Question

1. Is the transport of glucose into the cell at the gut epithelium using the sodium gradient active or passive transport? Is it symport or antiport?

2. Write a 1 sentence description of how G-proteins work and how their activity is regulated.

Answer 1

1)Active transport It is symport as both ions move in same direction 2)The first step in this complex signalling system involves the binding of specific ligands (hormones, neurotransmitters, growth factors, glycoproteins, cytokines, odorants and photons) at the cell surface to a GPCR, thereby activating the receptor. The signal is transmitted into the cell via a conformational change in the receptor, which results in the activation of the bound G protein. GPCRs act as guanine nucleotide exchange factors for the a subunit of the G protein, whereby activated receptor promotes the exchange of bound GDP (guanine diphosphate) for GTP on the a subunit, which is the rate-limiting step in G protein activation