Questions and Answers
What is the function of microvilli?
The nucleus is the primary site of ribosome subunit biogenesis.
True
What is the role of the plasma membrane?
Controls entry and exit of substances.
Match the following cell types with their characteristics:
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The _________ is responsible for cellular digestion.
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Which of the following is NOT a function of the plasma membrane?
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What structures are responsible for protein synthesis?
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Cholesterol is found in the plasma membrane and modulates the fluidity of membrane components.
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Which germ layer is the outermost layer?
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Which phase of the cell cycle comes after G1?
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DNA replication is often described as semiconservative.
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What are the two major classes of RNAs?
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The ______ bonds are broken by DNA helicase during replication.
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Match the following nitrogenous bases with their corresponding pairs:
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What does RNA polymerase do during transcription?
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Which type of mutation results in a premature stop codon?
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The lagging strand is synthesized continuously.
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What is the purpose of telomeres?
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What chemical is mentioned that prevents the formation of the mitotic spindle?
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What molecule is produced that protects mRNA from degradation?
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Where does transcription occur?
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What is the second step in getting from a gene to a protein?
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Match the following GDF factors with their functions:
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Which GDF factor is primarily involved in muscle tissue?
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What are caspases?
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What are apoptotic bodies?
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Which of the following tissues are classified as connective tissues?
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What is the role of smooth muscle tissue?
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The process of formation of the neural plate is called _______.
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What triggers extrinsic signals in apoptosis?
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What happens during necrosis?
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Somatic mesoderm lines the cytotrophoblast and amnion.
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Which components are included in blood?
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What is the function of dendrites in neurons?
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What does the term 'embryoblast' refer to?
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Which processes are involved in cellular respiration?
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The _______ is a transition step that prepares pyruvic acid for entrance into the Krebs cycle.
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What does the Bcl-2 family of proteins control?
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What causes neural tube defects?
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What is the genetic code composed of?
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Which types of muscle tissue are mentioned?
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What is the primary function of epithelial cells with secretory (glandular) epithelia?
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Exocrine glands carry secretions to specific sites through ducts.
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What structure is more motile than microvilli?
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What are the three basic secretory mechanisms of glands?
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The inner layer of the three germ layers is called the ______.
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Match the following types of epithelium with their descriptions:
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What are the primary functions of epithelial tissue?
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The basal membrane consists of two layers: the basal lamina and the reticular lamina.
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What is a defining feature of pseudostratified epithelium?
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Study Notes
Microvilli and Plasma Membrane Transport
- Microvilli are extensions of the plasma membrane containing microfilaments, enhancing the surface area for absorption and secretion.
- They can be modified to function as sensory receptors.
- Diffusion allows for the transport of small, nonpolar molecules directly through the lipid bilayer.
- Water crosses the membrane slowly, while lipophilic molecules diffuse readily.
Overview of Cell Structures and Functions
- Cells are the building blocks of all living organisms, providing structure and performing specialized functions.
- Eukaryotic cells have membrane-bound organelles, including a nucleus that regulates cellular activities and protein synthesis.
- Prokaryotic cells lack membrane-bound organelles and have a smaller ribosome size.
- The plasma membrane consists of a lipid bilayer, mainly phospholipids and cholesterol, with embedded proteins that control substance entry and exit.
Key Organelles
- Nucleolus: Largest nuclear organelle, site of ribosome subunit production in eukaryotic cells.
- Rough Endoplasmic Reticulum: Synthesizes proteins due to attached ribosomes, consisting of membranous tubules and flattened sacs.
- Smooth Endoplasmic Reticulum: Involved in lipid and carbohydrate synthesis, detoxification, and calcium storage; lacks ribosomes.
- Golgi Apparatus: Modifies, packages, and distributes proteins and lipids.
- Lysosomes: Contain digestive enzymes for cellular digestion.
- Peroxisomes: Break down lipids and amino acids, and degrade hydrogen peroxide.
- Mitochondria: Major site of ATP synthesis, with a double membrane and cristae projections for increased surface area.
Transport Mechanisms
- Diffusion: Involves the passive movement of molecules across membranes.
- Channels: Proteins forming pores that facilitate the transport of ions and small molecules. Aquaporins specifically allow water transport.
- Carriers: Proteins that undergo conformational changes to translocate molecules across the membrane.
- Endocytosis: Process by which cells internalize macromolecules, including phagocytosis (“cell eating”) and pinocytosis (“cell drinking”).
- Exocytosis: Movement of large molecules from inside the cell to the outside using vesicular transport.
Germ Layers and Derivatives
- The trilaminar germ disc develops during early gastrulation, consisting of:
- Ectoderm: Outermost layer that forms the nervous system and skin.
- Mesoderm: Middle layer forming muscle, bone, and connective tissues.
- Endoderm: Innermost layer that creates the lining of internal organs.
Specialized Tissues
- Muscular Tissue: Composed of elongated cells specialized for contraction; includes smooth, cardiac, and skeletal muscle types.
- Nervous Tissue: Contains cells that receive, generate, and transmit nerve impulses; composed of neurons and supportive glial cells.
Epithelial Cell Functions
- Glandular epithelia are specialized for secretion, with apical surfaces often modified with microvilli to increase surface area.
- Exocrine glands have ducts that transport secretions to specific sites, whereas endocrine glands release hormones directly into the bloodstream.### Stereocilia and Cilia
- Stereocilia are long microvilli with mechanosensory functions, found in cells of the inner ear and the male reproductive tract.
- Cilia are long, motile apical structures, larger than microvilli, containing internal microtubule arrays.
Endocrine and Exocrine Glands
- Endocrine glands lack ducts; they secrete hormones directly into interstitial fluid and bloodstream for targeted cell action.
