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Laboratory Exercise 5 Photosynthesis and Cellular

Laboratory Exercise #5

Photosynthesis and Cellular Respiration I. Introduction

All organisms, except for a few types of chemosynthetic bacteria, are ultimately dependent upon photosynthesis for their source of food. Photosynthesis is a photo-biochemical process that converts light energy into chemical energy by utilizing water and carbon dioxide to produce sugar, usually glucose, while releasing oxygen gas as a by-product. Light energy is trapped by the plant pigment molecules known as chlorophylls, xanthophylls, and carotenes. The sugar molecules made by photosynthesis may be used by the plant cells for energy production in the process of cellular respiration or may be converted to starch, cellulose, fats, amino acids, and other molecules, which may be used in function, structure, or stored for later use. These molecules of the plant cell may serve as food for other organisms such as animals or microbes.

Several types of organisms carry out photosynthesis and are thus self-feeding, or autotrophic. These include cyanobacteria, protistans, and plants. Perhaps the most noticeable photosynthetic organisms are the seed plants, many of which we are dependent on for food, shelter, clothing, and medicines. Most seed plants carry out photosynthesis in specially adapted organs known as leaves. Photosynthesis is a very complex multi-step process that can be represented by the following equation:

Light

6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O

Energy is the ability to do work. Energy comes in many forms: heat, light, electrical, mechanical, chemical, and nuclear. All living organisms use energy for movement, for heat production, for active transport, for growth, and for reproduction. In fact, one of the most basic activities of a cell is the transformation of energy from less useful forms to more useful forms. During photosynthesis, energy from sunlight is stored in sugars. During cellular respiration, sugar molecules are oxidized (broken down) and energy is released. All living things get their energy by cellular respiration. In your body, reactions that release energy occur within the cytoplasm and in the mitochondria of your cells. Cellular respiration can be represented by the following generalized equation:

C6H12O6 + O2→ CO2 + H2O + ATP + Heat

Activity #1: Leaf Transverse Sections

1.Examine a prepared slide of transverse sections of a leaf with the 4X, 10X, and 40X

objectives. Notice how the cells of each area are different in size, shape, and

arrangement. The upper or dorsal leaf surface facing the sun will have a single layer

of cells that have an external protective waxy coating, the cuticle, which protects the

leaf from water loss. The upper epidermal cells do not contain chloroplasts.

2.Immediately under the upper epidermis you will find an array of rectangular cells

called the palisade mesophyll, which contains chloroplasts. The palisade mesophyll

cells are tightly packed together along their axis so as to efficiently trap light. The

lower part of the leaf is composed of a loosed array of spongy mesophyll cells

among which are air spaces for gas and water vapor movement. Spongy mesophyll

cells contain chloroplasts. At intervals in the mesophyll region you will find leaf

veins, which are part of the plant’s vascular apparatus. Because the leaf veins run in

various directions, you may see cross, longitudinal, or tangential sections. Leaf veins

are composed of xylem and phloem cells. Xylem cells are usually stained red and

are located on the upper side of the vein toward the palisade mesophyll layer. Xylem

cells have an extra thick cell wall and are empty and dead at time of maturity. The

function of the xylem is to transport water and mineral ions to upward in the plant

from the roots to the leaves. In addition, xylem provides structural support for the

entire plant. Xylem helps keep the leaf blade expanded for absorption of sunlight,

and large masses of xylem, called wood, keep the stem and branches upright. Below

the xylem in the vein will be a number of smaller, thin walled cells, the phloem.

These living cells transport products of photosynthesis in all directions throughout the

plant. The lower or ventral side of the leaf has a single layer of epidermal cells called

the lower epidermis. It also has stomata. Stomata consist of two guard cells,

containing a few chloroplasts that surround a tiny opening, the stoma. The guard

cells can open and close the stoma. When the stoma is open, carbon dioxide for

photosynthesis diffuses into the mesophyll while oxygen and water vapor diffuse out.

3.Sketch the leaf cross section and label the structures in boldface.

