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.
Because yogurt is much thicker than buttermilk, it can be thinned out with regular milk to make an excellent buttermilk substitute. Simply add 1/2 cup yogurt to 1/2 cup milk (2 percent fat or higher) and whisk until smooth. Sour cream, another cultured milk product, can be used in the same manner.