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Questions and Answers
What is the basic living structural and functional unit of the body?
What is the basic living structural and functional unit of the body?
cell
Which of the following are parts of a cell? (Select all that apply)
Which of the following are parts of a cell? (Select all that apply)
What is the thickness range of the plasma membrane?
What is the thickness range of the plasma membrane?
6.5 – 10 nm
What are the main components of plasma membranes? (Select all that apply)
What are the main components of plasma membranes? (Select all that apply)
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What function do glycolipids serve in the plasma membrane?
What function do glycolipids serve in the plasma membrane?
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The plasma membrane is completely impermeable to all substances.
The plasma membrane is completely impermeable to all substances.
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What role do ribosomes play in the cell?
What role do ribosomes play in the cell?
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What is the main function of the Golgi complex?
What is the main function of the Golgi complex?
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What substance is primarily created by mitochondria in the cell?
What substance is primarily created by mitochondria in the cell?
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The cytoplasm consists of approximately ___% water.
The cytoplasm consists of approximately ___% water.
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Which of the following is NOT a type of organelle?
Which of the following is NOT a type of organelle?
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What is the function of lysosomes?
What is the function of lysosomes?
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What do centrosomes contain that play a role in cell division?
What do centrosomes contain that play a role in cell division?
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What is stored in the cells of the skin, hair, and eyes to protect from ultraviolet rays?
What is stored in the cells of the skin, hair, and eyes to protect from ultraviolet rays?
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Match the following organelles with their primary function:
Match the following organelles with their primary function:
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What is the basic living structural and functional unit of the body?
What is the basic living structural and functional unit of the body?
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Which of the following are principal parts of a cell? (Select all that apply)
Which of the following are principal parts of a cell? (Select all that apply)
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The plasma membrane is typically thicker than 10 nm.
The plasma membrane is typically thicker than 10 nm.
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What type of molecules stabilize the cell membrane?
What type of molecules stabilize the cell membrane?
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What is selective permeability in relation to the plasma membrane?
What is selective permeability in relation to the plasma membrane?
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Match the following components with their primary functions:
Match the following components with their primary functions:
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What is the primary function of lysosomes?
What is the primary function of lysosomes?
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What component of the cytoskeleton is made of protein actin?
What component of the cytoskeleton is made of protein actin?
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Lipids are stored in adipocytes.
Lipids are stored in adipocytes.
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The plasma membrane is composed mainly of ______ and proteins.
The plasma membrane is composed mainly of ______ and proteins.
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Study Notes
The Cell
- The cell is the basic unit of life, fundamental for structure and function in the body.
- A cell is composed of four main parts: plasma membrane, cytoplasm, organelles, and inclusions.
The Plasma Membrane
- The outer boundary of a cell, separating the internal environment from the extracellular space.
- Thin, measuring 6.5-10nm in thickness.
- Composed of phospholipids, proteins, cholesterol, glycolipids, water, carbohydrates, and ions.
Phospholipids
- Arranged in two parallel rows forming a lipid bilayer.
- Have a hydrophilic head group and two long hydrophobic hydrocarbon chains.
Glycolipids
- Located on the outer surface of the plasma membrane.
- Contain an oligosaccharide in the hydrophilic head, projecting into the surrounding environment.
Proteins
- Found embedded in the lipid matrix.
- Extend through the entire membrane or anchored to the outer or inner layer.
- Some provide channels for water and ion diffusion.
- Hydrophobic parts are within the lipid membrane, hydrophilic groups on the outer surfaces.
- Many proteins on the outer surface have glycoproteins acting as receptor sites for cell recognition, hormones, nutrients, and other chemicals.
Cholesterol
- Present in nearly equal numbers to phospholipids.
- Inter-dispersed among phospholipids.
- Stabilize the cell membrane.
Functions of the Plasma Membrane
- Flexible boundary enclosing cellular contents, separating them from the external environment.
- Facilitates cell-to-cell contact with other cells or foreign substances.
- Provides receptors for hormones, neurotransmitters, enzymes, nutrients, and antibodies.
- Mediates the passage of certain substances, restricting others - selective permeability.