Photosynthesis: An organic endothermic reduction reaction

When a leaf makes sugar the sugar is converted into starch almost immediately. The starch is stored right on the membranes of the chloroplasts in which its glucose subunits were made. Thus, a positive starch test indicates that sugar had been made by photosynthesis. We will use iodine as an indicator for the presence of starch and thus and indicator that photosynthesis did occur.

Activity #2: Determining that light is necessary for photosynthesis.

Geranium leaves were partially covered with a piece of cardstock with holes cut into it and then put in the dark overnight to “destarch”.

1)What does this mean?

______________________________________________________________________________ The plants were then put into high intensity light.

2)What process will happen?

________________________________________________________________________

3)What products will be made?

and

(2) Take a leaf covered with cardstock. Before removing the cardstock, draw a picture of the leaf showing the placement of the hole.

A.Remove cardstock.

B.Boil leaf in water until limp, about 2 minutes. DO NOT over boil.

C.Boil the same leaf in ethyl alcohol. BE CAREFUL! Alcohol boils at a much

lower temperature than water. Turn your hot plate down to simmer and do not let

the alcohol boil away. What color does the leaf turn?

What color(s) does the alcohol turn?

Chlorophyll is soluble in alcohol but not in water. Boiling the leaf in water breaks

up the cells. Boiling the leaf in alcohol removes the chlorophyll from the leaf.

That is why the alcohol turns green.

D.Put the leaf into a Petri dish and put iodine on it. Remember that a positive starch

test is a dark color. (It might look more dark brown that blue-black.) Do you see

a darker spot? Draw a picture of the leaf indicating the spot. Does the placement

of the spot correspond to the original hole in the tin foil? You have proved that

is necessary for photosynthesis.

Acitivty #3 (optional): Determining that chlorophyll is necessary for photosynthesis

If a plant needs light, it must have a way of absorbing it. Pigments are molecules that absorb some colors of light and reflect others. White light is made of all the colors of the spectrum. The pigment chlorophyll is green because it reflects green light and absorbs red and blue light. The chlorophyll molecules are on the grana membranes inside the chloroplasts, but chlorophyll isn’t the only pigment found in plants. Carotenes are yellow to orange.

Xanthophylls are yellow. Anthocyanins are red, pink, blue, or purple. Carotenes and xanthophylls are also found in plastids. Anthocyanins are found in the plant cells’ large central vacuole.

A. Pick a leaf from either a variegated Coleus or Geranium.

A.Draw the leaf, labeling the exact placement of the different colors. Which parts of the

leaf contain chlorophyll? Which do not contain chlorophyll? Can you see other

pigments? Where are they located?

B.Boil the leaf in water until limp. Remove it and draw it, noting any color change.

Did any of the colors leach out?

C.Boil the leaf in ethyl alcohol. Draw it again, noting other color changes.

D.Now, put the leaf into a Petri dish and put iodine on it. Any area that turns dark

contains starch. Draw the leaf, indicating the areas of positive starch.

E.The areas of starch correspond to which original pigment areas?

This experiment proves that is necessary for photosynthesis.

Activity #5: Separation and Identification of Leaf Pigments

The technique of chromatography is used widely to separate the individual components of a mixture of related substances – for example a mixture of amino acids, or one of sugars. The term “chromatography” refers to the fact that after separation, the individual substances may be visualized as spots of color, either because of their own natural color, or more commonly by causing them to react with reagents to yield a colored product. The first step in a chromatographic procedure is to apply a variety of substances to a supporting medium (i.e. chromatography paper). A suitable solvent is then used to move through the medium, and carries with it the mixture of components to be separated. Different components of the mixture travel at different speeds, depending on their affinity for the medium and their solubility in the solvent.

One of the simplest chromatographic techniques is that of paper chromatography, in which the supporting medium is filter paper. In today’s laboratory you will separate plant pigments by paper chromatography. The predominant pigment in the leaves of green plants is chlorophyll, which occurs in two slightly different chemical forms called chlorophyll a and chlorophyll b. Most leaves contain at least two additional types of pigments, carotenes and xanthophylls, which are ordinarily not visible because they are masked by the more abundant chlorophyll.

