Module 2 Exam Intro to Biology
gene expression in eukaryotes
- Transcription occurs in the nucleus - RNA is processed - RNA is moved to the cytoplasm - Translation occurs in the cytoplasm
mRNA translation
-cytoplasm has proteins that determine whether translation takes place -environmental conditions can delay translation (ex: red blood cells cannot produce hemoglobin unless heme is available) -the longer mRNA remains in the cytoplasm before it is broken down, the more gene product is produced (can be affected by length of ply A tail or presence of hormones)
gene expression in prokaryotes
-no nucleus -transcription and translation are coupled
3 phases of translation
1. Initiation 2. Elongation 3. Termination
Microtubules
13 long chains of tubulin dimers (2 linked tubulin molecules) that can change in length by removing dimers. (controlled by centrosomes, microtubule organizing center, near nucleus)
actin filaments
2 globular chains actin monomers to form a long filament-- supports cell by forming a web under the plasma membrane
What do nucleotides consist of?
5 carbon sugar, phosphate group, nitrogenous base
External signals
> growth factors and hormones > stimulate cells to go through the cell cycle
p53 tumor suppressor gene
> produces a protein that checks the DNA for damage before it proceeds through the G1 checkpoint > if there are breaks in the DNA, the cell is instructed to enter into G0 phase > if these repairs cannot be repaired, the cell undergoes apoptosis
Chargaff's Rule
A=T and C=G
Telomerase
An enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule of RNA that serves as a template for new telomere segments.
Bacterial structure
Cytoplasm surrounded by plasma membrane and cell wall, capsule, enzymes, nucleoid, ribosomes, flagella
Central Dogma of Molecular Biology
DNA -> RNA -> Protein
cell recognition proteins
Enable our body to distinguish between our own cells and cells of other organisms-without it pathogens would invade
Watson and Crick
Figured out structure of DNA was a double helix
What are the three checkpoints in a cell cycle?
G1 checkpoint, M checkpoint, checkpoint,
three phases of interphase
G1, S, G2
Heterchromatin
Highly compacted chromatin that is not accessible for transcription (inactive) ex barr body
Mitochondria
Powerhouse of the cell-- can form long moving chains or remain in one location (where energy isnt needed) -bound by a double membrane.
What happens during interphase?
The cell grows, copies its DNA, and prepares for cell division.
Rosalind franklin
Woman who generated x-ray images of DNA
housekeeping genes
active genes that govern functions that are common to many types of cells including glucose metabolism
mRNA processing
after transcription, removal of introns and splicing of exons occur before mature mRNA leaves nucleus and passes into the cytoplasm. (ex fruit fly gene)
senescence
aging of cells
channel proteins
allow one/few types of specific molecules to move readily through the membrane (Ex: aquaporins- allow water to enter or exit a cell)
Motor proteins:
allows cells and organelles to move
Ex of what to view through an electron microscope:
amino acid
cellular reproduction
an original cell divides and produces two identical daughter cells (growing, tissue repair, single celled orgs reproduce etc
Ex of what you can view through an electron OR light microscope:
animal cell, chloroplast, plant cell
Junction proteins
assist cells in cell adhesion and communication
smooth ER
attached to rough er, no ribosomes, synthesizes lipids (phospholipids, steroids)- forms transport to the golgi apparatus
DNA replication in eukaryotes:
begins at specific sites on a double helix (called origins of replication) and proceeds in both directions -- replication bubble is where the process of replication occurs -- proceeds until double helix is copied
Transcription process:
begins when RNA polymerase binds to a promoter -- rna polymerase opens DNA helix so complementary base pairing cna occur-- polymerase adds new rns nucleotides complementary to those in the templates dna strand-- resulting mRNA transcript is a copy of sequence of bases in template dna strang, mRNA is ready to be processed
M checkpoint
between metaphase and anaphase to ensure proper attachment of chromosomes and will be distributed to the daughter cells (cycle wont continue until ever chromosome is ready for nuclear division)
M phase
both division of the nucleus and the cytoplasm
cellular respiration
breakdown of carbohydrates involving the cytoplasm-- oxygen needed, carbon dioxide is given off
Initiation
brings all translation components together (subunit attaches, anticodon pairs with tRNA, large subunit joins the small)
Motile
can travel through blood and lymphatic vessels to other parts of the body -- leads to metastasis
G1 phase
cell doubles organelles (mito and ribo), accumulates materials used for DNA replication-- integrates internal and external signals and decides whether to continue the cell cycle
Apoptosis
cell rounds, nucleus collapses, chromatin condense, dna fragments, plasma mebrane blisters forming blebs, cell fragments
cytokinesis in plants
cell wall doesnt permit cytokinesis by furrowing--involves the building of new plasma membranes and cell walls between daughter cells
Plasma membrane
cells outer membrane which acts as the boundary between the inside and outside of a cell.
