End of year

Concept 8.2 The light reactions convert light energy to chemical energy

Key terms:

• wavelength: distance between adjacent waves
  
• electromagnetic spectrum: range of types of electromagnetic energy from gamma waves to radio waves
  
• pigment: chemical compound that determines a substance's color
  
• paper chromatography: laboratory technique used to observe the different pigments in a material
  
• photosystem: cluster of chlorophyll and other molecules in a thylakoid
  

Light:

• Sunlight form of electromagnetic energy
  
• Electromagnetic energy travel in waves
  
• Forms of electromagnetic energy different wavelength
  
• From short gamma rays to long radio waves, electromagnetic spectrum
  
• Visible light make short part of spectrum, 400 to 700 nm
  
• Short wavelegnths more energy
  
• Waves longer visible light damage C-molecules, protein, nucleic acid, etc
  
• Thus, sunburn and skin cancer
  

Pigment:

• Substance color determined by pigment, chemical compound
  
• Light shines pigment, absorbed, transmitted, or reflected
  
• Chloroplast convert some trapped energy into chemical energy
  
• Pigment in chloroplast well absorb blue-violet, red-orange
  
• Green mostly bounces back
  
• Thus, leaves look green
  

Identify chloroplast pigments:

• Use paper chromatography
  
• Stain filter paper with leaf
  
• Seal paper in cylinder with solvents, in vented lab hood
  
• Solvents move up paper strip, pigments dissolve and move up
  
• Different pigments travel different speed, dissolve and cohesive to paper
  
• Chlorophyll alpha mostly blue-violet, red, reflect green major in light reactions
  
• Chloroplast include helper pigments
  
• chlorophyll beta, mostly blue, orange, reflect yellow-green
  
• carotenoids, mostly blue-green, reflect yellow-orange
  

Absorbing light energy:

• Photosystems in thylakoid membrane, each contain few hundred pigment molecules
  
• Photosystem act like light-gathering panel
  
• When pigment absorb light energy, e- gain energy, excited
  
• Excited state unstable
  
• Almost immediately, e- back to ground state by transfer energy to near molecule
  
• Thus energy jumps from molecule to molecule, arrive at reaction center of photosystem
  

Reaction center:

• Consist chlorophyll alpha molecule next to primary e- acceptor
  
• Primary e- acceptor is molecule traps excited e- from chlorophyll alpha
  
• Other molecules in thylakoid membrane can use trapped energy make ATP and NADPH
  

Chemical products of light reactions:

• One photosystem split water, other make NADPH
  
• O2 released as H2O split recover e- sent to e- transport chain
  
• p+ also released
  
• e- transport pump p+ into thylakoid
  
• e- make NADP+ NADPH
  
• p+ pump through ATP synthase, across thylakoid membrane, make ATP
  
• Cellular respiration food provide e-, photosynthesis light-excited e- from chlorophyll
  
• NADP+ plus e- and p+ make NADPH
  

Concept Check 8.2

1. Explain why a leaf appears green.

Chlorophyll alpha do not absorb green light

2. Describe what happens when a molecule of chlorophyll a absorbs light.

e- excited, transfers e- to next molecule to primary e- acceptor.

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?

Inside and in the membrane of the thylakoid.

Concept 8.1 Photosynthesis uses light energy to make food

Key Terms

• chloroplast: organelle found in some plant cells and certain unicellular organisms where photosynthesis takes place
  
• chlorophyll: pigment that gives a chloroplast its green color; uses light energy to split water molecules during photosynthesis 
  
• stroma: thick fluid contained in the inner membrane of a chloroplast
  
• thylakoid: disk-shaped sac in the stroma of a chloroplast; site of the light reactions of photosynthesis
• light reactions: chemical reactions that convert the sun's energy to chemical energy; take place in the membranes of thylakoids in the chloroplast
  
• Calvin cycle: cycle in plants that makes sugar from carbon dioxide, H+ ions, and high-energy electrons carried by NADPH

