: 1-10 micrometers in length.
Can move, fuse, and break apart.
Outer membrane: smooth.
Inner membrane: folded to increase surface area (cristae).
Mitochondrial matrix: enclosed by the inner membrane, where ATP production takes place.

Chloroplasts: Capture of Light Energy

Belong to a family of plant organelles called plastids.
Contain chlorophyll, enzymes, and proteins for photosynthesis.
2-5 micrometers in length.
Outer and inner membranes: separate chloroplast from cytoplasm.
Thylakoids: interconnected, coiled membranes inside the chloroplasts; stacked like poker chips into granum.
Stroma: fluid surrounding thylakoids, containing DNA and ribosomes.
Can move and divide.

Peroxisomes

Specialized metabolic compartments bound by a single membrane.
Contain enzymes that transfer hydrogen from substrates to oxygen, producing hydrogen peroxide as a byproduct.
Breakdown fatty acids using oxygen, providing fuel for mitochondria.
Detoxify alcohol in the liver.
Contain enzymes to break down hydrogen peroxide into water.
Glyoxysomes: specialized peroxisomes in plants that convert stored fatty acids into usable sugars.
Made of proteins from cytosol and lipids from the ER and itself.
Can split into multiple peroxisomes after reaching a certain size

Cytoskeleton

Network of fibers extending throughout the cytoplasm.
Supports cell shape, assists in movement, and regulates activities.
Components:
- Microtubules: hollow rods that act as tracks for organelle movement; made of tubulin protein.
- Microfilaments: thin fibers that help with cell shape and movement.
- Intermediate filaments: durable fibers providing structure, anchoring organelles and helping the cell withstand stress.

Roles of the Cytoskeleton

Maintains cell shape, especially in animal cells lacking cell walls.
Assists in cell movement (cell motility) through interaction with motor proteins.
Organizes organelles in the cytoplasm.
Contributes to the movement of substances within the cell.

Microtubules

Found in all eukaryotic cells.
Hollow rods: 25 nanometers in width and 200-25 micrometers in length.
Walls of the tubules are made of tubulin protein dimers.
Act as tracks for organelle transport, guide cell division, and contribute to cilia and flagella formation.

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Description

Test your knowledge on the components and functions of eukaryotic cell organelles, including animal cells. This quiz covers essential structures like the plasma membrane, mitochondria, and cytoskeleton. Understand how these organelles contribute to the overall functioning and size limitations of the cell.