Why are cells so small?
cells rapidly exchange materials with the external environment--needs surface area large enough to allow efficient movements of nutrients into the cell and waste materials out
m phase
centrosomes separate and move to opposite sides of the nucleus where poles of spindles are formed-- nuclear envelope breaks down and spindle fibers take over center of cell (spindle equator)
growth factor
chemical signal activates cell signaling pathways bu bringing phosphorylation of signaling proteins
Endosymbiosis
chloroplasts derived from photosynthetic bacteria enter a eukaryotic cell
Metaphase
chromosomes align at the spindle equator
prophase
chromosomes condense, each consists of 2 chromatids held at centromere-- nucleolus disappears and nuclear envelope is broken down
cytokinesis in animals
cleavage furrow constricts like a drawstring to separate the cells
gap junction
communication, 2 identical plasma membrane channels join
Organelles
compartments of a eukaryotic cell-carry out specialized functions that together allow the cell to be more efficient and successful
G2 phase
completion of the DNA replication to the onset of mitosis-- cell synthesizes proteins needed fir division (microtubule protein) important in division
chromosomes
condensed, coiled chromatin with rod like structures
chromosome
consists of DNA complexed with proteins, transmits genetic info from previous generation to the next
Exons
contain protein-coding regions of the gene
Carcinogenesis
development of cancer
Angiogenesis
development of new blood vessels
Cytokinesis
division of the cytoplasm
Mitosis
division of the nucleus
When does cytokinesis begin?
during telophase and continues after nucelei formed in daughter cells--cycle complete
S phase
each chromosome has 1 chromatid consisting of single dna doible helix, each chromose has 2 sister chromatids (1 double helix), remains attached to the centromere-- dna replication produces duplicate chromosomes
codon
each sequence of three bases standing for one of the 20 possible amino acids. *can help protect against possibly harmful mutations that might change sequence of AA*
Proteosomes
enzyme complex that destroys proteins when they are no longer needed
Kinases
enzymes remove phosphate from ATP and add it to different molecules (on and off switch for cellular activities)-- active in the removal of nuclear membrane and condensation of chromosomes in early prophase.
contact inhibition
eukaryotic cells stop diving preventing cells from overgrowing
inborn errors of metabolism
family members have same metabolic disorder due to lack of functional enzyme in a metabolic pathway
Chromatin
fibrils consist of dna and proteins, eukaryotic cell isnt undergoing cell division, wound around core of 8 protein molecules (histones) network of dna, rna and protein found in the nucleoplasm
Cristae
folds in the inner membrane of mitochondria to increase surface area
angiogenesis
formation of new blood vessels
oncogenes
forms when proctooncogenes mutate and become cancer causing genes
Ex of what to view through a light miscroscope:
frog egg
What do proteins determine?
function
The protein ras
functions in signal transduction pathways that lead to transcription of many genes -- normally inactive but reception of a growth factor leads to activation (cancer can occur due to repeated cell division)
Cell
fundamental unit of life, diverse in shape and function
Introns
genes in humans interrupted by segments of DNA not coding for protein (intervening segments)
Operon
group of structural and regulating genes functioning as a single unit
what are the 2 processes of cellular reproduction?
growth- cell duplicates contents including including organelles and dna cell division- dna and other cellular contents of parent cell distributed to the daughter cell.
G2 checkpoint
halts until DNA replication verified-- prevents initiation of m phase
eukaryotic cells
has nucleus that houses their dna
Receptor proteins
has shape that allows signal molecule to bind to it (causes protein to change shape and bring on a cellular response)
sister chromatids
held together at the centromere, contains identical double helix
Process of DNA replication:
helix separates and unwinds by breaking hydrogen bonds between nucleotides and unwinding helix using the enzyme helicase-- new nucleotides added to parental template strand-- nucleotides ever present in the nucleus will complementary base pair to a single stranded parental strang--- addition of new strand completed using DNA polymerase-- daughter strand is synthesized by DNA polymerase in a 5'-3' direction-- any breaks sealed by DNA ligase
endomembrane system
helps compartmentalize the cell so enzymatic reactions are restricted, increasing efficiency-- nuclear envelope, ER membranes, golgi apparatus, and vesicles
Surface are to volume ratio
higher ratio of surface area to internal volume, faster the exchange of materials within an environment.