Photosynthesis feature:

• Photosynthesis takes place chloroplast
  
• Chlorophast contain chlorophyll, make green
  
• Leaves are major site of photosynthesis
  

Structure of a leaf:

• In a leaf, chloroplast concentrated in mesophyll
  
• Stomata (stoma) on surface of leaf
  
• CO2 enter and O2 exit through stomata
  
• Veins branch in leaf, deliver produce of leaf to other parts
  

Structure of chloroplast:

• Inner and outer membrane
  
• Inner holds thick fluid, stroma
  
• Stroma suspend thylakoid, disk-shaped stacked in grana (granum)
  
• Chemical reactions in thylakoid membrane or stroma
  

Photosynthesis:

• Cellular respiration of falling e-
  
• Photosynthesis rise of e-, by energize sunlight
  
• Chloroplast use excited e- and p+ to produce glucose
  
• Of light reactions and Calvin cycle

Light reactions:

• Convert energy of sunlight to chemical energy, NADPH and ATP
  
• Need molecules in membrane thylakoid
  
• Chlorophyll molecules in membrane capture light energy
  
• Chloroplast use energy remove e- from H2O, waste O and p+
  
• O2 leave through stomata
• Left e- and p+ used make NADPH, e- carrier similar NADH
  
• Chloroplast also use energy make ATP
  

Calvin cycle:

• Make sugar from CO2, p+, e- from NADPH
  
• Enzymes for Calvin cycle outside thylakoid, dissolved in stroma
  
• ATP made by light reaction used make sugar
  
• AKA "light-independent reactions," not directly need light
  

Concept check:

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 and H2O, products glucose and O2.

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

Light reactions and Calvin cycle, supply chain. Calvin cycle requires energy produced during the light reactions. Both work together to make glucose for cellular respiration.

Chapter 5 Review Questions # 1-12, 14, 15

Reviewing Concepts
Multiple Choice
Choose the letter of the best answer.

1. Which of the following is not an organic molecule?
a. cellulose
b. sucrose
c. water
d. testosterone

2. Which of the following terms includes all the other terms on this list?
a. polysaccharide
b. carbohydrate
c. monosaccharide
d. glycogen

3. Which term is most appropriate to describe a molecule that dissolves easily in water?
a. hydrocarbon
b. hydrophobic
c. hydrophilic
d. organic

4. Cholesterol is an example of what kind of molecule?
a. protein
b. lipid
c. amino acid
d. carbohydrate

5. The 20 amino acids vary only in their
a. carboxyl goups.
b. side groups.
c. amino groups.
d. lipid groups.

6. A specific reactant an enzyme acts upon is called the
a. catalyst.
b. sucrase.
c. active site.
d. substrate.

7. An enzyme does which of the following?
a. adds heat to a reaction, speeding it up
b. lowers the activation energy of a reaction
c. cools a reaction, slowing it down
d. raises 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?

One might eat pasta before a race to consume starch, long chains of glucose. Out of the many forms of carbohydrates, monosaccharides are the shortest, allowing them to take the least time to digest. Eating pasta before a race will enable you to consume the energy from glucose broken down fairly quickly - not running out of energy during the race.

9. How are glucose, sucrose, and starch related?

All three contain glucose monomers. Glucose is glucose, sucrose is glucose and fructose, and starch is many glucose in a chain.

10. What are steroids? Describe two functions they have in cells.

Steroids can circulate in one's body as chemical signals and is used in creating cell membranes.

11. How are polypeptides related to proteins?

Polypeptides are chains of many many amino acids linked, what makes up proteins, too.Proteins are composed of one or more polypeptide chains.

12. How does denaturation affect the ability of a protein to function?

Denaturation being the distortment in shape of a protein by heat or other factors, the protein cannot work to its original purpose or function. Function of proteins are determined by shape.