Paper Chromatography Procedure:

A.Pigment Extraction. The leaf extract will be supplied to you. Or you may

collect leaf samples of your choice (directions given in the following section).

B.Setting up the Chromatography “Chamber”. Study the apparatus shown in Figure

5-1. You will use a large test tube as a chromatography chamber. The tube will

be sealed by means of a rubber stopper which has a wire hook attached. The filter

paper holding the pigment sample to be separated (directions given in the

following section) will be suspended from the hook so that the tip of the paper

dips into the solvent, but none of the pigment is in the solvent.

C.Add solvent (9 parts petroleum ether: 1 part acetone) to a depth of approximately

? cm to the chromatography chamber. Stopper the tube tightly, and place it an

upright position in a clamp attached to a ring stand or in a flask. Allow the tube

to stand while you prepare the paper. During this time the air in the tube will

become saturated with solvent vapor.

Rubber Stopper

Hook

Solvent Front

Separated Pigments

Solvent

Figure 5-1 Paper Chromatography Apparatus (courtesy, G.B. Reid)

D.Preparation of Chromatography paper.

1.Obtain a strip of Whatman #1 filter paper for use as your chromatogram.

Handle the chromatography paper only by its edges, as oils and

perspiration from your fingers can interfere with movement of the

substances on the chromatogram.

2. Place the strip on a clean sheet of ordinary paper and mark a line with a

pencil about 2cm from the tip. Do not use ink (Why not?)

3.Place your leaf sample at the bottom of the strip and use a ruler to mark 2

cm from the bottom.

https://www.wendangku.net/doc/504637853.html,ing a coin with a serrated edge, press down firmly and roll along the

ruler edge several times to form a definite green line. Shift to a fresh area

of the leaf and repeat several times until the pencil line is covered

completely with a narrow green band. Allow to dry.

5.Dispense 2mL of chromatography solvent in the large chromatography

test tube.

6.Hold your chromatography paper next to the stoppered test tube

containing the solvent. Try to determine the exact point at which the wire

should be inserted into the paper strip so that the tip of the strip will just

reach the solvent. Make a small hole in the paper strip at this location.

7.Remove the stopper from the test tube containing the solvent. Insert the

hook through the upper end of the paper strip into the hole you made.

8.Carefully lower the chromatography paper into the test tube until the tip

touches the solvent. Do not allow the solvent to touch the green line.(The

strip should be positioned on the hook in such a way that when suspended

inside the tube, no part of the strip touches the side of paper.)

9.When the pigments have separated into distinct bands, lift the paper out of

the tube.

E.“Developing” the Chromatogram. The solvent will move rapidly up the paper

by capillary action. In its upward movement pass the pigment spot, the solvent

will carry the pigments with it. However, because of their varying affinities for

the paper, as well as different solubilities in the solvent, the different pigments

will be carried different distances, and will be seen on the paper as irregular

“spots” or bands of color

Remove the paper strip from the tube when the solvent is approximately 2 cm

below the hook from which the chromatogram is hanging. With a pencil, quickly

mark the distance traveled by the solvent through the chromatography paper

This is called thesolvent front. Delay will allow the solvent to evaporate and the

solvent front will no longer be visible. As soon as the paper is dry, outline each

region of pigment with pencil as faint spots fade.

DO NOT POUR THE SOLVENT INTO THE SINK! Return it instead to the

“Waste Solvent” container.

