AP Biology Book Notes Chapter 4: Cells v Cell theory implications Ø Studying cell biology is in some sense the same as studying life Ø Life is

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1 AP Biology Book Notes Chapter 4: Cells v Cell theory implications Ø Studying cell biology is in some sense the same as studying life Ø Life is continuous v Small cell size is becoming more necessary as the surface area to volume ratio decreases Ø As any object increase in volume its surface area also increases Ø The volume of a cell determines the amount of metabolic activity it carries out per unit of time Ø The surface area of a cell determines the amount of substances that can enter it from the outside of the environment and the amount of waste products that can exit to the environment Ø As a cell grows larger its metabolic activity and thus its need for resources and its rate of waste production increases faster than its surface area Ø The smaller the cell the easier it is to move substances around the cell v Plasma membrane Ø Made of lipids and proteins Ø Selectively permeable membrane allows some substances in and keeps others out allowing the cell to maintain homeostasis Ø Communicate with adjacent cells and a boundary form the external environment Ø Cell shape the plasma membrane has proteins protruding from the membrane which allows for adhering and binding to other cells v Prokaryotes Archaea and bacteria Not have membrane enclosed department No nucleus Plasma membrane keeps separate from environment and regulates what goes in and out Nucleoid is the region in the cell where DNA is located The rest of the cell is cytoplasm Cytosol mostly water containing dissolved ions small molecules and soluble macromolecules such as proteins Also has insoluble suspended particles ribosomes included, complexes of RNA and proteins that are sites of protein synthesis where the information encoded in nucleic acids directs the sequential linking of amino acids to form proteins Cytoplasm in constant motion Some have cell walls Supports the cell and maintains its shape Peptigoglycan polymer of amino sugars that are cross linked by covalent bonds to peptides Capsule can enclose the cell wall slimy, protect from infection, keep cell from drying out, help attach to other cells Internal membranes

2 Have molecules needed for photosynthesis Flagella Cause movement Made of protein flagelin Cytoskeleton Maintaining cell shape v Eukaryotes Ø Membrane bound compartments organelles specific metabolic functions occur Ø Nucleus Where most of the cells DNA is located and where gene expression begins (where DNA replication occurs) DNA transcribed to RNA Has nucleolus, where ribosomes begin to be assembled from RNA and proteins

3 Two lipid bilayers making nuclear envelope separate DNA transcription (nucleus) and translation (cytoplasm) Nuclear pores connect the interior of the nucleus to the cytoplasm some allowed to move some not, allows nucleus regulate information seeking processes Proteins + DNA = Chromatin = chromosomes Ø Ribosomes Not membrane enclosed compartments Ø Endomembrane system Vesicles shuttle substances from the various components of the endomembrane system and the plasma membrane Endoplasmic reticulum RER Has ribosomes A protein enters the RER only if it contains specific short sequence of amino acids that signals the ribosome to attach to the RER Proteins chemically modified to alter their functions and to chemically tag them for delivery to specific cellular destinations The RER participates in transporting these proteins to other locations in the cell the proteins are transported in vesicles that pinch off of the ER all secreted proteins pass through the RER Most membrane bound proteins are made on the RER SER Lacks ribosomes, more tubular Responsible for the chemical modification of small molecules taken in by the cell including drugs and pesticides make targeted molecules more polar so they are more water soluble and easily removed Site for glycogen degradation in animal cells Site for the synthesis of lipids and steroids Golgi apparatus Concentrates packages and sorts proteins before they are sent to their cellular or extracellular destinations It adds some carbohydrates to proteins It is where some polysaccharides for the plant cell wall are synthesized Cis near nucleus/rer, where vesicles fuse Trans near plasma membrane contents away from Golgi apparatus Medial in- between others Lysosomes Primary lysosome originate from the Golgi apparatus Contain hydrolases (digestive enzymes) sites where macromolecules are hydrolyzed into their monomers Phagocytosis macromolecules hydrolyzed from the environment outside the cell

