I think it is organic compounds
It was plants. Plants used photosynthesis, basically the sun's energy. And other animals ate the plants, and other animals ate the animals that ate the plant.
Answer:
b. steroid
Explanation:
Steroids can cross the lipid membrane bilayer thus being able to relay the secondary message.
Bacterial cells are usually single celled while eukaryotic cells are multi-celled.
The answer is a
Answer:
The correct answer would be active transport by proteins.
When a molecule is transported against the concentration gradient it requires cellular energy and the process is termed as active transport.
The energy is either provided by the hydrolysis of the ATP (adenosine triphosphate) in primary active transport or by the electrochemical gradient in secondary active transport
Active transport takes place with the help of integral membrane proteins or transport proteins which form carriers or channels across the membrane.
Examples may include a sodium-potassium pump, uptake of glucose in small intestine et cetera.
