Biology Quiz: Cell Biology and Stem Cells

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Questions and Answers

What distinguishes embryonic stem cells from adult stem cells?

Embryonic stem cells are multipotent.

Adult stem cells are pluripotent.

Embryonic stem cells can differentiate into any cell type. (correct)

Adult stem cells can differentiate into any cell type.

Which of the following is NOT a cause of cancer?

Mutations in cell cycle regulating genes

Infection by bacteria only (correct)

Inherited genetic mutations

Environmental factors like radiation

What is a characteristic of benign tumors?

They invade surrounding tissues.

They do not metastasize. (correct)

They cause significant harm immediately.

They spread to other body parts.

What type of stem cells are hematopoietic stem cells considered?

Multipotent stem cells Signup and view all the answers

Which treatment option directly enhances the body's immune response against cancer?

Immunotherapy Signup and view all the answers

What is the primary location of DNA in prokaryotic cells?

Nucleoid region Signup and view all the answers

Which of the following structures is responsible for protein synthesis in eukaryotic cells?

Rough endoplasmic reticulum Signup and view all the answers

What organelle is known as the site of ATP synthesis?

Mitochondria Signup and view all the answers

Which structure is critical for maintaining turgor pressure in plant cells?

Vacuole Signup and view all the answers

Which type of microscope provides a 3D image of a specimen's surfaces?

Scanning electron microscope (SEM) Signup and view all the answers

Which of the following is NOT a part of the cell theory?

Cells can spontaneously generate from non-cellular materials Signup and view all the answers

What type of ribosomes are found in mitochondria?

70S Signup and view all the answers

What is the function of the Golgi apparatus?

Modification and sorting of proteins and lipids Signup and view all the answers

What is the primary role of cholesterol in cell membranes?

Modulates membrane fluidity and mechanical stability Signup and view all the answers

Which type of transport involves the movement of molecules against their concentration gradient?

Active transport Signup and view all the answers

What is the function of glycolipids and glycoproteins in membranes?

Facilitate cell recognition and signaling Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

S Phase Signup and view all the answers

Which statement about telomeres is true?

They prevent chromosomes from degradation Signup and view all the answers

What is the role of receptor proteins in cell signaling?

Bind signaling molecules and initiate cellular responses Signup and view all the answers

Which process is characterized by the engulfing of liquids or small solutes?

Pinocytosis Signup and view all the answers

What occurs during anaphase of mitosis?

Sister chromatids are pulled apart to opposite poles Signup and view all the answers

What is the significance of the G1 checkpoint in the cell cycle?

Verifies cell size, nutrients, and DNA integrity Signup and view all the answers

Which of the following correctly describes a function of integral proteins?

They facilitate the movement of specific molecules across membranes Signup and view all the answers

What does passive transport NOT require?

Energy in the form of ATP Signup and view all the answers

Which signaling type involves the signal acting on the same cell that produced it?

Autocrine signaling Signup and view all the answers

Which of the following best describes the structure of chromosomes?

Composed of two sister chromatids joined at a centromere Signup and view all the answers

What is the primary structure of a protein?

The sequence of amino acids in a polypeptide chain Signup and view all the answers

Which statement about enzyme-substrate complexes is correct?

They follow the lock-and-key model or the induced fit model. Signup and view all the answers

What role do cofactors play in enzyme activity?

They assist in enhancing the activity of enzymes. Signup and view all the answers

How does temperature affect enzyme activity?

Optimal temperature increases enzyme efficiency. Signup and view all the answers

What happens to enzyme activity when the pH is not at its optimum level?

It can lead to denaturation or reduced activity. Signup and view all the answers

Which of the following statements about water is correct?

Water molecules have strong adhesive properties. Signup and view all the answers

Competitive enzyme inhibitors affect enzyme activity by:

Competing for the active site with the substrate. Signup and view all the answers

How is enzyme affinity measured?

Using the Michaelis-Menten constant (K_m). Signup and view all the answers

What is a characteristic of irreversible inhibitors?

They form covalent bonds, permanently disabling the enzyme. Signup and view all the answers

What defines the quaternary structure of a protein?

The interaction between multiple polypeptide chains. Signup and view all the answers

Which property of water is responsible for stabilizing aquatic environments?

