How to learn biology, chapter 3, section 2

Accidents happen to everyone, but accidents happen to me. My good intentions have done bad things. Mom and Dad have been very busy lately, and when they come back from work, they are very tired, and if they go to soak in boiling water again, they will definitely be exhausted, so I am the only one who helps run errands!

I was walking with a thermos and dangled the thermos around. Suddenly, because I didn't hold the thermos steady, I only heard a "clang"; I saw the hot water bottle innocently falling to the ground; I only saw that the plastic shell of the bottle had been shattered; Only the sound of fragments in the bottle was heard. Seeing such a tragic situation of the hot water bottle, I was immediately very scared, with my mother's hot temper, I will definitely be furious, what kind of lesson will there be, I don't know yet!

What am I going to do? I just felt my face burning and my heart pounding. When I came back, I was still worried about what would happen to my mother.

Later, my mother came back and knew that after I broke the hot water bottle, she didn't scold me, but also educated me: "In the future, you must be careful in doing things, don't be careless." Remember next time!

The big stone in my heart finally landed. After this incident, I don't do things in a mess anymore. Always remember not to do bad things with good intentions!

Don't be like me.

Listen carefully in class, practice the questions a lot, and find out the feelings.

The key is also to develop your own interests.

Answer: Chapter 3 Section 3 DNA Replication.

a) Question**.

Hint: The raw materials used for the two emblems should be selected from a single stone; A model should be made first, and the emblem should be made according to the model; An electronically controlled engraver should be used; The engraving machine should be operated by a skilled master, or fully numerically controlled, etc. (The above can be speculated by the students based on their own experience, and the fact is that the raw material was indeed selected from a single stone, but due to the time constraints, the two emblems were hand-carved by two of the most skilled masters).

The easiest way to verify this is to compare the drawings of the two seals on a blank piece of paper (students may also propose a more scientific and modern approach).

2) Sidebar reflection questions.

Tip: This experiment was designed based on the principle of semi-preserved replication and changes in DNA density. In this experiment, it is possible to distinguish the DNA of the parent and the offspring according to the position of the DNA band in the test tube.

c) Practice. Basic questions.

1.Adenine deoxynucleotide, guanine deoxynucleotide, cytosine deoxynucleotide and thymine deoxynucleotide.

2.Template, raw material, energy, enzyme, double helix, base complementary pairing.

Chapter 3 Enzymes.

First, the group of enzymes is scattered.

Simple enzymes: Enzymes that are made up of only amino acid residues.

Conjugating enzymes: enzyme proteins: determine the specificity of the reaction;

Cofactors: determine the type and nature of the reaction; It can be metal ions or small molecule organic compounds.

It can be divided into coenzymes: it binds loosely to enzyme proteins and can be removed by dialysis or ultrafiltration.

Prosthetic group: tightly bound to enzyme proteins, cannot be removed by dialysis or ultrafiltration.

The complex formed by the combination of enzyme proteins and cofactors is called holoenzyme, and only holoenzyme has a catalytic effect.

Vitamins involved in the composition of coenzymes.

The group that transfers the coenzyme or prosthetic group of the vitamin contained.

Hydrogen atom NAD + NADP + Niacin amide (vitamin PP).

FMN FAD Vitamin B2

Aldehyde TPP vitamin B1

Acyl CoA lipoic acid pantothenic acid, lipoic acid.

Alkyl cobalamins, coenzymes, vitamin B12

Carbon dioxide, biotin, biotin.

Amino pyridoxal phosphate Pyridoxal (vitamin B6).

Methyl, equal one-carbon unit tetrahydrofolate folic acid.

Second, the active center of the enzyme.

The active center of the enzyme is composed of the essential groups of the enzyme, which are close to the specific spatial structure in the spatial position, and can specifically bind to the substrate and convert the substrate into a product. For conjugate enzymes, cofactors are involved in the composition of the enzyme's center of activity. However, there are some essential groups that do not participate in the composition of the active center.

3. Enzyme reaction kinetics.

The speed of the enzymatic reaction depends on substrate concentration, enzyme concentration, pH, temperature, agonists and inhibitors, etc.

