Biology Cell Structure

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Questions and Answers

What is the main function of microvilli in absorption cells?

To regulate the pH of the cell

To reduce surface area per unit volume

To increase surface area per unit volume (correct)

To control the temperature of the cell

What is the primary difference between prokaryotic and eukaryotic cells?

The size of the cell

The presence or absence of a membrane-bound nucleus (correct)

The number of chromosomes

The type of cell wall

What is the function of the glycocalyx in bacteria cells?

To synthesize proteins

To store nutrients for later use

To maintain the shape of the cell

To protect the cell from drying out and resist the host's immune system (correct)

What is the composition of the plasma membrane?

Lipid bilayer with imbedded and peripheral proteins Signup and view all the answers

What is the function of mesosomes?

To form internal pouches Signup and view all the answers

What is the location of a single, circular DNA molecule in prokaryotic cells?

Nucleoid Signup and view all the answers

What is the composition of cytoplasm?

Semifluid solution containing water, inorganic and organic molecules, and enzymes Signup and view all the answers

What is the function of ribosomes?

To synthesize proteins Signup and view all the answers

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

To modify and package proteins and lipids for transport Signup and view all the answers

Where do the protein-filled vesicles that enter the Golgi apparatus come from?

The rough ER Signup and view all the answers

What is the primary function of lysosomes in a cell?

To digest large molecules that enter the cell Signup and view all the answers

What type of vesicles are produced by the Golgi apparatus?

Transport vesicles Signup and view all the answers

What is the purpose of the enzymes within the Golgi apparatus?

To modify carbohydrates that were placed on proteins in the ER Signup and view all the answers

What is the role of lysosomes in white blood cells?

To digest bacteria that enter the cell Signup and view all the answers

What is the primary function of the endomembrane system?

To compartmentalize the cell and restrict enzymatic reactions Signup and view all the answers

What is the outer membrane of the nuclear envelope continuous with?

Endoplasmic reticulum Signup and view all the answers

What is the function of rough ER?

Synthesis and modification of proteins Signup and view all the answers

What is the characteristic of smooth ER?

No ribosomes Signup and view all the answers

What is the function of the Golgi apparatus?

Modification and transport of molecules Signup and view all the answers

What is the purpose of vesicles in the endomembrane system?

To transport materials between organelles Signup and view all the answers

What is the relationship between the nuclear envelope and the endoplasmic reticulum?

The nuclear envelope is continuous with the endoplasmic reticulum Signup and view all the answers

What is the function of the endoplasmic reticulum?

To synthesize proteins and lipids Signup and view all the answers

What is the pattern of microtubules in a eukaryotic cilium or flagellum?

9 + 2 pattern of microtubules Signup and view all the answers

What is the main difference between the movement of cilia and flagella?

Cilia move in a coordinated wave-like motion, while flagella move in a propeller-like motion Signup and view all the answers

What is the structure that anchors the microtubule doublets to the central pair of microtubules in the flagellum?

Ring of microtubule doublets Signup and view all the answers

What is the function of dynein in the flagellum?

To generate movement in the flagellum Signup and view all the answers

What is the difference between the length of cilia and flagella in eukaryotes?

Cilia are shorter than flagella Signup and view all the answers

What is the structure that surrounds the microtubules in a cilium or flagellum?

Matrix Signup and view all the answers

What is the function of the radial spoke in the flagellum?

To provide structural support to the flagellum Signup and view all the answers

What is the central component of the flagellum?

Central pair of microtubules Signup and view all the answers

What is the composition of the side arms of each doublet?

Dynein motor molecules Signup and view all the answers

What is the function of dynein side arms in the presence of ATP?

They reach out to their neighbors and cause bending Signup and view all the answers

What is the diameter of the flagellum cross section?

25 nm Signup and view all the answers

What is the structure of the basal body of a flagellum?

A ring of nine microtubule triplets Signup and view all the answers

What is the function of ATP in the movement of flagella?

It provides energy for the movement of the flagellum Signup and view all the answers

What is the diameter of the basal body cross section?

100 nm Signup and view all the answers

What is the characteristic of the microtubules in the basal body of a flagellum?

They are arranged in a triplet Signup and view all the answers

What is the location of the dynein motor molecules?

In the side arms of each doublet Signup and view all the answers

Study Notes

Cell Structure and Function

Living cytoplasm demands nutrients and produces wastes.
Cells specialized in absorption utilize membrane modifications like microvilli to increase surface area per unit volume.

Cell Types

There are two main types of cells: prokaryotic and eukaryotic cells.
Prokaryotic cells lack a membrane-bound nucleus, are structurally smaller and simpler than eukaryotic cells, and are classified into two taxonomic domains: Bacteria and Archaea.

Cell Envelope

The cell envelope includes:
Plasma membrane: a lipid bilayer with embedded and peripheral proteins, which can form internal pouches (mesosomes).
Cell wall: maintains the shape of the cell and is strengthened by peptidoglycan.
Glycocalyx: a layer of polysaccharides on the outside of the cell wall, which protects the bacteria cell from drying out and resists the host's immune system.

Cytoplasm

Cytoplasm is a semifluid solution containing water, inorganic and organic molecules, and enzymes.
Ribosomes are particles with RNA- and protein-containing subunits that synthesize proteins.
Mesosomes are plasma membrane folds into the cytoplasm.
Inclusion bodies store nutrients for later use.
The nucleoid is the location of a single, circular DNA molecule.

Endomembrane System

The endomembrane system is a series of intracellular membranes that compartmentalize the cell, restricting enzymatic reactions to specific regions.
It consists of:
Nuclear envelope
Membranes of endoplasmic reticulum
Golgi apparatus
Vesicles

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a system of membrane channels and saccules (flattened vesicles) continuous with the outer membrane of the nuclear envelope.
Rough ER:
Is studded with ribosomes on the cytoplasmic side, synthesizing and modifying proteins.
Forms vesicles that transport molecules to other parts of the cell, notably the Golgi apparatus.
Smooth ER:
Has no ribosomes.
Synthesizes lipids.
Is the site of various synthetic processes, detoxification, and storage.
Forms vesicles that transport molecules to other parts of the cell, notably the Golgi apparatus.

Golgi Apparatus

The Golgi apparatus consists of a stack of slightly curved saccules.
It receives protein-filled vesicles from the rough ER and lipid-filled vesicles from the smooth ER.
Enzymes within the Golgi apparatus modify carbohydrates on proteins.
Proteins and lipids are sorted and packaged within the Golgi apparatus.
Vesicles formed from the membrane of the outer face of the Golgi apparatus move to different locations in the cell, discharging their contents as secretions.

Lysosomes

Lysosomes are membrane-bound vesicles produced by the Golgi apparatus.
They contain powerful digestive enzymes and are highly acidic.
Lysosomes digest large molecules that enter a cell by vesicle formation.
They are involved in autodigestion, apoptosis (programmed cell death), and the digestion of engulfed bacteria in white blood cells.

Cilia and Flagella

Cilia are short, move in coordinated waves, and are found in eukaryotes.
Flagella are long, move like a propeller, and are found in both prokaryotes and eukaryotes.
The structure of a flagellum includes a shaft with a ring of nine microtubule doublets anchored to a central pair of microtubules.
Dynein side arms, composed of motor molecules, cause bending and movement of the flagellum in the presence of ATP.

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Test your knowledge of cell structure and function, including specialization for absorption and differences between prokaryotic and eukaryotic cells.