Plasmodesmata
how living cells in plants are connected, membrane lines channels passing through the cell wall (water and small molecules)
G1 checkpoint
if cell cycle passes this checkpoint it can divide, can enter G0 if it doesnt divide. Apoptosis can occur if DNA damaged beyonf repair
Centrioles
in centrosome, organelles composed of microtubules
DNA Transcription factors:
in eukaryotes, is the DNA binding proteins that help RNA polymerase bind to a promoter
alt mRNA splicing
increases number of protein products that can be made from a single gene (passes from cell nucleus into cytoplasm for translation after processed)
tumor suppressor genes
inhibit the cell cycle and promote apoptosis
Stroma
inner space
adhesion junction
intercellular cytoplasm plaques attach to cytoskeleton and joined by intercellular filaments (sturdy but flexible)
Cytoskeleton
interconnected protein filaments and tubules extending from the nucleus to the plasma membrane in eukaryotic cells. (microtubules, intermediate filaments, active filaments)
How are checkpoints controlled?
internal and external signals (molecules that stimulate or inhibit cell function)
Thykaloid space
internal compartment formed by lumens of thykaloid sacs
Cyclins
internal signaling proteins that increase and decrease as the cell cycle continues
chromatin condensation
keeps genes turned on or off, more tightly chromatin is compacted less often genes within it are exposed
prokaryotic cell
lack membrane bound nucleus, dna is located in the nucleoid (bacteria-first cells on earth)
Characteristics of cancer:
lack of differentia, abnormal nuclei, dont undergo apoptosis, form tumors, undergo metastasis and promote angiogenesis
how is lac operon turned on?
lactose binds to repressor and changes shape which makes it unable to bind to operator, RNA polymerase binds to promoter.
Translation process:
leads to protein synthesis, requires several enzyme mRNA, tRNA, and rRNA -- tRNA takes AA to ribosomes, AA binds to one end of the molecule, opposite end contains anticodon, group of three bases complementary to specific codon of mRNA-- order of codons in mRNA determine order of tRNAs and bind at ribosomes-- when complete, protein contains sequence of AA originally specified by DNA
euchromatin
less compact form of chromatin containing active genes (forms when heterchromatin undergoes unpacking)
Nuclear pore
located in the nuclear envelope that allows nucleus to communicate with the cytoplasm
Regulatory gene
located outside of the operon and codes for a repressor (protein that binds to the operator which is next to the promoter)
Capsid
made of protein and inner core DNA-- results show viral dna enters bacteria causing formation of new viruses.
Vacuoles
membranous sacs larger and more specialized than vesicles
Vesicles
membranous sacs that enclose molecules and keep them separate from cytoplasm-move around the cytoskeleton which maintains cell shape and assists with cell movement
Which two organelles are responsible for generating the majority of energy needed to perform cellular processes?
mitochondra and chloroplast
Thykaloids
mix of enzymes and disclike sacs
cillia
move stiffly, short, projection from plasma membrane
major motor proteins
myosin, kinesin, dynein (myosin interacts with actin filaments when movement occurs, kinesin and dyenin move along the microtubules)
Cell plate
newly formed plasma membrane expanding outward reaching old plasma membrane and fuses--- new releases molecules that form new plant cell walls
mRNA processed:
newly synthesized primary mRNA must be processed to be used properly (capping, addition of poly A tail, splicing) --- after processing=matire mRNA molecule
Animal cells
no cell wall, extracellular matrix (fibrous proteins and polysaccharides) collagen and elastin
Where is ribosomal RNA produced?
nucleolus
Cell signaling
occurs because a chemical signal binds to a receptor protein in a target cell's plasma membrane
Cell cycle
orderly sequence of stages take place between time new cells arisen from division of a parent to point of rise of two daughter cells
Golgi apparatus
organelle consisting of sacs and vesicles that processes, packages, and distributes molecules about or from the cell
DNA
organized into genes and has a specific sequence of nucleotides
Translocations
part of one chromosome breaks off and attaches to another -- can lead to cancer
Enzymatic proteins
participate in metabolic reactions
transport proteins
passage of molecules and ions through the membrane-combine with substance with input energy for help (Ex; sodium and potassium ions across the nerve cell membrane-nerve conduction)
Interphase
period of the cell cycle between cell divisions, cell performs usual functions
Plasma membrane structure:
phospholipid bilayer with embedded proteins, outer layer- phospho heads face towards ext environment, inner layer- phospho heads face interior of cytoplasm
tight junctions
plasma membrane proteins attach to eachother
3 characteristics of cells:
plasma membrane, cytoplasm, dna
Elongation
polypeptide increases in length one amino acid at a time
Transcription
portion of DNA serves as a template for mRNA formation
Plant structure
primary cell wall contains cellulose fibrils and non-cellulose substances allowing the wall to stretch. (adhesive substances outside the wall holds two plant cells together) Secondary cell wall used for added strength and has more cellulose fibrils and lignin-common ingredient
Centrosome
primary microtubule organizing cell center - two barrel like structures in an animal cell, centrioles and microtubules (plants have centrosomes but lack centrioles)
tRNA
produced in nucleus in eukaryotes, transfers amino acids in cytoplasm to the ribosomes, 20 different AA (each has its own tRNA molecule) Translation joins the AA to form a polypeptide chain.
