sci lt review

Discoveries on cell

  • Robert Hooke 

    • Introduced the term “cell” in 1665

  • Anton Van Leeuwenheok 

    • 1677 described spermatozoa of insects and man

    • First to discover bacteria

    • Father of microbiology

  • Robert Brown

    • 1831 found nucleus

    • Recognized existence of stomata in plant cells

Proponents of cell theory

  • Matthias Schleiden - 1831, plants were made of cells

  • Theodore Schwann - 1839, animals were made of cells

  • Rudolf Virchow - 1858, proposed cells self-reproduced



Cell structure



Cell membrane        “Gate in a Factory”

Components

  • Phospholipid bilayer

    • Head - Hydrophilic (does not repel water)

    • Tail - Hydrophobic (repels water)

  • Protein - Serves as channels transporting materials

  • Cholesterol - Stabilizes fluidity and solidity of the membrane

  • Glycoprotein - Cell to cell recognition

Functions

  • Encloses cell making boundary between it and external environment

  • Controls movement of substance going in and out

  • It is semi permeable. ( allows some substances to pass through)

  • Allows cell to change shape

  • Allows cell to communicate with each other



Cytoplasm            “Floor in a Factory”

Components

  • Consisting of fluidlike substances and organelles

Function

  • Most cell activities occur here, like glycolysis, cell division, and protein synthesis



Nucleus             “Ceo in a Factory”

Components

  • Nucleus ( most inside ), Nucleoplasm ( middle part ), Nucleus Envelope ( outside ), Nuclear pore ( dots on Nuclear Envelope )

Functions

  • Nuclear envelope enclosed in nucleus

  • Nuclear pore provides a channel to transport materials inside nucleus

  • Nucleoplasm is a fluidlike substance where nucleolus and chromatin are suspended

  • Nucleolus is site of ribosome synthesis

  • Controls all activities in cell

  • Contains ribonucleic acid (RNA) and proteins

  • Multinucleated cells ( Many nucleus in a cell)

    • Liver cells and Osteoclast of the bone

  • Anucleate cells ( cells that lack nucleus )

    • Red blood cells

  • Lobed nucleus cells (Lobular-shaped)

    • White blood cells



Mitochondria     “Electrical Room in the Factory”, “Powerhouse of the cell”

Components

  • spherical/sausage shape and double membrane

  • Inner membrane folded into folds called cristae

  • Matrix contains important materials like enzymes, DNA, and Ribosomes

  • Has its own DNA and RNA which allows it to make its own proteins

  • Capable of division

Functions

  • Involved in production of energy in cell (ATP)

  • ATP is important for the cell to grow and develop

  • Human cell consists of 3-5k mitochondria



Ribosomes       “Workers in a Factory”

Components

  • Produced by the nucleolus of the nucleus

  • Composed of RNA and proteins

  • Bound ribosomes are attached to the endoplasmic Reticulum

  • Free ribosomes are floating in the cytoplasm

Functions

  • Involved in production of proteins. Hence it is the site of protein synthesis in cells



Endoplasmic Reticulum      “Assembly line in a factory”

Components

  • Rough endoplasmic reticulum

    • Flattened canal structure and attached to ribosomes

  • Smooth endoplasmic reticulum

    • Tubular canal structure and smooth appearance

Functions

  • Structure that forms a network canal where protein and other molecules are transported

  • Rough ER has most ribosomes attached. Proteins produced in the ribosomes are transported through the ER

  • Smooth ER serves as a transport canal for large molecules in the cell. Some steroids are produced in the SER, also stores calcium ions in muscle cells.



Golgi Apparatus      “Packaging center and cart in a factory”

Components

  • Cisternae - flattened membrane

  • Lumen - Internal space

  • Vesicles - small sac used to transport materials from ER to golgi then to cell membrane going out of the cell.

