Cell: The Fundamental Unit of Life
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Questions and Answers

What is the functional unit of the kidney?

Nephron

What is the primary function of red blood cells (RBCs)?

To transport oxygen, carbon dioxide, and hormones.

Do red blood cells (RBCs) contain a nucleus?

No

What is the unit of nerve cells called?

<p>Neuron</p> Signup and view all the answers

List the levels of organization from a cell to an organism.

<p>Cell, Tissue, Organ, Organ System, Organism</p> Signup and view all the answers

Who proposed the cell theory together?

<p>Schleiden and Schwann</p> Signup and view all the answers

Who stated that all cells arise from preexisting cells?

<p>Rudolf Virchow</p> Signup and view all the answers

What is the largest cell?

<p>Ostrich egg</p> Signup and view all the answers

What is the smallest cell?

<p>PPLO (Mycoplasma)</p> Signup and view all the answers

What is the longest cell in humans?

<p>Nerve cells or Neuron</p> Signup and view all the answers

Who discovered the dead cell and in what year?

<p>Robert Hooke, 1665</p> Signup and view all the answers

Who discovered the living cell?

<p>Antonie van Leeuwenhoek</p> Signup and view all the answers

Who discovered the nucleus of a cell?

<p>Robert Brown</p> Signup and view all the answers

Who first observed protoplasm and what name was initially given to it?

<p>Dujardin, Sarcode</p> Signup and view all the answers

Who proposed that all animals are made up of cells?

<p>Schwann</p> Signup and view all the answers

Who discovered the nucleus of the cell?

<p>Robert Brown</p> Signup and view all the answers

What are non-living parts of the cell called that don’t perform any metabolic activity?

<p>Cell inclusion</p> Signup and view all the answers

What is considered the living part of the cell and provides ground for cellular activity?

<p>Cytoplasm</p> Signup and view all the answers

What is the fluid content of the cytoplasm called?

<p>Cytosol</p> Signup and view all the answers

What organelle has tiny pores between the nucleoplasm?

<p>Nucleus</p> Signup and view all the answers

Who discovered the nucleus?

<p>Robert Brown</p> Signup and view all the answers

What is the nuclear membrane composed of?

<p>It is double membranous.</p> Signup and view all the answers

What is the largest structure within the nucleus?

<p>Nucleolus</p> Signup and view all the answers

What is the function of the nucleolus?

<p>It forms ribosomes and is the storehouse of RNA.</p> Signup and view all the answers

What is nucleoplasm similar to?

<p>It is similar to protoplasm (Karyoplasm).</p> Signup and view all the answers

What structure inside the nucleus condenses to form chromosomes before cell division?

<p>Chromatin fibers</p> Signup and view all the answers

What is the primary function of chromosomes?

<p>Inheritance of genes</p> Signup and view all the answers

How many chromosomes do humans have?

<p>46</p> Signup and view all the answers

What macromolecules make up chromosomes?

<p>DNA and proteins</p> Signup and view all the answers

Why is the nucleus referred to as the 'brain of the cell'?

<p>It controls all activities of the cell.</p> Signup and view all the answers

What are the essential components present in every cell?

<p>Cell membrane, cytoplasm, nucleus</p> Signup and view all the answers

What type of nucleus do prokaryotic cells have?

<p>Prokaryotic cells have a primitive nucleus.</p> Signup and view all the answers

What is the range in size for prokaryotic cells?

<p>Prokaryotic cells range from 0.5 to 5 micrometers in size.</p> Signup and view all the answers

How do prokaryotic cells reproduce?

<p>Prokaryotic cells reproduce through binary fission.</p> Signup and view all the answers

What term is used to describe the region where DNA is found in prokaryotic cells?

<p>The region where DNA is found in prokaryotic cells is called the nucleoid.</p> Signup and view all the answers

Name two structural components found on the external surface of a prokaryotic cell.

<p>The external surface of a prokaryotic cell has a capsule and flagella.</p> Signup and view all the answers

Where are the chromosomes located in prokaryotic cells?

<p>Nucleoid</p> Signup and view all the answers

Do prokaryotic cells have membrane-bound organelles?

<p>No</p> Signup and view all the answers

What is the method of cell division in prokaryotic cells?

<p>Binary fission</p> Signup and view all the answers

What role do mesosomes play in prokaryotic cells?

<p>Help in making cell walls</p> Signup and view all the answers

Do prokaryotic cells have a nucleus?

<p>No</p> Signup and view all the answers

What makes ATP a flexible molecule?

<p>It can be broken and reunited.</p> Signup and view all the answers

What is passive transport and which direction does it move materials?

<p>Passive transport is a type of transport through the plasma membrane done without energy expenditure, moving materials from higher to lower concentration.</p> Signup and view all the answers

What occurs during diffusion?

<p>Materials move from their higher concentration to their lower concentration through the plasma membrane.</p> Signup and view all the answers

What type of transport is osmosis and what does it specifically move?

<p>Osmosis is a type of diffusion that moves water from its higher concentration to its lower concentration through the plasma membrane.</p> Signup and view all the answers

What happens to a cell in a hypotonic solution?

