AP Biology Cells create and maintain internal environments that are different from their external environment 2013 Cells Unit – Chapter 6

AP Biology Prokaryote bacteria cells Types of cells Eukaryote animal cells Eukaryote plant cells

AP Biology I. Why organelles?  Organisms must exchange matter with the environment to grow/communicate Cell membranes, golgi, vesicles  Exchange energy  unique combinations of lipids & proteins  embedded enzymes & reaction centers  chloroplasts & mitochondria  Maintain organization/homeostasis  partition cell into compartments  create different local environments  separate pH, or concentration of materials  distinct & incompatible functions  lysosome & its digestive enzymes, vacuoles mitochondria chloroplast Golgi ER

AP Biology II. Cell FUNCTION  What jobs do cells have to do?  communication  proteins control every cell function  make energy  for daily life  for growth  homeostasis  growth  reproduction  repair

AP Biology DNA Why study protein production? - communication/cell signaling cells proteins organism Repeat after me… DNA gets the glory, but Proteins do all the work!

AP Biology Protein Synthesis  Organelles are cooperative  nucleus  ribosomes  endoplasmic reticulum (ER)  Golgi apparatus  vesicles nucleusribosomeER Golgi apparatus vesicles The Protein Assembly Line

AP Biology DNA RNA ribosomes endoplasmic reticulum vesicle Golgi apparatus vesicle protein on its way! protein finished protein Making Proteins TO: nucleus TO:

AP Biology proteins transport vesicle Golgi apparatus vesicle smooth ER rough ER nuclear pore nucleus ribosome cell membrane protein secreted cytoplasm Transcription/Translation Putting it together…

AP Biology Cell Junctions Animal Cells  Tight junctions  Desmosomes  Gap Junctions Plant Cells Plasmodesmata Refer to the Campbell website Chapter 6 Activity Cell Junctions

AP Biology Cells FUNCTION  What jobs do cells have to do?  communication  proteins control every cell function  make energy  for daily life  for growth  homeostasis  growth  reproduction  repair ATP

AP Biology Cells need power! “Cell Respiration  Making energy  take in nutrients & digest it  take in oxygen (O 2 )  make ATP  remove waste ATP

AP Biology From food to making Energy  Cells must convert incoming energy to forms that they can use for work  mitochondria: What is this? from glucose to ATP  chloroplasts: What is this? from sunlight to ATP & carbohydrates  ATP = immediate energy  carbohydrates = stored energy + ATP

AP Biology Mitochondria & Chloroplasts  Important to see the similarities  transform energy  generate ATP  double membranes = 2 membranes  semi-autonomous organelles  move, change shape, divide  internal ribosomes, DNA & enzymes

AP Biology Membrane-bound Enzymes glucose + oxygen  carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ Specialized areas

AP Biology Membrane-bound Enzymes + water + energy  glucose + oxygen carbon dioxide 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ More membranes working together and efficiently

AP Biology Mitochondria are everywhere!! animal cells plant cells

AP Biology Cells FUNCTION  What jobs do cells have to do?  communication  proteins control every cell function  make energy  for daily life  for growth  homeostasis  growth  reproduction  repair

AP Biology Lysosomes  Function  little “stomach” of the cell  digests macromolecules  “clean up crew” of the cell  cleans up broken down organelles  Structure  vesicles of digestive enzymes only in animal cells Where old organelles go to die!

AP Biology Lysosomal enzymes  Lysosomal enzymes work best at pH 5  organelle creates custom pH  how?  proteins in lysosomal membrane pump H + ions from the cytosol into lysosome  why?  enzymes are very sensitive to pH  why?  enzymes are proteins — pH affects structure  why is this an adaptation: digestive enzymes which function at pH different from cytosol?  digestive enzymes won’t function well if some leak into cytosol = don’t want to digest yourself!

AP Biology But sometimes cells need to die…  Lysosomes can be used to kill cells when they are supposed to be destroyed  some cells have to die for proper development in an organism  apoptosis – during development  “auto-destruct” process  lysosomes break open & kill cell  ex: tadpole tail gets re-absorbed when it turns into a frog  ex: loss of webbing between your fingers during fetal development  ex: self-destruct of cancerous cell

AP Biology Fetal development 15 weeks 6 weeks syndactyly

AP Biology When things go wrong…  Diseases of lysosomes are often fatal  digestive enzyme not working in lysosome  picks up biomolecules, but can’t digest one  lysosomes fill up with undigested material  grow larger & larger until disrupts cell & organ function  lysosomal storage diseases  more than 40 known diseases  example: Tay-Sachs disease build up undigested fat in brain cells

AP Biology Cytoskeleton  Function  structural support  maintains shape of cell  provides anchorage for organelles  protein fibers microfilaments, intermediate filaments, microtubules  motility  cell locomotion  cilia, flagella, etc.  regulation  organizes structures & activities of cell

AP Biology  actin  microtubule  nuclei Cytoskeleton

AP Biology Centrioles  Cell division  in animal cells, pair of centrioles organize microtubules  guide chromosomes in mitosis

AP Biology Effects of Cell Size

AP Biology Limits to cell size  Lower limit  smallest bacteria  mycoplasmas  0.1 to 1.0 micron (µm = micrometer)  most bacteria  1-10 microns  Upper limit  eukaryotic cells  microns  micron = micrometer = 1/1,000,000 meter  diameter of human hair = ~20 microns

AP Biology What limits cell size?  Surface to volume ratio  as cell gets bigger its volume increases faster than its surface area  smaller objects have greater ratio of surface area to volume 6:1~1:16:1 s:v Why is a huge single-celled creature not possible?

AP Biology Why is cell size an issue?  Metabolic requirements set upper limit  in large cell, cannot move material in & out of cell fast enough to support life CHO aa CH CO 2 NH 3 aa O2O2 CH What’s the solution? What process is this? O2O2 O2O2 aa CHO aa CH O2O2 aa CHO CH aa O2O2 CO 2 NH 3 CO 2 NH 3

AP Biology How to get bigger?  Become multicellular (cell divides) O2O2 CHO aa CH CO 2 NH 3 aa O2O2 CH But what challenges do you have to solve now? aa CO 2 NH 3 O2O2 aa CH aa CHO O2O2

AP Biology Phospholipid Cholesterol Membrane proteins Cell membrane  Exchange structure  plasma membrane functions as selective barrier  allows passage of O 2 & nutrients IN  allows passage of products & wastes OUT

AP Biology Any Questions??