Selective Permeability of the Plasma Membrane
- Based on several factors:
- Size of molecules: Small molecules (water, amino acids) pass more easily than large molecules (proteins).
- Lipid solubility: Lipid-soluble substances (oxygen, carbon dioxide, steroid hormones) pass more readily.
- Charge on ions: Charged ions are attracted to the membrane based on their charge, making it easier to cross.
- Presence of carrier molecules: Integral proteins can attract and transport substances regardless of size, solubility, or charge.
Cytoplasm
- The substance within the plasma membrane, excluding the nucleus.
- The matrix or ground substance of the cell.
- Thick, semitransparent, elastic fluid containing the cytoskeleton.
- Composed of water (75-90%), proteins, carbohydrates, lipids, and inorganic substances.
Functions of Cytoplasm
- Site of chemical reactions like synthesis of new substances and packaging chemicals for transport.
- Facilitates excretion of waste material.
Organelles
- Specialised portions of the cell responsible for growth, maintenance, repair, and control.
Types of Organelles
- Nucleus: Control center of the cell, usually round or oval, separated from the cytoplasm by the nuclear membrane. Contains DNA and RNA for protein synthesis.
- Ribosomes: Tiny granules composed of rRNA, found on rough ER or scattered in cytoplasm. Site of protein synthesis.
-
Endoplasmic Reticulum (ER): System of parallel membranes surrounding a network of channels, continuous with the nuclear membrane.
- Granular (rough) ER: Dotted with ribosomes.
- Agranular (smooth) ER: Does not have ribosomes.
- Golgi Complex: Located near the nucleus, composed of 4-8 flattened membranous sacs. Responsible for processing, sorting, and delivering proteins, lipid packaging, and secretion.
- Mitochondria: Sausage-shaped structures scattered throughout the cytoplasm, containing two membranes (outer-smooth, inner-folded into cristae). Produce ATP for the cell's energy.
- Lysosomes: Small spherical structures dispersed in the cytoplasm, containing digestive enzymes. Function is to remove cellular debris.
- Centrosome & Centrioles: Centrosome is a dense area near the nucleus, containing centrioles (cylindrical structures). Play a role in spindle formation during cell division.
Cell Inclusions
- Melanin: Pigment stored in skin, hair, and eyes, protecting from ultraviolet radiation.
- Glycogen: Polysaccharide stored in the liver, skeletal muscle, and vaginal mucosa. Broken down into glucose by the liver.
- Lipids: Stored in adipocytes, can be decomposed to produce energy.
- Mucus: Provides lubrication and protection.
The Cytoskeleton
- A network of protein filaments and cylinders that determine cell shape, provide structural support, organize cell contents, and move substances through the cell.
Types of Cytoskeletal Elements
- Microfilaments: 6nm thick, made of the protein actin, keep phospholipids together.
- Intermediate Filaments: 8-10nm thick, stiffer, resist stress.
- Microtubules: 25nm in diameter, cylindrical structures made of protein filaments.
