Biology 8 Lesson 3: Cells
1. Summary of theory
1.1. Cell structure
All living organisms are made up of cells.
– A living organism can have one (e.g. single-celled organism) or many cells (e.g. human).
All human organs are made of cells. The human body has a very large number of cells about 75 trillion (75 × 10¹²). There are many types of cells that vary in shape, size, and function.
– There are spherical cells (egg cells), discs (red blood cells), cubes (epidermal cells), cones, rods (retinal cells), rhombus (muscle cells), astrocytes (nerve cells (neurons)), filaments (hair, hair) or like other organisms (white blood cells, sperm), …
– Although different in many aspects, but all types of cells have 3 basic parts: plasma membrane, cytoplasm and nucleus.
A typical cell includes:
– Plasma membrane:
– Cell substance:
- Ribosomes, endoplasmic reticulum, Golgi apparatus
- Central body
- Human child
1.2. Functions of parts of the cell
– The plasma membrane: is the outer layer of the cell, made of proteins and lipids, responsible for exchanging substances with the environment around the cell.
– Cell substance:
+ Endoplasmic reticulum:
- A system of membrane-bound flat sinuses and sacs that may or may not carry ribosomes (granular endoplasmic reticulum) or no (smooth endoplasmic reticulum).
- Ensures the connection between organelles, synthesis and transport of substances
+ Ribosomes: Consists of two subunits containing rRNA (ribosomal RNA), attached to the endoplasmic reticulum or floating in the cytoplasm (free ribosomes), where protein synthesis takes place
+ Mitochondria: Consists of an outer membrane and an inner membrane that folds to form a crest containing the substrate, participates in respiration, releases energy, produces ATP (adenoxin triphosphate).
Golgi apparatus: A system of flattened membranous vesicles stacked on top of each other, with cysts budding from the stack of vesicles, collecting, completing, distributing, and storing products.
+ Centrosome: Is a center that organizes microtubules, consisting of two centrioles arranged at right angles, surrounded by amorphous substances, participating in the process of cell division.
- Chromatin: Located in the nucleus. At a certain stage, when gathered to form chromosomes, containing DNA (deoxyribonucleic acid) plays the role of the body’s genetics.
- Nucleus: Contains rRNA (ribosomal RNA) that makes up the ribosome
1.3. Chemical composition of cells
Cells are composed of a complex mixture of many organic and inorganic substances. The main organic substances are proteins, carbohydrates, and lipids.
Protein, also known as protein, is a complex substance consisting of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S) and several other elements. . Protein molecules are very large, containing thousands of atoms, so they belong to the macromolecule category. Proteins are the basic building blocks of the body, found in all cells.
– Glucose, also known as powdered sugar, is a compound of sugar and powder. It consists of C, H and O where the ratio between H and O is always 2H ÷ 1O. In the body, glucose is in the form of glucose (found in the blood) and glycogen (found in the liver and muscles).
– Lipids, also known as fats, are found on the underside of the skin and in many organs, it also consists of 3 main elements, C, H, and O, but the ratio of those elements is not the same as that of glucose. The ratio of H ÷ O varies depending on the type of lipid. Lipids are the body’s reserve.
Nucleic acids (DNA or RNA) are mainly found in the nucleus of cells. Both of these are macromolecules that play an important role in heredity.
– In addition to the above-mentioned organic substances, there are also inorganic substances which are mineral salts.
1.4. Cell activity
– Every living cell in the body is always supplied with nutrients brought by the blood stream and there is always a synthesis process so complex organic compounds from simple substances are absorbed into the cell. .
– Simultaneously in the cells, there is always a process of breaking down organic compounds into simple substances and releasing necessary energy for the body. The process of synthesizing and breaking down organic substances in the cell is called anabolism and catabolism. These are the two fundamental aspects of cell life.
2. Illustrated exercise
Question 1: Prove that the cell is the functional unit of the body?
Cells are the functional units of the body because:
– All organisms are made up of cells
– Cells carry out life activities such as metabolism; growth and development; reproduction and induction.
Cells store and transmit genetic information across generations.
– When cells divide -> the body grows and reproduces
→ Cells are the basic structural units of the living world, they perform and maintain life functions.
Verse 2: Say that all cells in the body have a common structure. Tell me how that general structure is expressed?
Cells are composed of:
The plasma membrane is also known as the cell membrane.
– The cytoplasm contains organelles such as: endoplasmic reticulum (smooth endoplasmic reticulum and granular endoplasmic reticulum), Golgi apparatus, mitochondria, centrosomes…
– The nucleus: this is the most important part because it plays the role of controlling the living activities of the cell. The nucleus contains chromosomes, a structure that regulates protein formation, which plays a decisive role in heredity; The nucleus synthesizes ribosomal RNA (rRNA).
Question 3: How is cell viability expressed?
Cells are characterized by the following characteristics:
– Cells always exchange substances with the environment through blood and tissue water (clear medium):
– Get O2 and nutrients from the environment and release waste products into the environment.
– Through the process of metabolism that cells have the ability to accumulate matter, grow, divide to help the body grow.
– Cells are also capable of sensing environmental stimuli: receiving environmental stimuli and responding to them.
Verse 4: Choose the answer to fill in the blanks to complete the following sentences: Cells are …(l)… and also …(2)… of the body. Cells are surrounded by ….(3)… function to exchange substances between cells and the environment in the body.
A. plasma membrane
B. structural unit
C. cell wall
D. functional unit
Cells are the structural and functional units of the body. Cells are surrounded by a plasma membrane that functions to exchange substances between the cell and the environment in the body.
⇒ Answer: 1-B; 2-D; 3-A
3.1. Essay exercises
Question 1: Why is the cell the functional unit of the body?
Verse 2: Match column 1 ideas with column 2 ideas to get the function of the organelles in the cell:
2. Endoplasmic reticulum
4. Golgi apparatus
A. Protein synthesis
B. The energy center of the cell
C. Receiving and distributing products
D. Transport of substances in the cell
E. Carry out metabolism between the inner environment and the cell
G. Is a place to store genetic information
Question 3: The following statements are true or false:
1. The heart contracts to push blood into the vascular system and create blood circulation
2. Mitochondria are the place where organelles are made in cells
3. The plasma membrane is the place where the function of protein synthesis is performed
4. The cytoplasm is the place where the organelles are stored.
Verse 4: Which organelle is considered the ATP energy producer?
3.2. Multiple choice exercises
Question 1: Cells are:
A. Structural unit of the body
B. Functional unit of the body
C. Body mass unit
D. Both A and B
Verse 2: Plant cells are different from animals
A. Has a cell wall
B. There are plastids but no centrioles
C. Has large vacuoles
D. Both A, B and C
Question 3: Animal cells have
A. Thin cell membranes
B. No chloroplast
C. There are small vacuoles, centrosomes
D. Both A, B and C
Verse 4: The functional unit of the body is:
C. Environment in the body
D. Nervous system
Question 5: Which part controls all cell activities?
B. Central body
C. Endoplasmic reticulum
D. Biological membranes
After studying the lesson cell Here you need:
Describe the structural components of cells in accordance with their functions.
– Prove that the cell is the structural and functional unit of the organism.