Khan Academy is great! Also, Alison (it's a website) has some free courses as well.
Answer:
the endpoint not pH scale is 14
Explanation:
the answer should be d because of the concentration gradient see if that makes sense
The double membrane. It's theorized that chloroplasts used to be their own single-celled organism in the environment (and therefore with its own membrane). Then, the theory states, a larger cell took in the chloroplast by endocytosis, which involves surrounding the chloroplast in the large cell's own membrane. The chloroplast would then have two membranes surrounding it. This is similar to the thinking for mitochondria becoming an organelle as well. Hope this helps! :)