F.Identification of Pigments.The distance the pigment molecules travel through

the chromatograp hy paper, called the “relative front” or, is relative to the distance

traveled by the solvent front. In the solvent system which you used, the golden

pigment called carotenes move the fastest and appear near the top of the solvent

front. In some leaves this pigment is followed in turn by a lighter band of paler

yellow xanthophyll. Some chromatograms may contain bands of grayish leaf

break-down products in the region of the xanthophylls. These can be ignored. A

band of chlorophyll a lies below the xanthophyll layer. This band is followed by

chlorophyll b. Some leaf specimens may contain a water-soluble pigment

called anthocyanin that shows at the base of the chromatogram. Besides their

location on the chromatogram, pigments can be identified by their characteristic

colors:

PIGMENT CHARACTERISTIC COLOR

carotenes orange to yellow

xanthophylls pale yellow to grayish

chlorophyll a bright green to grass-green

chlorophyll b olive-green

anthocyanins purplish-pink

The ratio of the distance traveled by a particular substance to the distance traveled by the solvent, both measured from the original spot, constitutes the so-called ratio of fronts, or R f,for that substance. This R f value is constant for a given set of conditions, but changes when the conditions are changed, for example if a different solvent is used.

1.Determine the R f values for each pigment on your chromatogram by measuring the

distance from the origin to (a) the solvent front and to (b) the center of each of the

pigment spots. Compute the ratio in each case as follows:

R f = distance from origin to center of pigment

distance from origin to solvent front

2.Express the R f value as a decimal (e.g., 0.75 or 0.24) without units.

NOTE:

For a precise identification of the pigments in an unknown mixture, a chromatogram of that unknown mixture is compared with chromatograms of known compounds run simultaneously using identical reagents and techniques.

Activity #6: Yeast Fermentation

Fermentation is a metabolic pathway that produces ethanol, carbon dioxide and two molecules of ATP in yeast during the anaerobic breakdown of one molecule of glucose. In this

experiment you will be testing the ability of yeast to metabolize several carbohydrates and gelatin.

You will work in pairs. Each table will test one solution. Your instructor will demonstrate how to do the set up. Data from all groups will be compared to determine which compounds yeast are able to break down anaerobically to produce energy (ATP).

Equipment and supplies per table

1. One fermentation tube

2. Yeast

3. One 25 or 50 ml graduated cylinder for measurement of solution into small tubes

DO NOTPOUR SOLUTIONS BACK INTO STOCK BOTTLES IF YOU POUR TOO MUCH!!

4. 5% solutions for testing.

PROCEDURE

1.Measure 20 mL of 5% test solution into the fermentation tube using a graduated cylinder.

Set up the fermentation chambers as demonstrated, making sure there are no bubbles.

https://www.wendangku.net/doc/504637853.html,ing a weigh boat, weigh 0.5g of yeast and place it into fermentation tubewith the test

solution (make sure all the yeast goes into the tube). Invert to mix.

3.BEGIN TIMING IMMEDIATELY!!

4.Allow to ferment for 45 minutes.

5.After 45 minutes record how much water was displaced by gas produced during

fermentation. Report to the class whether or not yeast was able to break down your

solution by fermentation to produce ATP energy.

6.When finished rinse the fermentation tubes and graduated cylinders and leave at your

station.

DATA TABLE: Fermentation analysis of yeast at 400 C for 20 minutes

REVIEW QUESTIONS

1. On the basis of what you know about carbohydrates and anaerobic respiration, make predictions about which compound will ferment. Which do you think will react the fastest? WHY?

