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Questions and Answers
What is a primary function of the smooth endoplasmic reticulum?
Which type of hormones are synthesized in the smooth endoplasmic reticulum?
What role does the Golgi apparatus play in cellular function?
What happens to transport vesicles that bud off from the rough endoplasmic reticulum?
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Which of the following is NOT a task performed by the smooth endoplasmic reticulum?
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What specific role does the sarcoplasmic reticulum serve in muscle cells?
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How are molecules sorted and packaged in the Golgi apparatus?
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What is the structural form of the Golgi apparatus?
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What role do ciliated cells play in the respiratory tract?
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Which protein helps in the movement of cilia?
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How does a cilium achieve its bending motion?
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What is a key difference between cilia and flagella?
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What structural feature do microvilli possess that allows them to increase surface area?
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What is the primary function of the dynein arms in cilia?
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Which of the following correctly describes how cilia move?
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Which statement is true regarding the flagellum in human physiology?
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What percentage of membrane lipid is cholesterol?
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How does cholesterol affect the fluidity of the membrane?
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Which type of membrane proteins are firmly inserted into the lipid bilayer?
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What is one function of integral proteins in the plasma membrane?
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Which of the following statements accurately describes peripheral proteins?
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What role might peripheral proteins play in a cell?
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What are lipid rafts primarily composed of?
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Which of the following is a characteristic of integral proteins?
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What role do inclusions serve in a cell?
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Which organelles lack membranes?
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What is a key function of mitochondria?
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What is the primary reason for the compartmentalization of organelles?
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Which statement about mitochondria is true?
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What describes the inner membrane of mitochondria?
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What metabolic process do mitochondria primarily perform?
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In which scenario would you expect to find a higher density of mitochondria?
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What is one of the roles of lysosomes during the development of a fetus?
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What condition can cause lysosomes to become fragile?
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Which of the following is a symptom of Tay-Sachs disease?
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What role do lysosomes play in muscle tissue during long periods of inactivity?
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What pH level do lysosomal acids typically operate at?
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Which component is NOT part of the endomembrane system?
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What is the consequence of lysosomal rupture in a cell?
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What do lysosomes specifically degrade in the brain?
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Study Notes
Cell Membrane Structure and Function
- Cholesterol makes up about 20% of membrane lipids.
- Cholesterol is amphipathic like phospholipids.
- Cholesterol helps stabilize membranes, decreasing phospholipid mobility and membrane fluidity.
- Plasma membrane proteins allow cells to communicate with their environment.
- Membrane proteins are responsible for specialized membrane functions.
- Two types of membrane proteins: Integral and Peripheral.
Integral Proteins
- Integral proteins are embedded in the lipid bilayer.
- Integral proteins can be transmembrane (spanning the entire membrane) or peripheral.
- Integral proteins have both hydrophobic and hydrophilic regions, allowing interaction with both the lipid tails and the aqueous environment.
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Transmembrane proteins can function as:
- Channels for small molecules or ions
- Carriers for transporting substances across the membrane
- Enzymes
- Receptors for signaling molecules
Peripheral Proteins
- Peripheral proteins attach loosely to integral proteins on the cytoplasmic side of the membrane.
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Peripheral proteins contribute to membrane support and various cellular functions:
- Enzymes
- Motor proteins involved in cell shape changes and muscle contraction
- Cell-to-cell linking
Lipid Rafts
- Lipid rafts are specialized membrane regions containing concentrated proteins and lipids.
- Lipid rafts play a role in cell signaling and other functions.
Inclusions
- Inclusions are non-essential cellular components that vary among cell types.
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Inclusions include:
- Stored nutrients (glycogen, lipid droplets)
- Pigment granules (melanin)
- Crystals
Cytoplasmic Organelles
- Organelles are specialized compartments within cells, each performing specific functions.
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Membranous organelles are enclosed by membranes, enabling them to maintain distinct internal environments.
- Peroxisomes
- Lysosomes
- Endoplasmic reticulum
- Golgi apparatus
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Nonmembranous organelles lack membranes.
- Cytoskeleton
- Centrioles
- Ribosomes
Mitochondria
- Mitochondria are responsible for ATP production (cellular energy) and are abundant in metabolically active cells.
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Mitochondria are enclosed by two membranes:
- Outer membrane: smooth
- Inner membrane: folded into cristae, increasing surface area for energy production.
- Mitochondria contain their own DNA, RNA, and ribosomes, indicating their independent origin.
- Mitochondria are involved in aerobic cellular respiration (oxidative phosphorylation), requiring oxygen to produce ATP from food fuels.
Endoplasmic Reticulum (ER)
- ER is a network of interconnected membranes involved in protein synthesis, lipid metabolism, and detoxification.
- Rough ER: studded with ribosomes, responsible for protein synthesis and folding.
- Smooth ER: lacks ribosomes, involved in lipid metabolism, steroid hormone synthesis, detoxification, and glycogen breakdown.
Sarcoplasmic Reticulum
- Sarcoplasmic reticulum is a specialized smooth ER found in muscle cells.
- Sarcoplasmic reticulum stores and releases calcium ions, essential for muscle contraction.
Golgi Apparatus
- Golgi apparatus is a stack of flattened membranous sacs involved in protein modification, sorting, and packaging.
- Golgi apparatus receives proteins and lipids from the ER.
- Golgi apparatus modifies proteins by adding or removing sugar groups and phosphate groups.
- Golgi apparatus sorts and packages proteins into vesicles for export from the cell or delivery to other organelles.
Lysosomes
- Lysosomes are membrane-bound organelles containing enzymes that break down cellular waste, worn-out organelles, and ingested materials.
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Lysosomes are involved in:
- Digestion of endocytosed material
- Degradation of worn-out organelles
- Metabolic functions (glycogen breakdown)
- Tissue regression
- Bone breakdown
- Lysosomal rupture leads to autolysis (self-digestion).
- Lysosomes play a role in diseases like Tay-Sachs disease, where a lack of specific lysosomal enzymes leads to the accumulation of undigested lipids in nerve cells.
The Endomembrane System
- Endomembrane system is a network of organelles (ER, Golgi, vesicles, lysosomes, nuclear membrane) working together to produce, degrade, store, and export cellular molecules.
Cilia
- Cilia are short, hair-like projections on the cell surface, involved in movement of fluids or particles.
- Cilia contain microtubules and motor proteins (dynein) for movement.
- Cilia are found in respiratory tract cells, moving mucus and debris.
Flagella
- Flagella are longer, whip-like projections found in sperm cells for locomotion.
- Flagella share structural similarities with cilia but are longer and fewer in number.
Microvilli
- Microvilli are finger-like extensions of the plasma membrane, increasing surface area for absorption.
- Microvilli are found in cells involved in absorption, like intestinal and kidney tubule cells.
- Microvilli contain actin filaments for structural support.
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Description
This quiz covers the essential components of cell membrane structure, including the role of cholesterol and the different types of membrane proteins. Learn about integral proteins and their functions, such as channels, carriers, and enzymes. Test your knowledge on how these components contribute to membrane stability and cellular communication.
