Cell Structure and Functions Quiz

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Questions and Answers

What is the primary function of the nuclear envelope?

Facilitates protein synthesis

Acts as a transport pathway for enzymes

Provides protection and organization for genetic material (correct)

Helps in ribosome assembly

Which structure is responsible for ribosome assembly within the nucleus?

Nuclear envelope

Nucleoplasm

Nucleolus (correct)

Endoplasmic reticulum

How are the membranes in the endomembrane system connected?

They are always directly connected

They may connect directly or via vesicles (correct)

They only connect during protein transport

They are all completely independent of each other

What characterizes rough endoplasmic reticulum compared to smooth endoplasmic reticulum?

It is studded with ribosomes Signup and view all the answers

What is the function of nuclear pores in the nuclear envelope?

To allow transport of proteins and RNA Signup and view all the answers

Which component is NOT part of the endomembrane system?

Nucleus Signup and view all the answers

What occurs in the ER lumen of the rough endoplasmic reticulum?

Proteins are modified after entry Signup and view all the answers

What is the composition of the endoplasmic reticulum membranes?

Network of flattened, fluid-filled tubules Signup and view all the answers

What is one of the main functions of the Golgi apparatus?

Modification and packaging of proteins and lipids Signup and view all the answers

Which of the following correctly describes lysosomes?

Contain hydrolytic enzymes for digestion Signup and view all the answers

What process do lysosomes use to digest worn-out organelles?

Autophagy Signup and view all the answers

The inner face of the Golgi apparatus is oriented towards which structure?

Endoplasmic reticulum Signup and view all the answers

What are the three overlapping functions of the Golgi apparatus?

Secretion, processing, and protein sorting Signup and view all the answers

What is the main purpose of microscopy?

To examine the structure and function of cells Signup and view all the answers

Which of the following correctly describes the resolution of a light microscope?

0.2 µm Signup and view all the answers

What distinguishes prokaryotic cells from eukaryotic cells?

Prokaryotic cells are smaller and lack a membrane-enclosed nucleus Signup and view all the answers

Among the following characteristics, which is NOT true for prokaryotic cells?

Prokaryotic cells have a complex internal structure Signup and view all the answers

What is the primary function of the capsule in prokaryotic cells?

To protect against phagocytosis by cells Signup and view all the answers

Which of these parameters is NOT associated with microscopy?

Transmission Signup and view all the answers

Eukaryotic cells are characterized by which of the following features?

They contain membrane-enclosed organelles Signup and view all the answers

Which of the following cell types is typically not harmful and is abundant in the environment?

Bacteria Signup and view all the answers

What is the main function of the plasma membrane in a prokaryotic cell?

Regulating substance entry and exit Signup and view all the answers

What distinguishes mycoplasma from other bacteria regarding the cell wall?

They do not have a cell wall Signup and view all the answers

Which component of the cell envelope helps protect against the immune system?

Glycocalyx Signup and view all the answers

What are plasmids primarily known for in prokaryotic cells?

Carrying non-essential genes and resistance traits Signup and view all the answers

Which statement accurately describes the structure of the bacterial cell wall?

It consists of amino disaccharides and peptide fragments Signup and view all the answers

In bacteria, what does a 'capsule' refer to regarding the glycocalyx?

A firmly attached layer of polysaccharides Signup and view all the answers

What characteristic is true of the DNA in prokaryotic cells?

It is circular and lacks histone proteins Signup and view all the answers

What is the role of the glycocalyx in bacteria?

To aid in attachment and provide protection Signup and view all the answers

What is the main function of contractile vacuoles in protists?

Expelling excess water Signup and view all the answers

Which of the following is a true statement regarding peroxisomes?

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

What role do mitochondria play in cells?

Producing most of the ATP used by the cell. Signup and view all the answers

What characteristic makes mitochondria and chloroplasts semiautonomous organelles?

They divide by fission to produce more organelles. Signup and view all the answers

What substance is produced as a by-product of the β-oxidation process in peroxisomes?