High specific heat capacity. Signup and view all the answers

What is the role of membranes in cells?

To control the movement of substances into and out of cells. Signup and view all the answers

Which process involves the use of immobilized enzymes?

Reusing enzymes for continuous reactions in industrial processes. Signup and view all the answers

What is true about secondary structure in proteins?

It typically involves hydrogen bonding stabilizing α-helices and β-pleated sheets. Signup and view all the answers

What is the highest magnification possible with light microscopy?

x1500 Signup and view all the answers

Which structure is unique to plant cells as observed under a light microscope?

Chloroplasts Signup and view all the answers

What is the size range of prokaryotic cells?

1-10 μm Signup and view all the answers

What type of bond forms between the monomers of polysaccharides?

Glycosidic bonds Signup and view all the answers

What is a characteristic of electron microscopy compared to light microscopy?

Higher magnification Signup and view all the answers

Which is a function of lipids?

Energy storage Signup and view all the answers

What is the main structural component of bacterial cell walls?

Peptidoglycan Signup and view all the answers

What type of reaction builds polymers from monomers?

Condensation Signup and view all the answers

Which of the following is NOT a component of viruses?

Cell wall Signup and view all the answers

What is the unique component of ribosomes found in prokaryotic cells?

70S Signup and view all the answers

What distinguishes saturated fatty acids from unsaturated fatty acids?

Presence of double bonds Signup and view all the answers

What is the ratio of carbon, hydrogen, and oxygen in carbohydrates?

1:2:1 Signup and view all the answers

Which molecule serves as the building block for proteins?

Amino acids Signup and view all the answers

What process do viruses undergo to replicate within a host?

Lytic cycle Signup and view all the answers

Study Notes

Prokaryotic vs. Eukaryotic Cells

Prokaryotic Cells: Small (1-10 μm), lack a nucleus, DNA in a nucleoid region (single circular chromosome).
Prokaryotic Cells: Contain plasmids (small circular DNA, often for antibiotic resistance).
Prokaryotic Cells: Use 70S ribosomes for protein synthesis.
Prokaryotic Cells: Have a cell wall made of peptidoglycan, flagella for movement, and pili for attachment or conjugation.
Eukaryotic Cells: Larger (10-100 μm), possess a membrane-bound nucleus with linear chromosomes.
Eukaryotic Cells: Employ 80S ribosomes in the cytoplasm, and 70S ribosomes in mitochondria and chloroplasts.
Eukaryotic Cells: Have compartmentalized organelles bound by membranes.

Organelles and Their Functions

Nucleus: Houses the cell's DNA, controls cell activities via transcription, has a double membrane with pores, and contains a nucleolus for rRNA synthesis.
Mitochondria: Site of ATP synthesis through aerobic respiration; the inner membrane forms cristae, and the matrix contains enzymes for the Krebs cycle.
Ribosomes: Synthesize proteins; free in the cytoplasm (internal use) or bound to the rough endoplasmic reticulum (secretion).
Rough Endoplasmic Reticulum (RER): Processes and folds proteins synthesized by bound ribosomes.
Smooth Endoplasmic Reticulum (SER): Synthesizes lipids, steroids, and detoxifies harmful substances.
Golgi Apparatus: Modifies, packages, and sorts proteins and lipids into vesicles, and forms lysosomes.
Lysosomes: Contain hydrolytic enzymes for digestion (autophagy, autolysis).
Chloroplasts (plant cells): Site of photosynthesis in thylakoid membranes and stroma.
Vacuole (plant cells): Stores cell sap (ions, sugars), maintains turgor pressure for support.
Cytoskeleton: Provides structure and support; includes microtubules (shape, transport), microfilaments (movement, cytokinesis), and intermediate filaments (strength).

Microscopy

Light Microscope: Magnification up to x1500, resolution ~200 nm, observes live specimens.
Electron Microscope (TEM): High resolution, observes internal details.
Electron Microscope (SEM): 3D images of surfaces.

Cell Theory and Organisms

Cell Theory: All living organisms are made of cells, cells arise from pre-existing cells, and the cell is the basic unit of structure and function.
Unicellular Organisms: Single-celled organisms like bacteria and protozoa.
Multicellular Organisms: Made of many specialized cells, like plants (cell wall) and animals.

