What is the composition of the cell membrane?
- Separates one cell from another
- Thin layer of tissue
- Controls substance movement
- Communicates with other cells
- Provides structure/shape
The cell membrane is crucial for maintaining cellular integrity and function.
Define ICF and ECF.
- ICF: Intracellular fluid
- ECF: Extracellular fluid
ICF is the fluid within the cell membrane, while ECF is the fluid outside the cell membrane.
What is the phospholipid bilayer structure also known as?
Fluid mosaic model
This model describes the arrangement of phospholipids and proteins in the cell membrane.
What are the two types of membrane proteins?
- Integral proteins (transmembrane)
- Peripheral proteins
Integral proteins span the membrane, while peripheral proteins are attached to the surface.
What is a ligand?
Typically small molecules that are messages delivered to a receptor
Ligands bind to receptor proteins to initiate cellular responses.
What is the difference between active transport and passive transport?
- Active transport: Moves molecules against the concentration gradient, requires ATP
- Passive transport: Moves molecules with the concentration gradient, does not require energy
Active transport is essential for maintaining concentration gradients across membranes.
What is osmosis?
The diffusion of water through aquaporins
Osmosis is a specific type of facilitated diffusion.
Define tonicity.
Depends on the concentrations of non-penetrating solutes
Tonicity affects cell volume and shape when placed in different solutions.
What are the three types of RNA involved in protein synthesis?
- mRNA (messenger RNA)
- tRNA (transfer RNA)
- rRNA (ribosomal RNA)
Each type of RNA plays a specific role in the process of translating genetic information into proteins.
What is the first step of protein synthesis?
Transcription
In transcription, mRNA is created as a copy of DNA code.
What happens during translation?
Ribosome reads mRNA codons and assembles amino acids into a polypeptide chain
Translation is the process where the genetic code is converted into a functional protein.
What is the role of RNA polymerase in transcription?
Attaches to the DNA strand at the promoter
RNA polymerase synthesizes mRNA from the DNA template.
What is a polysome?
Several ribosomes reading a single strand of mRNA at the same time
Polysomes allow for the efficient production of multiple copies of a protein.
What is the function of the centrosome?
Assembles microtubules
The centrosome is crucial for cell division and maintaining cell structure.
What are inclusions?
Like organelles without membranes, directly contact the cytosol
Inclusions include structures like ribosomes and proteasomes.
What is the significance of mitochondrial DNA (mtDNA)?
Evidence for the endosymbiont theory of evolution
Mitochondria have their own DNA, supporting the idea that they originated from free-living prokaryotes.
What are the three fiber sizes in the cytoskeleton?
- Microfilaments (actin)
- Intermediate filaments (myosin, keratin, neurofilament)
- Microtubules (tubulin, centrioles, cilia, flagella)
These fibers provide structure, support, and movement to the cell.
What are the STOP codons in protein synthesis?
- UAA
- UAG
- UGA
These codons signal the termination of protein synthesis.
