Bio10 Cell Structure SRJC

Transcription

1 3.) Cell Structure and Function Structure of Cell Membranes Fluid mosaic model Mixed composition: Phospholipid bilayer Glycolipids Sterols Proteins Fluid Mosaic Model Phospholipids are not packed tightly Drift sideways Spin on their axis Phospholipid Bilayer Membrane and components are flexible and move like a fluid Membrane Proteins Adhesion proteins Help stick cells to one another or to proteins that are part of tissues Communication proteins Form cytoplasm-cytoplasm channels between adjoining cells Receptor proteins Receive outside chemical signals to which cell responds Recognition proteins Identify other cells as self or non-self Passive transporters Create channel for solutes to move freely along a gradient, some have gates Active transporters Also channels across membrane, but transport is against gradient. Requires energy Prokaryotic Cells Archae and bacteria DNA is not enclosed in nucleus Generally the smallest, simplest cells Eukaryotic Cells Have a nucleus and other organelles Eukaryotic organisms Plants Animals Protists Fungi Larger and more complex than prokaryotic cells Organelles form compartmentalized regions for separate or incompatible reactions to occur Substances move through cytoplasm in vesicles A CarranzaA. Carranza Page 1 7/24/2015

2 Eukaryotic Cell Features The Nucleus Keeps DNA molecules separated from metabolic machinery of cytoplasm Makes it easier to organize DNA and to copy it Components of Nucleus Chromosomes DNA and associated histone proteins Chromosome one or two copies of DNA Chromosomes condense when the cell divides Chromatin relaxed chromosomes in between cell divisions Nuclear Envelope Two outer membranes (lipid bilayers) Pores span bilayer Passage of messenger RNA out of nucleus Endomembrane System Related organelles where lipids are assembled and new polypeptide chains modified Sorts and ships products to various destinations Consists of endoplasmic reticulum, Golgi bodies, vesicles Endoplasmic Reticulum Starts at nuclear membrane and extends throughout cytoplasm Rough ER: ribosome covered, processes proteins Smooth ER: no ribosomes, builds lipids Rough ER Attached ribosomes Modification of polypeptide chains Smooth ER No attached ribosomes Lipid assembly Degrades toxins, breaks down fatty acids Numerous in seed forming cells Golgi Body Puts finishing touches on proteins and lipids that arrive from ER Packages finished material for shipment to final destinations Attaches sugars to proteins and lipids Modifies sugars used as mailing labels Material arrives and leaves in vesicles Vesicles Membranous sacs that move through cytoplasm Lysosomes Peroxisomes A CarranzaA. Carranza Page 2 7/24/2015

3 Food Vacuole Formation Food is taken into cell by phagocytosis Membrane surrounds food vacuole Lysosome Formation Formed at Golgi Powerful enzymes Membrane enclosed Intracellular digestion Lysosomes Joins with: food vacuole, bacteria, foreign particles Autophagy worn-out cell parts digested and recycled Digestion of food sponges & heterotrophic protists Peroxisomes Enzymes digest fatty acids and amino acids Converts fats to carbohydrates Byproduct hydrogen peroxide; potentially harmful Must be broken down by enzyme Detoxifies alcohol and toxins, especially in the liver and kidneys Mitochondria ATP-producing powerhouses Membranes form two distinct compartments ATP-making machinery embedded in inner mitochondrial membrane Site of Aerobic respiration Produces CO2 Require O2 Mitochondrial Functional Organization Strong ph gradient between outer compartment & inner compartment similar condition to a battery H+ moving from high conc. to low H+ concentration Electrons attach O2 to H+ H2O Chloroplasts Convert sunlight energy to ATP through photosynthesis Mitochondria Found in plants and some protistans Organelle Origins Chloroplast Nucleus and ER Infolding of membranes formed compartments Mitochondria and chloroplasts Endosymbiosis A CarranzaA. Carranza Page 3 7/24/2015

4 Mitochondrial & Chloroplast Origins Mitochondria & Chloroplast resemble bacteria Similar size Contain their own circular DNA Contain ribosomes with two small subunits Divide on their own Genetic code slightly different from eukaryotes May have evolved from ancient bacteria that were engulfed but not digested Endosymbiosis Bacterium engulfed in Amoeba-like cell by phagocytosis Membrane-bound bacterium not digested Became an endosymbiont Now two components cannot be separated Central Vacuole Fluid-filled membrane-bound organelle Functions: Stores amino acids, sugars, wastes Increases cell size Increases surface area Provides structural support Plant Cell Walls Plant Cuticle Cell secretions and waxes accumulate at plant cell surface Semitransparent Restricts water loss Matrices between Animal Cells Animal cells have no cell walls Some are surrounded by a matrix of cell secretions and other material Cell-to-Cell Junctions Plants Plasmodesmata Animals Tight junctions Adhering junctions Gap junctions Cytoskeleton Present in all eukaryotic cells Cell shape and internal organization Allows organelle movement within cells and, in some cases, cell motility Cytoskeletal Elements Microtubules Microfilaments Intermediate Filaments A CarranzaA. Carranza Page 4 7/24/2015

5 Microtubules Largest elements Composed of tubulin (a protein) Arise from microtubule organizing centers (MTOCs) Involved in shape, motility, cell division Microfilaments Thinnest elements Composed of actin (protein) Take part in movement, formation, and maintenance of cell shape Microfilaments and Motility Intermediate Filaments Only in animal cells of certain tissues Most stable cytoskeletal elements Mainly structural; i.e. holding organelles in place Motor Proteins Interact with microtubles and microfilaments to move parts within cells Flagella and Cilia Structures for cell motility internal structure Cilia, Flagellum, and Psuedopod microtubule A CarranzaA. Carranza Page 5 7/24/2015 dyneinn