Biology: Life and Systems - Cell Theory and Organelles

The Cell Theory: 1) All living organisms are composed of one or more cells. 2) The cell is the basic unit of structure and organization in organisms. 3) Cells arise from pre-existing cells.

Prokaryotic vs. Eukaryotic Cells: Prokaryotes lack a membrane-bound nucleus and organelles (e.g., bacteria), while Eukaryotes have a distinct nucleus and specialized organelles (e.g., plants and animals).

Organelles: Specialized structures within a cell. Key examples include the Nucleus (contains DNA), Mitochondria (site of aerobic respiration), and Ribosomes (site of protein synthesis).

Plant vs. Animal Cells: Plant cells possess a rigid cell wall made of cellulose and chloroplasts for photosynthesis, whereas animal cells lack these but may have small, temporary vacuoles and centrioles.

Cellular Respiration: The process by which mitochondria convert glucose into energy, represented by the chemical equation: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$.

Photosynthesis: The process in chloroplasts that converts light energy into chemical energy: $6CO_2 + 6H_2O + \text{light} \rightarrow C_6H_{12}O_6 + 6O_2$.

Surface Area to Volume Ratio: As a cell increases in size, its volume ($V$) increases faster than its surface area ($SA$), which limits the efficiency of diffusion across the cell membrane.