Unit 4: Photosynthesis

Question 1

Compare photosynthesis and cellular respiration

Answer 1

Products of one are reactants of other
PS purpose: capture/store energy
CR purpose: release energy

Question 2

Define

Autotroph

Answer 2

Organism capable of using inorganic molecules to make organic molecules (sugars)

Question 3

What organisms are autotrophic?

Answer 3

Plants
Algae, some other protists
Some bacteria

Question 4

Define

Heterotroph

Answer 4

Organisms that rely on organic molecules made by autotrophs for their source of energy / organic matter

Question 5

What tissue type contains the most chloroplasts?

Answer 5

Mesophyll
Found in leaves

Question 6

Define

Stomata

Answer 6

Pores on leaf surface that allow for the exchange of O2 and CO2

Question 7

Identify the parts of the chloroplast

Answer 7

a - outer membrane
b - stroma (liquid portion)
c - thylakoid
d - granum
e - inner membrane

Question 8

State

Reaction for Photosynthesis

Answer 8

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

Question 9

What is the purpose of the light dependent reactions?

Answer 9

Capture solar energy and convert it into chemical energy (in ATP and NADPH)

Question 10

What is the purpose of the light independent reactions?

Answer 10

Save energy from ATP and NADPH (made during LDR) into molecules of glucose

Question 11

What is the electron carrier in photosynthesis?

Answer 11

NADP+ (oxidized)
NADPH (reduced)
NADP⁺ + 2 e^- + H⁺ → NADPH

Question 12

Define

Electromagnetic energy

Answer 12

Energy that travels as waves, which makes up the electromagnetic spectrum

Question 13

What is visible light?

Answer 13

Electromagnetic energy, which can be detected by the human eye (about 380 to 750 nm; you do not need to memorize these numbers)

Question 14

Define

Photon

Answer 14

A “unit” of energy
Think of a photon as the energy that a single electron pair can absorb, which then allows it to become excited / move to a higher electron orbital

Question 15

Define

Pigment

Answer 15

Molecules that absorb certain wavelengths of light

Question 16

Define

Absorption

Specifically, absorption of light energy

Answer 16

Energy that is used by a molecule to excite electron(s)

Question 17

What can happen to light when it hits matter?

Answer 17

It can be:
* absorbed (excite electrons)
* reflected (bounce off)
* transmitted (go through)

We don’t discuss transmission but I didn’t want this to be inaccurate

Question 18

Light Dependent Reactions: Location

Answer 18

On thylakoid membranes

Question 19

Light Dependent Reactions:
Reactant

Answer 19

Water

Question 20

Light Dependent Reactions:
Product

Answer 20

O₂

Question 21

Light Dependent Reactions: Energy Transformation

Answer 21

Sunlight → Chemical (in ATP and NADPH)

Question 22

Light Independent Reactions: Location

Answer 22

Stroma

Question 23

Light Independent Reactions: Reactant

Answer 23

CO₂

Question 24

Light Independent Reactions: Product

Answer 24

G3P (and ultimately, glucose)

Question 25

Light Independent Reactions: Energy Transformations

Answer 25

Chemical energy from ATP and NADPH → G3P / glucose

Question 26

# Define Photosystem

Answer 26

A group of proteins and pigments that absorb light and focus it to a pair of electrons, which can then be passed on

Question 27

Describe the movement of electrons during the light dependent reactions

Answer 27

1. Water 2. PSII (where it will stay until excited by a photon of light) 3. Electron transport chain (as it moves through, its energy is used to pump H+ into thylakoid lumen) 4. PSI (where it will stay until excited by a photon of light) 5. Electron transport chain 6. NADP+ reductase 7. NADPH

Question 28

How is NADPH made during photosynthesis?

Answer 28

Electrons are passed to NADP+ reductase, which then bind NADP+ to a H+, making NADPH

Question 29

What is the other name for the light independent reactions?

Answer 29

Calvin Cycle

Question 30

# State 3 "phases" of the light independent reactions

Answer 30

1. Fixation 2. Reduction 3. (RuBP) Regeneration

Question 31

What happens during LIR: Fixation

Answer 31

Rubisco (enzyme) binds RuBP (five carbon) to CO₂ (1 carbon), making a 6-carbon molecule that quickly breaks into two 3-carbon molecules of 3PG

Question 32

What happens during LIR: Reduction

Answer 32

3PG is reduced by ATP and NADPH into G3P

Question 33

What happens during LIR: Regeneration

Answer 33

1/6 of G3P molecules made by reduction phase are used for making glucose (2 G3P = 1 glucose) 5/6 of G3P molecules are rearranged back into 3 molecules of RuBP

Question 34

Enzyme that adds RuBP + CO₂

Answer 34

Rubisco This is the most abundant protein on Earth!

Question 35

# Define Fixation

Answer 35

Incorporation of an inorganic molecule to an organic one Namely, carbon fixation involves adding a CO₂ onto RuBP, making an organic 6-carbon molecule

Question 36

What organisms are heterotrophic?

Answer 36

Animals Decomposers (fungi, most bacteria)