Hydrogen peroxide (H2O2) Signup and view all the answers

Which of the following is NOT a function of vacuoles?

Protein synthesis Signup and view all the answers

What is the primary role of the plasma membrane in a cell?

Serving as a barrier and regulating transport. Signup and view all the answers

Which statement about the inner membrane of mitochondria is correct?

It is the primary site of ATP production. Signup and view all the answers

Study Notes

Nucleus

Nuclear membrane has pores to allow transport of proteins and RNA to the cytoplasm.
It protects, organizes, and expresses genetic material.
Ribosome assembly occurs in the nucleolus.
Nucleoplasm is the fluid inside the nucleus.

Endomembrane System

A network of membranes enclosing the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.
Includes the plasma membrane.
Membranes may be directly connected or pass materials via vesicles.
Restricts enzymatic reactions to specific cell compartments.

Nuclear Envelope

A double-membrane structure enclosing the nucleus.
The outer membrane is continuous with the endoplasmic reticulum membrane.
Nuclear pores provide passageways for materials to move in and out of the nucleus.
Materials within the nucleus are not part of the endomembrane system.

Endoplasmic Reticulum

A network of membranes that form flattened, fluid-filled tubules called cisternae.
The ER membrane encloses a compartment called the ER lumen.
Physically continuous with the outer membrane of the nuclear envelope.
Rough endoplasmic reticulum (rough ER) has ribosomes attached on the side of the membrane facing the cytoplasm.
- Involved in protein synthesis and sorting.
- Modifies proteins after they enter the ER lumen.
- ER enzymes add carbohydrate chains to proteins.
- Other enzymes assist in protein folding.
Smooth endoplasmic reticulum (smooth ER) is continuous with rough ER.
- Has no attached ribosomes.

Cell Theory

All living things are composed of one or more cells.
Cells are the smallest units of living organisms.
New cells come only from pre-existing cells by cell division.

Microscopy

Cells are too small to be seen with the naked eye.
Microscopes are magnification tools that enable researchers to study the structure and function of cells.
Magnification, resolution, and contrast are important parameters in microscopy.
- Magnification is the ratio between the size of an image produced by a microscope and its actual size.
- Resolution is the ability to distinguish between two adjacent objects.
- Contrast is the ability to visualize a particular cell structure based on its difference from adjacent structures.

Microscope Types

Microscopes are categorized based on the source of illumination:
- Light microscopes use light for illumination and have a resolution of 0.2 µm.
- Electron microscopes use an electron beam for illumination and have a resolution of 2 nm.

Cell Types

Based on cell structure, there are two types of cells:
- Prokaryotic cells (bacteria and archaea)
- Eukaryotic cells

Prokaryotic Cells

Simple cell structure lacking a membrane-enclosed nucleus.
Much smaller than eukaryotic cells.
Abundant in air, water, soil, and human organs.
Two categories: bacteria and archaea.
- Bacteria are abundant, most are not harmful.
- Archaea are less common and often found in extreme environments.

Prokaryotic Cell Structure

All prokaryotic cells contain:
- Cell wall
- Cell membrane
- Cytoplasm
- DNA
- Ribosomes
Some prokaryotic cells contain:
- Capsule
- Plasmids
- Flagella
- Pili
- Membrane infolding

Typical Bacterial Cell

Contains cell envelope, cytoplasm, and appendages.

Prokaryotic Cell Envelope

Includes the plasma membrane, cell wall, and glycocalyx.
- Plasma membrane:
  - Phospholipid bilayer like in eukaryotic cells.
  - Regulates the entrance and exit of substances into the cytoplasm.
- Cell wall:
  - Composed of peptidoglycan (amino disaccharides and peptide fragments).
  - Maintains the overall shape of a bacterial cell (coccus, bacillus, and spiral).
  - Bacteria without a cell wall (Mycoplasma) have no definite shape.
  - The cell wall is above the plasma membrane.
  - Bacteria are categorized as gram-positive or gram-negative based on the cell wall.
- Glycocalyx:
  - Layer of polysaccharides outside the cell wall.
  - Aids in preventing drying out by trapping water and helps bacteria resist a host's immune system.
  - Allows bacteria to attach to inert surfaces (teeth, rocks), eukaryotes, or other bacteria.
  - Secreted from the inside of the cell and forms a layer outside.
  - Viscous.

