MODULE 4: Chapter 6.1 Flashcards
What is the active substance used by tribesmen in Eastern Africa to poison arrows?
Ouabain
Ouabain is a specific inhibitor of the Na⁺–K⁺ ATPase transporter protein.
What is the effect of ouabain on heart muscle?
Heart muscle contracts but cannot relax
This effect can be lethal in large doses but can stimulate the heart in controlled doses.
What are the five major functional classes of proteins?
- Metabolic enzymes
- Structural proteins
- Transport proteins
- Cell signaling proteins
- Genomic caretaker proteins
What is the role of metabolic enzymes?
Catalyze biochemical reactions involved in energy conversion pathways
They are responsible for the synthesis and degradation of macromolecules.
How do enzymes function as chemical catalysts?
By lowering the activation energy of a reaction
This increases the rate of product formation.
What is an example of a metabolic enzyme?
Malate dehydrogenase
It catalyzes the oxidation of malate to form oxaloacetate.
What are structural proteins primarily responsible for?
Maintaining the integrity of cell structures and promoting changes in cell shape
They are the most abundant proteins in living organisms.
What are two abundant structural proteins in animal cells?
- Actin
- Tubulin
What is the role of transport proteins?
Facilitate movement of molecules both within and between cells
They can be passive or active transporters.
What distinguishes passive transporters from active transporters?
Passive transporters do not require energy, while active transporters do
Active transporters use energy from ATP hydrolysis or ionic gradients.
What type of proteins are responsible for cell signaling?
Cell signaling proteins
They include membrane receptors, nuclear receptors, and intracellular signaling proteins.
What are the two large classes of membrane receptors?
- G protein–coupled receptors
- Receptor tyrosine kinases
What is the function of nuclear receptor proteins?
Regulate gene expression in response to ligand binding
Important examples include estrogen and progesterone receptors.
What is a common mechanism for signal transduction in cells?
Reversible protein phosphorylation
It involves protein kinases that phosphorylate target proteins in response to signals.
Fill in the blank: The enzyme malate dehydrogenase catalyzes the reaction that oxidizes malate to form _______.
Oxaloacetate
True or False: Enzymes are consumed in the chemical reaction they catalyze.
False
What is the function of the Ca²⁺-ATPase transporter protein?
Pumps Ca²⁺ ions across cell membranes against a concentration gradient
It is critical for muscle contraction and relaxation.
What are the components of muscle tissue largely composed of?
Structural proteins
Actin and myosin are key examples.
What is the sliding filament model related to?
Skeletal muscle contraction
It describes how actin and myosin interact during muscle movement.
What do transport proteins allow to pass through the plasma membrane?
Polar and charged molecules
This is crucial for maintaining cellular homeostasis.
What is the role of adenylate cyclase?
It is an enzyme that responds to activation of G protein–coupled receptors
Adenylate cyclase converts ATP to cyclic AMP, a second messenger in signal transduction.
What is reversible protein phosphorylation?
It is a widely used cytosolic signal transduction mechanism involving the addition and removal of phosphate groups on proteins.
What do protein kinases do?
They phosphorylate serine and threonine residues on downstream target proteins in response to upstream receptor activation signals.
What is the function of Src kinase?
It phosphorylates tyrosine residues on target proteins.
What does phosphoinositide 3-kinase do?
It is activated by insulin receptor signaling and phosphorylates the carbohydrate functional group of phosphatidylinositol.
What are genomic caretaker proteins?
They ensure the integrity of genomic DNA and regulate gene expression to reflect the biochemical needs of the organism.
What is the role of DNA polymerase enzymes?
They are required for DNA replication, repair, and recombination.
How many types of DNA polymerases are found in cells?
At least five different types occur in prokaryotic and eukaryotic cells.
What proteins assist DNA polymerase during DNA replication?
Single-stranded binding proteins, DNA ligase, topoisomerase, and DNA primase.
What are photolyase enzymes responsible for?
They repair thymine dimers formed by ultraviolet radiation.
What is DNA recombination?
It occurs when DNA strands recombine due to sequence-specific DNA cleavage or random DNA breaks.
What is the function of the RecBCD protein complex?
It binds to double-stranded DNA, unwinds it, and cleaves one strand to facilitate DNA repair or recombination.
What do RNA polymerases do?
They copy information stored in DNA into nascent nucleic acid strands.
How many primary RNA polymerases are there in eukaryotes?
There are three primary RNA polymerases.
What does RNA polymerase I transcribe?
Ribosomal RNA genes.
What does RNA polymerase II transcribe?
Protein-coding genes.
What does RNA polymerase III synthesize?
A variety of small RNA molecules encoded in DNA.
What are transcription factors?
Proteins that bind DNA or form complexes to regulate gene transcription.
What is the role of histone acetylase and deacetylase enzymes?
They modify histone proteins to activate or repress gene expression.
Why are proteins called the workhorses of living cells?
They mediate or regulate nearly all aspects of cell structure and function.
What are metabolic enzymes?
Proteins that catalyze biochemical reactions involved in energy conversion pathways.
What is the enzyme active site?
The region of an enzyme where the catalytic reaction takes place.
What are structural proteins?
The most abundant proteins in living organisms that provide the architectural framework for cells and tissues.
What are cytoskeletal proteins?
Structural proteins responsible for cell shape, migration, and signaling.
What is a transport protein?
A protein that spans the width of a cell membrane, allowing polar or charged molecules to enter or exit the cell.
What is a passive transporter?
A transport protein that allows specific molecules to move across a membrane down their chemical gradients.
What is an active transporter?
A membrane transport protein that requires energy to induce conformational changes for molecule transport.
What is an ion channel?
A type of passive transporter allowing ions across a cell membrane.
What is a membrane receptor?
A transmembrane protein that changes conformation upon ligand binding.
What is a nuclear receptor?
A transcription factor regulating gene expression in response to ligand binding.
What is an intracellular signaling protein?
A protein that acts as a molecular switch, undergoing conformational changes in response to signals.
What is a genomic caretaker protein?
A protein that ensures the integrity of genomic DNA, including DNA repair and RNA synthesis.
