Questions and Answers
Which of the following components is NOT embedded in the phospholipid bilayer of the plasma membrane?
Which function of the plasma membrane is responsible for maintaining cellular shape and structure?
Which type of transport mechanism uses energy to pump molecules against their concentration gradient?
Which of the following is NOT a type of molecule that can bind to receptors on the plasma membrane?
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Which factor determines the selective permeability of the plasma membrane?
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What is the primary function of the plasma membrane in terms of maintaining cellular homeostasis?
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What is the primary function of the plasma membrane?
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What is the composition of the cytoplasm?
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What is the function of the rough endoplasmic reticulum?
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What is the primary function of ribosomes?
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What is the function of lysosomes?
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What is the main component of the cytoplasm?
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What is the function of the smooth endoplasmic reticulum?
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What is the function of the plasma membrane in maintaining cell shape and structure?
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Study Notes
Plasma Membrane
Structure
- The plasma membrane is a thin, semi-permeable membrane composed of:
- Phospholipid bilayer (hydrophobic tails and hydrophilic heads)
- Proteins (integral and peripheral)
- Cholesterol (embedded in the phospholipid bilayer)
- The fluid mosaic model describes the dynamic structure of the plasma membrane
Functions
- Regulates what enters and leaves the cell
- Maintains cell shape and structure
- Provides mechanical support and protection
- Facilitates cell signaling and communication
- Involved in cell adhesion and recognition
Transport Mechanisms
- Passive transport:
- Diffusion (simple and facilitated)
- Osmosis
- Active transport:
- Primary active transport (uses energy to pump molecules)
- Secondary active transport (uses energy to pump ions)
Cell Signaling
- Receptors on the plasma membrane receive and respond to signals from:
- Hormones
- Neurotransmitters
- Growth factors
- Other cells
- Signals can be transmitted through:
- Binding of ligands to receptors
- Activation of G-proteins and secondary messengers
Selective Permeability
- The plasma membrane allows certain molecules to pass through while restricting others
- Permeability depends on:
- Size and charge of molecules
- Hydrophobicity and hydrophilicity
- Presence of transport proteins and channels
- Selective permeability maintains cellular homeostasis and regulates the internal environment
Plasma Membrane
Structure
- Phospholipid bilayer forms the backbone of the plasma membrane, with hydrophobic tails facing inward and hydrophilic heads facing outward.
- Integral proteins are embedded within the phospholipid bilayer, while peripheral proteins are attached to the surface.
- Cholesterol molecules are embedded in the phospholipid bilayer, contributing to the membrane's fluidity.
- The fluid mosaic model describes the dynamic arrangement of phospholipids and proteins in the plasma membrane.
Functions
- The plasma membrane acts as a selective barrier, controlling the movement of molecules into and out of the cell.
- It maintains cell shape and structure by providing mechanical support and protection.
- The plasma membrane facilitates cell signaling and communication by transmitting and receiving signals.
- It plays a crucial role in cell adhesion and recognition, allowing cells to interact with each other.
Transport Mechanisms
- Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration.
- Facilitated diffusion involves the use of transport proteins to facilitate diffusion.
- Osmosis is the movement of water molecules from an area of higher concentration to an area of lower concentration.
- Primary active transport uses energy to pump molecules across the membrane, often against their concentration gradient.
- Secondary active transport uses energy to pump ions, which then drive the transport of other molecules.
Cell Signaling
- Receptors on the plasma membrane receive signals from hormones, neurotransmitters, growth factors, and other cells.
- Signals can be transmitted through the binding of ligands to receptors, activating G-proteins and secondary messengers.
- Cell signaling pathways allow cells to respond to changes in their environment and communicate with each other.
Selective Permeability
- The plasma membrane allows certain molecules to pass through while restricting others, based on their size, charge, and hydrophobicity.
- Transport proteins and channels enhance the membrane's permeability to specific molecules.
- Selective permeability is crucial for maintaining cellular homeostasis and regulating the internal environment.
Cell Organelles
Plasma Membrane
- Thin, semi-permeable membrane that surrounds the cell
- Composed of phospholipid bilayer with embedded proteins
- Regulates what enters and leaves the cell
- Maintains cell shape and structure
- Provides mechanical support and protection
Cytoplasm
- Jelly-like substance inside the cell membrane
- Composed of 90% water, salts, sugars, and various organelles
- Provides a medium for metabolic reactions
- Supports cell division and growth
- Maintains cell shape and structure
Endoplasmic Reticulum (ER)
- Network of membranous tubules and cisternae found in eukaryotic cells
- Two types: Rough ER (with ribosomes) and Smooth ER (without ribosomes)
- Functions: protein synthesis, lipid synthesis, detoxification, and storage of toxins
- Rough ER: involved in protein synthesis and transport
- Smooth ER: involved in lipid synthesis and detoxification
Ribosomes
- Small organelles found throughout the cytoplasm
- Composed of RNA and proteins
- Site of protein synthesis (translation of mRNA)
- Found in both prokaryotic and eukaryotic cells
Lysosomes
- Membrane-bound sacs containing digestive enzymes
- Found in eukaryotic cells
- Breakdown and recycling of cellular waste and foreign substances
- Autophagy: self-digestion of damaged organelles
- Essential for cell maintenance and survival
Mitochondria
- Energy-producing organelles found in eukaryotic cells
- Composed of outer and inner membranes
- Generate energy for the cell through cellular respiration
- Regulate cell growth and division
- Essential for cell survival and function
Nucleus
- Control center of the cell
- Found in eukaryotic cells
- Composed of nuclear envelope, nucleoplasm, and chromatin
- Stores genetic information (DNA)
- Regulates gene expression and cell growth
- Coordinates cell division and replication
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Description
Learn about the structure and functions of the plasma membrane, including its composition and the fluid mosaic model. Understand how it regulates cell activities and maintains cell shape.