mRNA
produced in nucleus of eukaryotic cell and in the nucleoid of prokaryotic cell, transcription- DNA serves as a template for formation -- once formed, mRNA carries genetic info form DNA in the nucleus of ribosomes in the cytoplasm where protein synthesis occurs
rRNA
produced in the nucleolus in eukaryotic cells, portion of DNA serves as a template for formation, rRNA joins with proteins made in cytoplasm to form ribosomes -- each subunit has its own proteins and rRNA-- subunits leave the nucleus and join in the cytoplasm when protein synthesis is about to begin-- proteins are synthesized at the ribosomes.
Microvilli
projections that increase the cell's surface area
Why are telomeres important in regulating cell division?
promote chromosomal stability so replication can occur
Procto-oncogenes
promote the cell cycle and inhibit apoptosis
4 phases of mitosis in order:
prophase, metaphase, anaphase, telophase
fluid mosaic model
protein embedded in membrane and have pattern within a fluid bilayer
Histone
protein molecule around which DNA is tightly coiled in chromatin-- looks like beads on a string
What does the DNA sequence of bases determine?
proteins in a call
Cell wall
provides support, found in plants, fungi, and protists
splicing
removal of introns, joining of exons
how is lac operon turned off?
repressor attaches to operator, transcription unable to take place due to RNA polymerase unable to bind to promoter
Philadelphia chromosome
result of translocation between chromosomes 9 and 22
intermediate filaments
run between the nuclear envelope and plasma membrane
Translation
sequence of mRNA bases determines sequence of amino acids in a polypeptide
Glycoproteins
short chain sugars attached to protein (helps protein perform function ; identity of cell)
RNA structure and function:
single-stranded, found in nucleus and cytoplasm, dna assistant, ribose suagr, AUCG, mRNA translated to make proteins, rna allows protein synthesis to occur according to the genetic info dna provides.
anaphase
sister chromatids separate become daughter chromosomes
2 ribosomal subunits
small, large -- subunits leave the nucleus and join in the cytoplasm to form ribosomes as protein synthesis begins
flagella
snakelike, long, used for locomotion
sexual reproduction
sperm and egg produces offspring different from parents
binary fission
splitting of a cell into two new cells, asexual reproduction because it produces two cells identical to the orginal
Granum
stack of thylakoids
Centrosome duplication
starts at s phase and complete by g3
Termination
stop codon appears at A site, polypeptide and assembled components that carried out protein synthesis separate--- release factor binds to stop codon and cleaves polypeptide from last tRNA
Nucleus
stores genetic information
Spindle
structure of the cytoskeleton to pull chromatids apart (has fibers made of microtubules able to assemble and disassemble)
Rough ER
studded with ribosomes on the side of the membrane facing the cytoplasm allowing it to synthesize polypeptides.
Endoplasmic Reticulum (ER)
system of membranous channels continuous with the outer membrane of the nuclear envelope
epigenetic inheritance
the inheritance of changes in gene expression that are not the result of changes in the sequence of nucleotides on the chromosome (ex calico cat)
DNA replication
the process of making a copy of DNA: dna/proteins packaged into a set of chromosomes which allows dna to be distributed to the daughter cells (due to proteins and enzymes in the nucleus)
Telophase and Cytokinesis
the spindle disappears as new nuclear envelopes form around the daughter chromosomes. Each nucleus contains the same number and kinds of chromosomes as the original parent cell. Remnants of spindle fibers are still visible between the two nuclei. Division of the cytoplasm begins.
3 types of junctions
tight junctions, adhesion junctionw, gap junctions
Two processes of gene expression
transcription and translation
Ribosomes
use genetic information to manufacture proteins needed for cellular structure and metabolic activities.
Chloroplast
use solar energy to synthesize carbohydrates, bound by a double membrane (outer and inner)
gene expression
using information within a gene to synthesize a protein
What are the four characteristics of dna structure?
variability, ability to replicate, storage of info, ability to change or mutate
Lysosomes
vesicles produced by golgi apparatus that digest molecules coming into a cell and breakdown damaged organelles
How does euchromatin become active?
when histones no longer bar access to DNA -- only possible for a gene to be turned on and expressed in a eukaryotic cell
Lumen
where proteins take shape