CELL ORGANELLES MS. GAYNOR AP BIOLOGY / CHAPTER 6 (PART 2)

ORGANELLES Very small Perform various functions for cell Found in the cytoplasm May or may not be membrane- bound

BASIC ANIMAL CELL ORGANELLES Ribosome (attached) Nucleolus Ribosome (free) Nucleus Cell Membrane Nuclear envelope Mitochondrion Smooth endoplasmic reticulum Rough endoplasmic reticulum Centrioles Golgi apparatus

BASIC PLANT CELL ORGANELLES

CELL OR PLASMA MEMBRANE STRUCTURE Made of double layer (bilayer) of: phospholipids and proteins Surrounds outside of ALL cells FUNCTION (JOB) Controls what enters or leaves the cell Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

PHOSPHOLIPIDS Heads Tails glycerol & phosphate hydrophilic (attract water) Tails fatty acids hydrophobic (repel water) Make up a bilayer where tails point inward toward each other Can move laterally to allow small molecules (O2, CO2, & H2O to enter)

CELL MEMBRANE IN PLANTS ADDITIONAL FUNCTION IN PLANTS: Pushes out against the cell wall to maintain cell shape and protect

CELL WALL STRUCTURE Found in: plants Made of cellulose Fungi Made of chitin Bacteria Made of peptidoglycan FUNCTION (JOB) Protect Maintain shape CELL WALL Cell wall

CYTOPLASM (CYTOSOL) STRUCTURE Jelly-like substance Mostly water aqueous solution FUNCTION (JOB) Provides a solution (SOLVENT) for chemical reactions to take place in Holds organelles in place cytoplasm

NUCLEUS STRUCTURE Contains the DNA in chromosomes Bounded by a nuclear envelope (membrane) with pores Usually the largest organelle FUNCTION (JOB) Controls the normal activities of the cell

NUCLEAR ENVELOPE (membrane) STRUCTURE Double membrane  surrounds nucleus Contains nuclear pores (holes) Connected to the rough ER FUNCTION (JOB) pores (holes) allow materials to enter & leave nucleus Nuclear pores

INSIDE THE NUCLEUS The genetic material (DNA) is found DNA is condensed & wrapped around proteins forming as CHROMOSOMES in dividing cells (TIGHTLY COILED) DNA is spread out And appears as CHROMATIN in non-dividing cells (NOT TIGHTLY COILED)

Genes that make up the DNA molecule code for different proteins WHAT DOES DNA DO? DNA is the hereditary material of the cell Genes that make up the DNA molecule code for different proteins

NUCLEOLUS STRUCTURE Inside nucleus Cell may have 1 to 3 nucleoli Disappears when cell divides FUNCTION (JOB) Makes ribosomes (ribosomal subunits)

CYTOSKELETON STRUCTURE FUNCTION (JOB) Made of proteins Microfilaments are threadlike Microtubules are tube-like FUNCTION (JOB) Network of fibers that help cell maintain cell shape Also help move organelles around

Table 6.1

MITOCHONDRION (PLURAL = MITOCHONDRIA) STRUCTURE Bean shape DOUBLE membrane Has its own DNA and ribosomes FUNCTION (JOB) “Powerhouse” of cell Makes cellular energy (ATP) Site of CELLULAR RESPIRATION (burning glucose)

INTERESTING FACT Mitochondria Come from cytoplasm in the EGG cell during fertilization Therefore … You inherit your mitochondria from your mother!

CHLOROPLASTS STRUCTURE Bean shape DOUBLE membrane Has its own DNA and ribosomes FUNCTION (JOB) Carries out photosynthesis NOT in animal OR fungi cells In plants and some protists

 RIBOSOMES STRUCTURE Made of PROTEINS and rRNA FUNCTION (JOB) Make proteins amino acids to make proteins Process called TRANSLATION 

RIBOSOMES (CON’T) Can be attached to Rough ER (makes proteins that exit cell) **Think: “a”ttached = “a”way OR Be free (unattached) in the cytoplasm (proteins made stay INSIDE cell)

ROUGH ENDOPLASMIC RETICULUM (RER) STRUCTURE Has ribosomes on its surface FUNCTION (JOB) Helps to make proteins for export out of cell

