40 Questions
Where does the metabolism of carbohydrates, amino acids, and nucleotides occur in a cell?
Cytoplasm
What is the primary function of the rough endoplasmic reticulum?
Translation of mRNA into membrane-associated proteins or for secretion out of the cell
Where does protein synthesis occur in a cell?
Cytosol
What is the function of the smooth endoplasmic reticulum?
Synthesis of lipids, Ca2+ storage, and steroid production
What is the primary function of the Golgi apparatus?
Modifying and packaging of proteins and lipids for delivery to other organelles
Where does fatty acid synthesis occur in a cell?
Cytoplasm
What is the term for a protein as it is being formed by a ribosome before it folds into its active shape?
Nascent protein
Where does the metabolism of amino acids occur in a cell?
Cytoplasm
What is the primary function of the nucleolus?
RNA synthesis
What is the characteristic of heterochromatin?
Condensed DNA with no active RNA synthesis
What is the purpose of the central dogma of molecular biology?
To outline the flow of genetic information from DNA to RNA to protein or RNA to protein
What is a characteristic of prokaryotic cells?
Their genome is found as circular plasmid DNA
What is the function of the nuclear envelope?
To allow macromolecules to pass through when entering or exiting the nucleus
What is the function of the nucleus?
To store DNA and coordinate the cell's activities
What is the significance of plasmid DNA?
It is important for gene modification
What is the difference between heterochromatin and euchromatin?
Heterochromatin is condensed, while euchromatin is uncondensed
What is the main function of the ribosome in the cell?
Site of protein synthesis
Which organelle is responsible for the degradation of intracellular proteins?
Proteosome
What is the pH of the acid hydrolases found in lysosomes?
pH 5
What is the function of the cristae in the mitochondria?
To increase the surface area for ATP production
What is the characteristic of an amphipathic molecule?
Having a polar head and a hydrophobic tail
What is the main function of the endosome in the cell?
Sorting and delivery of lipid vesicles
What type of molecule can pass through the plasma membrane passively?
Small, non-polar molecules
Which type of stem cell can produce all cell types necessary to give rise to a new organism?
Totipotent
What is the function of microfilaments, intermediate filaments, and microtubules in the cytoskeleton?
Providing structural support and facilitating cellular transport
What is the function of the mitochondria in the cell?
ATP production
From which face of the Golgi body do vesicles leave?
Concave face
How are nucleosomes compacted to form chromosomes?
By compacting into solenoid fibres and then hierarchical loops
What is the correct order of DNA organisation from the nucleus to chromosome?
Nucleus -> Nucleosomes -> Solenoid fibres -> Hierarchical loops -> Chromosome
What is the characteristic of the DNA helix?
A double-stranded molecule with a helical structure
What is the primary function of cytoskeleton in cellular transport?
Facilitating vesicle transport along microtubules
What is the difference between pluripotent and multipotent stem cells?
Pluripotent stem cells can form almost all cell types, while multipotent stem cells can form a few cell types of the same family
What was Arthur Kornberg's discovery in 1957?
DNA polymerase I
What is the function of the 5' to 3' exonuclease activity of DNA polymerase I?
To remove nucleotides from the growing DNA strand
During DNA replication, what is the role of the RNA primer?
To provide a binding site for DNA polymerase
What is the outcome of the initiation stage of DNA replication?
The formation of a replication fork
During DNA replication, which enzyme is responsible for joining Okazaki fragments on the lagging strand?
DNA ligase
What is the direction of DNA synthesis on the leading strand?
5' to 3'
What is the role of DNA polymerase's 3' to 5' exonuclease activity during DNA replication?
To proofread DNA synthesis
In which stage of the cell cycle does DNA replication occur?
Synthesis phase (S phase)
Study Notes
Cell Components and Functions
- Cytoplasm: metabolism of carbohydrates, amino acids, and nucleotides, and fatty acid synthesis
- Cytosol: metabolism, protein synthesis (free ribosomes)
- Endoplasmic Reticulum (ER):
- Rough ER: translation of mRNA into membrane-associated proteins or for secretion out of the cell, has ribosomes attached to the outer surface
- Smooth ER: synthesis of lipids, Ca²⁺ storage, and steroid production
- Golgi Apparatus: modifies and packages proteins and lipids for delivery to other organelles or for secretion out of the cell
- Mitochondria:
- Double-membraned organelles with smooth outer and folded inner lipid bilayer membrane
- Inner membrane forms cristae, boosting surface area for ATP production
- Matrix houses Krebs cycle, mitochondrial DNA, ribosomes, and enzymes crucial for ATP generation
- Ribosome: composed of two rRNA subunits that wrap around mRNA to begin translation and protein synthesis
- Lysosomes: membrane-bound organelles containing acid hydrolases at pH 5 for intracellular digestion
- Peroxisomes: membrane-bound organelles for chemical detoxification and lipid metabolism
- Proteasome: degrades intracellular proteins
- Endosome: sorts and delivers lipid vesicles and their contents to and from the plasma membrane
- Plasma Membrane:
- Acts as a selective barrier, allowing only small, non-polar molecules to pass through passively
- Controls what enters and exits the nucleus
- Nucleus:
- Contains DNA, nucleoproteins, and RNA
- Stores DNA and coordinates cell activities such as growth, metabolism, protein synthesis, and cell division
- Nucleolus: site of ribosomal RNA (rRNA) synthesis
- Nuclear Envelope: double-layered membrane with nuclear pores allowing macromolecules to pass through
- Cytoskeleton: provides structural support, enables cell shape change and movement, and facilitates intracellular transport
DNA Structure and Replication
- Central Dogma of Molecular Biology: genetic information flows from DNA to RNA to protein
- Prokaryotic Cell: lacks a nucleus, has membrane-bound organelles, and a circular plasmid DNA genome
- Eukaryotic Cell Structure:
- Organelles are compartments with specific functions
- Nucleus contains DNA and coordinates cell activities
- DNA is found in two forms: heterochromatin (condensed, tightly packed) and euchromatin (uncondensed)
- Stem Cells:
- Totipotent: can produce all cell types necessary to give rise to a new organism
- Pluripotent: can produce nearly all cell types
- Multipotent: can produce cells of a closely related family
- Oligopotent: can produce only a few cell types of the same family
- Unipotent: can only produce one type of cell
DNA Organisation and Replication
- DNA Organisation:
- DNA is wrapped around histones to form nucleosomes
- Nucleosomes form 'beads on a string' DNA
- Solenoid structures are compacted into hierarchical loops to create chromosomes
- Arthur Kornberg's Discovery (1957): demonstrated the existence of DNA polymerase I
- DNA Polymerase I:
- Has 5' to 3' DNA polymerizing activity
- Has 3' to 5' exonuclease activity
- Has 5' to 3' exonuclease activity
- Semi-Conservative DNA Replication:
- Occurs in the Synthesis phase (S phase) of the cell cycle
- Initiation: DNA helicase untwists DNA strands, primase makes RNA primer, and DNA polymerase starts replication
- Elongation:
- Leading strand: continuous 5' to 3' strand synthesis
- Lagging strand: Okazaki fragments synthesis, joined by DNA ligase into a continuous chain
This quiz covers the different components of a cell, including cytoplasm, cytosol, endoplasmic reticulum, and golgi apparatus, and their functions in cellular metabolism and protein synthesis.
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