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Photosynthesis

1.

Photosynthesis means

1. the green material in plants that traps energy from sunlight and uses it to break down water molecules into atoms of hydrogen and oxygen.

2. in a plant, the growth tissue that produces the xylem and the phloem.

3. the process by which green plants use chemicals from the environment and energy from the sun to make their own food.

2.

Photosynthesis is an instance of

1. homeostasis.

2. reproduction.

3. metabolism.

4. growth and development.

5. cell structure.

3.

The first step in photosynthesis is the

1. absorption of light energy.

2. synthesis of water.

3. production of oxygen.

4. formation of ATP.

4.

In a typical plant, all of the following factors are necessary for photosynthesis EXCEPT

1. chlorophyll.

2. light.

3. oxygen.

4. carbon dioxide.

5.

In photosynthesis, water undergoes                     , while carbon dioxide undergoes                     .

1. oxidation; reduction

2. reduction; oxidation

3. no change; oxidation

4. none of the above

6.

Oxygen made during photosynthesis results from the

1. absorption of light.

2. splitting of water molecules.

3. mitochondrial membranes.

4. splitting of carbon dioxide molecules.

7.

Many plants are excellent at photosynthesis because they

1. have few mesophyll cells in their leaves.

2. are equipped with many leaves that have many mesophyll cells, which in turn have many chloroplasts.

3. are able to transform light energy into heat energy for cellular work.

4. can carry out photosynthesis in their roots, stems, flowers as well as their leaves.

5. produce an abundant supply of oxygen that is an important input for photosynthesis.

8.

What is the equation for photosynthesis?

9.

Many people say that people depend on plants as much as plants depend on people. Using your knowledge of cellular respiration and photosynthesis, explain why this statement is true.

10.

Draw a picture of a chloroplast. Be sure to label the parts that are significant to photosynthesis and give me a brief explanation of each part.

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Xylem and phloem make up the big transportation system of vascular plants. As you get bigger, it is more difficult to transport nutrients, water, and sugars around your body. You have a circulatory system if you want to keep growing. As plants evolved to be larger, they also developed their own kind of circulatory systems. The main parts you will hear a lot about are called xylem and phloem.

It all starts with a top and a bottom. Logically, it makes sense. Trees and other vascular plants have a top and a bottom. The top has a trunk, branches, leaves, or needles. The bottom is a system of roots. Each needs the other to survive. The roots hold the plant steady and grab moisture and nutrients from the soil. The top is in the light, conducting photosynthesis and helping the plant reproduce. You have to connect the two parts. That's where xylem and phloem come in.

Zippy Xylem

The xylem of a plant is the system of tubes and transport cells that circulates water and dissolved minerals. As a plant, you have roots to help you absorb water. If your leaves need water and they are 100 feet above the ground, it is time to put the xylem into action! Xylem is made of

vessels that are connected end to end for the maximum speed to move water around. They also have a secondary function of support. When someone cuts an old tree down, they reveal a set of rings. Those rings are the remains of old xylem tissue, one ring for every year the tree was alive.

Phloem Fun

The fun never stops in the plant's circulatory system. Most plants have green leaves, where the photosynthesis happens. When those sugars are made, they need to be given to every cell in the plant for energy. Enter phloem. The phloem cells are laid out end-to-end throughout the entire plant, transporting the sugars and other molecules created by the plant. Phloem is always alive. Xylem tissue dies after one year and then develops anew (rings in the tree trunk). What is the best way to think about phloem? Think about sap coming out of a tree. That dripping sap usually comes from the phloem

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Sure we said that there are some roots above the surface, but the majority of the plant you see is made up of stems and leaves. Think about a tree. The stems are the trunks and branches. Leaves are self-explanatory. Stems are all about transporting food and water and acting as support structures. Leaves are all about photosynthesis, creating food molecules and absorbing carbon dioxide for the plant. These parts are connected by the vascular system of xylem and phloem that spreads through the entire plant.

