We all enjoy the beautiful show of colours as leaves change each autumn. But did you ever wonder how and why this happens?Leaves are nature’s food factories. Plants take water from the ground through their roots and take carbon dioxide (二氧化碳) from the air. Plants use sunlight to turn water and carbon dioxide into glucose (葡萄糖). Glucose is a kind of sugar, which plants use as food for energy and growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis that means “ putting together with light”. A chemical called chlorophyll helps photosynthesis. It gives plants their green colour. As summer ends and autumn comes, the days get shorter and shorter, and trees “know” to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food-making factories. As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves. Small amounts of these colours have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green chlorophyll. The bright reds and purples we see in leaves are made mostly in autumn. In some trees, like maples (枫树), glucose is caught in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn turn this glucose into a red colour. The brown colour of trees like oaks (橡树) is made from waste left in the leaves. It is the mixture of all these things that makes the beautiful colours we enjoy during autumn. 【小题1】The word “chlorophyll” in the third paragraph means _______ in Chinese. A．叶绿素B．氧气C．胡萝卜素D．蛋白质【小题2】The leaves of the trees in autumn turn yellow because of the short of _____. A．water and carbon dioxideB．glucose and energyC．sunlight and waterD．sunlight and carbon dioxide【小题3】The way that _______________________ is called Photosynthesis . A．plants change water and carbon dioxide into sugarB．plants turn water and carbon dioxide into sugar with the help of sunlightC．plants use glucose as food for energy and growingD．chlorophyll is a great help【小题4】Which of the following is NOT true?A．When autumn and winter come, the days get shorter and shorter. B．During winter trees rest and live on the food they store during the summer. C．During winter small amounts of yellow and orange colours are kept in the leaves all the time. D．Trees begin to stop making food in summer.【小题5】This passage tells us __________________. A．all the plants can grow well with the strong sunlightB．there are all kinds of plants on the earthC．all the colours of the leaves aren’t made from chlorophyllD．maples and oaks have the same reason as other trees for the change of colours - 跟谁学
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在线咨询下载客户端关注微信公众号&&&分类：We all enjoy the beautiful show of colours as leaves change each autumn. But did you ever wonder how and why this happens?Leaves are nature’s food factories. Plants take water from the ground through their roots and take carbon dioxide (二氧化碳) from the air. Plants use sunlight to turn water and carbon dioxide into glucose (葡萄糖). Glucose is a kind of sugar, which plants use as food for energy and growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis that means “ putting together with light”. A chemical called chlorophyll helps photosynthesis. It gives plants their green colour. As summer ends and autumn comes, the days get shorter and shorter, and trees “know” to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food-making factories. As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves. Small amounts of these colours have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green chlorophyll. The bright reds and purples we see in leaves are made mostly in autumn. In some trees, like maples (枫树), glucose is caught in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn turn this glucose into a red colour. The brown colour of trees like oaks (橡树) is made from waste left in the leaves. It is the mixture of all these things that makes the beautiful colours we enjoy during autumn. 【小题1】The word “chlorophyll” in the third paragraph means _______ in Chinese. A．叶绿素B．氧气C．胡萝卜素D．蛋白质【小题2】The leaves of the trees in autumn turn yellow because of the short of _____. A．water and carbon dioxideB．glucose and energyC．sunlight and waterD．sunlight and carbon dioxide【小题3】The way that _______________________ is called Photosynthesis . A．plants change water and carbon dioxide into sugarB．plants turn water and carbon dioxide into sugar with the help of sunlightC．plants use glucose as food for energy and growingD．chlorophyll is a great help【小题4】Which of the following is NOT true?A．When autumn and winter come, the days get shorter and shorter. B．During winter trees rest and live on the food they store during the summer. C．During winter small amounts of yellow and orange colours are kept in the leaves all the time. D．Trees begin to stop making food in summer.【小题5】This passage tells us __________________. A．all the plants can grow well with the strong sunlightB．