Cytoplasm Of The Cell Flashcards
What does the cytoplasm contain?
includes all cellular contents except the nucleus
What are the two portions of the cytoplasm?
cytosol and organelles
How much volume of the cell does the cytosol take up?
55%
What are the components of the cytosol?
water (75-90%) and dissolved and suspended components
Where do many metabolic reactions of the cell occur?
in the cytoplasm
Where is the cytoskeleton contained?
in cytosol
What forms the cytoskeleton?
three protein filaments: microfilaments, intermediate filaments, and microtubules
What do microfilaments include?
actin and myosin
What are the functions of microfilaments?
helps generate movement: muscle contraction, cell division, cell locomotion, providing mechanical support: anchoring cytoskeleton to integral proteins, support for microvilli
Which part of the cytoskeleton contains exceptionally strong filaments?
intermediate filaments
Where are intermediate filaments located?
in parts of the cell subjected to mechanical stress
What are the functions of intermediate filaments?
keep the organelles in position, help attach cells to one another
What part of the cytoskeleton consists of hollow tubes and made of tubulin
microtubules
What are the functions of microtubules?
help to determine cell shape, and movement of organelles, chromosomes, cilia, and flagella
What are organelles?
specialized functional compartments within the cell
The number and types of organelles depend on what?
the functions of the cell
Where is the centrosome located?
near the nucleus
What does the centrosome consist of?
who centrioles, pericentriolar material
What are the functions of the centrosome?
growing of mitotic spindle in reproduction and the formation of microtubules in non-reproducing cells
What are cilia and flagella?
moving projections composed of microtubules
What do cilia do?
move-in coordination on the surface of cells and help sweep foreign particles out
How do flagella differ from cilia?
similar in structure but singular and much longer, moves entire cell and are only present in sperm cells
What are ribosomes?
the site for the synthesis of proteins
What do ribosomes contain?
ribosomal RNA
True or false: all ribosomes in a cell are attached to the endoplasmic reticulum
false: some are but there are some free ribosomes in the cytoplasm
What do ribosomes attached to the ER do?
synthesize proteins for organelles, the membrane, or for export
What do free ribosomes do?
synthesize proteins to be used in the cytosol or for other organelles
What is the Endoplasmic Reticulum?
network of flattened sacs and tubules extending from the nuclear envelope
What makes up more than 50% of membranous surfaces in the cell?
ER
What are the two types of ER? How do they differ?
Rough: studded with ribosomes, produces secretory, membrane, and organelle proteins; Smooth: extends from rough ER, not studded, has enzymes for the synthesis of fatty acids and steroids, release free glucose, Ca2+
What is the Golgi Complex and what does it do?
a small stack of flattened sacs close to the nucleus that produces secretory products and lysosomes
What organelle do secretory cells have many of?
Golgi complex
Proteins produced by the rough ER are transported to where?
Golgi complex
What are lysosomes
membrane-enclosed vesicles formed in the golgi complex
What pH are the digestive and hydrolytic enzymes at?
pH 5
What are the functions of lysosomes?
digest worn-out organelles, entire cells, contents of endosomes, phagosomes and pinocytic vesicles
What organelle generates most of the ATP? How?
mitochondria through the aerobic glycolysis
What organelle is more abundant in active cells?
mitochondria
What organelle can self replicate, why can they do that?
mitochondria have their own DNA inherited only from the mother
What are peroxisomes?
microbodies containing oxidases
What are the functions of peroxisomes?
eliminate toxic metabolic by-products
Can peroxisomes are proteasomes self replicate?
peroxisomes
What are proteasomes?
• Contain enzymes for degrading unneeded, damaged, or faulty proteins • “Cut” proteins into smaller pieces for other enzymes to break them down into amino acids
What is usually the most prominent feature of the cell?
The Nucleus
True or false: cells can only have one nucleus
Most cells have one, but some more than one, or none
What does the nuclear envelope consist of?
The nuclear envelope consists of a double membrane
(two lipid-bilayers) with pores
True or false: nuclear pores are 10x smaller than the plasma membranes
True
How do small molecules and ions move through nuclear pores?
Small molecules and ions move through pores by diffusion
How do RNA and proteins pass through nuclear pores?
RNA and proteins pass through pores by active transport
How many nucleoli does the nucleus usually contain?
several nucleoli
What are nucleoli?
Nucleoli are clusters of proteins, DNA, and RNA not enclosed by a membrane
What produces ribosomes?
Nucleoli
Where in the cell are chromosomes?
The Nucleus
Contains the genes aligned in
the chromosomes
What makes up a chromosome?
Each chromosome is one DNA molecule, coiled with proteins
DNA with proteins and some RNA is called what?
The DNA with the proteins and some RNA is called the chromatin
The total genetic information carried by one cell is called what?
genome
How many chromosomes do human somatic cells have?
