Người ta nuôi cấy một chủng vi khuẩn E. Coli trong môi trường chỉ chứa đồng vị N14 sau đó thu lấy 100 con chuyển sang môi trường mới có chứa đồng vị N15. Giả sử pha lag kéo dài trong 30 phút, thời gian thế hệ là 20 phút và phân tử ADN của E. Coli có chiều dài 10200A0. Sau 4 giờ 50 phút nếu các tế bào đều phân chia bình thường thì: a. Có tối đa bào nhiêu khuẩn lạc được tạo ra?
b. Có bao nhiêu liên kết hóa trị trong các phân tử ADN được tạo thành hoàn toàn từ N15? (Chủng vi khuẩn này không có Plasmit).

question#1

ans:

cell is the basic unit of organization of all living things. cells are often called the building block of life and it is the smallest unit of life. the study of cell is called cell biology. cell consists of cytoplasm enclosed within membrane, which contain bio-molecules such as proteins and nucleic acid.

two third of cell is water, which means that two-third of your whole body is water. the rest is the mixture of molecules, mainly proteins, lipids and carbohydrates.

question#2

ans:

organ:

an organ is a group of tissues specialized to form a functional unit. an example is the heart in animals.

organ system:

an organ system is a group of several organs whose functions are synchronized to release an effective action in a living organism. an example is digestive system.

question#3

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#4

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system—working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#5

our body works because of the interactions that happen between organs and organ systems.  

for example:  

the heart to regulate blood flow throughout the body. the blood carries oxygen and nutrients to the cells and carries carbon dioxide and waste away from the cells. body systems work together in maintaining a constant internal environment. when this balance is disrupted, the body systems may not function properly, and human health can suffer.   you start to feel bad.

the tricuspid valve is present between right atrium and right ventricle