Unit 6: Energy Pathways: Photosynthesis and Cellular Respiration

ATP

Adenosine Triphosphate

- Cellular Energy currency (cell batteries)

- Contains three phosphate groups

ADP

 Adenosine Diphosphate


- Contains two phosphate groups

Phosphorylation

transfer of a phosphate group to a molecule

ATP Cycle

1. Energy is stored in ATP via cellular respiration; ATP Synthase enzyme forms ATP

2. Energy is released as needed for vital cell functions by breaking the “high energy” phosphate bond; ATP becomes ADP as ATPase enzyme breaks bond

3. Energy from chemical bonds in foods is used to “recharge the battery”; reform ATP

Photosynthesis

- sunlight converted into P.C.B.E. within glucose - occurs within the chloroplasts of producers/autotrophs

Chloroplasts

membrane-bound organelles where photosynthesis occurs

Chlorophyll

 green pigment; absorbs red/blue wavelengths of light

Accessory (Antennae) Pigments

Help chlorophyll collect a greater amount of sunlight; broadens the absorption spectra  Ex. Carotene and Xanthophyll

Thylakoids

 membrane structures that contain photosystems; groups of enzymes that contain light absorbing pigments; site of light dependent reactions

Grana

stacks of thylakoids; maximize membrane area for light absorption and photosystems; more membrane surface area = greater light absorption

Stroma

cytosol like liquid of the chloroplast; site of light independent reactions

Photosynthetic Reaction

 occurs in two steps: Light dependent/ Light Independent Rxn

 Light dependent Reactions

- Require H₂O and sunlight; water split, energy saved

- Produce O₂ as a waste product

- Occurs in the thylakoid membrane/photosystems
     H₂0 + ADP + P + NADP   —----->  O₂ + ATP + NADPH

 Light independent Reactions

“Calvin Cycle”, Require CO_2, Produces glucose
   CO₂ + ATP + NADPH —---->  C₆H₁₂O₆ + ADP + P + NADP

RuBisCO enzyme and Carbon Fixation

______ turns atmospheric carbon (in carbon dioxide) into a usable/organic  form; process is called ________; all organic molecules originate from this

Stomata

open or close depending on the amount of H₂O and CO₂ in the guard cells; lots of water in guard cells causing swelling/turgor pressure resulting in stomata opening.

CAM Plants

  -     Open stomata at night and close them during the day, water conserved  

• At night, they fix CO₂ into a variety of organic compounds that can be released later during the daytime

• Allows water conservation; slow growth but possible in deserts

Ex: Cacti, Jade

C₄ Plants

  -      Contain special leaf cells that perform rapid uptake of CO₂

• Allows for efficient photosynthesis during morning and evening 

• Stomata close during the hottest part of day

Ex: Corn, Crabgrass

Cellular Respiration

 the process by which cells break down organic compounds (i.e. glucose) to form ATP;  ATP provides immediate energy for metabolic function

Anaerobic Cellular Respiration (Fermentation) 

- Production of ATP without the presence of O₂ or use of mitochondria

- Two Forms of Anaerobic Cellular Respiration:

Lactic Acid Fermentation is used by?

 most bacteria and some animal muscle cells

Ethyl Alcohol Fermentation used by?

most yeast and some bacteria

  Glycolysis

the first stage in all forms of respiration

• one glucose molecule is broken down into 2 pyruvic acid molecules; energy is released to phosphorylate 2 ATP molecules

• occurs outside the mitochondria in the cytoplasm; no mitochondria/O₂ required

Aerobic Cellular Respiration

  -    Requires the presence of O₂ and mitochondria

• produces much more ATP from 1 glucose molecule than anaerobic respiration (38 ATP); 19X more efficient.