"Proteins are the main carriers of life activities" PPT courseware of molecules that make up cells

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"Proteins are the main carriers of life activities" PPT courseware of molecules that make up cells

Part One: Curriculum Standards

It is clarified that proteins are usually composed of 20 kinds of amino acid molecules. Its function depends on the amino acid sequence and the spatial structure formed by it. The functions of cells are mainly completed by proteins.

Interpretation of curriculum standards

1. Explain the structural characteristics of amino acids and the process of amino acids forming proteins.

2. Outline the structure and function of proteins.

3. Recognize that protein is the main carrier of life activities.

Proteins are the main carriers of life activities PPT, Part 2: Functions of proteins

The basic unit of protein - amino acids

1. amino acid structure

(1) General structural formula:

(2) Structural characteristics: Each amino acid molecule contains at least one ______ (-NH2) and one ______ (-COOH), and has an amino group and a carboxyl group connected to ____________. The difference between various amino acids is the difference in ______.

Regular method: Amino acid identification skills

You can imagine an amino acid as a person. The R group is the face. When we identify a person, we mainly look at the person's face; the carboxyl group and the amino group represent the person's hands; H represents the legs. In this way, you can vividly remember the general structural formula of amino acids.

2. Types of amino acids

There are approximately _______ types of amino acids that make up proteins in living organisms. According to whether they can be synthesized in human cells, amino acids can be divided into ____________ and ____________.

Thought activation

1. Based on the general structural formula of amino acids, what are the elements that make up proteins?

Tip: Contains at least four elements: C, H, O, and N.

2. The amino acids that make up proteins have at least one amino group and one carboxyl group. What does "at least" mean? If there is more than one amino group and one carboxyl group in an amino acid molecule, where are the other amino groups and carboxyl groups located?

Tip: The number of amino groups and carboxyl groups in the amino acid molecule is at least one each, and can also be several. Other amino and carboxyl groups are located on the R group.

Protein is the main carrier of life activities PPT, the third part: the structure and diversity of proteins

1. protein structure hierarchy

amino acids

Concept: The carboxyl group of one amino acid molecule is connected to the amino group of another amino acid molecule, and a molecule of water is removed at the same time. This combination method is called a chemical bond formed by dehydration condensation: peptide bond, expressed as -NH-CO-

Dipeptide: A compound formed by the condensation of _____________

Polypeptide: A compound formed by the condensation of _____________, usually in the form of a chain

Protein: Has a certain _____________.

Thought activation

1. Analysis of the dehydration and condensation process of amino acids

(1) When forming a peptide bond, the corresponding -COOH loses -OH, the corresponding -NH2 loses -H, forming a molecule of water; the correct way to write the peptide bond is:

or —CO—NH—.

(2) In the removed water molecules, H comes from both the amino group and the carboxyl group, and O comes from the carboxyl group.

(3) A peptide chain has at least one free -NH2 and one free -COOH, which are located at both ends of the peptide chain. -NH2 and -COOH in the R group do not participate in the dehydration condensation process. Therefore, the number of amino groups (or carboxyl groups) in the polypeptide = the number of amino groups (or carboxyl groups) in the R group + the number of peptide chains.

2. Calculations related to the formation of peptides (or proteins) from amino acids

The dehydration condensation reaction formula of amino acids is actually a chemical equation, which must follow the laws of mass conservation and atomic conservation. Combined with the general structural formula and reaction principle of amino acids, it is not difficult to understand the following related calculations.

(1) Assuming that the average relative molecular mass of amino acids is a, and n amino acids form 1 peptide chain or m peptide chains respectively, there should be the following quantitative relationship:

(2) The number of N and O atoms contained in the protein

Number of N atoms = number of peptide bonds + number of peptide chains + number of N atoms on the R group = total number of N atoms in each amino acid

Number of O atoms = number of peptide bonds + 2 × number of peptide chains + number of O atoms on the R group = total number of O atoms in each amino acid - number of water molecules removed

Expansion and deepening: For a cyclic peptide composed of n amino acids, the number of peptide bonds produced = the number of water molecules removed = n; the amino group (or carboxyl group) contained only exists in the R group.

Protein is the main carrier of life activities PPT, Part 4: Related calculations of proteins (or polypeptides)

[Example] The picture on the right shows a protein molecule composed of a peptide chain, where A to F respectively represent different amino acid molecules in the polypeptide chain. If the protein molecule in the figure is composed of n amino acid molecules, the R groups of B, D, and F contain 1 amino group (—NH2), 1 carboxyl group (—COOH), and 1 methyl group (—CH3) respectively. According to Figure answers the following questions.

(1) This protein molecule contains at least the number of amino groups and carboxyl groups as ________ and ________ respectively.

(2) This protein molecule is decomposed by hydrolase and broken at six points: A, B, C, D, E, and F. Then, ________ polypeptide molecules are formed, and ________ water molecules are needed for hydrolysis.

(3) If the average relative molecular mass of the amino acid molecules that make up this protein is a, then the total relative molecular mass of the hydrolyzed polypeptide molecules is ________.

mind Mapping:

In-depth analysis of the meaning of the question shows that this protein molecule is composed of a polypeptide chain and contains n amino acid molecules. The average relative molecular mass of the amino acids is a, and the R groups of amino acids B and D contain 1 amino group and 1 carboxyl group respectively. .

(1) A polypeptide chain contains at least 1 carboxyl group and 1 amino group, which are located at both ends of the polypeptide chain. It is also known that the R groups of amino acids B and D contain 1 amino group and 1 carboxyl group respectively, so the protein molecule Contains at least 2 amino groups and 2 carboxyl groups.

(2) This protein molecule is hydrolyzed at six locations A to F, which can form 7 polypeptide molecules. Hydrolysis at each location requires 1 water molecule, so 6 water molecules are required.

(3) The relative molecular mass of the polypeptide molecule formed after hydrolysis consists of two parts. One is the relative molecular mass of the original protein molecule, which is na; the other is the relative molecular mass of the water consumed during the hydrolysis process, which is 6×18= 108. Therefore, the relative molecular mass of all hydrolyzed polypeptide molecules is na+108.

Answer (1)2　2(2)7　6　(3)na＋108

Myth Alert: Common Myths About Protein

Misunderstanding 1: Think that all protein molecules are composed of 20 kinds of amino acid molecules;

Misunderstanding 2: It is believed that a polypeptide chain only contains 1 free amino group and 1 free carboxyl group;

Misunderstanding 3: When calculating the relative molecular mass of hydrolyzed polypeptide molecules, the mass of water molecules during hydrolysis is not included. When answering such questions, you should note that the -NH2 (or -COOH) contained in the peptide chain is actually the -NH2 (or -COOH) that does not participate in the condensation reaction when the amino acids are condensed into the peptide chain. They are located at both ends of the peptide chain and R base.

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Update Time: 2024-10-05

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