Chapter 4 - Photosynthesis

Question 1

heterotrophs

Answer 1

organisms (like humans) that obtain chemical energy from the food they eat

Question 2

autotrophs

Answer 2

make their own food

Question 3

photoautotrophs

Answer 3

like plants, capture solar energy and convert it to chemical energy by photosynthesis

Question 4

photosynthesis releases:

Answer 4

oxygen (necessary for cellular respiration)

Question 5

photosynthesis removes ____ from the air. without this:

Answer 5

carbon dioxide; co2 would accumulate in the atmosphere and trap heat (greenhouse effect)

Question 6

glucose provides plants with ___ ___

Answer 6

fixed carbon

Question 7

____ ___ occurs when inorganic carbon is incorporated into an organic molecule

Answer 7

carbon fixation

Question 8

Where does photosynthesis store solar energy?

Answer 8

in the carbon bonds of organic glucose molecules

Question 9

true or false: photosynthesis is exergonic and spontaneous

Answer 9

false - has a positive Gibbs free energy, so it is non-spontaneous and endergonic

Question 10

photosynthesis and cellular respiration are:

Answer 10

essentially opposite reactions

Question 11

How are photosynthesis and cellular respiration similar?

Answer 11

They both utilize a series of redox reactions, also have electron transport chains that create an electrochemical gradient with protons which allows for ATP synthesis by chemiosmosis

Question 12

Leaf anatomy from top to bottom of leaf

Answer 12

1. Upper epidermic
2. Palisade mesophyll
3. Spongy mesophyll
4. Lower epidermis containing guard cells and stomata

Question 13

Epidermis tissue is found:

Answer 13

on roots, stems, leaves, flowers, fruits, and seeds

Question 14

Epidermis tissue function

Answer 14

protects structures from injury, water loss, and infection

Question 15

Which type of cells conducts most photosynthesis?

Answer 15

palisade mesophyll cells

Question 16

Describe palisade mesophyll cells structure

Answer 16

contain many chloroplasts and are well organized as a single layer below the upper epidermis

Question 17

Which cells conduct some photosynthesis?

Answer 17

Spongy mesophyll cells

Question 18

Why do spongy mesophyll cells not do as much photosynthesis?

Answer 18

they have few chloroplasts and do not receive as much light because they are found toward the bottom of the leaf

Question 19

Primary role of spongy mesophyll cells:

Answer 19

facilitating the movement of gases within the leaf. this relates to their structure: the gaps between spongy mesophyll cells allows this gas exchange to occur

Question 20

stomata

Answer 20

pores mainly found in the bottoms of leaves. site of atmospheric gas exchange

Question 21

guard cells

Answer 21

surround stomata and control whether they are open or closed

Question 22

chloroplasts

Answer 22

dual membrane organelles found in plants and photosynthetic algae, they make ATP and have their own DNA

Question 23

____ are photosynthetic organisms that do not have a chloroplast

Answer 23

cyanobacteria

Question 24

plastid

Answer 24

double-membranes cytoplasmic organelles found within plant cells

Question 25

example of plastid in plant cell

Answer 25

chloroplast

Question 26

function of plastids

Answer 26

store molecules, like pigments and starch

Question 27

stroma

Answer 27

fluid that fills area inside inner membrane

Question 28

Where does the Calvin cycle occur?

Answer 28

stroma of chloroplast

Question 29

thylakoids

Answer 29

phospholipid bilayer structured organelle suspended within the stroma

Question 30

Where do light dependent reactions occur?

Answer 30

Thylakoids

Question 31

Stack of thylakoids is called:

Answer 31

granum

Question 32

Junction between two grana is called

Answer 32

lamella

Question 33

Thylakoid lumen

Answer 33

interior of the thylakoid where H+ accumulates

Question 34

What is the ATP from the light dependent reactions used for?

Answer 34

used to power the Calvin cycle, which makes glucose

Question 35

Each photosystem has a special pair of chlorophyll molecules located in the ___ of the protein, called:

Answer 35

center; reaction center

Question 36

Reaction center in Photosystem I:

Answer 36

P700 - absorbs 700nm wavelengths best

Question 37

Reaction center in photosystem II:

Answer 37

P680 - absorbs 680nm wavelengths best

Question 38

First step of non-cyclic photophosphorylation

Answer 38

Photosystem II splits a water molecule to release 2 protons, 2 electrons, 1/2 O2

Question 39

When photons reach photosystem II, they will ____ electrons at the ___ ___. This forces electrons to:

Answer 39

excite; reaction center; go to a higher energy level and be passed to primary electron acceptor

Question 40

Excited electrons are passed down the ___ in the _____. The energy released from these electrons is used to:

Answer 40

electron transport chain; thylakoid membrane; pump protons from the stroma into the thylakoid lumen

Question 41

What creates an electrochemical gradient in the thylakoid lumen?

Answer 41

water splitting and proton pumps

Question 42

Excited electrons from Photosystem II are eventually passed onto:

Answer 42

Photosystem I

Question 43

Electrons from Photosystem I travel down a short _____ and eventually reduces ____ to form ____

Answer 43

electron transport chain; NADP+; NADPH

Question 44

Cyclic photophosphorylation

Answer 44

cell recycles electrons through photosystem I, as opposed to using them too reduce NADP+

Question 45

Purpose of cyclic photophosphorylation

Answer 45

continue to bring more H+ into thylakoid lumen to make more ATP while NADPH is low

Question 46

Calvin Cycle is also known as:

Answer 46

dark reactions or light independent reactions

Question 47

What is the purpose of the calvin cycle?

Answer 47

fixes inorganic carbon dioxide into organic glucose sugars

Question 48

Calvin cycle occurs in the:

Answer 48

stroma

Question 49

Calvin cycle needs __ carbon dioxide molecules to synthesize 1 glucose

Answer 49

6

Question 50

First stage of calvin cycle is called ____ ____. What happens during this stage?

Answer 50

carbon fixation; CO2 combines with ribulose-1,5-bisphosphate (RuBP) which has 5 carbons. This is catalyzed by rubisco. Splits into 2 PGA molecules (phosphoglycerate)

Question 51

Where is rubisco found?

Answer 51

Wherever plants are photosynthesizing (most common protein in the world)

Question 52

What happens when CO2 combines with RuBP?

Answer 52

molecule is unstable so it splits into 2 PGA molecules (each 3 carbons)

Question 53

Second stage of calvin cycle

Answer 53

Where reduction takes place; ATP from light dependent reactions will phosphorylate PGA. NADPH reduces this intermediate to make G3P

Question 54

True or false: all G3P made during calvin cycle is used to generate sugars

Answer 54

False - some of it is used to regenerate RuBP. This requires ATP from light dependent reactions

Question 55

3rd stage of calvin cycle

Answer 55

Regeneration

Question 56

Overall calvin cycle reaction:

Answer 56

6 CO₂ + 18 ATP + 12 NADPH + H⁺ → 18 ADP + 18 Pᵢ +12 NADP⁺ + 1 glucose

Question 57

How many ATP is needed to convert G3P to RuBP

Answer 57

6 ATP to convert 10 out of 12 G3P

Question 58

How many G3P enter 4th stage of calvin cycle (carbohydrate synthesis)

Answer 58

2 G3P