Measuring Size and Magnification

Magnification Formula: Magnification = Image size / Actual size.
Units: Ensure consistent units (mm to μm: 1 mm = 1000 μm, 1 μm = 1000 nm).
Eyepiece Graticule: Calibrate against a stage micrometer to measure specimen size.

Plant and Animal Cells

Plant Cells: Visible features include cell wall, plasma membrane, nucleus, cytoplasm, chloroplasts, and a large central vacuole.
Animal Cells: Visible features include plasma membrane, nucleus, and cytoplasm (organelles not readily apparent without staining).
Comparison: Plant cells have a cell wall and chloroplasts, while animal cells typically lack both; plant cells have a large vacuole, while animal cells have smaller, temporary vacuoles.

Electron Microscopy

Advantages: Higher resolution (~0.1 nm), greater magnification (up to x500,000).
Disadvantages: Specimens must be dead (vacuum environment), preparation and staining is time-consuming (heavy metals).

Bacteria

Structure: Cell wall of peptidoglycan, plasma membrane, cytoplasm with 70S ribosomes and enzymes, nucleoid with circular DNA, plasmids as additional DNA, flagella for movement, and pili for attachment and conjugation.
Reproduction: Binary fission (asexual reproduction).

Comparing Prokaryotic and Eukaryotic Cells (Summary)

Size: Prokaryotic (1-10 μm), Eukaryotic (10-100 μm).
Nucleus: Prokaryotic (absent), Eukaryotic (present).
DNA: Prokaryotic (circular, not associated with histones), Eukaryotic (linear, associated with histones).
Organelles: Prokaryotic (non-membrane bound), Eukaryotic (membrane-bound).
Ribosomes: Prokaryotic (70S), Eukaryotic (80S).
Cell Wall: Prokaryotic (peptidoglycan), Eukaryotic (cellulose, not in animals).

Viruses

Description: Non-cellular, 20-300 nm size, protein coat (capsid) surrounding nucleic acid (DNA or RNA), some have a lipid envelope.
Types: DNA viruses (adenoviruses), RNA viruses (influenza, HIV).
Reproduction: Obligate intracellular parasites (replicate within a host). Lifecycle: Attachment → Entry → Replication → Assembly → Release.

Biological Molecules and Biochemistry

Biochemistry: Studies chemical processes in living organisms.
Biomolecules: Carbohydrates, lipids, proteins, nucleic acids, and water; important for structure, energy storage, and function.
Elements: Mostly carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S).

Carbohydrates

Structure: Contain C, H, O in a 1:2:1 ratio (e.g., glucose: (CH2O)6).
Monosaccharides: Single sugar units (glucose, fructose, galactose).
Disaccharides: Two monosaccharides linked by glycosidic bonds (e.g., maltose, sucrose, lactose).
Polysaccharides: Long chains of monosaccharides (starch, glycogen, cellulose).
- Starch (plant energy storage): Amylose (unbranched), amylopectin (branched).
- Glycogen (animal energy storage): highly branched.
- Cellulose (plant cell wall): β-glucose chains with hydrogen bonds.

Lipids

Structure: Contain C, H, and O, lower O proportion than carbohydrates.
Triglycerides: Glycerol + 3 fatty acids (ester bonds).
- Saturated fatty acids (solid at room temp).
- Unsaturated fatty acids (liquid at room temp).
Phospholipids: Glycerol + 2 fatty acids + phosphate group; hydrophilic head, hydrophobic tails - key membrane component.
Steroids: Four fused carbon rings (e.g., cholesterol, hormones).

Proteins

Structure: Contain C, H, O, N, and sometimes S.
Monomer: Amino acids (central carbon, amino group, carboxyl group, R group).
Peptide bonds: Link amino acids through condensation reactions.
Protein Structure Levels: Primary (sequence), Secondary (α-helix, β-sheet), Tertiary (3D folding), Quaternary (multiple polypeptide chains combined).
Functions: Enzymes, structural components (collagen, keratin), transport (hemoglobin), immune response (antibodies).

