8,11 Flashcards
Why can two different cell types with the same DNA be so different?
Different cell types express different genes, leading to the production of different proteins, which define the cells’ structure and function.
How is gene expression regulated in cells?
Gene expression can be controlled at multiple levels, including transcription initiation, RNA processing, mRNA export from the nucleus, mRNA stability, translation, and protein activity.
What is the function of the promoter region in gene expression?
The promoter contains sequences where RNA polymerase binds to initiate transcription.
How do regulatory proteins control transcription?
Regulatory proteins bind to specific DNA sequences (regulatory sequences) to switch genes on or off by interacting with RNA polymerase.
What is an operon in bacteria?
An operon is a set of genes transcribed into a single mRNA molecule and controlled by a single promoter.
How does the lac operon function?
The lac operon is controlled by an activator (CAP) and a repressor. When glucose levels are low, CAP binds and helps RNA polymerase initiate transcription if lactose is present to remove the repressor.
What are transcription factors in eukaryotes?
Transcription factors are proteins that assemble on promoters to help RNA polymerase initiate transcription.
What is the role of the TATA box in eukaryotic transcription?
The TATA box is a DNA sequence that helps position RNA polymerase and transcription factors at the correct site to start transcription.
How do glucocorticoid hormones influence gene expression?
Glucocorticoid hormones bind to receptors, which then bind to DNA and activate genes involved in glucose production, particularly during starvation or stress.
What is a key difference between transcription in bacteria and eukaryotes?
In eukaryotes, transcription requires multiple transcription factors, whereas bacterial RNA polymerase can initiate transcription on its own.
What is the main function of the plasma membrane?
The plasma membrane acts as a selective barrier, allowing the passage of nutrients and waste and containing proteins that sense environmental signals.
What are endocytosis and exocytosis?
Endocytosis is the process of importing materials into the cell, while exocytosis is the export of materials out of the cell.
What is the basic structure of the plasma membrane?
The plasma membrane consists of a lipid bilayer, composed mainly of phospholipids with hydrophilic heads and hydrophobic tails.
What is the role of cholesterol in the plasma membrane?
Cholesterol helps modulate membrane fluidity and stability by filling gaps between phospholipids.
What factors affect membrane fluidity?
Membrane fluidity is affected by the length of the hydrocarbon tails, the degree of unsaturation (double bonds), and the presence of cholesterol.
