Biology Chapter: Cells and Their Functions

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Questions and Answers

Which of the following components is NOT found in eukaryotic cells?

Cell wall (correct)

Cell membrane

True nucleus

Mitochondria

What type of molecules determine blood type and serve as receptors for cells?

Phospholipids

Glycoproteins (correct)

Lipids

Proteins

What is the primary function of the cell membrane?

Energy production

Regulation of nutrient and waste passage (correct)

Facilitation of cellular division

Genetic material storage

What is the process called when water moves through a semipermeable membrane?

Osmosis Signup and view all the answers

Which statement correctly describes prokaryotic cells?

They lack a true nucleus. Signup and view all the answers

What characterizes an isotonic solution?

Equal concentration of solute and solvent Signup and view all the answers

Which part of the phospholipid is hydrophilic?

Head Signup and view all the answers

Facilitated diffusion involves what type of proteins?

Carrier proteins Signup and view all the answers

What is the primary effect of a hypertonic solution on a cell?

The cell shrinks Signup and view all the answers

Which component of the nucleus is responsible for the assembly of ribosomes?

Nucleolus Signup and view all the answers

What function does the Rough Endoplasmic Reticulum primarily serve?

Export of protein products Signup and view all the answers

Which of the following statements about cytoplasm is true?

Cytoplasm is the site for most cellular metabolic reactions. Signup and view all the answers

What happens to chromatin when a cell begins to divide?

Chromatin threads coil and condense into chromosomes. Signup and view all the answers

Which organelle acts as the traffic director for cellular proteins?

Golgi Apparatus Signup and view all the answers

What is the function of lysosomes in a cell?

Demolition and breakdown of waste materials Signup and view all the answers

What happens to lysosomes under conditions of high Vitamin A and low oxygen?

They become fragile and may lead to self-digestion. Signup and view all the answers

What is the primary function of peroxisomes in kidney and liver cells?

Detoxification of harmful substances Signup and view all the answers

Which structure is responsible for directing the formation of the mitotic spindle?

Centrioles Signup and view all the answers

What do peroxisomes convert free radicals into?

Hydrogen peroxide Signup and view all the answers

What are microtubules primarily involved in?

Cell division and shape maintenance Signup and view all the answers

Which type of filament is primarily associated with cell motility?

Microfilaments Signup and view all the answers

What does the inner membrane of mitochondria form that is critical to its function?

Cristae Signup and view all the answers

What is a significant characteristic of mitochondria?

Presence of cristae Signup and view all the answers

What cellular structures are formed by the multiplication of centrioles?

Cilia Signup and view all the answers

What is the primary purpose of cell division?

To produce more cells for growth and repair processes Signup and view all the answers

During which stage of cell division do daughter chromosomes move toward the poles?

Anaphase Signup and view all the answers

What role does transfer RNA (tRNA) play in protein synthesis?

It transfers amino acids to the ribosome for protein building Signup and view all the answers

Which stage of cell division marks the beginning of cytokinesis?

Telophase Signup and view all the answers

What is the function of messenger RNA (mRNA) in cells?

It carries instructions for building proteins from the nucleus to the ribosome Signup and view all the answers

What occurs during transcription in protein synthesis?

DNA's base sequence is converted to a complementary mRNA sequence Signup and view all the answers

Which of the following is NOT a stage of mitosis?

Cytokinesis Signup and view all the answers

What is the significance of the mitotic spindle during cell division?

It attaches to chromosomes and aligns them at the center of the cell Signup and view all the answers

