organelles

The Nucleus

  • Control center of the cell

    • Contains genetic material (DNA)

  • Three major regions

    • Nuclear envelope (separate membrane): Holds genetic material in one area (certain stages of mitosis nuclear envelope breaks apart, allowing for the DNA to split in two)

      • Barrier of the nucleus

      • Consists of a double membrane

      • Contains nuclear pores (orange flowers) that allow for exchange of material with the rest of the cell

        • How ribosomes come out of the nucleus

    • Nucleolus (plural Nucleoli): Where ribosomes are located

      • Nucleus contains one or more nucleoli

      • Sites of ribosome assembly (where ribosomes are created)

      • Ribosomes migrate into the cytoplasm through nuclear pores

    • Chromatin: Where DNA is located

      • Composed of DNA and protein

      • Present when the cell is not dividing

      • Scattered throughout the nucleus

      • Condenses to form chromosomes when the cell divides

Plasma Membrane

  • Barrier for cell contents

  • Double/Biphospholipid layer

    • Hydrophilic heads: Water-loving heads, pointed on outside to touch liquid

    • Hydrophobic tails: Water-hating heads, pointed inward

    • Also contain proteins, (type of fat) cholesterol, and glycoproteins

      • Cholesterol allows for the flexibility and movement of the networks

      • Glycoproteins: Allow for transport

    • Membrane is sturdy, flexible, and doesn’t allow everything to go in and out of it (selective permeability)

    • Channel proteins: If something is insoluble (can’t get through membrane) it uses channel proteins to get through

Plasma Membrane Junctions

  • Membrane junctions

    • Tight junctions

      • Impermeable junctions

      • Bind cells together into leakproof sheets

        • Leakproof holds the contents in so it doesn’t dehydrate, but also keeps some substances out (protective mechanism)

          • If everything from the outside is allowed in (going from an area of high concentration to low concentration), the cell will swell and pop

    • Desmosomes

      • Anchoring junctions that prevent cells from being pulled apart

    • Gap junctions

      • Allow communication between cells

Cytoplasm

  • The material outside the nucleus and inside the plasma membrane

  • Site of most cellular activities

  • Contains three major elements

    • Cytosol: The liquid/fluid that suspends the elements

      • Fluid that suspends other elements

    • Organelles

      • Metabolic machinery of the cell

      • “Little organs” that perform functions for the cell

    • Inclusions

      • Chemical substances such as stored nutrients or cell products

Cytoplasmic Organelles

  • Mitochondria

    • “Powerhouses” of the cell

    • Change shape continuously

    • Carry out reactions where oxygen is used to break down food

    • Provides ATP for cellular energy

    • Where cells respirate; how they breathe; where energy is produced

  • Ribosomes

    • Made of protein and RNA

    • Sites of protein synthesis

    • Found at two locations

      • Free in the cytoplasm

      • As part of the rough endoplasmic reticulum

  • Endoplasmic reticulum (ER)

    • Fluid-filled tubules for carrying substances

    • Two type of ER

      • Rough endoplasmic reticulum

        • Studded with ribosomes

          • Ribosomes secrete mRNA which allows for protein synthesis; moving those proteins around the vesicle

        • Synthesizes proteins

        • Rough > ribosome

      • Smooth endoplasmic reticulum

        • Functions in lipid metabolism and detoxification of drugs and pesticides

          • Clean out harsh chemicals, making sure they aren’t affecting and changing the DNA

          • However does not work 100% of the time

  • Golgi apparatus

    • Modifies and packages proteins (substances)

    • Produces different types of packages

      • Secretory vesicles

      • Cell membrane components

      • Lysosomes

    • Packer + Shipper: Collects certain material and ships around, whether it be to a different part of the cell or a different cell entirely

    • When Golgi apparatus packs and sends out a substance, it is called exocytosis (to release)

      • The opposite of exocytosis is endocytosis (to take in)

        • Eat: Phagocytosis

        • Drink: Pinocytosis

  • Lys(to break apart)osomes

    • Contain enzymes produced by ribosomes

    • Packaged by the Golgi apparatus

    • Digest worn-out or nonusable materials within the cell

      • Eliminates

      • Lysosome breaks down sick organelles by releasing a chemical to be recycled

      • When too much chemicals are released, the entire cell ruptures/killed off

      • Apoptosis: Cells never die/aren’t broken down

    • Digestion

  • Peroxisomes

    • Membranous sacs of oxidase/oxidative enzymes

      • Detoxify harmful substances such as alcohol and formaldehyde

      • Break down free radicals (highly reactive chemicals)

        • Free radicals are not good for the body because the oxidize the inside

          • Antioxidants: Prevent oxidation from occurring

            • Vitamin C: Protects inside of cell/cytoplasm

            • Vitamin E: Fat-soluble vitamin

    • Replicate by pinching in half

    • Detoxifies the cell 

    • Protects against chemicals

  • Cytoskeleton 

    • Network of protein structures that extend through the cytoplasm

    • Provides the cell with an internal framework

    • Three different types of elements

      • Microfilaments (largest)

      • Intermediate filaments

      • Microtubules (smallest)

        • Next to the microtubules are projected out of the centrioles for DNA replication (?)

    • Skeleton/support structure that gives its shape and structure

  • Centrioles

    • Rod shapes bodies made of microtubules

    • Direct the formation of mitotic spindle during cell division

    • Little bundles that spit out cabled called microtubules and attach themselves to chromosomes. They will pair them up and split them apart, turning one cell into two, then four, etc.