Concept 8.4 Summary

Carbon Cycle-Carbon moves from inorganic (carbon dioxide) to organic (sugar) and back.
e.g: 1. producer (grass) >>> photosynthesis >>> organic
2. consumer eats producer >>> organic
3. consumer eats consumer >>> organic
4. both producer & consumer >>> inorganic

*No other chemical process on the planet matches the output of photosynthesis.

Greenhouse effect-CO2 in the atmosphere traps heat from the sun (would otherwise escape from Earth back to space.) >>> Keeps the world climate warm enough for living things.

*The greenhouse effect keeps the average temperature on Earth some 10'c warmer than it would be otherwise.


Concept Check 8.4
1. Give an example of carbon moving from an inorganic compound to an organic compound in the carbon cycle. Give an example of carbon moving from an organic to an inorganic compound.
Plants (producers) produce glucose (organic) through the process of photosynthesis. It uses carbon dioxide (inorganic).
Humans (consumers) release carbon dioxide (inorganic) through te process of respiration, which needs glucose (organic) as the reactant.

2. How is carbon dioxide important to Earth's climate?
Carbon dioxide in the atmosphere traps heat from the sun so that it would not escape from Earth back into space (greenhouse effect).


Vocabulary
Carbon cycle-the process by which carbon moves from inorganic to organic compounds and back.
Greenhouse effect-a property of carbon dioxide which keeps the world climate warm enough for living things.

Concept 8.3 Summary

A cycle=a process in which the starting material is regenerate each time the process occurs.

*The Calvin Cycle=RuBP, the starting material of the process, gets regenerated.

The Calvin Cycle

-input (reactant)=carbon (CO2), energy (ATP), high-energy electrons and hydrogen ions (NADPH)

-output (product)=G3P (energy-rich sugar molecule)

*The plant cell uses G3P as the raw material to make glucose and other organic molecules.

-steps:

(1) 3 carbon molecules (3CO2) enters the cycle, then combines with 3 RuBP molecules, producing 3 six-carbon molecules,

(2) 3 six-carbon molecules break down into 6 three-carbon molecules (3-PGA),

(3) ATP and NADPH from light reactions provide energy and electrons. It results 6 3-PGA

changing into 6 G3P (direct product of photosynthesis),

(4) Carbon (G3P) exits the cycle,

(5) 5 G3P (containing 15 carbon atoms) left in the cycle,

(6) ATP provides energy. It results G3P changing into RuBP,

ADP and NADP+ return to light reactions.

Photosynthesis Summary

-The Light Reactions:

-takes place in the thylakoid membranes

-converts light energy to the chemical energy of ATP and NADPH

-reactant: water

product: oxygen

-The Calvin Cycle:

-takes place in the stroma

-reactant: carbon dioxide

product: sugar (G3P) * uses ATP and NADPH from the light reactions.

Concept Check 8.3

1. Where are the inputs and outputs of the Calvin cycle?

The inputs are carbon dioxide, ATP and NADPH.

The outputs are sugar molecules (G3P).

2. Which stage of photosnthesis uses each reactant from the overall photosynthesis equation? Which stage generates each product from the overall photosynthesis equation?

The light reactions use water, and generate oxygen.

The Calvin Cycle uses carbon dioxide, and generates sugar (glucose).

3. Why is the Calvin cylce called a cycle?

Because it has a starting material, RuBP (a sugar with five carbons), that gets regenerated each time the Calvin cycle process occurs.

4. What molecule is the direct product of photosynthesis? How is that molecule then used by plant cells?

The direct product of photosynthesis is G3P. It is used by plant cells to make glucose and other organic compounds.

Concept 8.2 Summary

Wave lengths (the distance between two adjacent waves) that are shorter than those of visible light (400nm~700nm, seen as different colours by the eyes) can damage organic molecules such as proteins and nucleic acids.

*Being exposed to UV, which has shorter wavelengths than those of visible light, can cause sunburns and lead to skin cancer.

A substance's color is due to chemical compounds called pigments. When light shines on a material that contains pigments, three things can happen to the different wavelengths: absorbed, transmitted, or reflected.

*Leaves look green-because they don't absorb green light.
-they only absorb blue-violet and red-orange light.

Photosystem
-a cluste containing chlorophyll and other pigment molecules, including chlorophyll a, chlorphyll b, and carotenoids.
-steps: 1. One of the pigment's electrons gains energy when a pigment molecule absobs light energy --> the electron is raised from a low-energy "ground state" to a high-energy "excited state"
2. The excited electron falls back to the ground state.
3. It then transfers the energy to a neighbouring molecule.
4. It excites an electron in the receiving molecule.
5. The electron falls back to the grand state.
6. The energy is transferred in this way, until it reaches the reaction center of the photosystem.
*The reaction center consists of a chlorophyll a molecule and a primary electron acceptor.
7. The primary electron acceptor traps the excited electron from chlorophyll a.
8. Other teams of molecules built into the thylakoid membrane can now use that trapped energy to make ATP and NADPH.

