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What is the primary function of the plasma membrane?
What is the primary function of the plasma membrane?
- To store genetic information
- To regulate the movement of substances in and out of the cell (correct)
- To produce energy for the cell
- To synthesize proteins for the cell
Which of the following is a characteristic function of cells?
Which of the following is a characteristic function of cells?
- Inhibition of gene expression
- Reproduction and inheritance of genetic traits (correct)
- Production of heat only
- Permanent structural change
What role does the nucleus play in a cell?
What role does the nucleus play in a cell?
- It directs cell activities and contains genetic information (correct)
- It regulates the ion movement across the plasma membrane
- It serves as the cell's outer boundary
- It synthesizes lipids exclusively
Which statement accurately describes cell metabolism?
Which statement accurately describes cell metabolism?
What distinguishes a human cell from other cells?
What distinguishes a human cell from other cells?
What is the significance of selective permeability of the plasma membrane?
What is the significance of selective permeability of the plasma membrane?
What results in the generation of a membrane potential across the plasma membrane?
What results in the generation of a membrane potential across the plasma membrane?
Which structure is integral for the synthesis of specific cellular molecules such as proteins and lipids?
Which structure is integral for the synthesis of specific cellular molecules such as proteins and lipids?
What is the primary composition of the plasma membrane?
What is the primary composition of the plasma membrane?
What is the arrangement of phospholipids in the plasma membrane?
What is the arrangement of phospholipids in the plasma membrane?
What role does cholesterol play in the plasma membrane?
What role does cholesterol play in the plasma membrane?
What is the main function of glycoproteins and glycolipids in the plasma membrane?
What is the main function of glycoproteins and glycolipids in the plasma membrane?
What distinguishes integral membrane proteins from peripheral membrane proteins?
What distinguishes integral membrane proteins from peripheral membrane proteins?
What are the roles of cadherins and integrins in cell adhesion?
What are the roles of cadherins and integrins in cell adhesion?
What significant characteristic does the fluid-mosaic model of the plasma membrane highlight?
What significant characteristic does the fluid-mosaic model of the plasma membrane highlight?
How do phospholipids respond when the membrane is damaged?
How do phospholipids respond when the membrane is damaged?
What is the primary function of carrier proteins?
What is the primary function of carrier proteins?
Which of the following describes symporters?
Which of the following describes symporters?
What triggers the shape change in ATP-powered pumps?
What triggers the shape change in ATP-powered pumps?
Which property of transport proteins limits the transport rate?
Which property of transport proteins limits the transport rate?
What characteristic defines the specificity of transport proteins?
What characteristic defines the specificity of transport proteins?
What describes antiporters in the context of transport proteins?
What describes antiporters in the context of transport proteins?
What is the role of hydrolysis in ATP-powered pumps?
What is the role of hydrolysis in ATP-powered pumps?
What happens to the ATP-powered pump once the ion and phosphate are released?
What happens to the ATP-powered pump once the ion and phosphate are released?
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Study Notes
Functions of the Cell
- Plasma membrane serves as the outer boundary, facilitating interaction between the cell and its environment.
- Nucleus directs all cellular activities and houses genetic material.
- Cytoplasm is the region between the plasma membrane and nucleus, containing organelles that perform specific functions.
Characteristic Functions of the Cell
- Cell Metabolism: Encompasses all chemical reactions within the cell, involving energy transfer and heat production.
- Molecule Synthesis: Involves the creation of proteins, nucleic acids, and lipids specific to the cell type.
- Communication: Cells produce and exchange electrical and chemical signals for interaction.
- Reproduction and Inheritance: Each cell contains a complete set of DNA, determining structural and functional traits; specialized gametes transmit genetic information to offspring.
Plasma Membrane
- Acts as a barrier separating intracellular substances from the external environment.
- Provides structural support and encloses cell contents.
- Facilitates attachment to the extracellular matrix or neighboring cells.
- Plays a crucial role in cell recognition and communication.
- Exhibits selective permeability, controlling the movement of substances in and out of the cell.
Membrane Potential
- Establishes an electrical charge difference across the plasma membrane due to regulated ion movement.
- The extracellular side possesses a higher concentration of positively charged ions, resulting in a positive charge external to the membrane.
Composition of the Plasma Membrane
- Composed mainly of lipids and proteins, with minimal carbohydrates.
- Glycocalyx consists of carbohydrates and lipids (glycolipids) and proteins (glycoproteins) found on the outer surface.
Membrane Lipids
- Primarily consists of phospholipids and cholesterol.
- Phospholipids form a bilayer, with hydrophilic polar heads facing water and hydrophobic nonpolar tails directed inward.
- Cholesterol interspersed among phospholipids modulates membrane fluidity and stability, crucial for the fluid-mosaic model.
Functions of Membrane Fluidity
- Enables distribution of molecules within the membrane.
- Allows automatic reassembly of phospholipids if the membrane is damaged.
- Facilitates fusion between membranes.
Membrane Proteins
- Integral proteins extend through the membrane and may form channels.
- Peripheral proteins attach to integral proteins or phospholipid heads, contributing to various cellular functions.
- Functionality of membrane proteins is reliant on their three-dimensional shape and chemical properties.
Marker Molecules
- Glycoproteins and glycolipids serve as recognition factors for cells to identify each other and distinguish self from foreign cells.
- Play a role in intercellular communication, such as sperm recognition of oocytes.
Attachment Proteins
- Integral proteins that mediate cell adhesion.
- Cadherins facilitate cell-to-cell attachments, while integrins link cells to extracellular molecules.
Transport Proteins
- Includes channel proteins, carrier proteins, and ATP-powered pumps essential for substance movement across membranes.
Carrier Proteins
- Also known as transporters that transfer ions or molecules across the membrane.
- Function involves specific molecule binding, conformation change for transport, and returning to original shape post-transport.
Forms of Carrier Proteins
- Uniporters transport one molecule at a time.
- Symporters move two molecules simultaneously in the same direction (cotransport).
- Antiporters transport two molecules in opposite directions (countertransport).
ATP-Powered Pumps
- Utilize ATP breakdown, with binding sites for specific ions and ATP.
- Hydrolysis of ATP releases energy for shape change in the pump, enabling substance movement across the membrane before returning to its original form.
Transport Proteins: Specificity and Competition
- Characterized by specificity for a particular molecule based on shape.
- In applications involving several molecules, competition occurs among similar-shaped molecules.
- Transport saturation is determined by the number of available carrier proteins.
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