viruses

2. the first step in a virus's infection cycle
3. substance that helps your body's immune system fight off harmful germs
5. microscopic, single-celled organisms that are too small to see with the naked eye
7. a living cell that can be invaded by a virus or other infectious agent
10. occurs when a microorganism enters a person's body and causes harm.
12. a self-replicating material that is present in nearly all living organisms as the main constituent of chromosomes
14. membrane a protective skin around a cell, acting as a barrier that controls what goes in and out
16. a large, complex molecule that's essential for life
19. in the body that indicates a person may have a disease or condition
21. system the body's outer layer, made up of skin, hair, nails, glands, and nerves, that protects the body from the outside world

1. medicines that treat infections caused by bacteria by killing the bacteria or stopping them from growing
4. something is capable of causing harm or has a bad effect
6. the act of making an exact copy or duplication of something
8. Its role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins
9. a cell or group of cells that receives stimuli and causes a specific response in the body
11. abnormal condition that affects the body's structure or function, and is usually associated with specific signs and symptoms
13. infectious agent that replicates only inside the living cells of an organism
15. systema complex network of cells, tissues, and organs that protects the body from infections and other diseases
17. a tiny organism that causes disease in humans, also known as a germ
18. a virus that uses RNA as its genomic material
20. the protein shell that surrounds a virus