EXAM 2 FINAL Flashcards
Yeasts have cell walls composed of what molecule(s)?
polysaccharides glucan and mannan
What is a pellicle?
protozoans have a flexible outer covering CALLED PELLICLE
What are the components of the eucaryotic plasma membranes?
- functionally and structurally very similar to prokaryotic cells - in addition to phospholipids and proteins, eukaryotic
membrane contains carbohydrates (not found in prokaryotes)
- carbohydrates function in cell to cell recognition and provides
adherence for bacteria
- also contains sterols, which are not found in prokaryotic plasma membranes, with the exception of Mycoplasma membranes
- Sterols confer the ability of the membranes to resist lysis due to increased osmotic pressure
- type of transport mechanism: a. simple diffusion
b. facilitated diffusion
c. osmosis
d. active transport e. Endocytosis
f. Exocytosis
What role does the carbohydrates of the eucaryotic membrane play?
carbohydrates function in cell to cell recognition and provides
adherence for bacteria
What role does the sterols of the eucaryotic membrane play? What role does the sterols of the eucaryotic membrane play?
which are not found in prokaryotic plasma membranes, with the exception of Mycoplasma membranes
- Sterols confer the ability of the membranes to resist lysis due to increased osmotic pressure
Receptor-Mediated Endocytosis
Specific for a target molecule
Binding of ligand (target) to receptor triggers internalization of receptor and target in a coated vesicle
Coated vesicle fuses with a lysosome, freeing target from the receptor
Target molecule enters the cytoplasm through diffusion or active transport
Receptors can be recycled
What is the function of the smooth ER
no ribosomes attached; f(x)s in lipid and steroid synthesis (i.e. testosterone & estrogen); detoxify drugs and harmful substances (i.e. in liver)
RIBOSOMES
80S ribosome composed of:
- large subunit (60S): composed of 3 rRNAs and 50 proteins - small subunit (40S): composed of 1 rRNA and 33 proteins
- Chloroplasts and mitochondria contain 70S ribosomes, like the procaryotes.
What is the structure and function of the Golgi complex/apparatus?
- consists of 4 - 20 flattened sacs (cisterns) stacked one on
top of the other with expanded ends. - Functions:
- modify proteins: glycoproteins, lipoproteins, etc. 2. package proteins:
- secretory proteins in secretory vesicles sent out of cell via exocytosis
- proteins that are membrane bound
- proteins to be remained in the storage vesicles (i.e. lysosomes)
What is the structure, function, and characteristics of the mitochondrion?
power house
- have a double membrane similar to plasma membrane
- outer membrane is smooth
- inner membrane arranged in a series of folds called cristae; folds increase surface area for chemical reaction to occur
- function is to synthesize ATP along inner membrane during cellular respiration
- matrix: center of mitochondrium
- contain 70S ribosomes, DNA of its own, and the machinery to
transcribe and translate the information encoded by their DNA - can self replicate independent of the cell
What is the structure and function of the chloroplast?
photosynthesis
- are contained in algae and green plants
- are membrane-bounded structures that contain the pigment chlorophyll and the enzymes required for photosynthesis
- The chlorophyll is contained in flattened membrane sacs called thylakoids.
- stacks of thylakoids are called grana
- contain 70S ribosomes, DNA, and enzymes involved in
protein synthesis
- can self replicate on its own within the cell.
What is aerobic respiration?
yields way more ATP (= cellular energy) than less efficient anaerobic respiration
What is genotype?
the genetic makeup of an organism.
central dogma,
the central dogma, originally proposed by Francis Crick, states that the
flow of the genetic information in a cell is always from DNA to RNA to protein.
• Exception: in systems such as retroviruses like HIV, 14 DNA can be made from RNA
antisense
Only 1 strand of the 2 DNA strands serves as a template for RNA synthesis. This DNA strand is called the antisense strand.
sense
The other DNA strand is called the sense strand → similar to mRNA strand.
- What is the direction of RNA transcription?
5’ —–>3’
Promoter
a sequence that determines transcription (RNA synthesis) initiation.
It is always located at the 5’ end of the strand that is identical to RNA of the transcribed region.
Contain specific sequences (usually 5-10 bp) that allow
RNA polymerase and transcription factors to bind.
Regulatory elements:
Sequences that are not promoter but can also regulate transcription
Transcribed region
sequence that is actually copied into RNA
Terminator
transcription termination sequence that is always located at the 3’ end of the transcribed region.
Cistron
an old name for a gene
Polycistronic
1 promoter directs synthesis of 1 mRNA that can be translated to more than one polypeptide
– Prokaryotic genes
Monocistronic
1 promoter directs synthesis of 1 mRNA that translates to only 1 gene
– Eukaryotic genes
DNA-dependent RNA polymerase
Transcription requires an enzyme called DNA- dependent-RNA polymerase and a supply of RNA nucleotides (A, U, C, G).
what does peptidyl transferase do? Which molecule has this activity?
-A peptide bond is formed between the two aas by in the 50s
What binds to the 30S subunit?
Shine Dalgarno sequence in the mRNA binds with the 16 s rna of the small subunit
What does aminoacyl-tRNA synthetase
Amino acid covalently linked to tRNAs at the 3’ tail by the enzyme aminoacyl-tRNA synthetases
- Each aminoacyl tRNA synthetase recognizes one particular amino acid and all tRNAs that recognize codons for that aa
- ARS can proofread and remove incorrect aa; < 1/5000 error
POST-TRANSLATIONAL PROCESSING of the polypeptide chain:
Polypeptide undergoes some modificationfirst methionine is removed by an
enzymatic action and the final
polypeptide chain is formed
3 mechanisms to regulate gene expression in bacteria
Repression
b. Induction
c. Attenuation
Why does the cell want to regulate its gene expression?
wants to save Atp
- What are constitutive enzymes?
Enzymes that are present at all times in a cell are called
constitutive
These enzymes are produced from genes that are turned on all
the time..60-80% of genes are constitutive
lacZ
Beta-galactosidase, hydrolyzes lactose to glucose & galactose
lacY
lactose permease, transports lactose into the cell
lacA
transacetylase
lacI:
repressor protein, binds to the Operator (O) on DNA
Nitrous Acid -
converts Adenine to a form which no longer pairs with Thymine but instead pairs with cytosine.
- Nitrous acid is a base pair mutagen.
- When DNA containing the modified Adenine replicates,
one daughter DNA will be different from the parent.
Base/nucleoside Analogues
replicas that are kind of similar to the nitrogenous base but are slightly altered
a. Ex.: 2-aminopurine replaces Adenine and can pair with C b. Ex.: 5-bromouracil replaces Thymine and can pair with G
Ultraviolet light,
a nonionizing component of sunlight is another form of mutagenic radiation.
Adjacent pyrimidines in a DNA strand can crosslink to form
pryrimidine dimers (T-T, T-C, C-C)