Human somatic cells have 46 chromosomes, 23 from each parent
DNA and RNA are chains of what?
DNA and RNA are chains of repeating monomers called nucleotides
What does each nucleotide consist of?
- Nitrogenous base
- Pentose sugar
- Phosphate group
What are the nitrogenous bases of DNA?
Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T)
What is the sugar of DNA
Deoxyribose
What is the nitrogenous base pairing of DNA?
A – T
G – C
What are the types of DNA?
Nuclear DNA
Mitochondrial DNA
What are the nitrogenous bases of RNA?
Adenine (A)
Cytosine (C)
Guanine (G)
Uracil (U)
What is the sugar of RNA
Ribose
What is the nitrogenous pairing of RNA?
A – U
G - C
What are the types of RNA
mRNA (messenger)
tRNA (transfer)
rRNA (ribosomal)
DNA contains detailed plans for what?
The DNA contains the detailed plans for each protein the cell needs
The primary structure of a protein is determined by what?
The primary structure of a protein is determined by
the sequence of amino acids
Each amino acid is coded by what?
Each amino acid is coded by a three-nitrogenous base sequence in the DNA
How many bases at a time are used for protein synthesis?
3 Bases
How many amino acids do we need a code for in the body?
We only need a code for each of the 20 amino acids in the body!
codon CCG codes for what?
The codon CCG codes for glycine
Condon AGT codes for what?
The codon AGT codes for serine
Codon AUG codes for methionine?
The codon AUG codes for methionine
What is the first step in protein synthesis?
the first step of protein synthesis and is called
transcription
How are RNA molecules made?
transcription
What does mRNA mean? What does it do?
Messenger RNA (mRNA): • Direct the synthesis of the protein
What does rRNA mean? What does it do?
Ribosomal RNA (rRNA): • Joint ribosomal proteins to make ribosomes
What does tRNA mean? What does it do?
Transfer RNA (tRNA): • Binds to one amino acid on one end and holds it in place on a ribosome until incorporated into a protein. On the other end it has an anticodon complementary to the specific codon of the mRNA
What is an anticodon?
An anticodon is found at one end of a transfer RNA (tRNA) molecule.
How many strands of DNA serves as a template for RNA synthesis?
Only one of the two strands of the DNA serves as a template for RNA synthesis
What is a promoter?
Transcription begins in a special codon of the DNA called promoter, located near the beginning of the gene
What is a terminator?
Transcription ends in a special codon called terminator, which specifies the end of the gene
What are exons?
The exons are the parts of the gene that code for parts of a protein
What are introns?
The introns are between the exons and do not code for any part of the protein
True or false: in newly formed mRNA from the transcription process both exons and introns are copied and both are needed
True
What is pre-mRNA?
The RNA formed in the transcription process is called the pre-mRNA
How is the final functional mRNA formed?
The final functional mRNA is formed after enzymes cut out the introns and splice together the exons from the pre-mRNA
How do 500k-1mil human proteins come from 30k genes in the human genome?
By Alternate Splicing of the mRNA molecules and Chemical Modifications of proteins in the Golgi complex
What is alternative splicing of mRNA?
Produces many more different mRNAs than available genes in the DNA One gene may code for 10 or more different proteins
What is chemical modification?
Occurs in the Golgi complex One protein can produce two or more different proteins
Where does translation occur?
Occurs in the ribosomes within the cytoplasm of the cell
Where on the ribosomes is the binding site for mRNA?
The small subunit of the ribosome has a binding site for the mRNA
What are the binding sites for tRNA on the ribosome?
• P (peptidyl) site
For tRNA carrying the growing polypeptide chain
• A (aminoacyl) site
For the tRNA carrying the next amino acid to be added
• E (exit) site
Binds tRNA before releasing
What is the peptidyl site on a ribosome for?
For tRNA carrying the growing polypeptide chain
What is the aminoacyl site for on a ribosome?
For the tRNA carrying the next amino acid to be added
What is the exit site for on a ribosome?
Binds tRNA before releasing
When does translation start?
Translation starts when one mRNA binds to the small subunit of the ribosome
What is the start codon?
AUG codes for methionine, so this amino acid is always the first in a growing peptide chain
What is initiator-tRNA
A special tRNA called initiator-tRNA binds to the start codon (AUG) on the mRNA
At what rate does translation progress at?
15 peptide bonds per second
How can several identical proteins be assembled at the same time?
As one ribosome attaches and move along the mRNA, another ribosome may attach behind it and begin translation of the same mRNA
When does protein synthesis end?
Protein synthesis ends when the ribosome reached a stop codon at the A site
What are the stop codons?
- UAA
- UAG
- UGA
What happens when translation reaches one stop codon?
The completed protein detaches from the final tRNA