HL Biology 8.1 Metabolic Processes

Photosynthesis

Photosynthesis converts light energy (from the sun) into stored chemical energy (organic compounds)

* the conversion of light energy into chemical energy requires energy transfer molecules (electron carriers) and ATP
* this process requires photosynthetic pigments (chlorophyll), which are found in chloroplasts in most eukaryotic cells

Chloroplasts

the structure of a chloroplast is adapted to the function it performs (photosynthesis):

* granum are made up of stacks of thylakoids to increase the surface area available for the electron transport chain
* the thylakoid lumen is very small (maximises the electrochemical gradient that results from proton accumulation)
* the stroma contains suitable enzyme and an appropriate pH for the Calvin cycle to occur (light independent reactions)

Cell Respiration

Cell respiration converts stored chemical energy (organic compounds) into an immediate and usable energy molecule (ATP)

* the conversion of energy between stored and usable forms requires energy transfer molecules (electron carriers)
* the majority of ATP is produced via aerobic respiration which occurs within the mitochondria of a cell (requires oxygen)

Mitochondria

the structure is adapted to the function it performs (aerobic cell respiration)

* the inner membrane is folded into cristae to increase the surface area available for the electron transfer chain
* the intermembrane space is very small (maximises the electrochemical gradient that results from proton accumulation)
* the mitochondrial matrix contains suitable enzyme and an appropriate pH for the Krebs cycle to occur
* the outer membrane contains the necessary transport proteins for shuttling pyruvate into the mitochondria (link reaction)

Electron Tomography

Electron tomography is a technique by which a 3-dimensional image of an internal cellular structure can be generated

* samples are repeatedly imaged at different angles (using a transmission electron microscope) and the images are complied