AP Biology 3B

all living things (not just animals) experience or undergo

cellular respiration: uses food energy and produces ATP

photosynthesis

when plants convert solar energy to chemical energy (food)

• occurs in plants, algae, protists, and prokaryotes

chemical equation for photosynthesis

6CO₂ + 6H₂O > C₆H₁₂O₆ + 6O₂

site of photosynthesis

chloroplast (membrane bound organelle)

mesophyll

chloroplasts mainly found in these cells of leaf

stomata

pores in leaf (CO₂ enters / O₂ exits)

chlorophyll

green pigment in the thylakoid membrane of chloroplasts

• essential for photosynthesis

• converts sun light to electron energy

stroma

fluid filled space in the inner membrane

thylakoid

a membrane/sac

lumen

fluid filled space in the thylakoid

redox reaction (OIL RIG)

a process in which water is oxidized and carbon dioxide is reduced

• oxidation = loss of electrons (or losing H)

• reduction = gain of electrons (or gaining H)

OIL RIG meaning

Oxidation is Loss (losing H electrons)
Reduction is Gain (gaining H electrons)

stages of photosynthesis

• Light dependent reaction (photo)

• Calvin Cycle (synthesis)

Describe the light dependent reaction (photo) stage

• energy conversion reactions

• convert solar energy to chemical energy

• produce ATP & NADPH

• two photosystems in the thylakoid membrane

describe the calvin cycle (synthesis) stage

• sugar building reaction

• uses chemical energy (ATP & NADPH) to reduce CO₂ & synthesizes C₆H₁₂O₆

• in the stroma

describe the two photosystems in the thylakoid membrane

• a light-catching unit: large complex of proteins and pigments that capture the sunlight

• collections of chlorophyll (a) molecules

• transfers high energy electrons for ATP and NADPH

Name and function of Photosystem II

• P₆₈₀

• absorbs light energy at 680nm

name and function of photosystem I

• P₇₀₀

• absorbs light energy at 700nm

first step of a light dependent reaction

• Light excites chlorophyll electrons (in photosystems) and become energized

second step of a light dependent reaction

• Excited electrons pass through electron transport chain (ETC), making ATP via chemiosmosis

function of the proton pump in a light reaction

• pumps hydrogen from the stroma to the lumen (low to high concentration gradient)

• creates a high concentration of hydrogen for the ATP Synthase to make ATP

low pH means what type of environment

• acidic environment

• aka. pH2

• high hydrogen concentration

high pH means what type of environment

• normal environment

• aka. pH9

• low hydrogen concentration

function of ATP synthase

• phosphorylates ADP to ATP to make ATP energy

• uses hydrogen to make ATP

  • Phosphorylation: adding a phosphate to diphosphate to make it triphosphate

What is the energy source of active transport in a light dependent reaction?

from the electrons traveling down the electron transport chain (ETC)

Step 3 (last step) of a light dependent reaction

electrons reduce NADP+ (to form NADPH) and are replaced by photolysis of water

• NADP+ is reduced to NADPH

• NADP+ is the final electron acceptor

why would the process of the light dependent reaction stop

electrons are lost to the electron transport chain and therefore will no longer create ATP / energy

purpose of photolysis of water

water serves as an electron donor for the electron transport chain (photosystems) to compensate for the lost electrons (due to the ETC)

describe photolysis of water

• water is in the lumen and therefore is split (by the sun) in the lumen to make 2H+ electrons 

• eventually creates O₂ that will leave to the atmosphere via the stomata

in a light dependent reaction, when the H+ electrons are traveling to the stroma from the thylakoid space, what type of transport is it

passive transport because it moves from high to low concentration, and therefore does NOT use energy

photophosphorylation is

the process of using photosystems to make ATP & ADPH via ETC and Chemiosmosis

calvin cycle occurs in the

stroma

calvin cycle requires what products

ATP & NADPH

1st phase of calvin cycle

• Carbon Fixation

  • CO₂ from the air is imbedded in the cycle and combined with RuBP to make 3-Carbon compound called PGA

  • catalyzed by enzyme rubisco

  • aka. carbon fixation

2nd phase of calvin cycle

• Reduction

  • ATP and NADPH are used to convert PGA into G3P

  • PGA gains electrons (reduction)