Applying Concepts
Analyzing Information
14. Analyzing Diagrams The reaction below shows two amino acids joining together.
a. One product of this reaction is represented by a question mark. Which molecule is it?

The product be H2O, or water.

b. What is this kind of reaction called? Explain.

It is called a dehydration reaction because a water molecule is formed during the reaction and falls separate with the lump of combined molecules, making the combined molecules minus one potential water molecule.

c. If an amino acid were added to this chain, at what two places could it attach?

15. Analyzing Graphs Use the graph to answer the ques

tions below.
a. At which temperature does enzyme A perform best? Enzyme B?

The rates of reactions are highest for enzyme A just before 40'C and just before 80'C for enzyme B.

b. Knowing that one of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria, hypothesize which enzyme came from which organism.

Knowing enzymes are used to allow chemical reactions to happen at average temperatures to their host, enzyme A is probably in humans, and enzyme B, in thermophilic bateria.

c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40°C.

If the cell of enzyme A exceeds 40'C, then its cell wall we deteoriate.

Summary of Textbook Section 5.5

Assignment:
Write a summary of 5.5

Section 5.5: Enzymes are proteins that speed up specific reactions in cells

Key Terms:

• activation energy: minimum amount of energy required to trigger a chemical reaction
• catalyst: agent that speeds up chemical reactions
• enzyme: specialized protein that catalyzes the chemical reactions of a cell
• substrate: specific reactant acted on by an enzyme
• active site: region of an enzyme into which a particular substrate fits

Chemical reactions and activation energy:

• chemical reactions require bond of reactants to weaken -> apply energy
• specific amount of energy required to trigger reaction is activation energy
• one way of applying energy is heating
• heating causes many undesired reactions in organisms, including break down cell wall

Function of enzymes:

• in cellular reactions, use catalysts to speed up reactions
• main catalyst are enzymes, which lower activation energy
• thus allow reactions without heat, at normal temperature
  
• enzymes specialized for specific reaction

Workings of enzymes:

• enzymes physically fit substrates, adjust size to fit well
• thus placing certain functional groups to react
• or physically placing closely just helps
  
• tighter grip bends substrate -> weakens bond
• enzymes can be used many times

Concept check:

1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy? The activation energy is the amount of energy needed to trigger the reaction. Without reaching the activation energy, reactions can't take place. Enzymes catalyze this process by lowering the amount of energy required to activate the reaction.
   
2. Describe how a substrate interacts with an enzyme. Substrates fit into the active sites of enzymes, areas specifically designated for placing substrates. Once there, the enzyme adjusts the size of the active site to fit the substrates tightly, weakening the original chemical bonds. After that, substrates interact with each other as usual, just at a lower temperature than usual. Substrates leave then the process is finished and the enzyme waits for other substrates.
   

Summary of Textbook Section 5.4

Assignment:
Write a summary of 5.4

Section 5.4: Proteins perform most functions in cells


defining key terms

• protein: polymer constructed from a set of 20 amino acid monomers
• amino acid: monomer that makes up proteins; contains carboxyl and amino functional groups
• polypeptide: chain of linked amino acids
• denaturation: loss of normal shape of a protein due to heat or other factor

Functions of proteins

• vital in life
• form hair and fur
• make up muscles
• long-term nutrient storage
• circulate in blood, defend body
• conveying cellular messages
• controls chemical reactions of cell

Amino acids structure

• central carbon atom w/ 4 bonds
• 3 of 4 bonds same between all amino -> H, amino group, carboxyl group
• last link called "R-group"
• R-group is responsible for chemical properties of amino acid

image from: http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter5/concept5.4.html

Protein structure

• one or more chain of amino acids
• links created by dehydration reaction of amino and carboxyl groups of each amino
• huge variety by differing orders of aminos

20 amino acids kinds, 100 amino in protein chain

image from: http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter5/concept5.4.html