The Steps of the Light Reactions:
1. The first photosystem="water-splitting photosystem"
-traps light energy, and tranfers the light-excited electrons to an electron transport chain.
-releases oxygen (waste product), releases H+.

2. The electron transport cain="connection" between two photosystems
-releases energy, which the chloroplast uses to make ATP.

*It's really similar to the one in cellular respiration.
-similarity: an electron chain pumps H+ across a membrane-inner mitochondrial
-thylakoid membrane
-main difference: -in respiration, food provides electrons for the electron transport chain.
-in photosynthesis, light-excited electrons from chlorophyll travel down the chain.

3. The second photosystem="NADPH-producing photosystem"
-produces NADPH by transferring excited electrons and H+ to NADP+.

Concept Check 8.2:
1. Explain why a leaf appears green.
Because the pigments in the leaf's chloroplasts transmit or reflect the green light, not absorbing it.

2. Describe what happens when a molecule of chlorophyll a absorbs light.
The excited electron then transfers the energy to the chlorophyll a molecule, which then transfers its excited electron to the primary electron acceptor. Then, the light reaction goes on.

3. Besides oxygen, what two molecules are produced by the light reactions?
ATP and NADPH.

4. Where in the chloroplast do the light reactions take place?
In the membrane of thylakoids.

Vocabulary
wavelength-the distance between two adjacent waves
electromagnetic spectrum-the range of types of electromagnetic energy from the very short wavelengths of gamma rays to the very long wavelengths of radio waves
pigment-a chemical compound which a substance's colour is due to
paper chromatography-a laboratory technique in which you could observe the different pigments in a green leaf
photosystem-a cluster which within the thylakoid membrane, chlorophyll and other molecules are arranged in

Concept 8.1 Summary

Chloroplast-the cellular organelle where photosynthesis takes place

*The leaves contain the most chloroplasts and are the major sites of photosynthesis:

1. the chloroplasts are concentrated in the cells of the mesophyll

2. carbon dioxide enters and oxygen exits the leaf through the stomata (located on the surface)

3. Veins carry water and nutrients from the roots to the leaves. They also deliver organc molecules produced in the leaves to other parts of the plant.

*Some of the steps of photosynthesis take place in the thylakoid membranes, while others take place in the stroma.

1. The Light Reactions (takes plae in thylakoids' membranes)-
-converts the sunlight energy to chemical energy
-steps: 1. chlorophyll molecules (in the membrane) capture light energy
2. the chloroplasts use the captured energy to remove electrons from water
--> it splits H2O into O2 and H+
3. O2 goes out into the atmosphere through the stomata
4. the chloroplasts use electron and H+ to make NADPH
5. the chloroplasts use the captured enrgy to generate ATP
*NADPH is an electron carrier, similar to NADH, an energy-rich molecule.
-results=light energy-->chemical energy-NADPH
-ATP

2. The Calvin Cycle (takes place in the stroma)-
-makes sugar from the atoms in CO2 and H+ and high-energy electrons in NADPH
-the enzymes for the cycle are outside the thylakoids and dissolved in the stroma

Concept Check 8.1

1. Draw and label a simple diagram of a chloroplast that includes the following structures: outer and inner membranes, stroma, thylakoids.

2. What are the reactants for photosynthesis? What are the products?

Reactants: CO2, H2O

Products: C6H12O6, O2

3. Name the two main stages of photosynthesis. How are the two stages related?

The light reaction, and the Calvin cycle.

The Calvin cyce process needs the supply of ATP and NADPH from the light reaction process, in order to make sugar.

Vocabulary 8.1

Chloroplast-the cellular organelle where photosynthesis takes place

Chlorophyll-chemical compounds inside chloroplasts that give these organelles a green colour

Stroma-a thick fluid enclosed by the inner membrane of a chloroplast

Thylakoid-a disk-shaped sac suspended in the stroma

Light reaction-a process that converts te energy in sunlight to chemical energy

Calvin cycle-a process that makes sugar from the atoms in carbon dioxide plus the hydrogen ions and high-energy electrons carried by NADPH

Ch. 6 Vocabulary words

Organelle-meaning "mini-organ"; each part of a cell with a specific job to do
Plasma membrane-a thin outer covering of both animal and plant cells, and it defines the boundary of the cell and regulates the traffic of chemicals between the cell and its surroundings.
Nucleus-houses the cell's genetic material in the form of DNA
Cytoplasm-the entire region of the cell between the nucleus and the plasma membrane; consists of various organelles suspended in a fluid
Cell wall-protects the plant cell and maintains its shape
Prokaryotic cell-lacks a nucleus and most other organelles; includes bacteria and another group of organisms called the archaea
Eukaryotic cell-has a nucleus surrounded by its own membrane, and has other internal organelles bounded by membranes; protists, fungi, plants, and animals consist of eukaryotic cells
Diffusion-the net movement of the particles of a substance from where they are more concentrated to where they are less concentrated
Equilibrium-balance
Selectively permeable membrane-allows some substances to cross the membrane more easily than others and blocks the passge of some substances altogether.

