At the highest level of classification, there are four type of secondary structures

All a

All b

a+b

a/b

TLS Online TPP Program

#Id: 8098

#Unit 1. Molecules and their Interaction Relevant to Biology

The surfaces of the cells that form the alveoli (small air spaces of the lung) are coated with surfactant, which decreases the alveolar surface tension. 

Lung surfactant contains 80 to 90% phospholipid by weight, and 70 to 80% of the phospholipid is phosphatidylcholine, mostly the dipalmitoyl species.

TLS Online TPP Program

#Id: 5103

#Unit 6. System Physiology – Plant

Phytochrome interacting factors (PIFs) act as negative regulators of photomorphogenesis.

TLS Online TPP Program

#Id: 1070

#Unit 5. Developmental Biology

APETALA1 (Class A homeotic gene & meristem identity gene)

TF family -MADS

TLS Online TPP Program

#Id: 782

#Unit 3. Fundamental Processes

1100 sequences in the E. coli genome that fit these criteria, suggesting more than half of the cell’s transcripts are terminated at intrinsic terminators.

TLS Online TPP Program

#Id: 6478

#Unit 3. Fundamental Processes

Promoters that do not contain a TATA element are called TATA-less promoters. Surveys of promoter sequences suggest that 50% or more of promoters may be TATA-less.