Cell Biology: Structure and Function

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Questions and Answers

What is the role of ribosomes in protein synthesis?

To compartmentalize proteins within the cell

To transport proteins to the Golgi apparatus

To decode mRNA and synthesize proteins (correct)

To modify mRNA before it leaves the nucleus

Where are free ribosomes located and what is their main function?

On the rough ER; synthesize proteins for membrane structure

In the cytosol; synthesize proteins that function within the cytosol (correct)

In the nucleus; synthesize proteins for secretion

In the cytoplasm; synthesize proteins for the endoplasmic reticulum

Which statement about the endoplasmic reticulum is correct?

The endoplasmic reticulum does not assist in membrane synthesis.

Rough ER is responsible for compartmentalizing proteins from free ribosomes. (correct)

Smooth ER primarily synthesizes proteins.

Only rough ER contains ribosomes.

What process describes the conversion of DNA to RNA and then to protein?

Transcription and translation Signup and view all the answers

Which type of ribosomes are involved in synthesizing proteins that are eventually secreted from the cell?

Bound ribosomes Signup and view all the answers

What is the primary function of smooth endoplasmic reticulum?

To synthesize membranes and lipids Signup and view all the answers

What is a primary function of smooth endoplasmic reticulum?

Lipid synthesis Signup and view all the answers

Which statement about the Golgi complex is most accurate?

It has a cis and trans face for directional processing. Signup and view all the answers

What is the primary role of lysosomes in a cell?

Hydrolyzing macromolecules Signup and view all the answers

How do peroxisomes contribute to cellular metabolism?

They catalyze reactions that produce hydrogen peroxide. Signup and view all the answers

What type of vacuole is essential for maintaining water levels in certain cells?

Contractile vacuole Signup and view all the answers

What is a significant function of the central vacuole in plant cells?

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

What process allows lysosomes to recycle organic materials in a cell?

Autophagy Signup and view all the answers

What modification occurs to materials as they pass through the Golgi complex?

They gain molecular tags for sorting. Signup and view all the answers

What do all cells have in common?

Ribosomes Signup and view all the answers

Which of the following statements is true about prokaryotic cells?

Their DNA is located in the nucleoid region. Signup and view all the answers

What is the primary function of the nuclear pores?

To regulate entry and exit of materials Signup and view all the answers

Which of these is NOT an endomembrane organelle?

Mitochondria Signup and view all the answers

What allows compartmentalization to be effective in eukaryotic cells?

Double membranes in organelles Signup and view all the answers

Which unique cell component is found only in plant cells?

Cell wall Signup and view all the answers

Where is ribosomal RNA synthesized?

In the nucleolus Signup and view all the answers

What must occur for DNA to exit the nucleus?

It must be transcribed into mRNA. Signup and view all the answers

What is the primary site of the Krebs cycle within the mitochondria?

Mitochondrial matrix Signup and view all the answers

Which of the following components is found inside the chloroplast?

Thylakoids Signup and view all the answers

What role do microtubules play in the cytoskeleton?

Assisting in the separation of chromosomes during cell division Signup and view all the answers

Which of the following statements about mitochondria is true?

The number of mitochondria correlates with the cell's metabolic activity. Signup and view all the answers

What is the function of the cytoskeleton in cells?

Providing structural and mechanical support Signup and view all the answers

What is located in the stroma of a chloroplast?

Chloroplast DNA Signup and view all the answers

Which type of fiber is responsible for cell motility in the cytoskeleton?

Microtubules Signup and view all the answers

What distinct feature do mitochondria possess that is not found in many other organelles?

All of these features Signup and view all the answers

What is the primary function of albumin in the blood?

Regulates oncotic pressure Signup and view all the answers

What effect does hepatitis C have on liver cells?

Decreases blood-albumin levels Signup and view all the answers

Where is insulin synthesized in normal pancreatic cells?

Endoplasmic reticulum Signup and view all the answers

What is a consequence of the immune system attacking pancreatic cells in type 1 diabetes?

Inability to synthesize insulin Signup and view all the answers

According to the endosymbiont theory, what role did prokaryotic cells play?

They became endosymbionts within eukaryotic cells. Signup and view all the answers

What evidence supports the endosymbiont theory regarding mitochondria?

Ability to replicate independently Signup and view all the answers

What structural feature of mitochondria increases their surface area for cellular respiration?