<p>The cell absorbs water and swells or even bursts.</p> Signup and view all the answers

Describe what occurs in plasmolysis.

<p>Water moves out of the cell, causing it to shrink when the concentration of solute is high outside the cell.</p> Signup and view all the answers

What is the primary mode of reproduction for prokaryotic cells?

<p>Asexual reproduction (binary fission)</p> Signup and view all the answers

What is the typical size range of eukaryotic cells?

<p>10-100μm</p> Signup and view all the answers

What component of the cell is missing in prokaryotic cells but present in eukaryotic cells?

<p>Nucleus</p> Signup and view all the answers

What is a major structural component of the plasma membrane?

<p>Proteins and phospholipids</p> Signup and view all the answers

Why is the plasma membrane called selectively permeable?

<p>It regulates the entry and exit of substances from inside to outside of the cell.</p> Signup and view all the answers

Study Notes

Cell: The Fundamental Unit of Life

  • A cell is a structural and functional unit of life, comprising tissues, organs, organ systems, and organisms.
  • In humans, birds, and animals, the unit of kidney is nephron, nerve cells are neurons, and RBCs lack a nucleus.

Important Discoveries in Cell Biology

  • Dead cell: Discovered by Robert Hooke in 1665
  • Living cell: Discovered by Antona Van Leeuwenhoek in 1674
  • Nucleus: Discovered by Robert Brown in 1831
    • Protoplasm: Discovered by Purkinje in 1839
  • Electron microscope: Invented by Knoll and Ruska in 1940
  • Cell theory: Proposed by J.Schleiden (1838-39) and Schwann (1839)
    • All plants and animals are made up of cells
    • Cell is the basic unit of life
    • Rudolf Virchow: Modern cell theory (Omnia cellula e cellula)

Cell Theory Expanded

  • Cells arise from pre-existing cells
  • The theory explains the origin of the cell
  • The activities performed by an organism are the sum total of activities of its cells

Shape and Size of Cells

  • Largest cell: Ostrich egg
  • Smallest cell: PPLO (My Coplasma)
  • Longest cell: Nerve cells or neurons
  • Largest cell in human: Sperm or ovum

Important Constituents of the Cell

  • Protoplasm
  • Nucleus
  • Plasma membrane

Protoplasm

  • Cytoplasm
    • Organelles
    • Nucleoplasm
  • Cytosol: The fluid content of the cytoplasm
  • Functions: Provides ground for cellular activity, provides shape to the cell

Cell Inclusion

  • Non-living parts of the cell that don't perform metabolic activity
    • Examples: Pigments, minerals, lipids

Nucleus

  • Nuclear membrane
  • Nucleolus
  • Nucleoplasm (Karyoplasm)
    • Chromatin fibers
  • Functions: Controls all cellular activities, forms ribosomes and RNA, carries genetic material

RNA and Chromatin

  • RNA (Ribonucleic acid): The genetic material of many bacteria
  • Chromatin: A thread-like structure present inside the nucleus
    • When the cell divides, chromatin fibers condense to form chromosomes
    • Chromosomes are responsible for inheritance of genes

Human Chromosomes

  • 46 chromosomes (22 + 7 + XX/XY)

Functions of the Nucleus

  • Controls all cellular activities
  • Forms ribosomes and RNA
  • Carries genetic material
  • Helps in cell division

Cell Types

  • Prokaryotic cells: Have a primitive nucleus, lack a nuclear membrane
  • Eukaryotic cells: Have a true nucleus, membrane-bound organelles

Prokaryotic Cells

  • Characteristics:
    • Size: 0.5-5 micrometers
    • Lack of membrane-bound nucleus
    • Absence of well-defined nuclear region
  • Reproduce through binary fission
  • Examples: Bacteria, Mycoplasm, Cyanobacteria (BGA)

Eukaryotic Cells

  • Characteristics:
    • Can be unicellular or multicellular
    • Nucleus is always present
    • Cell size: 10-100 micrometers
  • Examples: Plants, animals, fungi

Plasma Membrane

  • A thin membrane that holds the cell contents
  • Made up of protein and phospholipids
  • Regulates the entry and exit of substances from inside to outside of the cell
  • Selectively permeable membrane

Transport of Materials

  • Passive transport: A type of transport that takes place without the expenditure of energy
    • Types: Diffusion, Osmosis
  • Active transport: A type of transport that requires energy

Osmosis

  • A type of diffusion that takes place in liquids
  • Movement of water from its higher concentration to its lower concentration through the plasma membrane
  • Examples: Absorption of water through roots
  • Types:
    • Hypotonic: Cell absorbs water and swells or bursts
    • Isotonic: Concentration of solute and solvent are the same inside and outside the cell
    • Hypertonic: Cell loses water and shrinks
    • Plasmolysis: When the concentration of solute is high outside the cell
    • Cremation: Cell shrinks while remaining intact

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Description

Learn about the structural and functional unit of life, including the hierarchy of cells, tissues, organs, and organ systems. Explore the units of kidney and nerve cells, and understand the functions of RBCs.

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