Welcome to Bio 10 Last day to add classes: Sat Apr 16 Peer-tutoring groups Meet Tu at 11:30, Th at 12:30 or Fri at 10:30 Skills Center in ATC302 Today: ATP, enzymes (Ch 5), Photosynthesis (Ch 7) Test 1 next Th, Ch 1-7 Study guide posted on my website Multiple choice, matching, short answer (100 pts) Bring scantron, #2 pencil Based on lectures, study guide and worksheets Cell Shape and Movement Maintaining Cell Shape Cytoskeleton A network of fibers extending throughout the cytoplasm Functions: support Helps cell maintain its shape Functions: movement Motor proteins move objects along the cytoskeleton inside the cell Cytoskeleton microtubules are stained with a fluorescent green dye Motor proteins Special motor proteins attach to cargo-filled vesicles and carry them along the cytoskeleton like trucks on a highway. Kinesin motor 1:11 http://www.youtube.com/watch?v=koejwq0oxc4&nr=1 How cells move Flagella propel the cell in an undulating whiplike motion. What human cell uses a flagellum to move? Cilia Shorter and more numerous move in a coordinated backand-forth motion. Ch. 5 How Cells Use Energy ATP and cellular work Enzymes
How cells use energy Mitochondria Cellular power plants The mitochondria are the engines of our cells Burn sugar for fuel Produce ATP for cellular work Generate most of the cell s ATP Surrounded by two membranes with different properties Outer membrane freely permeable to small molecules Inner membrane ATP synthesis Proteins of the electron transport chain Origin of mitochondria Thought to have evolved from small symbiotic prokaryotes Have many features in common with prokaryotes Single circular chromosome Genes are closely related to prokaryotic genes Reproduce in a similar manner Important role in evolution The ability of these bacteria to conduct cell respiration was an evolutionary advantage ATP powers cellular work Most cells receive energy in a form they can t use directly Energy from food This energy has to be converted into a usable form of energy ATP (adenosine triphosphate) NAD (nicotinamide adenine dinucleotide) The Structure of ATP A complex organic molecule Adenosine plus a tail of 3 phosphate groups containing a high-energy bond The energy in ATP is used to drive cellular work Cells use ATP to build macromolecules To transport molecules across the membrane To move by cilia or flagella
ATP Power It takes about 10 million ATP molecules per second to power an active muscle cell The ATP Cycle ATP stores energy obtained from food and releases it as needed at a later time How do cells store energy? ATP is a very reactive molecule As fat and some glycogen Energy Chemical reactions in the cell Substrate The making or breaking of chemical bonds Substrates starting molecules Products molecules at the end of the reaction Activation energy energy needed to start the reaction Cell chemistry catalyzed reactions Cells use enzymes to speed up chemical reactions Lower the activation energy This process is called catalysis We say that enzymes are catalysts Enzymes Lower the activation energy barrier for chemical reactions
4 characteristics of enzymes Proteins Act as catalysts speed up chemical reactions Decrease the activation energy Recycled enzymes can function over and over again How enzymes work Each enzyme is very selective it recognizes its substrate The substrate binds to a special region of the enzyme, the active site How enzymes work Enzymes in action Stonewashed jeans are no longer made using stones Using the enzyme cellulase gives better results It breaks down the polysaccharide cellulose, the main component of cotton Cells can control enzymes Enzyme inhibitors Molecules in the cell inhibit (slow down or stop) enzymatic reactions Many bind to the active site, as substrate imposters. Enzyme inhibitors: How penicillin works Many antibiotics work by inhibiting enzymes that are found only in bacteria Penicillin inhibits an enzyme that bacteria use in making their cell walls
Recap: Enzymes Workhorse proteins Speed up reactions Orchestrate the majority of chemical reactions needed for life How do we get energy from food? Cellular respiration The energy in food comes from the sun We use the energy that plants capture from the sun Producers Consumers Organisms are Producers or Consumers Producers Plants and algae convert solar energy to chemical energy and make sugars and other organic molecules Autotrophs or self-feeders Consumers Obtain their food by eating plants or animals that have eaten plants. Heterotrophs or other-feeders Energy flow Photosynthesis (plants) Cellular respiration (plants & animals)
Overview of photosynthesis Ch 7 Photosynthesis Using sunlight to make food Occurs in Leaves of plants Algae cells Some protists and bacteria Autotrophs! Plants: solar-powered chemical factories Overview of Photosynthesis The leaf is the primary site of photosynthesis Is it possible to make food from sunshine, water and air? Plants do it everyday Capture solar energy and use it to build carbohydrates from CO 2 and water Produce food for themselves and all other organisms Photosynthesis feeds nearly all life on earth Light energy, CO 2 and water sugars Releases oxygen Without plants we would have no food to eat or oxygen to breath Photosynthesis How plants capture solar energy Role of chloroplast & chlorophyll (pigment) How solar energy is converted to chemical energy and used to build carbohydrates Light reactions produce high-energy molecules (ATP, NADPH) Calvin cycle fixes CO 2 as carbohydrates How do plants capture solar energy? Plant cells contain chloroplasts that actually carry out photosynthesis
Inside the chloroplast The Overall Equation for Photosynthesis Chloroplasts convert solar energy into chemical energy Process = photosynthesis The chloroplast contains Stacks of membranes called thylakoids substrates products A Photosynthesis Road Map Photosynthesis is composed of two processes: The light reactions convert solar energy to chemical energy. ATP and NADPH The Calvin cycle uses this energy to make sugar from carbon dioxide and water. How plants capture energy from sunlight Photosynthesis starts with the photosystem It is a network of pigments in the membrane of the thylakoid The primary pigment is chlorophyll Pigments are molecules that capture solar energy Why are leaves green? Chloroplasts absorb certain wavelengths of light that drive photosynthesis Main pigment is chlorophyll absorbs mainly blue and red light, and transmits green light Accessory pigments Carotenoids absorb other light wavelengths Give color to flowers, fruits and vegetables A photosystem A cluster of chlorophyll molecules. Acts as a light-gathering antenna that focuses energy onto the reaction center.
How Photosystems Harvest Light Energy Chlorophyll molecules absorb photons. The absorption of a photon cause electrons in the pigment gain energy Photons captured by chlorophyll are converted to a current of electrons How the light reactions generate ATP and NADPH The energized electrons pass thru a series of proteins in membrane of chloroplast electron transport chain Energy is used to make ATP and NADPH Tony s movie The Calvin cycle: making sugar from CO 2 A review of photosynthesis CO 2 The ATP and NADPH of the light-dependent reactions are used to build sugars in the Calvin cycle Photosynthesis is a way of making sugars from sunlight, H 2 O and CO 2 Photosynthesis uses solar energy, water and carbon dioxide to make sugars 1. Light Reactions Use solar energy to make high-energy molecules (ATP and NADPH) 2. Calvin cycle Uses these high-energy molecules to capture CO 2 and make sugars Plants: photosynthesis (Britannica) 3:05 http://www.youtube.com/watch?v=ybfx3ocxs6a&feature=fvw