there are all kinds of plants on the earthC．all the colours of the leaves aren’t made from chlorophyllD．maples and oaks have the same reason as other trees for the change of coloursWe all enjoy the beautiful show of colours as leaves change each autumn. But did you ever wonder how and why this happens?Leaves are nature’s food factories. Plants take water from the ground through their roots and take carbon dioxide (二氧化碳) from the air. Plants use sunlight to turn water and carbon dioxide into glucose (葡萄糖). Glucose is a kind of sugar, which plants use as food for energy and growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis that means “ putting together with light”. A chemical called chlorophyll helps photosynthesis. It gives plants their green colour. As summer ends and autumn comes, the days get shorter and shorter, and trees “know” to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food-making factories. As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves. Small amounts of these colours have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green chlorophyll. The bright reds and purples we see in leaves are made mostly in autumn. In some trees, like maples (枫树), glucose is caught in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn turn this glucose into a red colour. The brown colour of trees like oaks (橡树) is made from waste left in the leaves. It is the mixture of all these things that makes the beautiful colours we enjoy during autumn. 【小题1】The word “chlorophyll” in the third paragraph means _______ in Chinese. A．叶绿素B．氧气C．胡萝卜素D．蛋白质【小题2】The leaves of the trees in autumn turn yellow because of the short of _____. A．water and carbon dioxideB．glucose and energyC．sunlight and waterD．sunlight and carbon dioxide【小题3】The way that _______________________ is called Photosynthesis . A．plants change water and carbon dioxide into sugarB．plants turn water and carbon dioxide into sugar with the help of sunlightC．plants use glucose as food for energy and growingD．chlorophyll is a great help【小题4】Which of the following is NOT true?A．When autumn and winter come, the days get shorter and shorter. B．During winter trees rest and live on the food they store during the summer. C．During winter small amounts of yellow and orange colours are kept in the leaves all the time. D．Trees begin to stop making food in summer.【小题5】This passage tells us __________________. A．all the plants can grow well with the strong sunlightB．there are all kinds of plants on the earthC．all the colours of the leaves aren’t made from chlorophyllD．maples and oaks have the same reason as other trees for the change of colours科目:最佳答案【小题1】A【小题2】C【小题3】B【小题4】D【小题5】C解析试题分析：这篇短文主要介绍了树叶颜色变化的原理，以及树叶在植物生长发育中的作用。【小题1】联系下文It gives plants their green colour它给指物提供了绿色。可知这个单词与绿色有关，故选A。【小题2】根据短文第四五段描述，可知树叶在秋天变黄主要是因为缺少光照和水分，故选C。【小题3】根据第三段The way plants turn water and carbon dioxide into sugar is called photosynthesis 描述，可知选B。【小题4】根据短文第四段描述，可知植物在秋天停止制造食物，故选D。【小题5】根据最后一段It is the mixture of all these things that makes the beautiful colours we enjoy during autumn. 及上文描述，可知并不是植物所有的颜色都是来自于叶绿素，故选C。考点：关于树叶颜色的说明文阅读点评：本文中长句较多，一时很难读懂句子含义，注意多读几遍，不要强求非得理解一词一句的含义，能把握文章大意就行。然后带着问题阅读短文，一般就能顺利找出答题依据。对于不能直接找到根据的问题注意联系上下文，根据短文中心总结出正确答案。知识点:&&基础试题拔高试题热门知识点最新试题
关注我们官方微信关于跟谁学服务支持帮助中心glucose + oxygen + water
As a chemical reaction it's like so:
CO2 + H2O + light energy
---> C6H12O6 + O2 + H2O
We'll get back to this equation
What else should we remember about photosynthesis?
Well, it's an important component of the
Oxygen-Carbon Dioxide Cycle.&
Organisms that carry-out photosynthesis
are like oxygen factories.& At the same time they are removing CO2
from the atmosphere.&
Increasing levels of CO2 appear
to go hand in hand with increasing global temperature ("Global Warming").&
So damaging the ecosystems where photosynthesis occurs (i.e. the rainforests,
the oceans) reduces the amount of oxygen being pumped into the air (that's
a bad thing) & slows the rate at which carbon dioxide is removed from
the atmosphere (which also appears to be a bad thing).
For the most part, when thinking of organisms
that carry-out photosynthesis, it is safe to picture plants.& It's
not that we have any right to ignore the photosynthetic Protists &
Monerans, but, well, it sure is easier to picture a tree than a Euglena.&
Don't you agree?
Remember, it turns out that most photosynthesis
on Earth is occurring in the oceans, & the organisms in the oceans
doing the job happen to be classified into the Protist Kingdom --- algae
(seaweeds), diatoms, etc.& So let's not forget them completely.
Having said that, let's take a look at plants
& how they are adapted for photosynthesis.
The leaves of plants are the photosynthesis
factories.& The structure of a "typical" leaf is illustrated in the
following table.
