Membrane-Bound Organelles

• Contains DNA; regulates the activity of a cell

  • • ***Some DNA can be found in mitochondria and chloroplasts

• Nucleolus

  • No membrane

  • Assembles ribosomal RNA and proteins into ribosomes

  • Synthesizes and stores RNA

• Nuclear envelope

  • Encloses nucleus

  • Is a double membrane (phospholipid bilayer) (see diagram above)

    • Inner nuclear membrane

    • Space inside is connected to endoplasmic reticulum

    • Outer membrane continuous with endoplasmic reticulum

    • Nuclear pores

      • For exchange of material between nucleus and cytoplasm

        • RNA, ribosomal subunits, proteins, ions, signaling molecules

      • Large molecules (ex. RNA, some proteins) use transporter proteins which work with the pores

      • Smaller molecules and ions diffuse through pores without transporter

• Some cells have one, others have 1000s

• Produces most of a cell's ATP 

  • • Operates on glucose; requires oxygen to produce ATP efficiently

• Two membranes

  • • Outer membrane

      • Selectively permeable

    • Intermembrane space

      • Where a proton motive force is used to drive chemiosmosis: the synthesis of ATP (this is related to cellular respiration - notes will be added soon)

    • Inner membrane (where most ATP is made)

      • Folded into cristae, within the folds is the electron transport chain for aerobic respiration

• Inside the mitochondrial matrix

  • Ribosomes 

  • Mitochondrial DNA

    • Carries 37 genes (in humans); required for normal mitochondrion function

• Semi-autonomous

  • Because each mitochondrion has its own genome and ribosomes + produces many of its own proteins

• Self-replication

  • Similar to bacteria; copy their circular DNA molecules before undergoing fission

    • Still rely on nuclear genes to produce many of the proteins for its DNA replication + other processes

• Apoptosis

  • Programmed cell death

  • Proteins of inner membrane can move into cell’s cytoplasm bc of oxidative stress, activating other proteins that begin cell degradation

Series of continuous membranes called cisternae

• • Form a tubular network - the transport system of a cell

  • Makes up half of the entire plasma membrane

Many f(x)

• • Protein synthesis, folding of proteins

  • Calcium storage

  • Lipid metabolism

Rough Endoplasmic Reticulum (Rough ER)

• • Continuous with the nuclear envelope

  • Synthesizes and processes proteins

    • Cisternae covered in bound ribosomes (on cytoplasmic side of rough ER)

      • Produce secretory proteins (ones for exporting out of cell) + ones for plasma membrane

      • How such a protein is made: growing polypeptide chain is pushed into the inside of the rough ER (cisternal space)

Once inside the ER:

• The chain/protein folds into its correct shape.

• Modified/packaged in vesicles

• Sent out to different parts of cell, often the golgi apparatus

Golgi apparatus modifies them more, sorts them based on destinations;

many shipped out of cell via exocytosis

• Ribosomes free in cytosol

  • Produce proteins that remain in cytosol

Smooth ER

• Lack ribosomes; continuous with rough ER and nucleus

• Looks tubular

• f(x)

  • Synthesizes lipids (phospholipids, cholesterol)

  • In liver cells: detoxifies drugs, toxins, and harmful metabolic products

• • In muscle cells: the smooth ER is the sarcoplasmic reitculum, regulating and storing calcium ions