➢ Nucleus
- Largest organelle of cell
- Directs what goes on in cell
- Responsible for cell’s ability to reproduce
- Home of hereditary information (DNA)
■ DN organized into large structures called chromosomes - Most visible structure of nucleus id nucleolus, which is where rRNA is made and ribosomes are assembled
➢ Ribosomes - Sites of protein synthesis
- Manufacture all proteins required/secreted by the cell
- Consists of RNA and other proteins
- Bind messenger RNA and transfer RNA to synthesize proteins
- Round structures consisting of 2 subunits:te large subunit and the small subunit
- Composed of RNA and proteins
- Can either be free floating or attached to the endoplasmic reticulum (ER)
➢ Endoplasmic Reticulum (ER)
- Continuous channel that extends into many regions of the cytoplasm
- Lipid proteins synthesis/transport
- Rough ER
■ Attached to nucleus
■ Studded with ribosomes
■ Proteins generated here are trafficked to/across plasma membrane, or used to
build Golgi bodies, lysosomes, or the ER. - Smooth ER
● Lacks ribosomes
● Makes: - Lipids
- Hormones
- Steroids
● Breaks down toxic chemicals
➢ Golgi Bodies - Process proteins
- Once the ribosomes on the rough ER have completed synthesizing proteins, the Golgi
bodies modify, process, and sort the products - packaging/distribution centers for materials destined to be sent out of cell
- Package final products into vesicles
■ Carry products to plasma membrane - Involved in production of lysosomes
➢ Mitochondria - “Powerhouse of the ceil”
- Responsible for converting the energy from organic molecules into useful energy for the cell
- Energy molecule in the cell is adenosine triphosphate (ATP)
- Unique oblong shape and characteristic double membrane consisting of an inner portion and an outer portion
- Inner membrane forms folds called cristae
■ Separates innermost area (called the matrix) from the intermembrane space
■ Outer membrane separates the intermembrane space from the cytoplasm
■ Production of ATP done on the cristae
➢ Lysosomes
- Tiny sacs that carry digestive enzymes
- Break down old/worn out organelles/debris/large ingested particles
- Cells clean-up crew
- Keep cytoplasm clear of unnecessary flotsam
- Sometimes contain hydrolytic enzymes that function only at an acidic pH, which is enclosed inside the lumen of the lysosome
➢ Centrioles
- Small. Paired, cylindrical structured often found within microtubule organizing centers (MTOCs)
- Most active during cellular division
■ When cell is ready to divide, centrioles produce microtubules, which pull the replicated chromosomes apart and move them to opposite ends of the cell - Common in animal cells but not in plants
➢ Vacuoles
- Latin for “empty cavity”
- Fluid-filled sacs that store water/food/wastes/salts/pigments for later use/removal
- Larger in plant cells
➢ Peroxisomes
- Breakdown of long fatty acids through beta-oxidation
➢ Cytoskeleton
- Network of fibers that maintain cell shape
- Most important:
■ Microtubules
● Made up of protein tubulin
● Participate in cellular division/movement
● Integral part of centrioles/cilia/flagella
■ Microfilaments
● Important for movement
● Composed of protein actin
● Actin monomers joined together and broken apart as needed to allow
microfilaments to grow and shrink
● Assist during cytokinesis/muscle contraction/formation of pseudopodia - extension during cell movement
➢ Cilia and Flagella
- Allow motion in single-celled organisms
- In respiratory tract, cilia sweep constantly back and forth to keep out pathogens/dust
- Every sperm cell has flagellum, enabling it to swim through the female reproductive organs to fertilize the waiting ovum
➢ Extracellular matrix
- Molecules secreted by cell
■ Mostly glycoproteins or other carb/containing molecules, esp. collagen - Provides structure/biochemical support
➢ Plant Cells vs. Animal Cells
- Plant have plasmodesmata
■ Connections between plant cells that allow communication amongst them - Plant cells have cell wall
■ Rigid layer of cellulose
■ Outside of plasma membrane
■ Provides support for cell
■ Prevents lysis - Plant cells have chloroplasts
■ Contain chlorophyll, making them green
■ Involved in photosynthesis - In plants, most of cytoplasm taken up by enlarged vacuole that crowds out other organelles
■ Contains cell sap in mature plants
■ Full vacuole means plant is not dehydrated - Plants do not contain