The Cell
- The basic functional and structural unit of the body
- Divided into 4 parts: Plasma Membrane, Cytoplasm, Organelles, Inclusions
The Plasma Membrane
- Outer layer of the cell and separates the cell's internal environment from the external environment
- 6.5 - 10nm thick
- Composed of phospholipids, proteins, cholesterol, glycolipids, water, carbohydrates, ions
Phospholipids
- Arranged in two layers forming a lipid bilayer
- Contains a hydrophilic head and two hydrophobic tails (hydrocarbon chains)
- Spontaneously form a bilayer, with hydrophilic heads pointing out towards water and hydrophobic tails packed together
Glycolipids
- Located on the outer surface of the plasma membrane
- Have an oligosaccharide in the hydrophilic head that projects into the environment
Proteins
- Main functional components of the membrane, embedded within the lipid matrix
- Some extend through the whole membrane, others are anchored to only the outer or inner layer
- Provide channels for water and ions to diffuse in and out of the cell
- Hydrophobic parts of proteins are located within the lipid membrane, with hydrophilic groups on the outside
- Many proteins are glycoproteins, acting as receptor sites for cells, hormones, nutrients, enzymes, antibodies
Cholesterol
- Found in almost equal numbers to phospholipids
- Interspersed among phospholipids
- Stabilize the cell membrane
Functions of the Plasma Membrane
- Flexible boundary enclosing the cellular content and separating it from the external environment
- Facilitates contact with other cells
- Provides receptors for various substances
- Mediates the entrance and exit of specific substances, restricting the passage of others
- Selective permeability
Factors Affecting Permeability of the Plasma Membrane
- Size of molecules: Small molecules like water and amino acids can enter and exit easily, larger molecules like most proteins cannot enter due to size restrictions of channels
- Solubility in lipids: Lipid soluble substances like oxygen, carbon dioxide, steroid hormones pass through quickly
- Charge on ions: The charge of an ion influences its permeability, attracting to or repelling from the membrane
- Presence of carrier molecules: Some integral proteins attract and transport substances across the membrane, regardless of other factors
Cytoplasm
- Substance within the plasma membrane and external to the nucleus
- Matrix or ground substance of the cell
- Thick, semi-transparent, elastic fluid containing the cytoskeleton
- Composed of water (75-90%), proteins, carbohydrates, lipids, inorganic substances
- Site where some chemical reactions occur, including synthesis of new substances and packaging of chemicals
Organelles
- Specialized portions of the cell, involved in growth, maintenance, repair, control
- Include: Nucleus, Ribosomes, Endoplasmic Reticulum, Golgi Complex, Mitochondria, Lysosomes, Centrosome, Centrioles
Nucleus
- Usually round or oval
- Largest structure in the cell
- "Control center" of the cell
- Separated from the cytoplasm by the nuclear membrane (contains pores)
- Contains DNA and RNA which control protein synthesis
Ribosomes
- Tiny granules made of ribosomal RNA (rRNA)
- Found on the rough endoplasmic reticulum or in the cytoplasm
- Site of protein synthesis
Endoplasmic Reticulum
- System of parallel membranes surrounding a network of channels
- Continuous with the nuclear membrane
- Two types:
- Granular (rough) ER: Dotted with ribosomes
- Agranular (smooth) ER: Without ribosomes
- Provides a surface area for chemical reactions
- Acts as a transport channel for substances throughout the cell
- Storage site for synthesized molecules
- Involved in packaging molecules with Golgi complex
Golgi Complex
- Located near the nucleus
- Composed of four to eight flattened membranous sacs, stacked upon one another
- Functions include:
- Processing, sorting, and delivering proteins to various parts of the cell
- Lipid packaging and secretion
Mitochondria
- Sausage-shaped structures scattered in the cytoplasm
- Consist of two membranes:
- Outer membrane - smooth
- Inner membrane - folded into cristae, increasing surface area for chemical reactions
- Provide energy for the cell by producing ATP through:
- Glycolysis of glucose to pyruvate
- Krebs' Cycle which utilizes pyruvate, fatty acids, and amino acids to produce ATP
Lysosomes
- Small spherical structures dispersed in the cytoplasm
- Contain powerful digestive enzymes
- Remove debris from within the cell
Centrosome and Centrioles
- Centrosome is a dense area of the cytoplasm near the nucleus
- Contains two cylindrical structures called centrioles
- Involved in spindle formation during cell division
Cell Inclusions
- Stored materials in the cell
- Melanin: Pigment stored in skin, hair, eyes, it protects against UV rays
- Glycogen: Polysaccharide stored in the liver, skeletal muscles, vaginal mucosa, broken down into glucose by the liver
- Lipids: Stored in adipocytes, can be decomposed to produce energy
- Mucus: Provides lubrication and protection
The Cytoskeleton
- Network of protein filaments and cylinders
- Determines cell shape, provides structural support, organizes contents, moves substances through the cell
- Composed of:
- Microfilaments: 6nm thick, made of protein actin, keep phospholipids together
- Intermediate filaments: 8-10nm thick, stiffer, resist stresses
- Microtubules: 25nm in diameter, cylinders made up of filaments
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Description
Explore the fundamental unit of life in this quiz on cell structure. Understand the components of the plasma membrane, including phospholipids, glycolipids, and various proteins. Test your knowledge on how these elements contribute to the cell's functionality.