- Exocrine glands form secretory units such as sac-like acini (alveoli) or elongated tubules, and secrete substances through ducts.
- Three basic secretory mechanisms of glands include:
- Merocrine: Secretion via exocytosis.
- Holocrine: Terminally differentiated cells release lipid products by cell lysis.
- Apocrine: Release of product-filled areas from the apical part of cells.
Epithelial Tissue Features
- Epithelial tissues line all external and internal body surfaces, facilitating absorption, secretion, and protection.
- Types of epithelial cells:
- Squamous: Flat, sheet-like cells.
- Cuboidal: Cube-like cells, equal in width, height, and depth.
- Columnar: Taller than wide, column-like cells.
Junctions in Epithelial Tissue
- Tight or Occluding Junctions: Provide seals between adjacent cells, restricting molecule passage.
- Adherent or Anchoring Junctions: Strong cell adhesion sites; include zonula adherens which encircle epithelial cells.
- Gap Junctions: Channels that allow communication between adjacent cells.
Basement Membrane
- Forms a thin extracellular layer beneath epithelial tissue, composed of basal lamina and reticular lamina.
- Plays a role in separating and supporting overlying tissues and aids in filtration and exchange of substances.
Types of Epithelium
- Simple Epithelium: Single layer of closely packed cells.
- Stratified Epithelium: More than one layer, providing protection against mechanical stress.
- Pseudostratified Epithelium: Appears stratified due to differing cell heights but consists of a single layer.
Connective Tissue Characteristics
- Composed of widely spaced cells embedded in an extracellular matrix (ECM), offering structural support and connection between tissues.
- Types of connective tissue include bone, cartilage, adipose, blood, etc.
Bone Structure
- Classified into compact and spongy types, providing a framework and protection for organs.
- Contains components such as periosteum, red and yellow bone marrow, and endosteum lining internal spaces.
Cartilage Composition
- A flexible connective tissue with a gel-like matrix that provides firmness and resilience, covered by a perichondrium except on exposed surfaces.
Blood Components
- A liquid connective tissue consisting of formed elements (red blood cells, white blood cells, platelets) suspended in plasma.
Apoptosis Mechanisms
- Apoptosis involves specific signals:
- Extrinsic Signals: Bind to cell surface receptors (e.g., Fas ligand).
- Intrinsic Signals: Triggered by mitochondrial release of cytochrome c.
- Apoptotic bodies are created during cell death, making it less inflammatory compared to necrosis, where cells swell and burst due to acute injury.### Blood Components
- Blood plasma is a pale yellow fluid primarily composed of water with dissolved substances.
- Red Blood Cells (RBCs) are responsible for oxygen transport.
- White Blood Cells (WBCs) are involved in phagocytosis and immune defense against bacteria, viruses, and malignant diseases.
- Platelets aid in coagulation to prevent bleeding.
Muscle Tissue
- Muscle tissue is specialized for contraction and force generation, providing motion, pumping blood, and structural support.
- Smooth Muscle Tissue is involuntary, non-striated, with a central nucleus, and lines visceral organs.
- Cardiac Muscle Tissue is involuntary with striations, intercalated disks, and branching fibers.
- Skeletal Muscle Tissue is striated, cylindrical, multinucleated, and under voluntary control.
Apoptosis
- Apoptosis is a rapid and regulated process that eliminates defective and unneeded cells without provoking local inflammation.
- Key Bcl-2 proteins regulate apoptosis onset and are linked to cell health and replication.
- Events in apoptosis include mitochondrial dysfunction, DNA fragmentation, nuclear and cell shrinkage, membrane blebbing, and phagocytic removal of apoptotic bodies.
Neurulation
- Neurulation is the formation of the neural plate, folds, and closure of tubes, essential for developing the spinal cord and brain.
- The notochord induces neural plate formation during early gestation (around the 8th day).
- Four stages of neurulation progress from neural plate development to the closure of the neural tube, with specific milestones regarding the cranial and caudal neuropores.
- The cranial neuropore closes by the 25th day, while the caudal closes by the 27th day of intrauterine life.
Cellular Respiration
- Cellular respiration oxidizes glucose to produce ATP through a series of processes, including glycolysis, the Krebs cycle, and the electron transport chain.
- Glycolysis occurs in the cytoplasm, producing pyruvic acid alongside ATP and NADH.
- The Krebs Cycle takes place in the mitochondrial matrix, involving oxidation-reduction reactions that generate ATP, CO2, and electron carriers (NADH and FADH2).
Genetic Code
- The genetic code is composed of nucleotides A, G, T, and C, structured into codons that code for amino acids in protein synthesis.
- The codon organization in DNA is critical for proper gene expression and regulation during cell reproduction.
Protein Synthesis
- Two main classes of RNAs are involved in protein synthesis: protein-coding (mRNAs) and non-protein coding RNAs (tRNAs, rRNAs, etc.).
- DNA serves as the template from which RNA is synthesized, with specific involvement of RNA polymerases.
- The process of replication entails intricate steps: initiation, elongation, and termination, ensuring accurate duplication of genetic material.
Mitosis and Cell Cycle
- Cell maturation involves the specialization and activity of cells, detailing the transition through various cell cycle phases: G1 (gap after mitosis), S (DNA synthesis), G2 (gap before the next mitosis), and M phase (mitosis).
- Correct control of cell cycle phases is essential to avoid uncontrolled proliferation, contributing to cancer.
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Description
This quiz covers essential topics in embryology, genetics, cells, and tissues, specifically focusing on microvilli and their role in increasing the surface area of the plasma membrane. It is designed for first-year medical students in their first semester. Test your knowledge on these foundational concepts!
