Plants that live in the Arctic have a relatively short growing season in which the light intensity
is always relatively low. Many species growing in these conditions have a high level of
anthocyanin pigments in their leaves. The combined effect of these red pigments with the
green chlorophyll makes the leaves appear dark purple or black.
Suggest why this adaptation is useful in increasing photosynthetic rates.
[3]
- light intensity is limiting
- more light and wavelengths absorbed
- less reflection and transmission of light
- so more ATP formed
- enzymes can work more efficiently
List three uses of ATP in birds and mammals.
[3]
- glycolysis
- protein synthesis
- muscle contraction
- cell division
- DNA replication
- active transport
- exocytosis / secretion
- movement within cells such as synaptic vesicles
- cilia beating
- electrical conduction
Name three ways that phosphorylation of ADP can occur in a photosynthetic plant
cell.
[3]
- cyclic photophosphorylation
- non-cyclic photophosphorylation
- chemiosmosis
- oxidative phosphorylation
- substrate level phosphorylation
There are a number of organic molecules in cells whose role is to transfer hydrogen atoms
from one compound to another.
Examples include NAD, FAD and NADP.
NAD, FAD and NADP are important molecules in plant cells.
Describe, in detail, the role of
these molecules within a palisade mesophyll cell.
[7]
NAD and FAD in Respiration:
- NAD and FAD in respiration have dehydrogenase enzymes that remove H atoms from molecules
- In glycolysis, 2 NAD molecules are reduced (gain electrons and protons) to form NADH
- In link reaction, 1 NAD molecule is reduced per molecule of pyruvate, producing NADH.
- Krebs cycle produces 3 NAD molecules which are reduced to NADH
- FAD is reduced in Krebs cycle to form FADH
- Both NADH and FADH transfer electrons and hydrogen to the electron transport chain (ETC) in cristae for ATP production.
NADP in Photosynthesis:
NADP reduced by accepting hydrogen atoms from water via photolysis
NADPH is used in the Calvin cycle to convert GP to TP
NADP also transports hydrogen from the grana, the site of light-dependent reactions, to the stroma - the site of the Calvin cycle.
