Bioenergetics
The Big Picture
- energy flows through
- matter recycles
Producers = Autotrophs
- organisms which can make their food
- plants, algae, some bacteria
- most use photosynthesis
Consumers = Heterotrophs
- organisms which get their food from other
organisms
- animals, fungi, most protists
- most use cellular respiration
ATP = Adenosine triphosphate
- normal molecule that cells use to store and
release energy
- used to power all cellular work
- stores small amounts of usable energy
- cells must recycle it quickly
Photosynthesis
- process by which plants use the energy of
sunlight to convert water and carbon dioxide
into high-energy carbohydrates (sugars +
carbs) and oxygen (a waste product)
6CO2 + 6H2O ---
light
--> C6H12O6 + 6O2
carbon dioxide + water ---light--> sugars + oxygen
- chlorophyll is the primary light-gathering
pigment of plants
- chlorophyll reflects green light
See diagram page 209 in text
Photosynthesis happens in mesophyll cells of a leaf.
- contain chloroplasts which have thylakoids
where reactions occur
- two sets of reactions:
1. Light-dependent reactions
2. Light-independent reactions = Calvin cycle
Light-dependent reactions
- require light
- happen in photosystems on thylakoid membranes
- sunlight splits water into H+ and O2
- also forms ATP and NADPH
-NADPH carries electrons (energy) to Calvin cycle
- excited electrons from photosystems give energy
to pump H+ into thylakoid spaces and then form
ATP
See diagram on page 211 of textbook.
- a concentration gradient of H+ in thylakoids is
balanced by diffusion through ATP synthase
Light-Independent Reactions = Calvin Cycle
- occur in the stroma of the chloroplast
- use the ATP and NADPH from the light reactions to
convert CO2 into C6H12O6
- six CO2 are needed to make one sugar molecule
Cellular Respiration – Ch. 9
- the energy captured in photosynthesis is released
by organisms by several chemical pathways
- breaks down glucose and other food molecules in
the presence of oxygen
6O2 + C6H12O6
Oxygen + glucose
6CO2 +6H2O + Energy
carbon dioxide + water + energy
- energy of food is measured in calories
- food Calorie = 1 kilocalorie (1,000 calories)
- energy of food must be released slowly and
captured in the bonds of ATP
See page 222 in textbook
Glycolysis
- breaks a molecle of glucose into two pyruvic acids
- occurs in the cytoplasm of all cells with or without
oxygen
- net gain of 2 ATP – not much, but very fast
- also produces 2 NADH’s which carry electrons and
H+ to other reactions in the cell
Fermentation
- when oxygen is not available fermentation occurs
- yeasts and a few other organisms form alcohol
- in our muscles fermentation forms lactic acid
Kreb’s Cycle = Citric Acid Cycle (pg. 227)
Krebs Cycle = Citric Acid Cycle
- in the presence of oxygen, pyruvic acids are
modified and taken into the mitochondria
- capture energy from bonds of pyruvates to form
ATP, NADH, and FADH2
- occurs in mitochondrial matrix
- releases CO2
Electron Transport Chain (pg. 228)
- NADH and FADH2 from glycolysis and Krebs Cycle
carry electrons (energy) to electron transport
chains on inner membrane of mitochondria
- movement of electrons through E.T.C. pumps H+
into outer compartment of mitochondria to
establish a concentration difference
- H+ can only diffuse out through ATP synthase and
the energy of their diffusion is used to form ATPs
See page 228
Summary of ATP production in Cellular Respiration