    • ATP converted to ADP

  • ADP & NADP⁺ return to light dependent reaction to start process again 

3rd phase of calvin cycle

• Regeneration of RuBP

  • Some G3P make glucose, and others will be recycled to regenerate RuBP

  • Allows for more CO₂ to be fixed in the cycle

  • requires ATP

describe G3P

• product of the Calvin Cycle

• 3 carbon sugar

factors that affect photosynthesis

• temperature

• light intensity

  • more light = more reaction rate

• concentration of CO₂

  • more CO₂ = more reaction rate

(experiment vocab) tissue culture

technique to grow cells in the laboratory

(experiment vocab) cell line

a type of cell grown in the lab for experiment 

• HeLa Cell

(experiment vocab) In Vitro

an experiment in a test tube

(experiment vocab) In Vivo

an experiment in a test tube

(experiment vocab) Nutrient medium

a liquid nutrient used to feed the cells in the lab

(experiment vocab) radioactive isotope

an isotope of an element is used to “tag” the molecules studied.

(experiment vocab) Assay

an experiment

• COVID-19 PCR test

ultimate source of energy

sun

photosynthesis is

endergonic (requires energy)

cellular respiration is

exergonic (releases energy)

Site of cellular respiration is

mitochondria

• double membrane

• mtDNA

• Folded inner membrane called cristae increase surface area

• interior is the matrix

Two ways of making ATP are

Oxygen is available

• Aerobic/cellular respiration

Oxygen is unavailable

• fermentation in cytoplasm

oxidation + reduction formulas

C₆H₁₂O₆ > CO₂ = glucose is oxidized

O₂ > H₂O = oxygen is reduced

1st stage of cellular respiration

Glycolysis

• breaks down glucose into two molecules of pyruvate

2nd stage of cellular respiration

The Krebs Cycle

• completes the breakdown of glucose , aka citric acid cycle

3rd stage of cellular respiration

Oxidative phosphorylation

• accounts for the most ATP synthesis

Glycolysis

• energy harvesting process in the cytoplasm of both eukaryotic and prokaryotic cells

• occurs in fermentation and aerobic respiration

• no oxygen needed

• converts glucose (6C) to 2 pyruvate (3C)

• produces: 2 ATP + 2NADH + 2 pyruvate

pyruvate oxidation

pyruvate converted to acetyl CoA before the krebs cycle

• pyruvate is transported from the cytosol (cytoplasm) to the matrix where oxidation occurs

• NADH is produced and CO₂ is released as waste

Krebs Cycle

CO₂ is released, ATP synthesized, electrons transferred to NADH and FADH₂

• occurs in mitochondrial matrix

Electron Transport Chain

• occurs in the cristae

• electrons stored in NADH and FADH₂ from glycolysis and Krebs cycle are transported to the ETC where oxygen is the final electron acceptor

purpose of NADH and FADH₂

to deliver electrons to the ETC

without oxygen in the ETC

proton pumps stop and therefore ATP production stops

The flow of protons allow for the formation of ATP from ADP and inorganic phosphate

• oxidative phosphorylation (cellular respiration)

• photophosphorylation (photosynthesis)

in chemiosmosis, electrons move from

intermembrane space to matrix 

terminal electron acceptor  in photosynthesis

NADP⁺

terminal electron acceptor  in cellular respiration

oxygen

bacteria does not have

krebs cycle because of no mitochondria

difference between NADH vs FADH₂

NADH has to travel through more protein complexes than FADH₂

• both have the same amount of electrons

factors that decrease ATP synthesis

poisons that block ETC or chemiosmosis

function of oligomycin (poison)

blocks the passage of H⁺ through ATP synthase

uncouplers such as DNP

destroy the H⁺ gradient by making the membrane leaky (permeable) to H⁺

uncoupling oxidative phosphorylation generates

heat

what type of fermentation does yeast undergo

alcohol fermentation

• acetaldehyde produced

what type of fermentation do humans undergo

lactic acid fermentation

• no acetaldehyde produced

plants in the dark continue to undergo

cellular respiration