Cell Structure and Functions Quiz

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Questions and Answers

What is one function of peroxisomes?

Synthesis of ribosomal RNA

Catabolism of long-chained fatty acids (correct)

Storage of glycogen and lipids

Proteolysis of malformed proteins

Which of the following correctly describes lysosomes?

Are the largest intracellular organelles

Contain hydrolytic enzymes and maintain acidic pH (correct)

Have a basic pH and store fatty acids

Contain both glycolytic and oxidative enzymes

What component of the cytoskeleton is primarily responsible for cellular motion?

Intermediate filaments

Microtubules

Nuclear filaments

Thin filaments (microfilaments) (correct)

What is not a characteristic of inclusions within a cell?

Possess metabolic activity Signup and view all the answers

Where is ribosomal RNA synthesized within the nucleus?

Nucleolus Signup and view all the answers

Which organelle is responsible for the proteolysis of malformed and ubiquitin-tagged proteins?

Proteasome Signup and view all the answers

How is the nucleus structured?

Surrounded by two lipid membranes Signup and view all the answers

Which of the following best describes the size and shape of peroxisomes?

Small and spherical to ovoid in shape Signup and view all the answers

What is the primary role of mitochondria in the cell?

Oxidative phosphorylation and lipid synthesis Signup and view all the answers

Which of the following best describes the functions of the rough endoplasmic reticulum (rER)?

Synthesis of secretory proteins and cell membrane proteins Signup and view all the answers

What distinguishes free ribosomes from attached ribosomes?

Free ribosomes synthesize proteins for use within the cell Signup and view all the answers

Which component is not found in the cytosol?

Cell wall Signup and view all the answers

What is the main function of the Golgi apparatus?

Packaging of export proteins and synthesis of carbohydrates Signup and view all the answers

What is the primary function of lysosomes in a cell?

Degradation of macromolecules and cellular waste Signup and view all the answers

Which of the following statements about cytosol is incorrect?

It contains cell organelles only Signup and view all the answers

What is true about the structure of mitochondria?

They possess porins in the outer membrane Signup and view all the answers

What function does the plasma membrane perform in a cell?

Selective permeability barrier Signup and view all the answers

Which characteristic is unique to eukaryotic cells compared to prokaryotic cells?

Presence of a nuclear envelope Signup and view all the answers

Which cellular structure is primarily responsible for the synthesis of proteins?

Rough endoplasmic reticulum Signup and view all the answers

What role do integral proteins play in the plasma membrane?

Transport and signaling Signup and view all the answers

What is a defining feature of prokaryotic cells?

No membrane-bound organelles Signup and view all the answers

What type of transport mechanism is endocytosis?

Movement of large particles into the cell Signup and view all the answers

Which type of junction is characterized by allowing cell-cell adhesion?

Adhesive junctions Signup and view all the answers

Cell movement and transport across the membrane can occur through which of the following?

Endocytosis and exocytosis Signup and view all the answers

Which of the following describes the fluid mosaic model of the plasma membrane?

Dynamic arrangement of proteins and lipids Signup and view all the answers

What is the primary reason for the variation in cell shape and size?

Specificity to tissue function Signup and view all the answers

Study Notes

Aim and Objectives

Aim: Introduce the structure of cells.
Objectives: Understand organization levels, define cells, distinguish cell types, explore cellular regions, describe organelles, and discuss transport mechanisms.

Levels of Organization

Chemical level: Forms atoms and molecules which aggregate into organelles.
Cell: Organelles combine to create cells.
Tissue: Groups of similar cells that perform common functions.
Organ level: Structures composed of at least two different tissues.
Organ system level: Combinations of two or more organs functioning together.
Organism level: Composed of multiple organ systems.

Definition and Types of Cells

Cells are the functional units of living organisms.
Two primary cell types:
- Prokaryotic: Small, lack nucleus and membranous organelles.
- Eukaryotic: Larger, contain nucleus and complex organelles.

Comparison of Cell Types

Prokaryotic cells (e.g. bacteria):
- Size: 1-5 micrometers
- Presence of cell wall
- No nuclear envelope or histones
- Lack membranous organelles
Eukaryotic cells:
- Larger size
- Have cell membrane and distinct nuclear envelope
- Histones associated with DNA
- Contain membrane-bound organelles.

General Characteristics of Mammalian Cells

Shapes and sizes vary widely among cell types (5-50 μm in diameter).
Functions include motility and communication.

Cellular Functions

Movement (e.g., muscle contractions)
Synthesis of enzymes, mucus, and steroids
Ion transport and intracellular digestion
Conversion of energy into nervous impulses
Absorption of metabolites.

Components of a Human Cell

Approximately 200 different cell types serve distinct roles.
Basic structure includes:
- Plasma membrane
- Cytoplasm (area between membrane and nucleus)
- Nucleus.

Plasma Membrane

Acts as a selectively permeable barrier.
Composed of lipids (phospholipids, cholesterol 20%, glycolipids 5%) and proteins.
Maintains a fluid mosaic structure.

Membrane Proteins

Two types:
- Integral proteins (transmembrane or embedded)
- Peripheral proteins.
Functions include transport, signaling, and enzymatic activity.

Cell Membrane Functions

Transport processes: diffusion, endocytosis, exocytosis.
Signal reception to detect foreign materials.
Generation of electrochemical gradients.
Structural integrity maintenance and cell interaction regulation.

Cell Surface Contacts

Adhesive contacts: General and specialized (tight junctions, intermediate junctions).
Gap junctions facilitate communication between cells.

Cytoplasm and Cytosol

Cytoplasm consists of organelles and cytosol.
Cytosol contains organic and inorganic substances, organelles, cytoskeleton, and inclusions.

Organelles

Membrane-bound: Golgi apparatus, endosomes, lysosomes, mitochondria, ER (rough and smooth).
Non-membrane-bound: Cytoskeleton, centrioles, and ribosomes.

Mitochondria

Flexible, rod-shaped organelles with double membranes.
Function in ATP production, lipid synthesis, and citric acid cycle.
Contain their own DNA and ribosomes.

Ribosomes

Small structures composed of rRNA and proteins.
Form two subunits and synthesize proteins.
Free ribosomes produce proteins for internal use; attached ribosomes for export.

Endoplasmic Reticulum (ER)

Largest membranous system in cells with two types:
- Rough ER: Synthesizes secretory and membrane proteins.
- Smooth ER: Involved in lipid metabolism and steroid hormones.

Golgi Apparatus

Stacks of membranous sacs for packaging export proteins and carbohydrate synthesis.

Endosomes and Lysosomes

Endosomes: Early (peripheral) and late (deeper) compartments.
Lysosomes contain hydrolytic enzymes for breakdown; linked to certain storage disorders.

Peroxisomes

Small organelles with oxidative enzymes.
Involved in fatty acid catabolism and detoxifying harmful substances.

Proteasomes

Complexes that degrade ubiquitinated proteins.

Inclusions

Non-living cellular components without metabolic activity (e.g., glycogen, lipid droplets).

Cytoskeleton

3D network of protein filaments that maintain cell shape and enable motion.
Composed of microfilaments (actin), intermediate filaments (keratins), and microtubules.

Nucleus

Largest organelle, typically spherical or ellipsoid.
Contains most DNA and mechanisms for RNA synthesis.
Bounded by nuclear membrane and includes chromatin, nucleolus, and nucleoplasm.
May vary in shape and has a generally uniform size across cell types.

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Description

This quiz will test your knowledge on the structure and functions of cells, including the different types of cells and their specific features. You will also explore the organelles present in human and mammalian cells and their roles. Prepare to dive into the fascinating world of cellular organization!