CHAPTER 7 THE WORKING CELL: ENERGY FROM FOOD

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CHAPTER 7THE WORKING CELLENERGY FROM FOOD
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Concept 7.1 Sunlight Powers Life
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Obtaining Food

• Autotrophs- organisms that make their own food
  (self-feeder)
• Photosynthesis- (from the Greek photo-meaning
  light and synthesis meaning to make something).
• Producers- produce organic molecules that serve
  as food for an ecosystem.

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• Heterotrophs- organisms that cannot make their
  own food depend on the energy from producers
• (also called consumers)

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Cellular Respiration

• Cellular respiration is a chemical process that
  utilizes oxygen to convert chemical energy stored
  in organic molecules into another form called ATP
  (adenosine triphosphate)

                                                                                                                                                                        
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7.2 Food stores chemical energy

• Kinetic Energy- the energy of motion
• Potential Energy- energy that is stored due to an
  object's position or arrangement.
• Thermal Energy- total amount of energy associated
  with the random movement of atoms and molecules
  in a sample of matter

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Chemical Energy

• Chemical energy- potential to perform work due to
  the arrangement of atoms within molecules

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Within your cells, organic molecules such as
glucose also react with oxygen in the process of
cellular respiration. And similar to an
automobile engine, working cells produce carbon
dioxide and water as their "exhaust."
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Calories

• the amount of energy required to raise the
  temperature of 1 gram (g) of water by 1 degree
  Celsius (C).

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Concept 7.3 ATP provides energy for cellular work

• Adenosine-contains adenine and a five carbon
  sugar called ribose.
• Triphosphate- three phosphate groups that are the
  source of energy used for most cellular work

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ATP and Cellular Work
                                                                                                                                                                            
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The ATP Cycle
                                                                                                                                                       

• ATP is recyclable
• Work consumes ATP and it is turned into ADP and
  then a phosphate group is added to regenerate the
  ATP

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Concept 7.4 Electrons fall from food to oxygen
during cellular respiration

• Cellular respiration is an aerobic process, it
  requires oxygen
• Gas exchange occurs (oxygen in, and carbon
  dioxide out)

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Overall Equation
                                                                                                                                                                                                                                          

• Glucose is a common fuel for cellular
  respiration, the double arrow represents many
  steps required not just one.

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Falling Electrons

• During cellular respiration, the carbon and
  hydrogen atoms change partners and bond with
  oxygen atoms instead.
• The carbon-hydrogen bonds are replaced by
  carbon-oxygen and hydrogen-oxygen bonds.
• As the electrons of these bonds "fall" toward
  oxygen, energy is released.

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Electron Transport Chains

• Sequence of electron carrier molecules that
  transfer electrons and release energy during
  cellular respiration
• Like a staircase, as electrons fall down a small
  amount of energy is released.

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7.5 Cellular respiration converts energy in food
to energy in ATP

• Mitochondria- powerhouse of cell
• Structure of folded membranes inside are the key
  to cellular respiration.

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Metabolic pathway

• metabolism all of a cell's chemical processes.

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The three stages of cellular respiration

• Stage 1- Glycolysis splitting of sugar

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Stage 1 Glycolysis

• Occurs in cytoplasm
• Glucose is converted into pyruvic acid
• (2-3 carbon molecules)
• (NAD) accepts 2 electrons and one hydrogen ion
  it is converted into (NADH)
• 2 ATP invested, 4 ATP are produced
• Net gain of 2 ATP

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Stage 2 The Krebs Cycle
                                                                                                                                                                                                                                                                                              
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Stage 2 The Krebs Cycle

• Occurs in the fluid matrix of the mitochondria
• Pyruvic acid is broken down into Acetyl Co-A,
  releasing carbon dioxide and more energy.
• Each of the two Acetyl Co-A (2 carbon molecules)
  goes through the Krebs cycle, generating 2 CO2 ,
  1 ATP, and 1 FADH2 , and 3 NADH
• Total after 2 cycles 4 CO2 , 2 ATP,
• 2 FADH2 , and 6 NADH

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Stage 3 Electron Transport Chain and ATP
Synthase Action
                                                                                                                                                                                                                                                                                              
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Stage 3 The E.T.C.

• Occurs in the inner membranes of the mitochondria
• There are two parts
• a) an e.t.c, b) ATP synthase which generates ATP
• NADH transfers electrons, water is split, and
  hydrogen ions are transferred across the membrane
  to create a
• H ion concentration gradient

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Adding up the ATP

• One Glucose molecule yields.
• Stage 1 Glycolysis 2 ATP
• Stage 2 Krebs Cycle 2 ATP
• Stage 3 E.T.C. 34 ATP
• MAXIMUM OF ABOUT 38 ATP PRODUCED

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Concept 7.6 Some cells can harvest energy without
oxygen

• Fermentation in human muscle cells occurs when
  oxygen is not readily available.

                                                                                                                                                                                                                                                                                              
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Lactic Acid Fermentation

• Makes ATP entirely from glycolysis
• 2 ATP are generated
• Even though there are only two ATP, by burning
  enough glucose, fermentation can regenerate
  enough ATP molecules for short bursts of activity
  such as a short sprint.
• Lactic acid is a waste product causing fatigue
  and soreness in muscles

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• Your body consumes oxygen as it converts the
  lactic acid back to pyruvic acid.
• You restore your oxygen supply by breathing
  heavily for several minutes after you stop
  exercising.

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Fermentation in Microorganisms

• Anaerobic- no oxygen environment
• These organisms ferment sugar and other foods
  creating alcohol as a waste product instead of
  lactic acid
• This process also releases CO2.

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Examples of fermentation

• Yeast makes bread rise
• Fungi and bacteria produce lactic acid and humans
  use these to transform milk into cheese and
  yogurt (sharpness and sour flavor), soy beans
  make soy sauce, cabbage into sauerkraut, potatoes
  into vodka