Photosynthetic cells contain chlorophyll and other light-sensitive pigments that capture solar energy. In the presence of carbon dioxide, such cells are able to convert this solar energy into energy-rich organic molecules, such as glucose.
Yes, you can add a little lemon juice or vinegar to the goat's milk to make it into a buttermilk or kefir. This will lower the pH of the milk, and allow it to release the CO2 stored in the sodium bicarbonate (baking soda), causing the bread to rise. Goat's milk generally has less fat and more vitamins.
Butin todays buttermilk, it's probably added salt to enhance the flavor. Buttermilk is a fermented dairy product produced from cow's milk with a characteristically sour taste. There are two ways in which this product is made. Originally, buttermilk was the liquid left over from churning butter from cream.