Action potentials in the heart spread from cell to cell through: desmosomes. coronary vessels. gap junctions. valves. interneurons.

carbohydrates

Explanation:

Carbohydrates are compound made up of carbon, hydrogen and oxygen. They are formed during photosynthesis in the chloroplast of green plants. They are build from four different types of unit including: monosaccharides, disaccharides and polysaccharides.

The carbohydrates are storage forms of food. Plants store food in form of starch while animals it is stored in form of glycogen. They are also components of structures that provide mechanical support in organisms. For example, cellulose in the plant cell walls, chitin in the exoskeleton and lignin in xylem vessels and tracheids.

In presence of water, hydrolysis occurs and glucose is formed which can be oxidized by respiratory enzymes to provide energy.