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AP Biology The Cell. AP Biology Why are cells so small? Why can’t they be as huge as an hippo?

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Presentation on theme: "AP Biology The Cell. AP Biology Why are cells so small? Why can’t they be as huge as an hippo?"— Presentation transcript:

1 AP Biology The Cell

2 AP Biology Why are cells so small? Why can’t they be as huge as an hippo?

3 AP Biology Overview: The Fundamental Units of Life  All organisms are made of cells  The cell is the simplest collection of matter that can be alive  Cell structure is correlated to cellular function

4 AP Biology Concept 6.1: Biologists use microscopes and the tools of biochemistry to study cells In a light microscope (LM), visible light is passed through a specimen and then through glass lenses -Lenses refract (bend) the light, so that the image is magnified Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3-D

5 AP Biology 1 m 0.1 m 1 cm 1 mm 100  m 10  m 1  m 100 nm 10 nm 1 nm 0.1 nm Atoms Small molecules Lipids Proteins Ribosomes Viruses Smallest bacteria Mitochondrion Most bacteria Nucleus Most plant and animal cells Human egg Frog egg Chicken egg Length of some nerve and muscle cells Human height Unaided eye Light microscopy Electron microscopy Super- resolution microscopy

6 AP Biology Cell Fractionation  Cell fractionation takes cells apart and separates the major organelles from one another

7 AP Biology Figure 6.4 TECHNIQUE Homogenization Tissue cells Homogenate Centrifugation Differential centrifugation Centrifuged at 1,000 g (1,000 times the force of gravity) for 10 min Supernatant poured into next tube 20,000 g 20 min 80,000 g 60 min Pellet rich in nuclei and cellular debris 150,000 g 3 hr Pellet rich in mitochondria (and chloro- plasts if cells are from a plant) Pellet rich in “microsomes” (pieces of plasma membranes and cells’ internal membranes) Pellet rich in ribosomes

8 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

9 AP Biology Cell characteristics  All cells:  surrounded by a plasma membrane  have cytosol  semi-fluid substance within the membrane  cytoplasm = cytosol + organelles  contain chromosomes which have genes in the form of DNA  have ribosomes  tiny “organelles” that make proteins using instructions contained in genes

10 AP Biology Prokaryote bacteria cells Types of cells Eukaryote animal cells - no organelles - organelles Eukaryote plant cells

11 AP Biology Types of cells Prokaryotic cell  DNA in nucleoid region, without a membrane separating it from rest of cell  Cell wall present in all (type differs) Eukaryotic cell  chromosomes in nucleus, membrane- enclosed organelle  Cell walls present in fungi and plants only  More complex  Membrane bound organelles present  Prokaryotic vs. eukaryotic cells

12 AP Biology The prokaryotic cell is much simpler in structure, lacking a nucleus and the other membrane-enclosed organelles of the eukaryotic cell.

13 AP Biology Why organelles?  Specialized structures  specialized functions  cilia or flagella for locomotion  Containers  partition cell into compartments  create different local environments  separate pH, or concentration of materials  distinct & incompatible functions  lysosome & its digestive enzymes  Membranes as sites for chemical reactions  unique combinations of lipids & proteins  embedded enzymes & reaction centers  chloroplasts & mitochondria mitochondria chloroplast Golgi ER

14 AP Biology Cells gotta work to live!  What jobs do cells have to do?  make proteins  proteins control every cell function  make energy  for daily life  for growth  make more cells  growth  repair  renewal

15 AP Biology Building Proteins  Organelles involved  nucleus  ribosomes  endoplasmic reticulum (ER)  Golgi apparatus  vesicles nucleusribosomeER Golgi apparatus vesicles The Protein Assembly Line

16 AP Biology Synthesizing proteins cytoplasm cisternal space mRNA ribosome membrane of endoplasmic reticulum polypeptide signal sequence ribosome

17 AP Biology Nucleolus  Function  ribosome production  build ribosome subunits from rRNA & proteins  exit through nuclear pores to cytoplasm & combine to form functional ribosomes small subunit large subunit ribosome rRNA & proteins nucleolus

