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Questions and Answers
What are the three principal parts of a generalized cell?
What are the three principal parts of a generalized cell?
- Organelle, Nucleus, Plasma substance
- Cytoplasm, Nucleus, Plasma membrane (correct)
- Cell wall, Cytoplasm, Membrane proteins
- Cytosol, Organelles, Ribosomes
What is the primary structure that gives cell membranes their fluid characteristics?
What is the primary structure that gives cell membranes their fluid characteristics?
- Cholesterol
- Protein channels
- Phospholipid layers
- Lipid bilayer (correct)
Which type of molecules can easily pass through the lipid bilayer of the plasma membrane?
Which type of molecules can easily pass through the lipid bilayer of the plasma membrane?
- Large macromolecules
- Polar molecules like glucose
- Ions and charged molecules
- Small, nonpolar, uncharged molecules (correct)
What role do transmembrane proteins play in the plasma membrane?
What role do transmembrane proteins play in the plasma membrane?
Where are sodium ions primarily concentrated in relation to the plasma membrane?
Where are sodium ions primarily concentrated in relation to the plasma membrane?
Which statement accurately reflects membrane permeability?
Which statement accurately reflects membrane permeability?
Which component is NOT part of the fluid mosaic model of the plasma membrane?
Which component is NOT part of the fluid mosaic model of the plasma membrane?
What does a concentration gradient represent in cellular biology?
What does a concentration gradient represent in cellular biology?
What process occurs in the nucleus to produce RNA from DNA?
What process occurs in the nucleus to produce RNA from DNA?
During which phase of cell division does the contractile ring begin to form?
During which phase of cell division does the contractile ring begin to form?
What best describes the outcome of DNA replication?
What best describes the outcome of DNA replication?
What occurs after RNA moves into the cytoplasm?
What occurs after RNA moves into the cytoplasm?
Which statement regarding the components of a replicated DNA molecule is true?
Which statement regarding the components of a replicated DNA molecule is true?
What are the three types of passive transport processes?
What are the three types of passive transport processes?
Which factor does NOT influence the rate of diffusion across plasma membranes?
Which factor does NOT influence the rate of diffusion across plasma membranes?
How does temperature affect the rate of diffusion?
How does temperature affect the rate of diffusion?
Which type of transport requires cellular energy?
Which type of transport requires cellular energy?
What effect does diffusion distance have on the rate of diffusion?
What effect does diffusion distance have on the rate of diffusion?
Which type of molecules can diffuse across the lipid bilayer most easily?
Which type of molecules can diffuse across the lipid bilayer most easily?
How does steepness of the concentration gradient affect diffusion?
How does steepness of the concentration gradient affect diffusion?
What type of transport involves the movement of materials into or out of the cell using vesicles?
What type of transport involves the movement of materials into or out of the cell using vesicles?
What determines the direction of net flow during osmosis?
What determines the direction of net flow during osmosis?
What occurs to red blood cells in a hypotonic solution?
What occurs to red blood cells in a hypotonic solution?
Which type of transport involves moving materials into a cell using a vesicle formed from the plasma membrane?
Which type of transport involves moving materials into a cell using a vesicle formed from the plasma membrane?
What is tonicity a measure of?
What is tonicity a measure of?
Which type of channel allows selective passage of inorganic ions?
Which type of channel allows selective passage of inorganic ions?
What happens to red blood cells in a hypertonic solution?
What happens to red blood cells in a hypertonic solution?
What is the role of carrier transport proteins?
What is the role of carrier transport proteins?
Which of the following describes exocytosis?
Which of the following describes exocytosis?
What is the primary composition of cytosol?
What is the primary composition of cytosol?
Which of the following is NOT a function of the cytoskeleton?
Which of the following is NOT a function of the cytoskeleton?
What is the main protein that makes up microfilaments?
What is the main protein that makes up microfilaments?
Which organelle serves as the center for organizing microtubules during cell division?
Which organelle serves as the center for organizing microtubules during cell division?
What role do ribosomes play in a cell?
What role do ribosomes play in a cell?
What type of filaments help anchor organelles such as the nucleus?
What type of filaments help anchor organelles such as the nucleus?
Which type of protein filament is primarily involved in intracellular transport?
Which type of protein filament is primarily involved in intracellular transport?
How are ribosomes organized in a cell?
How are ribosomes organized in a cell?
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Study Notes
Introduction to the Cell
- Cells are the basic living units of the body, structured for specific functions.
- A generalized cell model consists of various components not found in all cells.
- Three principal parts of the cell for study:
- Plasma (cell) membrane
- Cytoplasm (includes cytosol and organelles)
- Nucleus
Plasma Membrane and Structure
- The lipid bilayer, composed of two layers of phospholipids, forms the cell membrane.
- Hydrophobic tails face inwards, while hydrophilic heads face outward, creating a fluid structure.
- The Fluid Mosaic Model describes the membrane's diverse components:
- Phospholipids, glycolipids, sterols (cholesterol), and proteins.
Membrane Permeability
- Plasma membranes are selectively permeable, allowing certain substances to pass.
- Small, nonpolar, uncharged molecules can easily cross, while ions and charged polar molecules cannot.
- Water can permeate the membrane, aided by transmembrane proteins that act as channels or transporters.
Transport Mechanisms
- Transport across membranes involves active (energy-dependent) and passive (no energy) processes.
- Passive transport types include:
- Diffusion through the lipid bilayer
- Diffusion through ion channels
- Facilitated diffusion using carrier proteins
- Active transport requires cellular energy.
Principles of Diffusion
- Diffusion occurs due to kinetic energy; it's a passive process.
- Factors that influence diffusion rate:
- Concentration gradient steepness: Greater disparities accelerate diffusion.
- Temperature: Higher temperatures increase diffusion rates.
- Size/Mass of substance: Larger molecules diffuse slower.
- Surface area: More area leads to faster diffusion.
- Diffusion distance: Longer distances slow the process.
Osmosis
- Osmosis is the diffusion of water across a selectively permeable membrane.
- Direction of water flow depends on solute concentration: less concentration results in higher water concentration.
- Osmotic pressure is related to the concentration of solute particles that cannot cross the membrane.
Tonicity
- Tonicity refers to a solution's ability to change cell volume by altering water concentration.
- Isotonic solutions maintain red blood cell shape, hypotonic solutions cause hemolysis, and hypertonic solutions lead to crenation.
Filtration
- Filtration is the process whereby solvents and dissolved substances move through a membrane or filter.
Carrier Transport and Vesicular Transport
- Substances that cannot freely diffuse across membranes may use transport proteins.
- Common solutes transported include glucose, urea, and ions (e.g., Na+, K+).
- Vesicular transport involves endocytosis (moving materials into the cell) and exocytosis (releasing materials out of the cell).
Cytoplasm and Cytosol
- Cytosol is a semifluid medium containing inclusions and dissolved solutes, where metabolic reactions occur.
Organelles
- Organelles perform specific functions essential for cellular maintenance, growth, and reproduction.
- Key organelles include:
- Cytoskeleton: Provides structure and organization; consists of microfilaments, intermediate filaments, and microtubules.
- Ribosomes: Sites of protein synthesis composed of ribosomal RNA and proteins.
- Centrosomes: Organize microtubules; contain centrioles that aid in cell division.
Steps from DNA to Proteins
- DNA is transcribed to RNA in the nucleus, then RNA is translated into polypeptides in the cytoplasm.
- Each DNA molecule is replicated semi-conservatively, retaining one old and one new strand.
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