AP bio unit 2 quz

Cells

The basic structural and functional units of every organism

• All are:

1. Are bound by a plasma membrane

2. Contain cytosol

3. Contain chromosome(s)

4. Contain ribosomes

Prokaryotes (a type of cell)

• Domains Bacteria and Archaea

• DNA is in the nucleoid region

• Generally smaller in size than eukaryotes

Eukaryotes (another type of cell)

• Protists, fungi, animals, and plants

• DNA is in the nucleus

• Contain membrane-bound organelles

Organelles

membrane bound structures in eukaryotes

with two main classifications: Endomembrane organelles and Energy organelles.

Compartmentalization

• in organelles allows for different metabolic reactions to occur in different locations

  • Increases surface area for reactions to occur

  • Prevents interfering reactions from occuring in the same location

Plants components

• Chloroplasts

• Central vacuole

• Cell wall

• Plasmodesmata

Animals

• Lysosomes

• Centrosomes

• Flagella

Nucleus

• Contains chromosomes (genetic information)

  • Enclosed by the nuclear envelope

    • Double membrane

  •     Has pores

    • Pores regulate entry and exit of materials from the nucleus  

    • Contains a nucleolus

      • Dense region of the nucleus where ribosomal RNA (rRNA) is synthesized

        • rRNA is combined with proteins to form large and small subunits of ribosomes

        • Subunits exit via nuclear pores

        • Assemble into ribosomes

          • Ribosomes translate messages found on mRNA into the primary structure of polypeptides

Ribosomes

• Comprised of ribosomal RNA and protein

  • Function: synthesize proteins

  • Note: some texts do not classify ribosomes as organelles because they are not bound by a membrane

Where are the two locations ribosomes can be found?

1. Cytosol 

   • Proteins produced here generally function only within the cytosol (i.e. enzymes)

   • Known as “free ribosomes”

2. Bound to the endoplasmic reticulum or nuclear envelope

   • Proteins produced here can be secreted from the cell

     • Leave via transport vesicles

Endoplasmic Reticulum

• A network of membranous sacs and tubes

  • Functions:

    • Synthesizes membranes

    • Compartmentalize the cell to keep proteins formed in the rough ER separate from those of free ribosomes

Rough ER

Contains ribosomes bound to the ER membrane

Smooth ER

• Contains no ribosomes

• Synthesizes lipids, metabolizes carbohydrates, and detoxifies the cell

Golgi complex

Contains flattened membranous sacs called cisternae

• Separate the sacs from the cytosol

• Each cisternae is not connected

• Has directionality

  • Cis face:

    • Receives vesicles from the ER

  • Trans face:

    • Sends vesicles back out into cytosol to other locations or to the plasma membrane for secretion

What are the golgi complex functions?

• Receives transport vesicles with materials from the ER

• Modifies the materials

• Sorts the materials

• Adds molecular tags

• Packages materials into new transport vesicles that frequently exit the membrane via exocytosis

Lysomes

Membranous sac with hydrolytic enzymes

• Function:

  • Hydrolyzes macromolecules in animal cells

  • Autophagy: lysosomes can recycle their own cell’s organic materials

    • Allows the cell to renew itself

Peroxisomes

• Similar to lysosomes

• Membrane bound metabolic compartment 

  • Catalyze reactions that produce H₂O₂

    • Enzymes in peroxisomes then break down H₂O₂ to water

Vaculoues

Large vesicles that originally stem from the ER and Golgi

• Selective in transport

Types:

Food vacuole

• Form via phagocytosis (cell eating) and then are digested by lysosomes

Contractile vacuole

• Maintain water levels in many protist cells

Central vacuole

• Found in plants

  • Contains inorganic ions and water

  • Important for turgor pressure

Endosymbiont theory

•  ENERGY ORGANELLES

• the theory that explains the similarities mitochondria and chloroplasts have to a prokaryote

  • Theory states that an early eukaryotic cell engulfed a prokaryotic cell

    • Prokaryotic cell became an endosymbiont (cell that lives in another cell)

      • Became one functional organism over time

Evidence to the endosymbiont theory

• Double membrane 

• Ribosomes 

• Circular DNA

• Capable of functioning on their own

Mitochondria

Site of cellular respiration

• Structure of the double membrane:

  • Outer membrane is smooth

  • Inner membrane has folds called cristae

    • Divides the mitochondria into two internal compartments and increases the surface area

Intermembrane (mitochondria)

space between inner and outer membrane

Mitochondrial Matrix

1. enclosed by inner membrane

   • Location for the Krebs cycle

   • Contains: 

     • Enzymes that catalyze cellular respiration and produce ATP

     • Mitochondrial DNA

     • Ribosomes

 The number of mitochondria in a cell correlates with what?

metabolic activity

• Cells with high metabolic activity have more mitochondria

  • Example: cells that move/contract like muscles

Chloroplasts

• Specialized organelles in photosynthetic organisms

  • Site of photosynthesis

  • Contains the green pigment chlorophyll

• Inside of its double membrane:

  •    Thylakoids

    • Membranous sacs that can organize into stacks called grana

      • Light dependent reactions occur in grana

Stroma (chloroplast)

• fluid around thylakoids

  • Location for the Calvin cycle

  • Contains

    • Chloroplast DNA

    • Ribosomes

    • Enzymes

Cytoskeleton

• A network of fibers throughout the cytoplasm

  • Give structural support (especially for animal cells) and mechanical support:

    • Anchor organelles

    • Allow for movement of vesicles and organelles and/or the whole cell

      • Movement occurs when the cytoskeleton interacts with motor proteins

What are the 3 types of fibers in the cytoskeleton?

1. Microtubules

2. Microfilaments

3. Intermediate filaments

Microtubules

Hollow rod-like structures made of the protein tubulin

• Grow from the centrosome

  • Assist in microtubule assembly

What is the function of microtubules?

Functions:

• Serve as structural support (think: tracks) for the movement of organelles that are interacting with motor proteins

• Assist in the separation of chromosomes during cell division

• Cell motility (i.e. cilia and flagella)

Microfilaments

Thin solid rods made of the protein actin

Functions:

• Maintain cell shape

  • Bear tension

• Assist in muscle contraction and cell motility

  • Actin works with another protein called myosin to cause a contraction

• Division of animal cells

  • Contractile ring of the cleavage furrow

Intermediate filaments

• Fibrous proteins made up of varying subunits

•  Permanent structural elements of cells

Functions:

• Maintain cell shape

• Anchor nucleus and organelles

• Form the nuclear lamina

  • Lines the nuclear envelope