Cristae on the inner membrane Signup and view all the answers

What is found in the intermembrane space of mitochondria?

Space between inner and outer membranes Signup and view all the answers

Study Notes

Cells

Basic structural and functional units of organisms.
All cells have a plasma membrane, cytosol, chromosomes, and ribosomes.
Two main types of cells: prokaryotes and eukaryotes.

Prokaryotes vs Eukaryotes

Prokaryotes: Include Bacteria and Archaea, DNA located in a nucleoid region, generally smaller than eukaryotes.
Eukaryotes: Include protists, fungi, animals, and plants, DNA contained within a nucleus, possess membrane-bound organelles.

Organelles

Membrane-bound structures found in eukaryotic cells.
Classified into two groups: endomembrane organelles and energy organelles.

Endomembrane Organelles

Nuclear envelope, endoplasmic reticulum, Golgi complex, lysosomes, vesicles/vacuoles, plasma membrane.

Energy Organelles

Mitochondria and chloroplasts.

Compartmentalization

Organelles allow for different metabolic reactions in distinct locations, increasing surface area, and preventing interference between reactions.

Unique Cell Components

Plant unique components: chloroplasts, central vacuole, cell wall, plasmodesmata.
Animal unique components: lysosomes, centrosomes, flagella.

Nucleus

Houses chromosomes and enclosed by a double membrane nuclear envelope with pores that regulate material exchange.
Contains a nucleolus for ribosomal RNA (rRNA) synthesis, which forms ribosome subunits.

Protein Synthesis Process

DNA is transcribed into mRNA, modified, and transported out of the nucleus.
Ribosomes, composed of rRNA and proteins, translate mRNA into polypeptides.

Ribosomes

Located in cytosol ("free ribosomes") or bound to the endoplasmic reticulum ("bound ribosomes").
Free ribosomes synthesize proteins for cytosolic functions, while bound ribosomes produce proteins for secretion or membrane incorporation.

Endoplasmic Reticulum (ER)

Network of membranous sacs and tubes with two types:
- Rough ER: Contains ribosomes, synthesizes membranes, and compartments proteins.
- Smooth ER: Lacks ribosomes, synthesizes lipids, metabolizes carbohydrates, and detoxifies toxins.

Golgi Complex

Composed of flattened membranous sacs called cisternae, with directional flow:
- Cis face receives vesicles from the ER.
- Trans face sends vesicles to cytosol or for secretion.
Modifies, sorts, and packages materials, ensuring correct protein folding.

Lysosomes and Peroxisomes

Lysosomes: Hydrolytic enzyme sacs that recycle cellular materials through autophagy.
Peroxisomes: Membrane-bound compartments that break down hydrogen peroxide (H2O2) produced in metabolic reactions.

Vacuoles

Large vesicles from ER and Golgi with selective transport capabilities.
Types include:
- Food vacuole: Formed via phagocytosis, digested by lysosomes.
- Contractile vacuole: Maintains water levels in cells.
- Central vacuole (plants): Stores inorganic ions and water; crucial for turgor pressure.

Endosymbiont Theory

Explains how mitochondria and chloroplasts resemble prokaryotes, suggesting they originated from engulfed prokaryotic cells.
Evidence includes double membranes, ribosomes, circular DNA, and self-sufficient functioning.

Mitochondria

Powerhouse of the cell, site of cellular respiration.
Features include a smooth outer membrane and a folded inner membrane (cristae) that increases surface area.
Internal compartments include intermembrane space and mitochondrial matrix, where the Krebs cycle occurs.

Chloroplast

Found in photosynthetic organisms, site of photosynthesis containing chlorophyll.
Inner membrane features thylakoids arranged in grana for light-dependent reactions; stroma surrounds thylakoids for the Calvin cycle.

Cytoskeleton

Network of fibers providing structural and mechanical support in the cytoplasm; anchors organelles and facilitates vesicle movement.
Composed of three types of fibers: microtubules, microfilaments, and intermediate filaments.

Microtubules

Hollow, rod-like structures made from tubulin, formed from the centrosome.
Provide structural support for organelle movement and assist in chromosome separation during cell division.

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Description

This quiz explores the essential components of cells, including the differences between prokaryotic and eukaryotic cells. You will also learn about various organelles and their functions in cellular processes. Test your knowledge on the structural and functional units of life!