High School Biology About light and action, photosynthesis high school biology knowledge points

That's not what I said.

It is true that when the O2 produced by photosynthesis is > the O2 consumed by respiration, the oxygen produced can already support respiration, but you can't say that plant cells don't absorb oxygen from the outside because of that.

For example, let's say there are two pipes in a pool, one inlet and one out, and now, both pipes are open, and the water inflow is faster than the water outlet, so that the pool will gradually accumulate water, but you can't say that the pool is not draining.

In the same way, when photosynthesis is greater than respiration, it can only be said that the plant cell is "equivalent" not absorbing oxygen from the outside world, that is, it excretes more oxygen than it absorbs, and in fact still has to absorb it.

Photosynthesis is a biochemical process in which plants, algae, and certain bacteria use their cells themselves to convert carbon dioxide and water (hydrogen sulfide and water for bacteria) into organic matter and release oxygen (hydrogen for bacteria) under visible light.

It's better for you to find a book for your first year of high school.

No, it will always absorb, it will always breathe.

Both chloroplasts and mitochondria are cytoplasmic substrates.

So the oxygen released by chloroplast photosynthesis passes through the mitochondria, so the oxygen released is given to the mitochondria and then released to the outside world.

Of course, the O2 produced by photosynthesis > the O2 consumed by respiration throughout the day, but at night plants cannot photosynthesize and still need to absorb oxygen from the outside for respiration.

That's how I understand it, I'll tell you what I think first, and I'll ask the teacher in a few days.

The O2 produced by photosynthesis will be preferentially supplied to the respiration consumption, but it does not mean that the way to absorb O2 from the outside is blocked, the O2 produced in the chloroplast passes through the double membrane of the chloroplast to the cytoplasm, and then enters the mitochondria to be consumed, while the O2 from the outside world passes through the leaf pores at the same time, passes through the cell membrane and enters the cell and then enters the mitochondria, the two exist at the same time, but the way to absorb O2 from the outside takes a long time.

At night, plants cannot photosynthesize and still need to absorb oxygen from the outside for respiration.

Photosynthesis is the process in which green plants use light energy to convert carbon dioxide and water into organic matter and release oxygen through chloroplasts. The process of photosynthesis includes a photoreaction stage and a dark reaction stage, and the photoreaction stage includes photolysis of water and the formation of ATP. The dark reaction stage has the fixation of carbon dioxide and the reduction of C3 compounds.

Summary of high school biology knowledge points of photosynthesis

1. The concept of photosynthesis and its reaction formula.

Photosynthesis refers to the process in which green plants use light energy to convert carbon dioxide and water into organic matter that stores energy and release oxygen.

Total reaction formula: CO2 + H2O CH2O) + O2

The following points should be paid attention to in the writing of the reaction formula: (1) photosynthesis has water decomposition, although the product side of the reaction formula does not write water, but there is actually water generation; (2)" cannot be written as "=". The concept and reaction formula of photosynthesis should be grasped from the place of photosynthesis - chloroplasts, conditions - light energy, raw materials - carbon dioxide and water, products - sugars and other organic matter and oxygen.

2. The process of photosynthesis.

Photoreaction stage: a. Photolysis of water: 2H2O4[H]+O2 (providing hydrogen for dark reaction); b. Formation of ATP:

ADP+PI+Light Energy ATP (provides energy for dark reactions).

Dark reaction stage: a, CO2 fixation: CO2+C5 2C3;; B. Reduction of C3 compounds: 2 C3 + [H]+ATP (CH2O) + C5

The meaning of photosynthesis

1. Biological evolution: first, the O2 produced by photosynthesis provides the possibility for the emergence of aerobic organisms; Second, the ozone (O3) formed by O2 under certain conditions absorbs ultraviolet rays, weakens the impact of solar radiation on organisms, and provides the possibility for aquatic organisms to reach the land. Third, the large amount of organic matter produced by photosynthesis provides the possibility for the emergence of higher heterotrophic organisms.

2. Practical significance: improve the efficiency of photosynthesis and solve the problem of food shortage. The main conditions for photosynthesis should be met, the internal conditions - various mineral elements required by the plant, the area of photosynthesis (appropriate dense planting), and the external conditions - sufficient raw materials (CO2 and H2O), suitable light, and a long photosynthesis time.

There is a lot of content about photosynthesis, and the exam is often combined with knowledge points such as respiration and organelle structure, so it is recommended that you ask questions specifically about a specific item, and it is not clear that there are so many contents here.

Stages of photosynthesis.

Photoreaction phase.

The chemical reaction in the first stage of photosynthesis must have light energy to proceed, and this stage is called the photoreaction stage. The chemical reaction in the photoreaction stage is carried out on the thylakoids within the chloroplast.

Dark reaction phase.

The chemical reaction in the second stage of photosynthesis, which can be carried out without light energy, is called the dark reaction stage. The chemical reactions in the dark reaction phase are carried out in the matrix within the chloroplast. The light reaction stage and the dark reaction stage are a whole, and in the process of photosynthesis, the two are closely related and indispensable.

Carbon dioxide. CO2 is the raw material for photosynthesis of green plants, and its concentration affects the dark reaction of photosynthesis. Increasing the concentration of CO2 within a certain range can increase the rate of photosynthesis, and the rate of photosynthesis does not increase after the concentration of CO2 reaches a certain value, because the products of the photoreaction are limited.

Photosynthesis is a photobiochemical reaction, so the photosynthetic rate accelerates as the intensity of light increases. But beyond a certain range, the increase in photosynthetic rate slows down until it no longer increases. The photosynthetic rate can be expressed in terms of the amount of CO2 absorbed, and the greater the amount of CO2 absorbed, the faster the photosynthetic rate.

The chemical reactions in temperature photosynthesis are all carried out under the catalysis of enzymes, and temperature directly affects the activity of enzymes. The relationship between temperature and the rate of photosynthesis is like the relationship between temperature and enzymes, there is an optimal temperature.

1.The factors that affect photosynthesis are light intensity,

Carbon dioxide concentration,

temperature, moisture and mineral elements, etc. The effects of light intensity and carbon dioxide concentration on photosynthesis are within a certain range, and with the increase of light intensity and carbon dioxide concentration, the intensity of photosynthesis also increases.

Temperature affects the intensity of photosynthesis by affecting the activity of enzymes;

Water is necessary for the photolysis of water in the photoreaction stage of photosynthesis; At the same time, due to the lack of water, the stomata of the leaves of the plant body will close, resulting in carbon dioxide not being able to enter, and the intensity of photosynthesis will decrease or even stop [this is often the reason for the summer plant lunch break].

Mineral elements are necessary for plants to synthesize various enzymes, chlorophyll, etc.