Factors of protein shape

• a single protein not much use, functional when one or more polypeptides precisely twisted, folded, coiled into unique shape
• not clear how protein bends with such precision
• sequence of amino acids are important -> bonds of differing side groups, holds polypeptide together
• influenced by surrounding -> if aqueous, hydrophilic aminos parts surround, hydorphobic amino parts cluster in center
• denaturation, protein loses shape and tangled with other chain because heat, pH, etc
• some links of amino parts weak, heat colliding, takes apart
• function of protein being by shape, denaturation render protein useless
  

image of protein
image from: http://www.epobio.net/photos/protein_structure.jpg

Concept check:

1. 2 examples of proteins you can see in the world around you. Well, protein itself would be too small to see by itself. However, if you refer to visible objects formed by protein, two examples would be human hair and dog fur. If you'd like to group them together, I recommend dissected flog muscle tissue. Of course, the species are of your choice.
   
2. Relate amino acids, polypeptides, and proteins. A protein is a polymer of 100 amino acids linked together, and a polypeptide the unit in which protein gets useful. Polypeptides are protein chains twisted and coiled.
   
3. How can heat destroy protein? Protein being amino acids connected by the relatively weak bonds of the amino and carboxyl group on the ends of aminos acids, heat colliding with the weak links can break them apart; thus, rendering the protein useless towards its original purpose.
   
4. Similar and dissimilar parts in amino acids? Amino acids share the central C atom, along with the H and amino and carboxyl functional groups. The differing part is the R-group.

Summary of Textbook Section 5.3

Assignment:

Write a summary of 5.3

Section 5.3: Lipids include fats and steroids

defining key terms:

• lipid: "one if a class of water-avoiding compounds" (Campbell, 826)
• hydrophobic: "avoids water molecules" (Campbell, 825)
• fat: "organic compound consisting of three-carbon backbone (glycerol) attached to three fatty acids" (Campbell, 823)
• saturated fat: "fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms" (Campbell, 830)
• unsaturated fat: "fat with less than the maximum number of hydrogens in one or more of its fatty acid chains" (Campbell, 832)
• steroid: "lipid molecule with four fused carbon rings" (Campbell, 830)
• cholesterol: "steroid molecule present in the plasma membranes of animal cells" (Campbell, 821)

Lipids

• hydrophobic
• act as boundary surrounding aqueous material in cell (traps water)
  
• or circulate body as chemical signals
• or store energy -> fatimage from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/hydropho.htm
  

Fats

• structure with backbone of glycerol, has 3 chains, each with fatty acids protruding
• functions: energy, insulation, cushion organs
• if uses max number of H, CH single bonds and extra H, saturated
• if uses CH double bond, unsaturated
• unsaturated: fruits, vegetables, fish (e.g. olive and corn oil)
• saturated fat unhealthy, builds plaque in blood vessels -> reduce blood flow and increase heart disease

image from: http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter5/concept5.3.html

Steroids

• structured as 4 carbon skeleton rings and 2 functional groups on each end
• differing locations and types of functional groups
• are lipids and hydrophobic, but different from fat
• functions: chemical signals, surround water in cells

Types of steroids

• estrogen: female sex hormone
  
• testosterone: male sex hormone
  
• cholesterol: raw material for other steroids, can increase risk for cardiovascular disease
  

image from: http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter5/concept5.3.html

Concept check:

1. Property of lipids? All lipids are hydrophobic.
   
2. Parts of a fat molecule? Fat molecules "[consist] of three-carbon backbone (glycerol) attached to three fatty acids" (Campbell, 823).
3. Differences of steroids and fats? Steroids consist of 4 fused carbon rings, while fat consists of 3-carbon backbones attached to 3 fatty acids. Steroids are used as chemical signals and surround water in cells, while fat stores energy.
   
4. Meaning of unsaturated fat on food labels? Unsaturated fat has "less than the maximum number of hydrogens in one or more of its fatty acid chains" (Campbell, 832). Unsaturated fat is often healthier than saturated fat, and would be used to indicate vegetable oils on food labels.