Structure determines function.

All cells:

• Are bound by plasma membrane

• Contains cytosol

• Contains genetic information

• Contains ribosomes

Prokaryotes

• Single celled organisms

• Domains bacteria and archaea

• DNA is in nucleoid region (in cytosol, free floating)

• Generally smaller

Eukaryotes

• Multicellular organisms

• Protists, fungi, animals, plants

• DNA is contained within nucleus

Two classifications: Endomembrane Organelles and Energy Organelles

Compartmentalization in organelles allows for different metabolic reactions to occur in different places (giving them their own membranes to function).

• Increases surface area

• Prevents reactions from interfering with each other.

• A lot of complex reactions are going on at the same time, so this allows for efficiency and to manage specific conditions necessary for certain reactions.

  • Without this, everything would be occurring in the same place at the same time and it would be chaotic.

Unique cell components

Plants:

• Chloroplasts

• Central vacuole

  • Animals have vacuoles too, but the central vacuole helps to maintain water balance and rigidity in a plant

• Cell wall

• Plasmodesmata

Animals:

• Lysosomes

• Centrosomes

• Flagella

  • sperms

Endomembrane Organelles

Note: Metabolism means to break things down.

Nucleus: Contains chromosomes (genetic info)

• Enclosed by nuclear envelope

• Double membrane

  • Contains pores

• Regulates entry and exit of materials from the cell

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

• Combined with proteins to form large/small units of ribosomes

• Subunits exit via nuclear pores to be assembled

• Ribosomes translate messages found in mRNA

Ribosomes: Synthesizes proteins

• Composed of rRNA and protein

• Found in cytosol and/or bound to ER or nuclear envelope

  • Proteins produced here generally function within the cytosol (enzymes), free floating

• Proteins produced in the ER/Nuclear envelope are secreted from the ribosomes

• Rough ER is the one w/ ribosomes attached

Endoplasmic Reticulum: Network of membranous sacs and tubes; has membranes to help compartmentalize the cell

• Dots = rough ER (ribosomes), no dots = smooth ER

  • On Rough ER, the ribosomes make the proteins and the ER will transfer them out.

  • Smooth ER contains no ribosomes and instead synthesizes lipids.

Golgi body: Contains flattened membranous sacs called cisternae (are not connected) and vesicles

• Separates sacs from cytosol

• Has directionality

  • Cis face

    • Receives proteins from ER

  • Trans face

    • Sends proteins back out into the cytosol post-modification to other locations or back to the membrane

Function: Sorts and sends out proteins to be transported to the lysosomes, plasma membrane, or to be secreted

Lysosome: Membranous sac with hydrolytic enzymes

Function:

• Hydrolyzes macromolecules in animal cells

• Authophagy: Lysosomes can recycle their own cell’s organic materials

  • Allows the cell to renew itself

  • EG: Breaking up nucleic acids into nucleotides to be reused

Peroxisomes: Similar to lysosomes, more specific class

• Membrane bound metabolic compartments

Function:

• Catalyzes reactions that produce hydrogen peroxide (H₂O₂)

  • __Peroxi__some (peroxide).

Vacuoles: Large vesicles; Pockets used for organizing cellular substances and creating reaction chambers

• Stem from ER and Golgi, more selective in transport

• Multipurpose

Types:

• Food vacuole

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

• Contractile vacuole

  • Maintains water levels

• Central vacuole

  • Only in plants

Energy organelles

Mitochondrion: Site of cellular respiration

Structure of double membrane:

• Outer is smooth

• Inner has folds called cristae

  • Divides mitochondria into two internal compartments and increases surface area

  • Intermembrane: Space between inner/outer

  • Mitochondrial matrix: Enclosed in inner membrane

    • Location where Krebs cycle occurs

      • Has enzymes that catalyze ATP

    • Contains mitochondrial DNA and ribosomes

• More mitochondria = more metabolic activity

  • EG: Cells that move/contract; have to do a lot of work, needs more ATP (muscles)

Chloroplasts: Specialized organelles in photosynthetic organisms

• Performs photosynthesis

• Contains chlorophyll (green)

• Double membrane has:

  • Thylakoids

    • Membranous sacs that can organize into stacks called grana

    • Light dependent reactions

  • Stroma

    • Fluid around thylakoids

    • Location for Calvin cycle.

• Contains:

  • DNA

  • Ribosomes

  • Enzymes

*both organelles have the same building blocks

Misc.

Cytoskeleton: Network of fibers throughout cytoplasm

• Gives structural support, especially in animal cells

• Anchors organelles

• Not found in all cells

Endosymbiosis Theory:

• A prokaryote enveloped a eukaryote and instead of consuming it, it remained inside of itself.

• The prokaryotic cell would provide food molecules and energy.

• The eukaryotic cell would provide oxygen and a safe region for the eukaryotic cell to exist.

• Prokaryotic cell eventually lost independent function and evolved into the mitochondria/chloroplasts.

• They became one functional organism

Evidence: (boils down to the similarities between the types of cells)

• Both mitochondria and chloroplasts have double membranes

• Both have ribosomes

• Circular DNA

• Can function on their own

• Similar reproduction methods