2. Which of these compounds are monosaccharides? Which are disaccharides? Which are polysaccharides? Which are proteins?

3. Several of the compounds will not react much, if at all. Explain why.

研究生英语精读教程教师参考书(第三版下)中国人民大学出版社

Language Points 1.Subtitle:Toxin sniffers，missile jammers,dirty-bomb detectors： The post-9/11security blitz is affecting more than public safety—it’s changing the course of science. Toxin sniffers:毒素嗅探器missile jammers:导弹人为干发射机 dirty-bomb detectors:放射性核弹探测器全句可译为：毒素嗅探器、导弹人为干发射机、放射性核弹探测器：“9·11” 事件后闪电式的保卫行动不仅影响着公共安全——还在改变着科学的进程。 2.Par.[1]:In the race to prevent future9/11-style attacks—or worse—Washington has marshaled the U.S.science establishment on a scale not seen since Sputnik. 全句可译为：华盛顿以前苏联发射人造地球卫星以来所未有的规模对美国的科学机构做了安排。 3.Par.[2]:“A lot of it is security theater technology designed to make you feel better,”says Bruce Schneier，author of Beyond Fear：Thinking Sensibly about Security in an Uncertain World. 全句可译为：《超脱恐惧：明智地考虑变幻莫测世界的安全问题》的作者布鲁斯·施奈尔说：“这当中有许多都是做表面文章的保安技术，目的是让你感到更安全。 4.Par.[6]:As the archive of visa applicants balloons，scans of all10 fingers will provide more fail-safe identifications. 全句可译为：随着护照签证申请人的档案急剧增加，对十指全部进行扫描将使身份验证更加万无一失。 5.Par.[9]:Resembling a sleek outhouse，the$150,000walk-through machine sends a quick blast of air over your clothing to dislodge trace explosive particles. walk-through:（建筑物）从两端都可进入的全句可译为：这种价值15万美元的从两端都可进入的机器像个造型优美的户外小屋，它在你的衣服上面迅速地吹过一股气流，从衣服上吹下微量炸药粒子， 6.Par.[10]:Still,building technology today already seems light-years beyond pre-9/11days．全句可译为：然而，今天的建筑技术看来已经远远超过“9·11”事件以前的日子了。 7.Par.[11]:GPS:Global Positioning System全球卫星定位系统 8.Par.[12]:A cyber-attack on the country’s financial networks or power and telecommunications grids could make other means of protecting our physical assets moot. 全句可译为：对国家的金融网或电力和电信网进行的网络攻击，可使我们保护有形资产的其他手段变得无实际意义。 9.Par.[12]:Developers describe it as a“Google-esque”tool and predict

尊重的素材

尊重的素材（为人处世）思路人与人之间只有互相尊重才能友好相处要让别人尊重自己，首先自己得尊重自己尊重能减少人与人之间的摩擦尊重需要理解和宽容尊重也应坚持原则尊重能促进社会成员之间的沟通尊重别人的劳动成果尊重能巩固友谊尊重会使合作更愉快和谐的社会需要彼此间的尊重名言施与人，但不要使对方有受施的感觉。帮助人，但给予对方最高的尊重。这是助人的艺术，也是仁爱的情操。—刘墉卑己而尊人是不好的，尊己而卑人也是不好的。———徐特立知道他自己尊严的人，他就完全不能尊重别人的尊严。———席勒真正伟大的人是不压制人也不受人压制的。———纪伯伦草木是靠着上天的雨露滋长的，但是它们也敢仰望穹苍。———莎士比亚尊重别人，才能让人尊敬。———笛卡尔谁自尊，谁就会得到尊重。———巴尔扎克人应尊敬他自己，并应自视能配得上最高尚的东西。———黑格尔对人不尊敬，首先就是对自己的不尊敬。———惠特曼

每当人们不尊重我们时，我们总被深深激怒。然而在内心深处，没有一个人十分尊重自己。———马克·吐温忍辱偷生的人，绝不会受人尊重。———高乃依敬人者，人恒敬之。———《孟子》人必自敬，然后人敬之；人必自侮，然后人侮之。———扬雄不知自爱反是自害。———郑善夫仁者必敬人。———《荀子》君子贵人而贱己，先人而后己。———《礼记》尊严是人类灵魂中不可糟蹋的东西。———古斯曼对一个人的尊重要达到他所希望的程度，那是困难的。———沃夫格纳经典素材 1元和200元（尊重劳动成果）香港大富豪李嘉诚在下车时不慎将一元钱掉入车下，随即屈身去拾，旁边一服务生看到了，上前帮他拾起了一元钱。李嘉诚收起一元钱后，给了服务生200元酬金。这里面其实包含了钱以外的价值观念。李嘉诚虽然巨富，但生活俭朴，从不挥霍浪费。他深知亿万资产，都是一元一元挣来的。钱币在他眼中已抽象为一种劳动，而劳动已成为他最重要的生存方式，他的所有财富，都是靠每天20小时以上的劳动堆积起来的。200元酬金，实际上是对劳动的尊重和报答，是不能用金钱衡量的。富兰克林借书解怨（尊重别人赢得朋友）

