Level 2 Bio: Photosynthesis

Question 1

What is the Balanced Chemical Equation

Answer 1

Sunlight + 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 2

What is the word equation

Answer 2

Sunlight + Carbon dioxide + water → Glucose + Oxygen

Question 3

What is photosynthesis and what happens during photosynthesis (brief summary)

Answer 3

Photosynthesis is the process plants use to make their own food by converting sunlight, carbon dioxide and water into glucose (food) and oxygen in order to fuel all their activities. During photosynthesis, light energy from the sun converts groups of six carbon dioxide molecules and six water molecules (the reactants) into one glucose (sugar) molecule and six oxygen molecules (the products).

Question 4

What are the reactants of photosynthesis?

Answer 4

Sunlight, Carbon dioxide (CO₂) and Water (H₂O)

Question 5

What are the products of photosynthesis?

Answer 5

Glucose (C₆H₁₂O₆) and Oxygen (O₂)

Question 6

What is glucose’s chemical equation?

Answer 6

C₆H₁₂O₆

Question 7

What is water’s chemical equation?

Answer 7

H₂O

Question 8

What is carbon dioxide’s chemical equation?

Answer 8

CO₂

Question 9

What is oxygen’s chemical equation?

Answer 9

O₂

Question 10

What do you need to do at level 2 when giving a chemical equation?

Answer 10

Balance the equation.

Question 11

What are humans and most other animals?

Answer 11

Heterotrophs

Question 12

What is a heterotroph

Answer 12

Heterotroph means that we have to consume other organisms such as plants or other animals for food.

Question 13

What are plants?

Answer 13

Autotrophs

Question 14

What is an Autotroph

Answer 14

Autotroph means that they create their own food.

Question 15

How do plants get carbon dioxide?

Answer 15

Plants take in carbon dioxide from the air through small openings in their leaves called stomata. Some plants (most monocots) have stomata on both sides of their leaves, and others (dicots & some monocots) only have stomata on the underside or lower epidermis.

Question 16

How do plants get water?

Answer 16

Plants get water from the soil surrounding their roots, water gets to the leaves by travelling through the xylem. The xylem is part of the plants vascular system. In leaves the xylem and phloem are contained in the vascular bundle.

Question 17

What happens to the CO₂ and H₂O once it is inside the leaf?

Answer 17

Once inside the leaf, the CO₂ and H₂O water molecules move into the cells of the mesophyll, the layer of ground tissue between the upper and lower epidermis. Within these cells chloroplasts use the CO₂ and H₂O to carry out photosynthesis.

Question 18

What is the structure of chloroplasts in relation to the process of photosynthesis?

Answer 18

Chloroplasts: Their thylakoid membranes contain pigment called chlorophyll which absorbs photons (light energy) from the sun. Which initiates the light dependent reactions that take place within the thylakoids. During these reactions H₂O molecules are broken down.

Question 19

What is the waste product of photosynthesis and what happens to it?

Answer 19

Oxygen is a waste product of photosynthesis and it passes out of the leaves through the stomata.

Question 20

What is the light independent reactions of photosynthesis?

Answer 20

The light independent reactions of photosynthesis also known as the Calvin cycle use enzymes in the stroma along with energy carrying molecules (ATP & NADPH) from the light dependent reactions to break down CO₂ molecules into a form that is used to build glucose. Mitochondria in the plant cells use cellular respiration to break glucose down into ATP. (After the light independent reactions, glucose is often made into larger sugars like sucrose or carbohydrates like starch or cellulose. Sugar leaves the leaf through the phloem and can travel to the roots for storage or to other parts of the plant where it’s used as energy.)

Question 21

What are the 2 types of photosynthesis reactions?

Answer 21

Light dependent & light independent.

Question 22

Where do the light independent reactions take place?

Answer 22

They take place in the stroma of the chloroplast

Question 23

Where do the light dependent reactions take place?

Answer 23

They take place in the thylakoids of the chloroplast.

Question 24

What are the 5 main components of a chloroplast

Answer 24

1. Outer membrane
2. Inner membrane
3. Thylakoids
4. Granum
5. Stroma

Question 25

What is the structure of a chloroplast

Answer 25

Surrounding the chloroplast is a double membrane, consisting of an outer membrane and an inner membrane. This is a similar structure to the double membrane of the Mitochondria.

Interior to the chloroplast’s inner membrane and surrounding the thylakoids is a fluid called the stroma.

The chloroplast’s own genetic material (separate from that of the cell) is also stored in the stroma. The interior of the chloroplast contains another membrane: the thylakoid membrane which is folded into connected stacks of discs. Each disc is a thylakoid and each stack is granum (plural: grana).

Question 26

Where do the light independent reactions take place in DETAIL?

Answer 26

The light independent reactions of photosynthesis take place within the stroma. It contains enzymes that work with ATP and NADPH to “fix” carbon from carbon dioxide into molecules that can be used to build glucose.

Question 27

What does the stroma contain?

Answer 27

Enzymes that work with ATP and NADPH to “fix” carbon from carbon dioxide into molecules that can be used to build glucose.

Question 28

Where do the light dependent reactions take place in DETAIL?

Answer 28

The light dependent reactions of photosynthesis take place within the thylakoids. These reactions occur when the pigment chlorophyll located in the thylakoid membrane, captures energy from the sun (photons) to initiate the breakdown of water molecules.

Question 29

When do the light dependent reactions occur?

Answer 29

When the pigment chlorophyll located in the thylakoid membrane, captures energy from the sun (photons) to initiate the breakdown of water molecules.

Question 30

What is the aim of the light dependent reactions?

Answer 30

The aim of the light dependent reactions of photosynthesis is to collect energy from the sun and break down water molecules to produce ATP and NADPH.

These 2 energy storing molecules are then used in light independent reactions.