1. Substrate concentration.

1) When the substrate concentration is low, the reaction rate increases with the increase of substrate concentration, increases the substrate concentration, slows down the reaction speed, further increases the substrate concentration, and the reaction speed no longer accelerates with the increase of substrate concentration, reaching the reaction speed, at this time, the active center of the enzyme is saturated by the substrate.

2) Michaelis equation.

v＝vmax［s］／km＋［s］

a.The Michaelis constant km value is equal to the substrate concentration at half the speed of the enzymatic reaction.

The smaller the value, the greater the affinity of the enzyme for the substrate.

The value is one of the characteristic constants of the enzyme, which is only related to the structure of the enzyme, the substrate catalyzed by the enzyme and the reaction environment such as temperature, pH, and ionic strength, and has nothing to do with the concentration of the enzyme.

is the reaction rate when the enzyme is completely saturated with the substrate and is proportional to the enzyme concentration.

2. Enzyme concentration.

In the enzyme reaction system, when the substrate concentration greatly exceeds the enzyme concentration, so that the enzyme is saturated with the substrate, the reaction speed is proportional to the concentration of the enzyme.

3. Temperature Temperature has a dual effect on the speed of enzymatic reactions. On the one hand, increasing the temperature can speed up the enzymatic reaction, and at the same time, increase the denaturation of the enzyme. The ambient temperature at which the enzymatic reaction is fastest is called the optimal temperature for the enzymatic reaction.

Although the activity of the enzyme decreases with the decrease of temperature, the low temperature generally does not destroy the enzyme.

The optimal temperature of an enzyme is not a characteristic constant of the enzyme, it is related to the time when the reaction takes place.

1. Foliar temperature.

2. Coconut trees, palm trees and other plants that live in the tropics.

3. Hemlock, spruce, chain fir, ginseng, Coptis chinensis, Banxia Yiwubu and some mosses and lichens and other shade plants.

4. Morphological structure and lifestyle.

5. Adaptability.

1. Feulgen reaction is a reaction of specific dyeing of DNA, DNA is hydrolyzed by weak acid (1mol lhcl), and the bond between purine base and deoxyribose on it is opened, so that one end of deoxyribose sugar forms a free aldehyde group, which reacts with Schiff reagent (colorless magenta sulfurous acid solution) in situ to form a purple-red compound, so that the part containing DNA in the cell is purple-red positive. The production of purple red is due to the presence of a quinone group in the molecule of the reaction product, which is a chromophore, so it has color. The control group was pre-treated with hot trichloroacetic acid or DNase, and the DNA in the cells was extracted and a negative reaction was obtained, thus demonstrating the specificity of the Feulgen reaction.

2. Eukaryotes also have flagella, and the flagella of eukaryotes are curly, and they are generally lower eukaryotes.

1. The medium should contain at least nutrients such as carbon source, nitrogen source, growth factor, water and inorganic salts, and should meet the appropriate pH and oxygen.

2. To cultivate nitrogen-fixing microorganisms, nitrogen can be selected without adding nitrogen to the medium. With or without the addition of some substances, it allows the growth of specific microorganisms while inhibiting the growth and reproduction of other microorganisms.

The identification medium is used to identify a microorganism, e.g., Congo red can be added to identify microorganisms that break down cellulose.

1.Meet carbon sources, nitrogen sources, growth factors, water, inorganic salts, as well as pH and oxygen.

2.Choosing a medium is to select microorganisms with special properties Identification medium is to identify the presence or absence of microorganisms, such as eosin and melan, which can identify the presence of E. coli.

To put it simply, the selection of culture medium is to select the microorganisms that are needed, that is, the microorganisms that are not needed are to be killed. The identification medium is to identify, that is, according to the external characteristics that different microorganisms can exhibit in a certain method (for example, when identifying microorganisms that decompose cellulose, Congo red is added, and there will be white transparent circles around microorganisms that decompose cellulose.

to identify, without killing microorganisms.

The operation steps of genetic engineering (the knowledge of each step is the focus of the college entrance examination).