4 Ø Phagosome breaks free form the plasma membrane move into cytoplasm phagosome binds to primary lysosome to form secondary lysosome Ø Mitochondria Break energy rich molecules Covert chemical energy into energy cell can use such as ATP Divide independent central nucleus Calls require most chemical energy require most mitochondria Two membranes Outer large porous most substances pass through Inner separated biochemical process of mitochondria from cytosol Cristae Fluid filled = mitochondrial proteins Many enzymes for energy metabolism DNA Ribosomes make some mitochondrial proteins Ø Plastids Divide autonomously Differentiate many organelles Chloroplast Site of photosynthesis Anabolic process converting light energy to chemical energy contained between bonds between atoms and carbohydrates Thylakoids attack = granum Light à chemical in thylakoid Fluid surrounding = stroma Has ribosomes + DNA Ø Peroxisomes Accumulate peroxides (bi- products biochemical reactions in all eukaryotes) Single membrane Ø Glyoxysomes Only plants Stored lipids to carbohydrates for transport to growing cells Ø Vacuoles Storage can store poisons so predators don t eat plants Structure turgor pressure Reproduction pigments Catabolism in some plants seeds have vacu0les that contain enzymes tat hydrolyze stored seed proteins into monomers which are used for energy Contractile vacuoles rid of excess water v Cytoskeleton Ø Supports the cell and maintains shape Ø Controls positions and movements of organelles within the cell

5 Ø Involved with bulk movements of the cytoplasm called cytoplasmic streaming Ø Interacts with extracellular structures helping anchor the cell in place Ø Microfilaments Made up of the proteins strands actin Help entire cell of parts of the cell move Determine and stabilize cell shape Monomers attach at + end and detach at end Dynamic instability portions can break down or build up easily (cytoskeleton) Myosin motor protein help with contraction of muscles Formation pseudopodia Ø Intermediate filaments Made of fibrous proteins organized into tough ropelike appendages that stabilize the cell s structure and help maintain its shape They anchor cell structures in place Resist tension Ø Microtubules Made of the protein tubulin α tubulin and β tubulin Form a rigid internal skeleton for some cells or cell regions Framework along which motor proteins can move structures within the cell v Cilia Ø Move stiffly to propel cell or move fluid over a stationary cell Ø Short v Flagella Ø Longer Ø Push cell through aqueous environment v Motion of cilia and flagella cause sliding microtubule doublets past each other sliding driven by motor protein dynein which can change its 3D shape v Dynein molecules bind the neighbor microtubule doublets as the dynein changes shape they move the doublets past each other v Nexin protein can cross link doublets to prevent them from sliding past each other v Protein kinesin carry protein vesicles from one part of the cell to another v Extracellular Ø Prominent fibrous macromolecules Ø Gel like medium in which fibers are embedded Ø Cell wall Fibrous cellulose and gel like matrix Provides support for the cell and limits the volume of a mature cell by remaining rigid It acts as a barrier to infection by fungi and other organisms That can cause plant diseases Contributes to plant form by controlling the direction of cell expansion during growth and development

6 Plasmodesmata numerous plasma membrane lined channels Extend through cell walls Allow water ions small molecules hormones RNA and protein molecules to pass through connected cells Ø Extracellular matrix Fibrous collagen; gel like matrix consists of proteoglycans glycoproteins with long carbohydrate side chains Hold cells together in tissues Contribute physical properties of cartilage skin etc. Help filter materials passing between different tissues Help orient cell movements during embryotic development and tissue repair v Cell junctions Ø Tight junctions Prevent substances from moving through spaces between cells Ø Desmosomes Hold adjacent cells together with stable protein connections but materials can still move around in the extracellular matrix Provides mechanical stability for tissues such as skin Ø Gap junctions Channels that run between membrane pores in adjacent cells allowing substances to pass between cells