Study Notes

Cells: The Fundamental Units of Life

Cell Theory: Explains the basic principles of cells:
- All living things are composed of cells.
- Cells are the smallest units of structure and function in living organisms.
- New cells arise from pre-existing cells.
Types of Cells:
- Prokaryotic: Lack a true nucleus; energy production occurs within cell membranes.
- Eukaryotic: Possess a true nucleus; energy production occurs within mitochondria.
Major Parts of a Eukaryotic Cell:
- Cell Membrane (Plasma Membrane): A selectively permeable barrier composed of a phospholipid bilayer embedded with proteins:
  - Functions: Regulates the passage of nutrients, waste products, and secretions into and out of the cell.
  - Selective Permeability: Allows certain substances to pass through while restricting others.
  - Composition:
    - Phospholipids:
      - Head: Hydrophilic (water-loving), faces the watery environment.
      - Tail: Hydrophobic (water-hating), faces away from the water.
    - Proteins: Float within the lipid portion, serving diverse functions:
      - Enzymes: Catalyze biochemical reactions.
      - Carriers: Transport specific molecules across the membrane.
      - Receptors: Bind to hormones and chemical messengers, initiating cellular responses.
    - Glycoproteins: Determine blood type, act as receptors for bacteria, viruses, and toxins, and facilitate cell-to-cell interactions.
  - Transport Mechanisms: Various mechanisms move substances across the membrane:
    - Passive Diffusion: Movement of molecules from a high concentration to a low concentration across the membrane without energy input.
    - Facilitated Diffusion: Similar to passive diffusion but requires a protein carrier to assist movement.
    - Active Transport: Movement of molecules against their concentration gradient, requiring energy expenditure.
    - Endocytosis/Exocytosis: Bulk transport of materials into (endocytosis) or out of (exocytosis) the cell.
- Nucleus: The cell's control center; contains the genetic material (DNA):
  - Nuclear Membrane (Envelope): Double membrane surrounding the nucleus, containing pores for the passage of large molecules.
  - Nucleoplasm: A gel-like matrix within the nucleus, similar to cytoplasm.
  - Nucleolus: A dense region within the nucleus where ribosomes are assembled.
  - Chromatin/Chromosomes:
    - Chromatin: Uncoiled DNA, associated with proteins, within the nucleus when the cell is not dividing.
    - Chromosomes: Condensed, threadlike structures of DNA that become visible during cell division.
- Cytoplasm: The semi-fluid, gelatinous region between the cell membrane and nucleus; site of most cellular metabolic reactions:
  - Cytosol: The semitransparent fluid component of the cytoplasm, containing water, nutrients, and dissolved substances.
  - Inclusions: Non-functional units within the cytoplasm; storage sites for nutrients or cell products: - Fat droplets - Glycogen granules - Pigments (e.g., melanin) - Mucus - Crystals
  - Organelles: Specialized structures within the cytoplasm that carry out specific metabolic functions: - Ribosomes: Sites of protein synthesis, either free in the cytoplasm or attached to membranes. - Endoplasmic Reticulum (ER): A network of interconnected membranes that serves as a mini-circulatory system within the cell: - Rough ER: Contains ribosomes; abundant in cells that export protein products, such as pancreatic cells. - Smooth ER: Lacks ribosomes; involved in cholesterol synthesis, fat metabolism, detoxification of drugs, and steroid hormone production. - Golgi Apparatus (Complex): Modifies, sorts, and packages proteins synthesized by the ER: - Functions as a "traffic director" for cellular proteins. - Proteins accumulate in the Golgi apparatus, travel to the plasma membrane, and are released as secretory vesicles (exocytosis). - Lysosomes: "Demolition sites" of the cell, containing digestive enzymes: - Abundant in white blood cells (WBCs). - Breakdown worn-out organelles, cellular debris, and foreign substances. - Peroxisomes: Membranous sacs containing powerful oxidase enzymes that use oxygen to detoxify poisonous substances: - Found in kidney and liver cells. - Disarm dangerous free radicals by converting them to hydrogen peroxide which is then broken down to water. - Mitochondria: "Powerhouses" of the cell, responsible for energy production: - Double-walled structures with an outer membrane and an inner membrane folded into cristae. - Enzymes within the mitochondria break down food molecules using oxygen, releasing energy that is stored in ATP (adenosine triphosphate) molecules. - Cytoskeleton: A network of protein filaments that provides structural support, aids in intracellular transport, and facilitates cellular movement: - Composed of: - Microtubules: Involved in cell division, overall cell shape, and distribution of organelles. - Intermediate Filaments: Contribute to cell structure and provide attachment sites for desmosomes (cell junctions). - Microfilaments (Actin and Myosin): Essential for cell motility, changes in cell shape, and muscle contraction. - Centrioles: Small, cylindrical structures that play a role in cell division: - Direct the formation of the mitotic spindle (a structure that separates chromosomes during division). - Involved in the formation of cilia and flagella. - Cilia: Short, hair-like projections that beat rhythmically to create movement (e.g., in lung cells). - Flagella: Longer, whip-like projections that enable cell movement (e.g., sperm cells).

Cell Life Cycle:

The cell cycle consists of two main periods:
- Interphase: The period when the cell grows and carries out its ordinary metabolic activities.
- Cell Division: The process of a cell replicating itself to produce two daughter cells:
  - Function: For growth, replacement, and repair of the cell.
  - Mitosis: Division of the nucleus, resulting in two identical daughter nuclei.
  - Cytokinesis: Division of the cytoplasm, beginning near the end of mitosis, resulting in two daughter cells.

Stages of Cell Division:

Interphase: A period of growth, metabolic activity, and preparation for cell division, but no actual cell division occurs.
Prophase: The first stage of mitosis, where the chromosomes condense and become visible, and the spindle fibers start forming.
Metaphase: Spindle fibers are attached to chromosomes that align at the center of the cell.
Anaphase: The centromeres of the chromosomes separate, and sister chromatids are pulled toward opposite poles of the cell.
Telophase: The final stage of mitosis, where the chromosomes reach opposite poles of the cell and begin to uncoil, the nuclear envelope reforms around each set of chromosomes, and cytokinesis begins.

Protein Synthesis:

Gene: A segment of DNA that carries the instructions for building a specific protein.
Proteins: Essential for various cellular functions:
- Building materials for cells
- Act as enzymes (biological catalysts)
RNA (Ribonucleic Acid): Essential for protein synthesis:
- Transfer RNA (tRNA): Transfers amino acids to the ribosome for protein construction.
- Ribosomal RNA (rRNA): Combines with proteins to form ribosomes, the sites of protein synthesis.
- Messenger RNA (mRNA): Carries the genetic code from DNA in the nucleus to the ribosome in the cytoplasm.

Transcription and Translation:

Transcription: The process of transferring information from the base sequence of DNA to the complimentary base sequence of mRNA.
Translation: The process of converting the base sequence of mRNA into an amino acid sequence.
Amino acids are the building blocks of proteins.

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Description

This quiz explores the fundamental units of life, focusing on cell theory, the differences between prokaryotic and eukaryotic cells, and the major parts of a eukaryotic cell. Test your understanding of cell structures, functions, and the principles that govern cellular organization.