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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 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 Why is a huge single-celled creature not possible? What cell organelle governs this? 6:1 1.2:1 6:1 s:v

4 AP Biology Limits to cell size  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 O2O2 aa O2O2 CHO aa CH O2O2 aa CHO CH aa O2O2 CO 2 NH 3 CO 2 NH 3 CH What’s the solution? What process is this? O2O2

5 AP Biology How to get bigger?  Become multi-cellular (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

6 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

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

8 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

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

10 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

11 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

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

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

14 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

15 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

16 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 Which cells have lot of rough ER?

17 AP Biology Golgi Apparatus Which cells have lots of Golgi? transport vesicles secretory vesicles  Function  finishes, sorts, tags & ships cell products  like “UPS shipping department”  ships products in vesicles  membrane sacs  “UPS trucks”

18 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…

19 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

20 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 Where old organelles go to die!

21 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

22 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

23 AP Biology Fetal development 15 weeks 6 weeks syndactyly

24 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

25 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

26 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

27 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

28 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

29 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!

30 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

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

32 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

33 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


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