那一刻我感受到了幸福_初中作文

那一刻我感受到了幸福本文是关于初中作文的那一刻我感受到了幸福，感谢您的阅读！每个人民的心中都有一粒幸福的种子，当它拥有了雨水的滋润和阳光的沐浴，它就会绽放出最美丽的姿态。那一刻，我们都能够闻到幸福的芬芳，我们都能够感受到幸福的存在。在寒假期间，我偶然在授索电视频道，发现(百家讲坛)栏目中大学教授正在解密幸福，顿然引起我的好奇心，我放下了手中的遥控器，静静地坐在电视前，注视着频道上的每一个字，甚至用笔急速记在了笔记本上。我还记得，那位大学教授讲到了一个故事：一位母亲被公司升职到外国工作，这位母亲虽然十分高兴，但却又十分无奈，因为她的儿子马上要面临中考了，她不能撇下儿子迎接中考的挑战，于是她决定拒绝这了份高薪的工作，当有人问她为什么放弃这么好的机会时，她却毫无遗憾地说，纵然我能给予儿子最贵的礼物，优异的生活环境，但我却无当给予他关键时刻的那份呵护与关爱，或许以后的一切会证明我的选择是正确的。听完这样一段故事，我心中有种说不出的感觉，刹那间，我仿拂感觉那身边正在包饺子的妈妈，屋里正在睡觉的爸爸，桌前正在看小说的妹妹给我带来了一种温馨，幸福感觉。正如教授所说的那种解密幸福。就要选择一个明确的目标，确定自已追求的是什么，或许那时我还不能完全诠释幸福。当幸福悄悄向我走来时，我已慢慢明白，懂得珍惜了。那一天的那一刻对我来说太重要了，原本以为出差在外的父母早已忘了我的生日，只有妹妹整日算着日子。我在耳边唠叨个不停，没想到当日我失落地回到家中时，以为心中并不在乎生日，可是眼前的一切，让我心中涌现的喜悦，脸上露出的微笑证明我是在乎的。

爸爸唱的英文生日快乐歌虽然不是很动听，但爸爸对我的那份爱我听得很清楚，妈妈为我做的长寿面，我细细的品尝，吃出了爱的味道。妹妹急忙让我许下三个愿望，嘴里不停的唠叨：我知道你的三个愿望是什么?我问：为什么呀!我们是一家人，心连心呀!她高兴的说。那一刻我才真正解开幸福的密码，感受到了真正的幸福，以前我无法理解幸福，即使身边有够多的幸福也不懂得欣赏，不懂得珍惜，只想拥有更好更贵的，其实幸福比物质更珍贵。那一刻的幸福就是爱的升华，许多时候能让我们感悟幸福不是名利，物质。而是在血管里涌动着的，漫过心底的爱。也许每一个人生的那一刻，就是我们幸运的降临在一个温馨的家庭中，而不是降临在孤独的角落里。家的感觉就是幸福的感觉，幸福一直都存在于我们的身边!

研究生英语精读教程第三版上unit one原文

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Part Summary ?[1~2] ?John Tierney outlines the bet and the differences between the two sides.Two intellectual schools debate whether the world is getting better or going to the dogs. Part Summary ?[3~4] ?the doomster and his proposition ?Erhrich predicted that "before 1985 mankind will enter an age of scarcity" in which "the accessible supplies of many key minerals will be nearing depletion". Part Summary ?[5~6] ?the boomster and his point of view ?Simon believes that population growth constitutes not a crisis but a boon that will ultimately mean a cleaner environment and a healthier humanity. Part Summary

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