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Questions and Answers
What is one function of peroxisomes?
Which of the following correctly describes lysosomes?
What component of the cytoskeleton is primarily responsible for cellular motion?
What is not a characteristic of inclusions within a cell?
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Where is ribosomal RNA synthesized within the nucleus?
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Which organelle is responsible for the proteolysis of malformed and ubiquitin-tagged proteins?
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How is the nucleus structured?
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Which of the following best describes the size and shape of peroxisomes?
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What is the primary role of mitochondria in the cell?
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Which of the following best describes the functions of the rough endoplasmic reticulum (rER)?
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What distinguishes free ribosomes from attached ribosomes?
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Which component is not found in the cytosol?
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What is the main function of the Golgi apparatus?
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What is the primary function of lysosomes in a cell?
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Which of the following statements about cytosol is incorrect?
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What is true about the structure of mitochondria?
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What function does the plasma membrane perform in a cell?
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Which characteristic is unique to eukaryotic cells compared to prokaryotic cells?
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Which cellular structure is primarily responsible for the synthesis of proteins?
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What role do integral proteins play in the plasma membrane?
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What is a defining feature of prokaryotic cells?
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What type of transport mechanism is endocytosis?
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Which type of junction is characterized by allowing cell-cell adhesion?
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Cell movement and transport across the membrane can occur through which of the following?
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Which of the following describes the fluid mosaic model of the plasma membrane?
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What is the primary reason for the variation in cell shape and size?
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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!