The tip (terminal bud) of the main stem has a specialized structure that is the source of new growth for plants. You will find the apical meristem that develops into young leaves (primodium). There are other points of growth at each node where leaves and branches develop on the stems. Those branching points are home to axillary buds that can also develop into new branches.

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We're going to look at plant structure in this section. The plants we discuss will be vascular plants that have systems of tubes (xylem and phloem) for the transport of nutrients and water. Remember that there is a wide variety of plants on Earth and even a whole group that doesn't have

vascular systems. Mosses and liverworts may still have photosynthesis, but they do not have that 'classic' plant structure. Then you will find species such as cacti that don't have leaves. They conduct photosynthesis in their stems. Anyway, just remember that there are many other possibilities in the plant kingdom.

Alike But Different

We just told you about the many exceptions to the basic plant structure, so let's look at some similarities. An easy similarity is on a cellular level. Plants conduct photosynthesis. This process of converting the Sun's energy into molecular energy happens in chloroplasts with the help of chlorophyll molecules and a variety of enzymes. Vascular plants share a similar set of structures called roots, stems, and leaves. Many plants have specialized versions, but the basics are there. One specialization might be the petals of a flower. Those flower petals are specialized leaves that surround the reproductive structures of the plant.

Roots Below the Ground

We'll start at the bottom with the roots. These structures are designed to pull water and minerals from whatever material the plant sits on. For water plants, the roots may be in the water. For traditional trees, the roots go deep into the soil. There are even plants called epiphytes that live in trees and their root system clings to branches. Humans often capitalize on the roots of plants for food. Carrots are just one big orange root.

Root systems also provide support for plants in the form of an anchor in the soil. If the wind blows hard, those roots keep the plant from falling over. Some plant species have roots above ground that provide support for the entire plant. Roots are further broken down into the primary root and lateral roots that each has apical meristem at their tips. Root hairs are also a common structure on roots. They make the roots look fuzzy and help in the absorption of water and nutrients.

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The whole process doesn't happen all at one time. The process of photosynthesis is divided into two main parts. The first part is called the

light dependent reaction. This reaction happens when the light energy is captured and pushed into a chemical called ATP. The second part of the process happens when the ATP is used to make glucose (the Calvin Cycle). That second part is called the light independent reaction.

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We already spoke about the structure of chloroplasts in the cells tutorials. We want to reinforce that photosynthesis happens in the chloroplast. Within this cell organelle is the chlorophyll that captures the light from the Sun. We'll talk about it in a bit, but the chloroplasts are working night and day with different jobs. The molecules are moved and converted in the area called the stroma.

Part III: The Molecules

Chlorophyll is the magic compound that can grab that sunlight and start the whole process. Chlorophyll is actually quite a varied compound. There are four (4) types: a, b, c, and d. Chlorophyll can also be found in many microorganisms and even some prokaryotic cells. However, as far as plants are concerned, the chlorophyll is found in the chloroplasts. The other big molecules are water (H₂O), carbon dioxide (CO₂), oxygen (O₂) and glucose (C₆H₁₂O₆). Carbon dioxide and water combine with light to create oxygen and glucose. That glucose is used in various forms by every creature on the planet. Animal cells require oxygen to survive. Animal cells need an aerobic environment (one with oxygen).

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Photosynthesis -Part I: The Sun and Light

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Photosynthesis -Part I: The Sun and Light

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Not all of the light from the

Sun makes it to the surface of the Earth. Even the light that does make it here is reflected and spread out. The little light that does make it here is enough for the plants of the world to survive and go through the process of photosynthesis. Light is actually energy, electromagnetic energy to be exact. When that energy gets to a green plant, all sorts of reactions can take place to store energy in the form of sugar molecules.

Remember we said that not all the energy from the Sun makes it to plants? Even when light gets to a plant, the plant doesn't use all of it. It actually uses only certain colors to make photosynthesis happen. Plants mostly absorb red and blue wavelengths. When you see a color, it is actually a color that the object does NOT absorb. In the case of green plants, they do not absorb light from the green range.