Water

Structure: Polar molecule (O-H bonds).
Properties: Solvent (dissolves polar substances), high specific heat (regulates temperature), high latent heat of vaporization (cooling), cohesion/adhesion (capillary action), ice density (less dense than liquid water).

Enzymes

Definition: Biological catalysts that speed up reactions without being consumed.
Structure: Globular proteins with an active site (substrate binding).
- Lock-and-key model
- Induced-fit model
Action: Lower activation energy to speed up reactions. Highly specific to substrates. Reusability.
Investigation Techniques: Measure gas production (oxygen), color change (starch), mass loss.

Factors Affecting Enzyme Action

Temperature: Optimal temperature for maximum activity; denaturation at high temperatures.
pH: Optimal pH range; disruption at non-optimal pH.
Substrate concentration: Increased rate up to saturation point where all enzyme sites are occupied.
Enzyme concentration: Directly proportional to reaction rate (substrate not limiting).
Cofactors: Non-protein molecules (coenzymes, metal ions) aiding enzyme activity.

Enzyme Inhibitors

Competitive inhibitors: Compete with substrate for active site; overcomeable by increasing substrate concentration.
Non-competitive inhibitors: Bind to allosteric site, altering enzyme shape; not overcomeable by increasing substrate.
Irreversible inhibitors: Form covalent bonds with the enzyme, permanently inactivating it.

Immobilized Enzymes

Definition: Enzymes attached to a surface for reuse, stability and product separation.
Methods: Adsorption, entrapment, covalent bonding.
Applications: Industrial processes and biosensors.

Membranes

Definition: Selectively permeable barriers regulating substance movement.
Structure (Fluid Mosaic Model): Phospholipid bilayer (hydrophilic heads, hydrophobic tails); embedded proteins (integral, peripheral), cholesterol (stability), glycolipids/glycoproteins (recognition).
Components' Roles: Phospholipids (barrier), proteins (transport, signaling), cholesterol (fluidity), glycoproteins/glycolipids (recognition).

Cell Signaling

Process: Reception (ligand binding), transduction (intracellular events), response (cellular activity).
Signaling Types: Autocrine, paracrine, endocrine.
Receptor Types: Ion channel, G-protein coupled, enzyme-linked.

Movement Across Membranes

Passive Transport (no energy): Diffusion (high to low concentration), facilitated diffusion (channel/carrier protein assistance), osmosis (water movement).
Active Transport (requires energy): Moves substances against their concentration gradient (carrier proteins involved).
Bulk Transport: Endocytosis (phagocytosis, pinocytosis), exocytosis (release of substances).

Growth, Reproduction, and Chromosomes

Growth: Increase in cell number through mitosis (cell division).
Reproduction: Single-celled organisms reproduce via mitosis; multicellular organisms via cell division for repair, growth, development.
Chromosomes: DNA tightly coiled around histones (chromatin); sister chromatids joined at centromeres; telomeres (protective caps). Diploid (2n), haploid (n).

The Cell Cycle and Mitosis

Cell Cycle: The series of events from one cell division to the next. Interphase (G1, S, G2) and M phase (mitosis and cytokinesis).
Mitosis Stages: Prophase (condensation, spindle formation), metaphase (alignment), anaphase (separation), telophase (decondensation, nuclear envelope reformation).
Cytokinesis: Cytoplasm division. In animals - cleavage furrow, in plants - cell plate.

Telomeres and Stem Cells

Telomeres: Protective DNA sequences at chromosome ends, shortened with each division. Telomerase maintains them.
Stem cells: Undifferentiated cells with self-renewal and differentiation capacity (embryonic, adult).

Cancer

Definition: Uncontrolled cell division leading to tumors.
Causes: Mutations in genes regulating cell division, carcinogens, genetic predisposition.
Tumor Types: Benign (non-invasive), malignant (invasive, metastasizing).
Treatments: Surgery, chemotherapy, radiation, immunotherapy.

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Description

Test your knowledge on key concepts in cell biology, including stem cells, cancer, and the roles of organelles. This quiz covers essential topics such as the differences between embryonic and adult stem cells, characteristics of tumors, and the cell theory. Perfect for biology students wanting to reinforce their understanding of cellular functions.