Function

  • Modifies protein produced in the ribosomes that passed through the RER

  • Example of protein modification takes place in this in addition to carbs is glycoproteins



Lysosomes       “Janitor in a Factory”

Function

  • Contains different hydrolytic enzymes which digests bacteria, viruses, complex food particles, and damaged cell components

  • Lysosome as digestive sac – digests food particles, viruses, damaged cell organelle

  • Lysosome as suicide sac – initiates cell deaths or Apoptosis



Vacuoles   “Water Tank in a factory”

Components

  • Tonoplast - membrane that surrounds vacuoles

  • Cell sap - made of water with dissolved sugars, mineral salts, and amino acids

Functions

  • Serves as storage of water, food enzymes, and other minerals needed by the cell.



Cytoskeleton          “Framework of a factory”

Components and Function

  • Microfilaments and Intermediate filaments 

    • Attached to cell membrane and responsible for providing the cell shape and mechanical support

  • Microtubules

    • Not attached to the cell membrane and it provides anchorage of cell organelles



Centrosome, Centrioles, and Spindle Fibers

  • Centrosome is located in the cytoplasm and usually close to the nucleus. Contains centrioles which is composed of 2 microtubes

  • Spindle fiber only appears during cell division

  • Centrioles and Spindle Fibers are made up of microtubules and are involved in cell division.

Cell Wall       “Gate in a factory”

Components

  • Chitin – fungi

  • Cellulose – plants

  • Peptidoglycan – bacteria

  • Primary cell wall - First wall deposited by cells, outer wall and elongates and expands over life of the plant

  • Secondary cell wall - some cells deposit additional layers inside the primary wall. Occurs after growth stops or when cells begin to differentiate

  • Secondary wall is mainly for support, comprised primarily of cellulose, hemicelluloses and lignin

  • Woods consists mostly of secondary cell wall

  • Middle Lamella - outmost layer, mostly pectic polysaccharides

  • Acts as an interface between the other neighboring cells and glued them together

  • All cells of the plants have middle lamella

  • Only plant cells have a cell wall

Function

  • Provides definite shape, strength, and rigidity

  • Helps to control cell expansion due to intake of water

  • Helps in preventing water loss from cell



Chloroplast               “Canteen in a factory”

Components

  • Found in all green plants, they are food producers of plants, not present in animal cells

  • Outer membrane - encloses the chloroplast

  • Inner membrane - separate the stroma from the intermembrane space

  • Intermembrane space - separates outer and inner membrane

  • Stroma - colorless alkaline, aqueous, protein-rich fluid present within the inner membrane of the chloroplast

  • Thylakoid or Lamellae - membraned-sac where green pigments of the plant called chlorophyll are found

  • Granum - a Thylakoid arranged in stack

  • Lumen - space inside the Thylakoid

  • Stroma Lamellae - cytoskeleton that keeps the distance between the granum

Functions

  • Synthesize food by the process of photosynthesis

  • Has a structure called chlorophyll which functions by trapping solar energy used for synthesis of food in all green plants

Prokaryotes

  • Unicellular

  • Lacks nucleus

  • No membrane bound organelles

  • One of the earliest organisms on Earth

  • Ex. Staphylococcus aureus, Mycobacterium tuberculosis, Vibriochloerae, and Bifidobacteria

  • Bifidobacteria is a example of good bacteria

Structure

  • Capsule

    • protective layer of prokaryote

    • Helps in moisture retention

    • Helps attachment of cell to nutrients and surfaces

  • Cell Wall

    • Layer that gives shape to the cell


  • Cell membrane

    • Surrounds the cytoplasm

    • Regulates entry and exit of substances in the cell

  • Nucleoid Region

    • Region in the cytoplasm where genetic material is present

  • Cytoplasm

    • Jelly-like substance in the cell

    • Where structures of the cell are suspended

  • Ribosome

    • Site of protein-synthesis

  • Pilus

    • Hair-like outgrowths that attach to the surface of other bacterial cells

  • Flagellum

    • Long structures that helps in the locomotion (movement) of the cell

    • Tail-like thing on the cell



Prokaryotes

Eukaryotes

Example

Bacteria (Unicellular)

Plant and Animal Cells ( Multicellular)

Size

Smaller ( 1-10 μm)

Bigger ( 10-100 μm)

