cellular energy-notes.docx

7/27/2019 CELLULAR ENERGY-notes.docx

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Overarching Theme - Homeostasis

CELLULAR ENERGY How Organisms Obtain Energy

Big IdeaPhotosynthesis converts the Suns energy into chemical energy, while cellular

respiration uses chemical energy to carry out lifes functions.

A) Transfer of Energy All organisms need energy to live Directly or indirectly, nearly all energy for life comes from the Sun Some organisms make their own food = autotrophs, while others obtain it from other

organisms =heterotrophs

All chemical reactions in a cell are called metabolism Metabolic pathway = products of one chemical reaction are the reactants of another Important metabolic pathway allows energy to flow between organisms involves

photosynthesis (anabolic pathway that builds larger molecules) and cellular respiration

(catabolic pathway that breaks down large molecule to release energy)

B) ATP The Unit of Cellular Energya. What is it?

Adenosine triphosphate ATP is the cells useable form of energy Chemical energy is stored in its high energy phosphate bonds Usually created from adenosine diphosphate (ADP) bonding with a phosphate group Constant cycling in cells between ATP and ADP, to make energy available, bond between

2nd

and 3rd

phosphate groups broken, to store energy phosphate bond created.

b. FunctionsTo help synthesize biologically important molecules (e.g. enzymes)Supply energy for motilityGenerates heatSupply energy for transporting nutrients across membranes (active transport)


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C) Photosynthesis6 CO2 + 6 H2O + light energy ---------- C6H12O6 + 6 O2

Photosynthesis converts light energy from sun into chemical energy stored in bonds of

glucose molecule

Photosynthesis occurs in two phases called the light-dependent reaction (light reaction)and the light-independent reaction (dark reaction).

i) Light Reactions the energy in sunlight is trapped by organelles with light-absorbing pigments takes place in thylakoid membranes of grana (stacked discs) in chloroplasts light energy causes electrons to jump energy levels which splits a water

molecule and produces 1 ATP molecule

O2 is released (from split of H2O), ATP and H+ ion used for next phase ofphotosynthesis

ii) Dark Reactions the ATP and H+ react with CO2 from the atmosphere and form glucose

(chemical energy)

occurs in the stroma fluid filled space outside the grana

Confirm your learning IN ZEBRA BOOK, read page 131-137, do Questions #1-5 page 137.

D) Cellular Respiration

The process of capturing energy in the form of ATP from breaking apart sugar (glucose)molecules

Energy needed to perform all cellular activities Eukaryotic cells have mitochondria, which allows the process to create a net total of 36 ATP In contrast, prokaryotic cells, and those that function anaerobically, only make 2 ATPTwo Types of Respiration


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i) Anaerobic = without oxygen

Occurs when there is no oxygen available to the cell occurs in mammalian muscle during periods of intense exercise where oxygen supply

becomes limited

In animals and some microorganisms, called lactic acid fermentation, occurs in thecytoplasm of the cell

Glucose split to produce----- lactic acid and 2ATPo In yeast and some bacteria, called alcohol fermentation

Sugars are the most common substrate of alcohol fermentation, andtypical products are ethanol, carbon dioxide and hydrogen

Glucose --- ethanol + CO2 + 2ATP

Advantages

oRapid burst of energy (our muscle cells depend on this during intense exercise)

o Can produce ATP even when there is no oxygen availableDisadvantages

o Overall ATP production is only 2 ATPo End products are toxic to the cello Build up of lactic acid in muscle cells changes pHo This cause muscles to become fatigued, leads to crampso In alcohol fermentation, ethanol content eventually kills yeast/bacteria cells

Confirm your learning IN ZEBRA BOOK Read page 123-125 and do #1-3 page 130

ii) Aerobic = with oxygen

4 steps

1) Glycolysis

o Is an anaerobic process, therefore no oxygen required in this stepo Molecule of glucose is split to release energyo Requires input of 2 ATP to start reactiono End product is Pyruvate/Pyruvic Acido Occurs in cytoplasm

2) Transition Step

o This occurs when pyruvate moves from cytoplasm to mitochondria and isconverted to acetyl-CoA

o Requires the presence of oxygen3) Krebs Cycle

o Occurs in the matrix of the mitochondria
http://en.wikipedia.org/wiki/Mammalhttp://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Substrate_(biochemistry)http://en.wikipedia.org/wiki/Ethanolhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Ethanolhttp://en.wikipedia.org/wiki/Substrate_(biochemistry)http://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Mammal


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o Acetyl-CoA enters the cycle and CO2 and H atoms leave the cycleo Provides the hydrogen and electrons needed for the Electron transport chain.

o The 2C acetyl-CoA molecule will combine with a 4C molecule from the Krebscycle to form a 6C molecule

o As this 6C molecule moves through the cycle, decarboxylation occurs twice with2 carbons being lost as CO2

oAt the same time H is released as FADH2 and NADH2 (electron carrier molecules)

o CO2 is released into the atmosphere and the H (FADH2 and NADH2) continue onto the electron transport chain

4) Electron Transport Chain (ETC)

Occurs on the cristae of the mitochondria H carried from glycolysis and the Krebs Cycle to the ETC Process of H atoms going through the ETC produces the majority of ATP FADH2 and NADH2 are used to convert ADP to ATP At the end of the ETC the H ions combine with oxygen to form water.
http://simple.wikipedia.org/w/index.php?title=Electron_transport_chain&action=edit&redlink=1http://simple.wikipedia.org/w/index.php?title=Electron_transport_chain&action=edit&redlink=1


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NET TOTAL (aerobic respiration)

C6H12O6 + 6O2 ------------ 6CO2 + 6H2O + 36 ATP
http://simple.wikipedia.org/wiki/File:Cellularrespiration.JPG


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Connection to Biological Theme - Explain why each reaction (photosynthesis and cellular

respiration) is required to maintain homeostasis in an organism. What internal balances

must be regulated on a cellular level for an organism to survive?

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Confirm your learning IN ZEBRA BOOK complete Chapter Summary and Review, page 138 # 1-20 (omit #3 and 16)

cellular energy-notes.docx

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