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Questions and Answers
What is the primary function of the endomembrane system in eukaryotic cells?
What is the primary function of the endomembrane system in eukaryotic cells?
Which type of Endoplasmic Reticulum is responsible for protein modification and secretion?
Which type of Endoplasmic Reticulum is responsible for protein modification and secretion?
What role does the Golgi apparatus play in relation to proteins?
What role does the Golgi apparatus play in relation to proteins?
How does Smooth Endoplasmic Reticulum function in liver cells?
How does Smooth Endoplasmic Reticulum function in liver cells?
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What defines the function of lysosomes in animal cells?
What defines the function of lysosomes in animal cells?
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Which statement best describes the Smooth Endoplasmic Reticulum's metabolic function?
Which statement best describes the Smooth Endoplasmic Reticulum's metabolic function?
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What is a distinct characteristic of the Rough Endoplasmic Reticulum?
What is a distinct characteristic of the Rough Endoplasmic Reticulum?
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What role does vacuole play in plant cells?
What role does vacuole play in plant cells?
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What primary characteristic allows the plasma membrane to control the traffic of substances into and out of the cell?
What primary characteristic allows the plasma membrane to control the traffic of substances into and out of the cell?
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Which model describes the structure of the plasma membrane as a mosaic of different components?
Which model describes the structure of the plasma membrane as a mosaic of different components?
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What is one of the main functions of the plasma membrane?
What is one of the main functions of the plasma membrane?
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What does the term 'selectively permeable' imply about the plasma membrane?
What does the term 'selectively permeable' imply about the plasma membrane?
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In what way do membrane proteins contribute to the functions of the plasma membrane?
In what way do membrane proteins contribute to the functions of the plasma membrane?
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What is a notable property of the lipid bilayer in the plasma membrane?
What is a notable property of the lipid bilayer in the plasma membrane?
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What observation did Gorter & Grendel make about lipid molecules in the context of membrane structures?
What observation did Gorter & Grendel make about lipid molecules in the context of membrane structures?
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Which characteristic of phospholipids is crucial in forming a bilayer in the plasma membrane?
Which characteristic of phospholipids is crucial in forming a bilayer in the plasma membrane?
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What type of transport does not require energy from the cell?
What type of transport does not require energy from the cell?
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Which mechanism involves the movement of large molecules into the cell?
Which mechanism involves the movement of large molecules into the cell?
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Which of the following accurately describes active transport?
Which of the following accurately describes active transport?
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What occurs during phagocytosis?
What occurs during phagocytosis?
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What happens to the plasma membrane during the process of endocytosis?
What happens to the plasma membrane during the process of endocytosis?
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What distinguishes facilitated diffusion from simple diffusion?
What distinguishes facilitated diffusion from simple diffusion?
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Which of the following statements about exocytosis is true?
Which of the following statements about exocytosis is true?
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What characterizes the fluid mosaic model of the plasma membrane?
What characterizes the fluid mosaic model of the plasma membrane?
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What role do protein channels play in the cell membrane?
What role do protein channels play in the cell membrane?
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Which type of transport requires no energy and moves substances down their concentration gradient?
Which type of transport requires no energy and moves substances down their concentration gradient?
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What is a characteristic feature of osmosis?
What is a characteristic feature of osmosis?
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Which of the following correctly describes diffusion?
Which of the following correctly describes diffusion?
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What mainly determines the permeability of the cell membrane?
What mainly determines the permeability of the cell membrane?
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What is an example of active transport?
What is an example of active transport?
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Which of the following statements about the fluid-mosaic model is true?
Which of the following statements about the fluid-mosaic model is true?
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Which molecules can typically pass through the phospholipid bilayer directly?
Which molecules can typically pass through the phospholipid bilayer directly?
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Study Notes
Endomembrane System Overview
- The endomembrane system is composed of different membranes suspended in the cytoplasm of a eukaryotic cell.
- Key organelles involved in the endomembrane system include the nuclear membrane, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles (which are present in plant cells).