LEAF LAYERS
This pic shows a leaf cross section with
only the layers labelled.&
Please note that each roundish shape is
a single plant cell.& So each layer is a plant tissue (a group of
The top & bottom layers are both referred
to as an epidermis (outer layer).& The upper epidermis (colored
& the lower epidermis (colored red)
basically are protective layers.& They are coated with a waxy surface,
the cuticle, which further protects the leaf & prevents excess water
The area sandwiched in the middle of the
leaf is referred to as "mesophyll".& There are two layers in the mesophyll:
1) the palisade layer - packed tight w/
oval cells
2) the spongy layer - this area contains
circular cells that are spread out --- allowing gases to circulate within
THE VASCULAR BUNDLE (VEIN)
If you've ever looked closely at a leaf
you've noticed some pattern of lines running through it.&
These lines are veins, or "vascular bundles"
(the side of one bundle is colored light
Inside the vascular bundle are tubes that
transport materials from place to place in the plant.
The xylem (colored blue)
transport water & minerals from the roots, through the stem, &
into the leaves&
(remember ... we need water for photosynthesis).
Phloem (colored orange)
are tubes that transport "food" through the plant.& This "food" is
basically sugary water (sap).& The sugars are synthesized (made) during
photosynthesis.
STOMATES & GUARD CELLS
Scattered about the lower epidermis are small
openings called stomata.& It is through these holes that carbon dioxide
enters the leaf, & oxygen & water vapor exit.
Each stomate is surrounded by a pair of guard
cells.& When guard cells swell, the stomates close, when the guard
cells shrink, the stomates are open.& Plants respond to changes in
temperature & humidity by opening or closing their stomata (an example
of maintaining ... homeostasis).
CHLOROPLASTS
All of the "black dots" in the picture represent
chloroplasts, which are the cell organelles in plant cells where the chemical
reactions of photosynthesis take place.
You should notice that the vast majority
of chloroplasts are found in the cells of the mesophyll.& Even more
specifically, the palisade layer has the most chloroplasts, so the greatest
amount of photosynthesis occurs in that leaf layer.
Now let's revisit the summary equation for
photosynthesis & note how each of the raw materials end up in the chloroplasts
so that the whole photosynthesis deal can go down.
Now let's do the same, except pay attention
to what happens to the products of photosynthesis.
I should mention that glucose may be used
for things other than energy.& For example,
a whole bunch of glucoses could be combined
(by dehydration synthesis) to form cellulose,
which is the structural material of the
cell wall surrounding plant cells.& It could also be
converted to starch (again by dehydration
synthesis) & stored by the plant for future use.
Alright, that is "the big picture" --- what
photosynthesis is, why it's important, & how plants are adapted to
carry it out.& I'm afraid there is more chemistry to it, I have placed
that info on a separate page, the "yucky chemistry details".& Check
it out when you have a chance, but not on a full stomach.
Before you do anything else, have a go at
these sample questions about the material we learned here. Answers &
explanations can be found in the extremely secret answer area (no peeking!).
SAMPLE QUESTIONS
Write down your answers
(old-fashioned I know), & then dip into the secret answer area.
1. organic compound produced
during photosynthesis
2. source of energy for
photosynthesis
3. is both a reactant &
product of photosynthesis
4. an organism that can
synthesize organic materials using materials in its environment
5. the cell organelle where
photosynthesis occurs
6. the green pigment in
plant cells that absorbs sunlight
7. photosynthestic Protists
8. photosynthestic members
of the Kingdom Monera
B. autotrophe
C. blue-green algae
D. chlorophyll
E. chloroplast
F. glucose
G. sunlight
(Matching)
1. The waxy coating on
the surface of a leaf is the ....
a) epidermis
b) cuticle
c) palisade layer
d) chlorophyll
2. Water is lost from the
leaves of plants through openings called ...
a) root hairs
c) lenticels
d) stomates
3. The conversion of light
energy to chemical energy occurs in the cells of ...
b) invertebrates
d) teachers
4. The raw materials needed
for photosynthesis include ...
a) oxygen & water
b) carbon dioxide &
c) glucose & oxygen
d) glucose & carbon
5. Which word equation summarizes
photosynthesis?
a) water + starch --->
glucose + glucose + glucose
b) water + carbon dioxide
---> oxygen + glucose + water
c) glucose + oxygen --->
water + carbon dioxide + ATP
d) glucose + glucose --->
maltose + water
6. Autotrophic activity
in plant cells occur in organelles called ...
a) cytoplasm
b) chloroplasts
c) ribosomes
PICTURE QUESTIONS:
Base the next 7 questions
on the diagram below.