Glycocalyx or Capsule

When glycocalyx is firmly attached to the cell wall, it is called a capsule, otherwise it is a slime layer.
A well-organized layer of polysaccharide.
Protects the bacterial cell and is often associated with pathogenic bacteria as it serves as a barrier against phagocytosis by white blood cells.
Made from starch or glycolipid.
Protects bacteria from drying out (desiccation).
Prevents detection by the immune system.
Protects from viruses.
Has adhesion properties.

Prokaryotic Cell Structure cont.

No nucleus
Nucleoid floats in cytoplasm
One chromosome which is circular
DNA is "naked" because there are no histone proteins associated with it.

Prokaryotic Plasmids

Smaller circular DNA molecules.
Contain resistance genes that can be transferred to other organisms.
Non-essential genes.
Replication is independent of chromosomal DNA.
Involved in detoxification, carbohydrate metabolism, calcium balance, synthesis, and modification of lipids.

Golgi Apparatus

Also called Golgi body, Golgi complex, or simply Golgi.
Stack of flattened, membrane-bounded compartments, which are not continuous with the ER.
Plays roles in post-translational modification.
In animal cells, the inner face is directed toward the ER, and the outer face is directed toward the plasma membrane.
Modifies proteins and lipids and packages them in vesicles.
Vesicles transport materials between stacks.
Three overlapping functions: secretion, processing, and protein sorting.

Lysosomes

Membrane-bounded vesicles produced by the Golgi apparatus.
Have a very low pH and contain powerful hydrolytic digestive enzymes (acid hydrolases) to break down proteins, carbohydrates, nucleic acids, and lipids.
Digest food particles, engulfed viruses or bacteria through endocytosis.
Digest excess or worn-out organelles through autophagy ("self death").
The membrane surrounding a lysosome prevents the digestive enzymes inside from destroying the cell.

Vacuoles

Functions of vacuoles are extremely varied and differ among cell types and environmental conditions.
Central vacuoles in plants are used for storage and support.
Contractile vacuoles in protists expel excess water.
Phagocytic vacuoles in protists and white blood cells are involved in degradation.

Peroxisomes

Relatively small organelles found in all eukaryotic cells.
Their general function is to catalyze certain chemical reactions, typically those that break down molecules by removing hydrogen or adding oxygen.
Reaction by-product is hydrogen peroxide (H2O2).
Hydrogen peroxide is immediately broken down to water and oxygen by another peroxysomal enzyme called catalase.
Peroxisome enzymes are cell-specific.
In liver peroxisomes, enzymes produce bile salts from cholesterol and others break down fats.

Plasma Membrane

Boundary between the cell and the extracellular environment.
Membrane transport in and out of the cell.
Selectively permeable.
Cell signaling using receptors.
Cell adhesion.

Semiautonomous Organelles

Semiautonomous because they divide by fission to produce more of themselves.
Somewhat independent, as they have genetic material, synthesize some proteins, and divide independently of the cell.
Not entirely autonomous, as they depend on the cell for raw materials and most of their proteins.
Examples include mitochondria and chloroplasts.

Mitochondria

Involved in cellular respiration.
Carbohydrate + oxygen → carbon dioxide + water + energy (ATP).
Adenosine triphosphate (ATP) is used for all energy-requiring processes in cells.
Mitochondria produce most of the ATP utilized by the cell.
Mitochondria have two membranes: the outer and the inner membrane.
The inner membrane that encloses the matrix is called cristae.

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Description

Test your knowledge on the structure and functions of the cell organelles including the nucleus, endomembrane system, and endoplasmic reticulum. This quiz covers key aspects such as the nuclear membrane, ribosome assembly, and functions of different cell compartments. Perfect for students learning cellular biology!