DNA and its location

Nucleoid Region and DNA is in a circular loop

Nucleus and DNA is packed in chromosome

Organelle

No membrane-bound organelles

With membrane-bound organelles



Eukaryotes

  • Multicellular

  • possesses nucleus and membrane bound organelles

  • Ex. Animal Cell and plant cells


Animal Cell 

Plant Cell

Size 

Smaller (10-30 micrometers)

Bigger (10-100 micrometers)

Vacuoles

Small but numerous

One large vacuole

Chloroplast

Absent

Present

Cell Wall

Absent

Present

Centrioles

Present

Absent

Lysosome

Present

Absent

Nucleus

Present

Present

Mitochondria

Present

Present

Rough ER

Present

Present

Smooth ER

Present

Present

Golgi Apparatus

Present

Present

Cell Membrane

Present

Present

Cytoskeleton

Present

Present

Cytoplasm

Present

Present

Ribosome

Factors affecting cell transport

  • Size

    • Micromolecules or macromolecules

  • Charge

    • Non charged or charged

  • Solubility

    • Lipid-soluble or not

  • Concentration gradient

    • Difference in concentration of particles

    • Solute - higher concentration to lower concentration

    • Solvent (water) - moves to area with higher concentration of solute

  • Composition of the cell membrane

    • Phospholipid bilayer

      • Phospholipid head - Hydrophilic

      • Phospholipid tail - Hydrophobic

    • Cholesterol

      • Maintains fluidity of cell

    • Membrane proteins

      • Gates for molecule ( channel and carrier)

    • Carbohydrates

      • Cell to cell recognition

      • Glycoprotein / Glycolipid

General Rules

  • small non-charged, lipid soluble molecules can easily cross the cell membrane.

  • Cell transport follows concentration gradient or you have to pay ATP.

(Fluid Mosaic Model)




Passive Transport

  • Does not require energy (ATP)

  • Moves along concentration gradient: high to low concentration

  • Simple diffusion

    • Movement of solute, high to low concentration of solute

    • Oxygen

      • Can pass freely through cell membrane

      • Needed in cellular respiration

      • Low concentration within the cell than outside the cell

    • Carbon Dioxide

      • Can pass freely through cell membrane

      • Product of cellular respiration

      • High concentration within the cell than outside the cell

  • Facilitated diffusion

    • Ions

      • Moves through ion channels

      • Moves from high to low concentration

    • Glucose and Vitamins

      • Used by cell to produce ATP

      • Transport with help of GLUT transporter

      • Once inside, enzymes binds to glucose to stay inside cell

      • Glucose keep entering the cell through diffusion

  • Osmosis

    • Movement of water

    • Low to high concentration of solute

    • Water

      • Major component of living organism’s body

      • Component of cytoplasm

      • Can pass through membrane to some extent

      • Enters and exits with help of protein aquaporins

    • Tonicity

      • Ability of solution to cause the cell to gain or lose water

      • Isotonic Solution ( Normal / Flaccid )

        • Normal Saline solution

        • Contains 0.9% NaCl

        • Similar to tears and extracellular fluid ( ECF)

        • Salt and water inside and outside are balanced

        • Cell’s shape is normal

      • Hypotonic Solution ( Swollen / Turgid)

        • Low salt concentration compared to inside of cell

        • More salt in cell, thus making water go in cell

        • Cytolysis - bursting of cell due to excessive intake of water

      • Hypertonic Solution ( Shrunk / Plasmolyzed)

        • High salt concentration outside of cell

        • Contains over 0.9% NaCl

        • Water goes out of cell

        • Plasmolysis - shrinking of cell due to loss of water

Active Transport

  • Requires energy (ATP)

  • Moves against concentration gradient

  • Sodium-Potassium Pump ( Na+/K+ Pump)

    • Used to transport sodium ions out of cell and potassium ions in the cell

    • Happens in nerve and muscle cells

    • One at a time

  • Coupled transport

    • Na+/K+ Pump creates ion gradient

    • Sodium-glucose symport transporter loads glucose

    • Two at a time

  • Bulk transport

    • Endocytosis

      • Cell takes in large materials

      • Phagocytosis

        • Cell eating

      • Pinocytosis

        • Cell drinking

    • Exocytosis

      • Delivering products or excreting waste

Present

Present