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?
very tiny organelles that contain enzymes for degrading unneeded, damaged, or faulty proteins. They cut proteins into smaller pieces for other enzymes to break them down into aa
What is usually the most prominent feature of the cell?
the nucleus
True or false: cells can only have one nucleus
false: most cells have one, but some more than one, or none
What does the nuclear envelope consist of?
a double membrane (two lipid-bilayers) with pores
True or false: nuclear pores are 10x smaller than the plasma membranes
False: nuclear pores are 10x bigger than the plasma membranes
How do small molecules and ions move through nuclear pores?
by diffusion
How do RNA and proteins pass through nuclear pores?
active transport
How many nucleoli does the nucleus usually contain?
one or several
What are nucleoli?
clusters of proteins, DNA, and RNA not enclosed by a membrane
What produces ribosomes?
nucleolus
Where in the cell are chromosomes?
in the nucleus
What makes up a chromosome?
contains genes, is one DNA molecule coiled with proteins
DNA with proteins and some RNA is called what?
chromatin
The total genetic information carried by one cell is called what?
the genome
How many chromosomes do human somatic cells have?
46 chromosomes, 23 from each parent
DNA and RNA are chains of what?
repeating monomers called nucleotides
What does each nucleotide consist of?
- nitrogenous base, 2. pentose sugar, and 3. phosphate group
What are the nitrogenous bases of DNA?
adenine, cytosine, guanine, thymine
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?
nucelar and mitochondral
What are the nitrogenous bases of RNA?
adenine, cytosine, guanine and uracil
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, tRNA, rRNA
DNA contains detailed plans for what?
each protein the cell needs
The primary structure of a protein is determined by what?
the sequence of amino acids
Each amino acid is coded by what?
a three nitrogenous base sequence in the DNA
How many bases at a time are used for protein synthesis?
three bases at a time
How many amino acids do we need a code for in the body?
20
What is a codon?
each combo of three nitrogenous bases within the DNA, each codon codes for one specific amino acid
codon CCG codes for what?
glycine
Condon AGT codes for what?
serine
Codon AUG codes for methionine?
methionine
What is the first step in protein synthesis?
transcription
How are RNA molecules made?
the sequence of nucleotide triplets in the DNA (codon) serves as a template for copying info into a complementary sequence of codons that form the structure of the RNA molecule
What does mRNA mean? What does it do?
messenger RNA directs the synthesis of the protein
What does rRNA mean? What does it do?
ribosomal RNA that joins ribosomal proteins to make ribosomes
What does tRNA mean? What does it do?
transfer RNA binds to one aa on one end and holds it in place on a ribosome until incorporated into a protein.
What is an anticodon?
on the other end of an amino acid that is complementary to the specific codon of the mRNA
How many strands of DNA serves as a template for RNA synthesis?
two
What is a promoter?
special codon of the DNA located near the beginning of a gene, transcription begins here
What is a terminator?
a special codon that specifies the end of a gene, transcription ends here
What are exons?
The part of the gene in the DNA strand being transcribed that code for the parts of a protein
What are introns?
the part of the gene in the DNA strand being transcribed that 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
false: in newly formed mRNA from the transcription process both exons and introns are copied but only exons needed
What is pre-mRNA?
RNA formed in the transcription process
How is the final functional mRNA formed?
after enzymes cut out 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 mRNA than available genes in the DNA, one gene may code for 10+ different proteins
What is chemical modification?
occurs in Golgi complex, one protein can produce 2+ different proteins
Where does translation occur?
in the ribosomes within the cytoplasm of the cell
Where on the ribosomes is the binding site for mRNA?
a small subunit
What are the binding sites for tRNA on the ribosome?
P (peptidyle), A (aminoacyle), E (Exit)
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 to tRNA before releasing
When does translation start?
when one mRNA binds to the small subunit of the ribosome
What is the start codon?
AUG: methionine
What is initiator-tRNA
a special tRNA that binds to the start codon on 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 moves along the mRNA, another ribosome may attach behind it and begin translation of the same RNA
When does protein synthesis end?
when the ribosome reaches 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, the tRNA vacates the P site and the ribosome splits back into its large and small subunits