- The endomembrane system is responsible for producing membranes and carrying out many biosynthetic functions.
- Approximately 50% of membranes in eukaryotic cells are part of the endomembrane system.
Endoplasmic Reticulum (ER)
- The ER is a network of membranes connected to the nuclear envelope.
- Rough ER has ribosomes attached to its cytoplasmic surface. Ribosomes on the Rough ER make proteins that are incorporated into the lumen (inner space) of the ER. The Rough ER also helps modify proteins that will be secreted from the cell, and make phospholipids for other cellular membranes.
- Smooth ER lacks ribosomes and plays a role in metabolic processes such as lipid synthesis, detoxification, and carbohydrate hydrolysis. Steroids and sex hormones are synthesized in the smooth ER. Glycogen in the liver is broken down into glucose; drugs and poisons are also detoxified in the smooth ER. In muscles there is special smooth ER called sarcoplasmic reticulum, it surrounds each myofibril and stores and releases calcium.
Golgi Apparatus
- The Golgi apparatus is found in both plant and animal cells.
- Its function is packaging proteins and chemical products.
- It has a cis face (receiving) and a trans face (shipping). Incoming transport vesicles from the endoplasmic reticulum travel to the cis face. Newly forming vesicles are then moved to the trans face. Secretory vesicles containing the final products exit from the trans face.
- The Cisternae shape (flattened membrane sacs or stacks) of the Golgi apparatus are used for modifying the proteins.
Lysosomes
- Lysosomes contain digestive enzymes and act as the cell's recycling facility.
- They break down old and unnecessary cellular structures.
- Example: White blood cells called macrophages use phagocytosis (engulfing a particle) to destroy pathogens. Lysosomes work within the macrophage to digest and break down the pathogen.
Vacuoles (Plant Cells)
- Vacuoles in plants store water and waste, isolate harmful materials, and break down macromolecules and cellular components.
- Vacuoles help maintain water balance within the plant cell.
Peroxisomes
- Peroxisomes contain enzymes involved in oxidation reactions and produce hydrogen peroxide as a by-product.
- Some functions include bile acid synthesis; purine catabolism (breakdown); lipid biosynthesis; viral innate immune defense; thermogenesis (heat production), oxidation of fatty acids and production of ROS/NOS (reactive oxygen species/nitric oxide).
Endocytosis & Exocytosis
- Endocytosis is a process where the cell takes up material by forming a vesicle from the plasma membrane to surround and engulf the material.
- Types of Endocytosis: -Phagocytosis: "cellular eating" - engulfing large particles (e.g. bacteria, viruses) -Pinocytosis: "cellular drinking"- engulfing dissolved substances.
- Exocytosis is a process where the cell discharges material by fusing a secretory vesicle with the plasma membrane.
Plasma Membrane
- The plasma membrane is selectively permeable; allowing only certain substances to pass.
- It is a phospholipid bilayer, with a hydrophobic (nonpolar) interior and hydrophilic (polar) exterior.
- The fluid mosaic model depicts the membrane as a fluid structure with proteins embedded within the phospholipid bilayer.
Membrane Transport
-
Passive Transport: The movement of substances across the membrane down their concentration gradient (needs no energy).
- Diffusion - net movement of a substance from an area of high concentration to low concentration.
- Osmosis: A form of diffusion involving the movement of water across a semipermeable membrane. Water flows from an area of low solute concentration to high solute concentration.
- Facilitated Diffusion: Uses membrane channel proteins to enhance diffusion of substances (no energy required).
- Active Transport: Movement of substances across the membrane against their concentration gradient (requires energy). Example: Carrier mediated active transport, endocytosis and exocytosis.
Membrane Functions
- Protection
- Communication
- Selectively allow substances
- Respond to the environment
- Recognition
Types of Passive Transport
- Diffusion
- Osmosis
- Facilitated Diffusion
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Description
Explore the endomembrane system in eukaryotic cells, including its key organelles and functions. Learn about the roles of the nuclear membrane, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles. This quiz will enhance your understanding of cellular membranes and biosynthetic processes.