1. Write the number &
name of the principle area of photosynthesis.
2. Write the number &
name of the structure(s) that regulate the opening & closing of stomates.
3. Which number indicates
where oxygen exits the leaf?
4. Which numbers indicate
vascular tissues, which transport materials to & from the leaf?&
What are the names of the vascular tissues?
5. Write the number &
function of the cuticle.
6. The structure of which
area in the leaf allows for the diffusion of gases (carbon dioxide &
oxygen)? Give the number & name.
7. What do the "black dots"
represent?
(Pic Questions)
SECRET ANSWER AREA
to MC - correct choices in ORANGE
1. The waxy coating on
the surface of a leaf is the ....
a) epidermis
c) palisade layer
d) chlorophyll
2. Water is lost from the
leaves of plants through openings called ...
a) root hairs - ON ROOTS,
NOT NEAR LEAVES
b) xylem - TUBES THAT TRANSPORT
WATER IN THE PLANT
c) lenticels - OPENING
ON WOODY STEMS FOR GAS EXCHANGE
3. The conversion of light
energy to chemical energy occurs in the cells of ...
algae - ANSWER MUST BE AN AUTOTROPHE
b) invertebrates - ANIMALS
(HETEROTROHPIC)
c) fungi - HETEROTROPHIC
d) teachers - ;)
4. The raw materials needed
for photosynthesis include ...
a) oxygen & water -
THESE ARE PRODUCTS
carbon dioxide & water
c) glucose & oxygen
d) glucose & carbon
5. Which word equation summarizes
photosynthesis?
a) water + starch --->
glucose + glucose + glucose
water + carbon dioxide ---> oxygen + glucose + water
c) glucose + oxygen --->
water + carbon dioxide + ATP
d) glucose + glucose --->
maltose + water
6. Autotrophic activity
in plant cells occur in organelles called ...
a) cytoplasm - WATERY STUFF,
NOT AN ORGANELLE
chloroplasts
c) ribosomes - WHERE PROTEINS
ARE PRODUCED
d) nuclei - DIRECTS CELL
ACTIVITIES, CONTAINS DNA
to PIC QUESTIONS
Base the next 7 questions
on the diagram below.
1. Write the number &
name of the principle area of photosynthesis.
3 - the palisade layer
2. Write the number &
name of the structure(s) that regulate the opening & closing of stomates.
8 - guard cells
3. Which number indicates
where oxygen exits the leaf?
9 (stomata) - same place carbon dioxide enters
4. Which numbers indicate
vascular tissues, which transport materials to & from the leaf?&
What are the names of the vascular tissues?
5 - xylem, & 6 - phloem
5. Write the number &
function of the cuticle.
1 - protects inner layers & prevents excess water loss
6. The structure of which
area in the leaf allows for the diffusion of gases (carbon dioxide &
oxygen)? Give the number & name.
4 - spongy layer
7. What do the "black dots"
represent?
chloroplaSts, the organelles where the photosynthesis boogie occurs
to MatchingBiology of Plants: Making Food
Making Food
What is photosynthesis?
Photosynthesis is the process by which plants make food from light, water, nutrients, and carbon dioxide.
What is chlorophyll?
Chlorophyll is the green pigment, or color, found in plants that helps the plant make food.
Plants are very important to us.& All food people eat comes directly or indirectly from plants.
Directly from plants:
Indirectly from plants:
For example, apples come from an apple tree.& The flour used to make bread comes from a wheat plant.
Steak comes from a cow, and we all know that cows are animals, not plants, right?& But what does the cow eat?& It eats grass and grains—PLANTS!
So all the foods we eat come from plants.& But what do plants eat?& They make their own food!
What Do Plants Need to Make Food?
Plants need several things to make their own food.
They need:
chlorophyll, a green pigment found in the leaves of plants (see the layer of chlorophyll in the cross-section of a leaf below)
light (either natural sunlight or artificial light, like from a light bulb)
carbon dioxide (CO2)(a
one of the gases people and animals breathe out when they exhale)
water (which the plant collects through its roots)
nutrients and minerals (which the plant collects from the soil through its roots)
Plants make food in their leaves.& The leaves contain a pigment called chlorophyll, which colors the leaves green.& Chlorophyll can make food the plant can use from carbon dioxide, water, nutrients, and energy from sunlight.& This process is called photosynthesis.
During the process of photosynthesis, plants release oxygen into the air.& People and animals need oxygen to breathe.
Copyright&&&2009&