Chapter 5 Review

1. Which of the folloing is not an organic molecule? c. water
2. Which of the following terms includes all the other terms on this list? a. polysaccharide
3. Which term is most appropriate to describe a molecule that dissolves easily in water?
c. hydrophilic
4. Cholesterol is an example of what kind of molecule? b. lipid
5. The 20 amino acids vary only in their c. amino groups
6. A specific reactant an enzyme acts upon is called the d. substrate
7. An enzyme does which of the following? b. lowers the activation energy of a reaction
Short Answer
8. Besides satisfying your hunger, why else might you consume a big bowl of pasta the night before a race?
Because pasta contains fat and starch, which is a good source of energy for storage.
9. How are glucose, sucrose, and starch related?
Starch is made up of glucose monomers. Sucrose consists of glucose and fructose.
10. What are steroids? Describe two functions they have in cells.
A steroid is a lipid molecule in which the carbon skeleton forms four fused rings. Two steroid hormones: Testosterone and estrogen contribute to major differences in the appearance and behavior f male and female mammals.
11. How are polypeptides related to proteins?
Proteins are composed of one or more polypeptide chains.
12. How does denaturation affect the ability of a protein to function?
The polypeptide chains become tangled up with one another. Heating unfolds proteins because most of the forces that maintain folding are weak attractions between pairs of side group, an between side groups and water. Since a protein's function depends on its shape, a protein that becomes denatured and loses its shape also loses its ability to work properly.

14. Analyzing Diagrams
a. One product of this reaction is represented by a question mark. Which molecule is it?
Water
b. What is this kind of reaction called? Explain.
Dehydration reaction. When a monomer is added to another monomer, a water molecule comes out.
c. If an amino acid were added to this chain, at what two places could it attach?

15. Analyzing Graphs
a. At which temperature does enzyme A perform best? Enzyme B?
38 degrees. 78 degrees.
b. Knowing that one of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria, hypothesize which enzyme came frm which organism.
Enzyme A came from humans and enzyme B came from thermophilic bacteria.
c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40 degrees.
Because every enzyme have different conditions in which they work the best. Enzyme A may not work well after 40 degrees.

Concept 5.5 Summary

To start a chemical reaction, it is first necessary to weaken chemical bonds in the reactant molecules.

*When you start a chemical reaction, you need to provide "start-up" energy called activation energy in order to activate the reactants and trigger a chemical reaction.

Ways to provide activation energy:

1. heat up the mixture of molecules

-hotter molecules may collide with enough energy to weaken bonds

-cooler molecules colide with less energy

*BUT, heating up a cell would cause many unnecessary reactions to occur at once. (and some of them will destroy the cell's delicate structures.)

2. Using enzymes

-enzymes let reactions to occur at the cell's normal temperature (unlike heating up the molecules.) by lowering the energy requirement barrier. It means that the reaction needs less activation energy.

*Enzymes don't supply activation energy to the reacting molecules.

Enzyme-the main catalysts of chemical reactions in organisms

*catalysts-compounds that speed up chemical reactions

-specialized proteins

-each enzyme catalyzes a specific kind of chemical reaction.

-each catalyze only one type of reaction because te shape of each enzyme fits the shape of only particular reactant molecules.

Substrate-a specific reactant acted upon by an enzyme.

Active site-a particular region of the enzyme where it's substrate fits into.

-A substrate binds to an enzyme at an active site. The enzyme-substrate interaction lowers the activation energy required for the reaction to proceed. In this example, water is added to the weakend bond insucrose, breaking sucrose into glucose and fructose.

Concept Check 5.5

1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?

Activation energy activates the reactants and triggers a chemical reaction. An enzyme let a molecule need less active energy to proceed a reaction by lowering the active energy requirement barrier in the molecule so that the reaction can proceed at normal cell temperatures.

2. Descrbie how a substrate interacts with an enzyme.

As the substrate enters, the active site changes shape slightly, fitting the substrate more snugly. ths places certain functional groups of the active site in position to catalyze the reaction. The tighter grip may also bend the substrate, weaening its bonds.