In a multicellular organisms organs carry out a variety of life functions in a single cell led organism these functions are performed by

Single celled organisms such as bacteria have structures that enable them to carry out life functions and live. Some of these structures are  simply called organelles. The following are  some of the structures and their function in keeping the unicellular organism alive.

1. Ribosomes

These are structures  that are responsible for protein synthesis in the cell.

2. Plasma membrane

It is a selectively permeable barrier allowing nutrients in  and waste out and also forms the mechanical boundary of the cell. It is the location of many metabolic processes such as respiration and  photosynthesis.

3. Gas vacuole

Gives buoyancy for floating in aquatic environments.

4. Capsules and slime layers

Provide resistance to phagocytosis  and helps in adherence to surfaces.

5. Fimbriae and pili

Help in attachment to surfaces, facilitate bacterial mating.

6. Flagella

Helps in movement

a:

by the combination of an unlimited number of elements

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.