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Questions and Answers
What is the primary function of the cell membrane?
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Which component of the cell membrane is primarily responsible for creating the bilayer structure?
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How thick is the cell membrane as observed under an electron microscope?
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What two types of proteins are found in the cell membrane?
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What kind of molecules primarily form the hydrophilic heads of phospholipids?
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Which feature distinguishes transmembrane proteins from integral proteins?
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What is the composition of cytoplasm primarily made up of?
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What are organelles in the cytoplasm primarily responsible for?
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What is the structure of the Golgi apparatus as seen under electron microscopy?
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Which face of the Golgi apparatus is associated with the formation of vesicles?
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What is a primary lysosome?
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What process allows the cell to engulf fluid and form pinocytotic vesicles?
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How do primary lysosomes function in digestion?
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Which of the following is not a function of the Golgi apparatus?
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What do secretory granules arise from?
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What is the role of coated vesicles formed by the Golgi apparatus?
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What is the primary function of mitochondria?
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Which statement about ribosomes is true?
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What distinguishes rough endoplasmic reticulum from smooth endoplasmic reticulum?
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What is the role of carbohydrates in the cell membrane?
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What is the primary role of the smooth endoplasmic reticulum?
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Which mechanism involves the movement of substances without the use of energy?
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What is a unique feature of the Golgi complex?
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Which statement is true regarding the function of mitochondria?
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How are proteins secreted by the cell synthesized?
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What is the structure of the inner membrane of mitochondria characterized by?
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Which process is NOT associated with the smooth endoplasmic reticulum?
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What is the function of ribosomes linked with messenger RNA?
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What process allows the cell to engulf solid particles?
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Which of the following correctly describes passive diffusion?
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Which cells structures act as adhesions to hold adjacent cells together?
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What function does the intermembrane space serve in mitochondria?
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Study Notes
Cell Structure and Function
- Definition: The cell is the fundamental structural unit of all living organisms. It comprises the cytoplasm and nucleus.
The Cell
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Cytoplasm: Composed of a matrix containing organic and inorganic chemicals; also includes organelles and cytoskeleton, inclusions.
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Organelles: These are metabolically active structures within the cytoplasm performing specific functions.
- Membranous Organelles: examples include cell membrane, mitochondria, Golgi apparatus, endoplasmic reticulum (rough and smooth), lysosomes, secretory vesicles
- Non-membranous Organelles: examples include ribosomes, microtubules, microfilaments, intermediate filaments, centrioles, cilia, flagellum
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Cytoskeleton: Fibrillar elements within the cytoplasm providing structural support and facilitating movement. -Includes microtubules, microfilaments, intermediate filaments
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Cytosol: The liquid portion of the cytoplasm, the fluid component.
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Inclusions: Non-living material within the cytoplasm (e.g., stored nutrients).
I- Cell Membrane
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Structure: A thin, double-layered structure (unit membrane), composed of lipids, proteins and carbohydrates.
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Lipids: Primarily phospholipids and cholesterol, arranged in two layers (bilayer).
- Hydrophilic heads face outward, hydrophobic tails inward.
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Proteins: Integral and peripheral proteins embedded within or associated with the lipid bilayer.
- Integral proteins: partially or completely span the lipid bilayer
- Peripheral proteins: located on the inner side of the membrane.
- Carbohydrates: Polysaccharides attached to proteins and lipids on the outer surface forming the glycocalyx.
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Lipids: Primarily phospholipids and cholesterol, arranged in two layers (bilayer).
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Functions:
- Separates the cell from its environment.
- Controls movement of substances in and out of the cell.
- Utilizes mechanisms such as passive diffusion (ions, water), active transport, facilitated diffusion (glucose etc.)., selective transport (receptors).
II- Mitochondria
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Structure: Rod-shaped or spherical organelles with two membranes (inner and outer).
- Inner membrane is folded into cristae, creating more surface area for chemical reactions.
- The intermembrane space and matrix space are the spaces between the inner and outer membranes respectively, and filled with matrix containing DNA, RNA, ribosomes, and proteins.
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Functions: The powerhouse of the cell; site of oxidative phosphorylation, generating energy for cellular processes.
-Contains enzymes for the Krebs cycle. -Regulates calcium levels.
III- Ribosomes
- Structure: Small particles composed of proteins and ribosomal RNA (rRNA), having a large and small subunit.
- Location: Found free in the cytoplasm or attached to the rough endoplasmic reticulum (RER).
- Function: Sites of protein synthesis
IV- Endoplasmic Reticulum (ER)
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Structure: System of interconnected tubes, vesicles, and flattened saccules (cisternae) surrounded by a limiting membrane.
- Two types: rough and smooth.
- Rough ER (RER): Studded with ribosomes; involved in protein synthesis and transport.
- Smooth ER (SER): Lacks ribosomes; involved in synthesis of lipids, steroids, detoxification, glycogen metabolism and calcium regulation
V- Golgi Complex/Apparatus
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Structure: Stacks of flattened membranous sacs (cisternae).
-Has a forming (cis) face and a maturing (trans) face. - Function: Modifies, sorts, and packages proteins and lipids. It is involved in protein secretion. Processes and delivers various cellular constituents.
VI- Secretory Granules (Vesicles)
- Structure: Membranous sacs containing secretory products from the Golgi apparatus.
- Function: Store products for later release from the cell (exocytosis).
VII- Lysosomes
- Structure: Membranous sacs containing hydrolytic enzymes.
- Function: Digest cellular waste, worn-out organelles, or foreign materials
- Types: Primary lysosomes contain digestive enzymes within the vacuole. Secondary lysosomes result from the fusion of primary lysosomes with other vesicles.
Cell Membrane Processes
- Phagocytosis: Engulfing solid materials
- Pinocytosis: Engulfing liquid materials.
- Exocytosis: Releasing waste materials.
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Description
Test your knowledge on cell structure and function with this quiz. Cover topics such as organelles, cytoplasm, and the cytoskeleton. Understand the key components that make up the fundamental unit of life.