18 AP Biology membrane proteins Types of Ribosomes  Free ribosomes  suspended in cytosol  synthesize proteins that function in cytosol  Bound ribosomes  attached to endoplasmic reticulum  synthesize proteins for export or for membranes

19 AP Biology Rough ER function  Finalize protein formation and prepare for export out of cell (protein folding)  protein secreting cells will have lots  packaged into transport vesicles to golgi

20 AP Biology Golgi Apparatus transport vesicles secretory vesicles  Function  finishes, sorts, tags & ships cell products  like “UPS shipping department”  ships products in vesicles  membrane sacs  “UPS trucks”

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

22 AP Biology Smooth ER function  Membrane production  Many metabolic processes  synthesis  synthesize lipids  oils, phospholipids, steroids & sex hormones  hydrolysis  hydrolyze glycogen into glucose  in liver  detoxify drugs & poisons  in liver  ex. alcohol & barbiturates

23 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 only in animal cells synthesized by rER, transferred to Golgi

24 AP Biology Cellular digestion  Lysosomes fuse with food vacuoles  polymers digested into monomers  pass to cytosol to become nutrients of cell vacuole  lyso– = breaking things apart  –some = body

25 AP Biology When 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  “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

26 AP Biology Making Energy  Cells must convert incoming energy to forms that they can use for work  mitochondria: from glucose to ATP  chloroplasts: from sunlight to ATP & carbohydrates  ATP = active energy  carbohydrates = stored energy + ATP

27 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

28 AP Biology Mitochondria  Function  cellular respiration  generate ATP  from breakdown of sugars, fats & other fuels  in the presence of oxygen  break down larger molecules into smaller to generate energy = catabolism  generate energy in presence of O 2 = aerobic respiration

29 AP Biology Mitochondria  Almost all eukaryotic cells have mitochondria  there may be 1 very large mitochondrion or 100s to 1000s of individual mitochondria  number of mitochondria is correlated with aerobic metabolic activity  more activity = more energy needed = more mitochondria What cells would have a lot of mitochondria? active cells: muscle cells nerve cells

30 AP Biology Chloroplasts  Chloroplasts are plant organelles  class of plant structures = plastids  amyloplasts  store starch in roots & tubers  chromoplasts  store pigments for fruits & flowers  chloroplasts  store chlorophyll & function in photosynthesis  in leaves, other green structures of plants & in eukaryotic algae

31 AP Biology Chloroplasts  Function  photosynthesis  generate ATP & synthesize sugars  transform solar energy into chemical energy  produce sugars from CO 2 & H 2 O  Semi-autonomous  moving, changing shape & dividing  can reproduce by pinching in two Who else divides like that? bacteria!

32 AP Biology Mitochondria & chloroplasts are different  Organelles not part of endomembrane system  Grow & reproduce  semi-autonomous organelles  Proteins primarily from free ribosomes in cytosol & a few from their own ribosomes  Own circular chromosome  directs synthesis of proteins produced by own internal ribosomes  ribosomes like bacterial ribosomes Who else has a circular chromosome not bound within a nucleus? bacteria

33 AP Biology Endosymbiosis theory  Mitochondria & chloroplasts were once free living bacteria  engulfed by ancestral eukaryote  Endosymbiont  cell that lives within another cell (host)  as a partnership  evolutionary advantage for both  one supplies energy  the other supplies raw materials & protection Lynn Margulis U of M, Amherst

34 AP Biology Endosymbiosis theory Evolution of eukaryotes

35 AP Biology Food & water storage plant cells central vacuole contractile vacuole food vacuoles animal cells

36 AP Biology Vacuoles & vesicles  Function  little “transfer ships”  Food vacuoles  phagocytosis, fuse with lysosomes  Contractile vacuoles  in freshwater protists, pump excess H 2 O out of cell  Central vacuoles  in many mature plant cells

37 AP Biology Vacuoles in plants  Functions  storage  stockpiling proteins or inorganic ions  depositing metabolic byproducts  storing pigments  storing defensive compounds against herbivores  selective membrane  control what comes in or goes out

38 AP Biology Putting it all together, try labeling.. animal cells plant cells


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