SMOOTH ENDOPLASMIC RETICULUM (SER) STRUCTURE Has NO ribosomes on its surface Usually attached to RER FUNCTION (JOB) Makes lipids (membranes) Regulates calcium (muscles) Destroys toxins (Liver)

ENDOMEMBRANE SYSTEM Includes nuclear membrane connected to ER connected to cell membrane (transport)

GOLGI APPARATUS (Bodies) STRUCTURE Hollow flattened sacs Looks like a stack of pancakes with syrup dripping off FUNCTION (JOB) Receives cell products (like proteins) from Rough ER Modifies (changes) and packages proteins for shipment OUT of the cell Proteins are packages into vesicles (the “syrup drips”) Transport vesicle

GOLGI BODIES flattened sacs Have a receiving side (cis) & a shipping or transporting side (trans) Receive proteins made by ER Transport vesicles with modified proteins pinch off CIS TRANS Transport vesicle

Membrane proteins and lipids Are synthesized in the ER and Golgi apparatus Figure 7.10 Transmembrane glycoproteins Secretory protein Glycolipid Golgi apparatus Vesicle glycoprotein Membrane glycolipid Plasma membrane: Cytoplasmic face Extracellular face Secreted 4 1 2 3 ER

CILIA & FLAGELLA STRUCTURE Made of protein tubes called microtubules Shorter more numerous Flagella Longer fewer (usually 1-3)

Moves fluids or small particles across cell surface CILIA & FLAGELLA FUNCTION (JOB) of Flagella Moves WHOLE cells FUNCTION (JOB) of Cilia Moves fluids or small particles across cell surface Used in reproduction (bacteria)

CENTRIOLES STRUCTURE FUNCTION (JOB) Found only in animal cells inside CENTROSOMES Paired structures near nucleus (“t” shape”) Made of microtubules FUNCTION (JOB) Appear during cell division Help to pull chromosome pairs apart to opposite ends of the cell

CENTRIOLES & THE MITOTIC SPINDLE **Made of MICROTUBULES (cytoskeleton)

LYSOSOMES STRUCTURE FUNCTION (JOB) Have a low pH (acidic) Contain hydrolytic digestive enzymes FUNCTION (JOB) Break down food, bacteria & old cell parts Help carry out cell death (APOPTOSIS) Think= “Lysol” cleaner Usually only in animal cells (a) Phagocytosis: lysosome digesting food 1 µm Lysosome contains active hydrolytic enzymes Food vacuole fuses with lysosome Hydrolytic enzymes digest food particles Digestion Food vacuole Plasma membrane Lysosome Digestive Nucleus

VACUOLES STRUCTURE Fluid filled sacks for storage Small or absent in animal cells Plant cells have a large Central Vacuole Surrounded by a membrane called a TONOPLAST No vacuoles in bacterial cells

VACUOLES (CON’T) In plants, vacuoles store Cell Sap FUNCTION (JOB) In plants, vacuoles store Cell Sap Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes

CONTRACTILE VACUOLE STRUCTURE Found in FRESHWATER unicellular protists like paramecia FUNCTION (JOB) Regulate water intake by pumping out excess (homeostasis) Keeps the cell from lysing (bursting)

PEROXISOMES FUNCTION (JOB) Take in hydrogen peroxide (H2O2) and convert it to water H2O2 is also toxic to a cell, and an enzyme made by the peroxisome can break down H2O2 Chloroplast Peroxisome Mitochondrion 1 µm Figure 6.19

INTRACELLULAR JUNCTIONS ANIMALS: Tight junctions: btw neighboring cells; prevents leakage between cells Desmosomes: riveted, anchoring junction; strong sheets of cells Gap junctions: cytoplasmic channels; allows passage of materials or current between cells INTRACELLULAR JUNCTIONS

INTRACELLULAR JUNCTIONS PLANTS: Plasmodesmata: cell wall “holes”; water and solute passage in plants Similar to GAP JUNCTIONS in animals

NOW…LET’S PRACTICE 

LIMITS Diffusion limits cell size Movement from higher [ ] to lower [ ] Larger the distance, slower the diffusion rate A cell 20 cm would require months for nutrients to get to the center DNA limits cell size larger cells need more DNA…Needs more of everything! Most cells have just one nucleolus

Surface area to volume ratio limits size Volume increase more rapidly than surface area. Cell size doubles, 8x as much volume, but only 4x as much surface area