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Questions and Answers
What is the basic structural and functional unit of the living body?
What is the basic structural and functional unit of the living body?
Cell
What are the varying shapes cells can take? (Select all that apply)
What are the varying shapes cells can take? (Select all that apply)
The two basic components of a cell are ______ and ______.
The two basic components of a cell are ______ and ______.
cytoplasm, nucleus
Which of the following is NOT a function of cells?
Which of the following is NOT a function of cells?
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What is cytoplasm formed of?
What is cytoplasm formed of?
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Match the following types of organelles with their characteristics:
Match the following types of organelles with their characteristics:
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The cell membrane is the innermost covering of the cell.
The cell membrane is the innermost covering of the cell.
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Which of the following layers is a part of the cell membrane's trilaminar structure?
Which of the following layers is a part of the cell membrane's trilaminar structure?
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What molecules restrict the movement of phospholipids in the cell membrane?
What molecules restrict the movement of phospholipids in the cell membrane?
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What are the two main types of proteins found in the cell membrane?
What are the two main types of proteins found in the cell membrane?
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The carbohydrate layer over the cell membrane is called the ______.
The carbohydrate layer over the cell membrane is called the ______.
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Passive diffusion requires energy in the form of ATP.
Passive diffusion requires energy in the form of ATP.
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What are the two types of endocytosis?
What are the two types of endocytosis?
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Study Notes
Cytology
- The cell is the basic building block of all living things.
- Cells can vary in size from 4 µm to 150 µm.
- Cells come in a variety of shapes, including rounded, oval, flat, stellate, polygonal, cubical, and columnar.
- Cells are responsible for various essential functions including absorption, respiration, secretion, excretion, sensation, conduction, movement, and contraction.
- The cell is comprised of two main components: cytoplasm and nucleus.
Cytoplasm
- Cytoplasm is made up of three primary elements:
- Cytoplasmic matrix (cytosol): Contains carbohydrates, minerals, ions and salts, RNA, metabolites, oxygen, and carbon dioxide.
- Cytoplasmic organelles: Structures within the cytoplasm that perform specific functions.
- Cytoplasmic inclusions: Non-living components within the cytoplasm.
Cytoplasmic Organelles
- Cytoplasmic organelles are divided into two categories based on their structure:
- Membranous organelles: Enclosed by membranes, contain enzymes, and include:
- Cell membrane
- Ribosomes
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus
- Lysosome
- Peroxisome
- Endosome
- Coated secretory vesicle
- Non-membranous organelles: Lack membranes, do not contain enzymes, and include:
- Cytoskeleton
- Microtubules: Responsible for forming cilia, centrioles, and flagella.
- Microfilaments: Form microvilli.
- Proteasome
- Cytoskeleton
- Membranous organelles: Enclosed by membranes, contain enzymes, and include:
Cell Membrane
- The cell membrane is the outermost covering of the cell.
- It is extremely thin (7.5-10 nm), making it difficult to see under a light microscope (LM).
- It can be stained using specific techniques like silver (Ag) stain and PAS stain.
- The cell membrane appears trilaminar under an electron microscope (EM), consisting of two electron-dense (dark) layers separated by one electron-lucent (light) layer.
Molecular Structure of the Cell Membrane
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The cell membrane is composed of lipids and proteins:
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Lipids
- Phospholipids: Form a bilayer structure in the cell membrane.
- Heads (phospholipid): Charged, polar, hydrophilic, and directed towards aqueous solutions.
- Tails (fatty acids): Non-charged, non-polar, hydrophobic, and face inward, away from aqueous solutions.
- Cholesterol: Located within the hydrophobic fatty acid tails, stabilizing the cell membrane by restricting phospholipid movement.
- Phospholipids: Form a bilayer structure in the cell membrane.
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Proteins
- Integral (intrinsic): Embedded within the phospholipid bilayer, forming channels for transport of ions and water, and carrier proteins for transport of small polar molecules and ions like the sodium-potassium pump.
- Peripheral (extrinsic): Loosely attached to both surfaces of the cell membrane, playing a role in various cellular functions.
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Carbohydrates within the Cell Membrane
- Carbohydrates form a surface layer called the glycocalyx, composed of glycoproteins and glycolipids.
- The glycocalyx is located on the external surface of the cell membrane.
- It contains receptors for drugs, hormones, bacteria, and viruses, playing essential roles in cell adhesion, protection, recognition, immunity, and receptor functions.
Functions of the Cell Membrane
- The cell membrane performs various critical functions:
- Passive Diffusion: Allows the movement of gases, water, and ions across the membrane.
- Active Transport: Uses energy (ATP) to move large molecules and ions across the membrane.
- Selective Transport (Permeability): Allows specific molecules to cross the membrane using receptors.
- Endocytosis: Brings substances into the cell through:
- Phagocytosis (cell eating): Engulfing solid particles.
- Pinocytosis (cell drinking): Taking up fluids.
- Exocytosis: Expels substances from the cell.
- Surface Modifications: Creates specialized structures on the cell surface:
- Cilia: Generate currents (e.g., in the trachea).
- Flagella: Allow for movement (e.g., in sperm cells).
- Microvilli: Increase surface area (e.g., in intestinal epithelial cells).
- Desmosomes: Provide cell adhesion (e.g., in epithelial cells).
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Description
Test your understanding of cytology and the various components of cells. This quiz covers essential functions, structure, and organelles found within cytoplasm. Discover how these elements work together to sustain life.
