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Questions and Answers
What defines selective permeability in relation to cellular membranes?
What defines selective permeability in relation to cellular membranes?
- Membranes selectively allow certain substances to enter or exit. (correct)
- Membranes allow all substances to pass freely.
- Membranes are impermeable to all substances.
- Membranes only allow gases to pass through.
Which process is classified as an active transport mechanism?
Which process is classified as an active transport mechanism?
- Exocytosis (correct)
- Osmosis
- Facilitated diffusion
- Diffusion
What is the primary effect of placing a cell in a hypertonic solution?
What is the primary effect of placing a cell in a hypertonic solution?
- The cell fills with nutrients.
- The cell shrinks as water leaves. (correct)
- The cell swells and may burst.
- The cell remains the same size.
What distinguishes facilitated diffusion from simple diffusion?
What distinguishes facilitated diffusion from simple diffusion?
Which type of osmosis solution is considered isotonic to human cells?
Which type of osmosis solution is considered isotonic to human cells?
The rate of diffusion is affected by which of the following factors?
The rate of diffusion is affected by which of the following factors?
In terms of ion channels, what is the function of voltage-gated channels?
In terms of ion channels, what is the function of voltage-gated channels?
What is the term for the net movement of water across a semipermeable membrane due to concentration differences?
What is the term for the net movement of water across a semipermeable membrane due to concentration differences?
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Study Notes
Cellular Transport Overview
- Interstitial fluid is the fluid between cells that facilitates exchange of molecules.
- Selective permeability refers to the cell membrane's ability to control what enters and exits the cell, allowing specific substances while restricting others.
Types of Transport Mechanisms
- Transport processes are categorized as either active (requiring energy) or passive (no energy required).
- Passive Transport: Includes diffusion, osmosis, and filtration, which occur along concentration gradients without energy expenditure.
- Active Transport: Requires energy to move substances against their concentration gradient.
Passive Transport Details
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Diffusion:
- Movement of molecules from high to low concentration.
- Simple diffusion involves gases like oxygen, carbon dioxide, and nitrogen, as well as fatty acids and steroids.
- Factors influencing diffusion include concentration gradient steepness, temperature (increased temperature enhances movement), mass of the substance, surface area, and distance of diffusion.
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Facilitated Diffusion:
- Mediated by integral proteins and divided into channel-mediated and carrier-mediated transport.
- Channel-mediated involves ion channels for hydrophilic ions, while carrier-mediated transport utilizes specific transport proteins for larger molecules, e.g., glucose and fructose.
- Ion channels can be voltage-gated (opened by voltage changes) or ligand-gated (opened by chemical signals).
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Osmosis:
- The diffusion of water across a selectively permeable membrane.
- Solutions are classified as:
- Isotonic: Equal solute concentration (0.9% NaCl).
- Hypertonic: Higher solute concentration (2.0% NaCl).
- Hypotonic: Lower solute concentration (0.2% NaCl).
Effects of Solutions on Cells
- Cells behave differently in various solutions:
- Isotonic Solution: No net movement of water; cell remains stable.
- Hypertonic Solution: Water moves out, causing cell shrinkage (crenation).
- Hypotonic Solution: Water moves in, potentially causing cell swelling and lysis (bursting).
Practical Considerations
- Beakers in experiments can illustrate different tonicity effects on cells.
- Hypertonic solutions will cause the most significant mass loss in living cells due to water leaving the cells to balance solute concentrations.
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