Question 31

Within chloroplasts what is chlorophyll and where is it stored?

Answer 31

Within chloroplasts, chlorophyll is the pigment that absorbs sunlight It is stored in the thylakoid membranes in protein complexes called photosystem 1 and photosystem 2.

Question 32

(What is the 1st stage of the light dependent reactions?)
When does the light dependent reactions begin?

Answer 32

The light dependent reactions occur when the pigment chlorophyll captures energy from the sun (photons) to initiate the breakdown of water molecules, to produce ATP and NADPH.

Question 33

What happens when sunlight hits a molecule of chlorophyll located in photosystem 2?

Answer 33

It excites an electron which leaves the chlorophyll molecule, travels along the thylakoid membrane via a series of carrier proteins (known as the electron transport chain). Then photosystem 2 splits a water molecule to restore the lost electron and fill the “energy vacuum” that has been created.

Question 34

(What is the 2nd stage of the light dependent reactions?)
What happens after chlorophyll captures light energy from the sun?

Answer 34

An electron then leaves the chlorophyll molecule & travels along the thylakoid membrane via carrier proteins.

Question 35

(What is the 3rd stage of the light dependent reactions?)
What happens after the electron leaves the chlorophyll molecule?

Answer 35

Then photosystem 2 splits a water molecule to restore the lost electron. Each water molecule breaks down into 2 hydrogen atoms and 1 oxygen atom. The oxygen is released as a waste product.

Question 36

(What is the 4th stage of the light dependent reactions?)
What happens after the water molecules are broken down into hydrogen and oxygen atoms?

Answer 36

The hydrogen ions build up in the lumen of the thylakoid. They then pass through an enzyme called ATP synthase, their movement provides the energy needed to add a 3rd phosphate to ADP to form ATP.

Question 37

(What is the 5th stage of the light dependent reactions?)
What happens after the hydrogen ions pass through ATP synthase and help provide the energy to turn ADP into ATP?

Answer 37

The electron from photosystem 2 then arrives at photosystem 1. Another electron then gets more energy from the sun and passes across the membrane into the stroma, where it joins with a hydrogen ion & an NADP⁺ to create NADPH.

Question 38

(What is the 6th & final stage of the light dependent reactions?)
What happens after the electron arrives from photosystem 2 to 1 and another electron starts moving?

Answer 38

ATP and NADPH then move from the thylakoid into the stroma where the energy stored is used to power the light independent reactions.

Question 39

(What is the 1st stage of the light independent reactions?)
What happens to an enzyme in the Stroma?

Answer 39

An enzyme in the Stroma called ruBisCo combines a 5 carbon molecule of RubP (ribulose bisphosphate) with a molecule of CO₂. This creates a 6 carbon molecule that is broken down into two 3 carbon molecules (3 phosphoglycerate). This is called carbon fixation.

Question 40

(What is the 2nd stage of the light independent reactions?)
What happens after carbon is broken own into 3 phosphoglycerate?

Answer 40

Then the energy carriers: ATP & NADPH from the light dependent reactions each give 3 phosphoglycerate and a hydrogen atom which creates 2 molecules of the simple sugar G3P (glyceraldehyde 3 phosphate). These 2 molecules of G3P are then used to build 1 glucose molecule. This is called reduction.

Question 41

(What is the 3rd stage of the light independent reactions?)
What happens after reduction

Answer 41

The Calvin cycle usually uses 6 molecules of CO₂ at a time. This means that 12 molecules of G3P are generated. However, only 2 are used to produce a glucose molecule. The rest of them are “recycled” back to RubP so that the cycle can begin again.

Question 42

What is the goal of the LIGHT DEPENDENT reaction?

Answer 42

To convert light energy into chemical energy

Question 43

What is the location of the LIGHT DEPENDENT reactions?

Answer 43

Chloroplasts - Thylakoids

Question 44

What is the input of the LIGHT DEPENDENT reactions?

Answer 44

Sunlight, H₂O, NADP⁺ and ADP

Question 45

What is the output of the LIGHT DEPENDENT reactions?

Answer 45

NADPH, ATP and O₂

Question 46

What is the goal of the LIGHT INDEPENDENT reaction?

Answer 46

To use stored chemical energy to “fix” CO₂ & create a product that can be converted into Glucose.

Question 47

What is the location of the LIGHT INDEPENDENT reactions?

Answer 47

Chloroplasts - Stroma

Question 48

What is the input of the LIGHT INDEPENDENT reactions?

Answer 48

CO₂, NADPH and ATP

Question 49

What is the output of the LIGHT INDEPENDENT reactions?

Answer 49

NADP⁺, ADP, G3P (two G3P can be made into C₆H₁₂O₆)

Question 50

Draw the process of photosynthesis in a chloroplast

Answer 50

Insert Picture

Question 51

What are the limiting factors of photosynthesis?

Answer 51

Carbon Dioxide (Increased CO₂ usually means increased rate of PS, BUT only up to a point of maximum then it levels off. Low levels of CO₂=slower rate of PS)

Chlorophyll (It absorbs the red & blue parts of the spectrum of light. In general more light= greater rate of PS. Increasing light intensity will also increase PS, but only up to a certain point. Low level of chlorophyll=low rate of PS)

Temperature

Question 52

What is enzyme activity affected by?

Answer 52

pH
Temp.
Enzyme concentration
Substrate concentration
Product concentration
Enzyme inhibitors

Question 53

What is the palisade layer

Answer 53

Part of a leaf where most chloroplasts are found, most photosynthesis occurs here.

Question 54

What is the definition of photosynthesis

Answer 54

Photosynthesis is the process of converting light energy into chemical energy. It uses water molecules and carbon dioxide molecules to go through a series of reactions to form glucose & a byproduct of oxygen.