CELLULAR STRUCTURE The Composition of Cells A.Introduction Cells can be complicated with many parts that work together like a factory producing a commodity like a scarf Two types of cells based on their internal structure: Eukaryotes: large & complicated (single or multiple cells) o Plants & animals (and archaea) Prokaryotes: small & single cells o Bacteria B.Eukaryotes o Have internal membrane-bound structures called organelles & cytoskeleton (shape & organization) o Allow thousands of chemical reactions to occur simultaneously o Contains nucleus (manages cellular function) DNA (deoxyribonucleic acid) stored here Blueprints = HOW TO for EVERYTHING! o Contains endoplasmic reticulum (ER) - system of folded sacs & interconnected channels in which chemical reactions occur rough ER synthesizes new proteins due to ribosomes studded on membranes smooth ER modifies lipids or fats, and detoxifies drugs/pollutants such as alcohols, barbiturates, and other drugs Rough ER vs. Smooth ER o Contains Golgi apparatus - modifies or packages newly made proteins into vesicles which then move to plasma membrane for secretion Sometimes vesicles with packaged proteins become digestive enzymes entire package called lysosome - breaks down broken cell parts and recycles them o Contains mitochondria - produces energy needed for all cellular functions Fats, proteins, carbohydrates (mostly glucose) are broken down to form CO 2, H 2 O, and ENERGY! Energy unusable until converted to ATP (adenosine triphosphate) (way more detail later) o May contain cilia, short hair-like structures protruding from surface to allow movement o May contain flagella SEM micrograph of the cilia projecting from respiratory epithelium in the lungs o Contain vacuoles which store water, nutrients, waste, ions Animal cells have many small vacuoles Plant cells have one large vacuole stores juice in fruit, vegetables which make it crispy or rigid Animal Cell Plant Cell o Plant cells only contain chloroplasts which use light energy to convert CO 2 + H 2 O into carbohydrates during photosynthesis (way more later) o Animal cells only have centrioles which aid in cell division (mitosis and meiosis) by producing spindle fibers (like spider webs) o Always found near nucleus, contains microtubules C. Cell Structure Determines Function Many different types of eukaryotic cells within multicellular species Structure of cell gives clues to its function D. Prokaryotes: o NO internal membrane-bound structures or compartments like a nucleus o Cant carry out specialized functions o Represented by the Kingdom Monera Divided into Eubacteria & Archaea Eubacteria almost all bacteria, amoeba, paramecium Archaea few bacteria strains that live in extreme environments (ice, boiling water, salt) Contain: Enzymes, ribosomes, circular DNA free-floating in cytoplasm Contain cell walls surrounding plasma membrane which give support & regulation Contain flagella, long thread-like structures protruding from surface to allow movement Typical Prokaryotic Structure E. Comparing Prokaryotes to Eukaryotes Both have common structural features: Cell (plasma) membrane: outer boundary through which all items (gases, nutrients, wastes) enter or leave cell (like door) membrane inside outside Cytoplasm: cell interior that holds organelles in place (like air) Ribosomes: structure on which protein is made (like a machine) DNA: instructions or code for making proteins, regulates cellular activities, enables reproduction (like CEO); genetic material = Cell wall: outside plasma membrane; made of cellulose to give cell rigid support o Only found in plants (eukaryotes) Structure (Organelle)EukaryoteProkaryote Cell wallPlants onlyYes CentriolesAnimals onlyNo ChloroplastPlants onlyNo CiliaSomeNo CytoplasmYes DNAYesCircular Endoplasmic reticulumYesNo FlagellaSomeYes Golgi apparatusYesNo LysosomeYesNo MitochondriaYesNo NucleusYesNo Plasma membraneYes RibosomesYes VacuoleYesNo VesicleYesNo