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Questions and Answers
Which type of substances easily diffuse across a cell membrane?
What type of transport proteins help specific substances like sugar, amino acids, and ions to diffuse across the membrane?
Why is the diffusion of water through a membrane's hydrophobic interior relatively slow?
Which mechanism is used by a cell to move bulky molecules out of the cell?
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In which process does a cell use energy to move solutes against their concentration gradient?
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What is the function of tight junctions in animal tissues?
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Where are many embedded protein molecules that function in ATP synthesis found?
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What is the main function of anchoring junctions in animal tissues?
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What is the primary purpose of thylakoids in chloroplasts?
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What type of molecules can flow through gap junctions between cells?
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What is the main characteristic of diffusion?
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How do molecules of dye typically move in a system involving diffusion?
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In the process of osmosis, what determines the direction of water movement across a selectively permeable membrane?
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How does diffusion differ from active transport?
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If a selectively permeable membrane separates two solutions with different solute concentrations, what would happen in terms of water movement through osmosis?
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What happens to a cell in a hypotonic solution?
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How does an isotonic solution affect cell volume?
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What is the main factor that determines tonicity of a solution?
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In a hypertonic environment, what happens to plant cells?
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Why is osmoregulation important for animal cells in non-isotonic environments?
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Which feature of the plasma membrane is critical for the origin of life?
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What type of molecules are known to diffuse easily through the plasma membrane?
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What is a characteristic of passive transport across the plasma membrane?
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Which process involves the spontaneous formation of membrane-enclosed collections of molecules?
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In osmosis, water molecules move across a selectively permeable membrane from an area of _______ concentration to an area of _______ concentration.
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Which organelle is the largest component of the endomembrane system?
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Which type of ER is abundant in cells that secrete proteins?
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What is the main function of rough endoplasmic reticulum (Rough ER)?
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Which organelle is responsible for the distribution, storage, and export of molecules within a eukaryotic cell?
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Which organelle is characterized by tiny vesicles transferring membrane segments between membranes?
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Which organelle in the cell fuses with food vacuoles to digest food?
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What is the main function of contractile vacuoles in freshwater protists?
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In a cell, which organelle acts as a recycling center by breaking down damaged organelles?
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Which organelle found in mature plant cells holds organic compounds and water?
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What organelle contains pigments and poisons that protect the plant?
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Which type of vacuole forms as a cell ingests food?
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What is the primary function of transport vesicles in the cell?
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Which organelle is derived from the endoplasmic reticulum (ER) and Golgi apparatus?
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What function do central vacuoles perform in many mature plant cells?
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What is the role of rough endoplasmic reticulum in the cell?
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Study Notes
Endomembrane System
- The endomembrane system is a network of connected membranes and organelles that work together to synthesize, distribute, store, and export molecules.
- The system includes the nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, and plasma membrane.
Endoplasmic Reticulum (ER)
- The ER is the largest component of the endomembrane system and is an extensive network of flattened sacs and tubules.
- There are two types of ER: rough ER and smooth ER.
- Rough ER has bound ribosomes that stud the outer surface of the membrane, whereas smooth ER lacks attached ribosomes.
- Rough ER is involved in the synthesis of proteins that are to be secreted or inserted into membranes.
- Smooth ER is involved in various metabolic processes, including the production of lipids, oils, and steroids.
Diffusion
- Diffusion is the passive transport of particles from an area of higher concentration to an area of lower concentration.
- Net diffusion continues until equilibrium is reached, where there is no net change in concentration on either side of the membrane.
Osmosis
- Osmosis is the diffusion of water across a selectively permeable membrane.
- If a membrane separates two solutions with different solute concentrations, water will cross the membrane, moving down its concentration gradient, until the solute concentration on both sides is equal.
Facilitated Diffusion
- Facilitated diffusion is the transport of specific molecules down their concentration gradient using transport proteins.
- Hydrophobic substances can easily diffuse across a cell membrane, but polar or charged substances require specific transport proteins to cross the membrane.
Active Transport
- Active transport is the movement of solutes against their concentration gradient, requiring energy input from ATP.
- Transport proteins use ATP to pump solutes across the membrane, often against their concentration gradient.
Exocytosis and Endocytosis
- Exocytosis is the process of exporting bulky molecules out of a cell, while endocytosis is the process of importing molecules into a cell.
- Phagocytosis is a type of endocytosis where the cell engulfs large particles or cells.
Tonicity
- Tonicity refers to the ability of a surrounding solution to cause a cell to gain or lose water.
- Isotonic solutions have the same solute concentration as the cell, whereas hypotonic solutions have a lower solute concentration, and hypertonic solutions have a higher solute concentration.
Cell Junctions
- There are three types of cell junctions in animal tissues: tight junctions, anchoring junctions, and gap junctions.
- Tight junctions prevent leakage of fluid between cells, anchoring junctions fasten cells together, and gap junctions allow small molecules to pass between cells.
Cell Wall
- Plant cells have a rigid cell wall that provides support and protection.
- The cell wall is composed primarily of cellulose, with other polysaccharides and proteins embedded in the matrix.
Plasma Membrane
- The plasma membrane is a fluid mosaic model, with a phospholipid bilayer embedded with protein molecules.
- The plasma membrane exhibits selective permeability, allowing certain molecules to pass through while keeping others out.
- Phospholipids spontaneously self-assemble into simple membranes, a critical step in the origin of life.
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Description
Learn about the interconnected membranes within a eukaryotic cell that make up the endomembrane system. Discover how organelles like the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles work together in synthesis, distribution, storage, and export of molecules.