summery Flashcards
Basic structures of viruses:
1) a nucleic acid genome
2) a protein capsid that covers the genome.
Cell Theory:
- All living organisms are composed of one or more cells.
- The cell is the most basic unit of life.
- All cells arise only from pre-existing cells.
Basic properties of cells (9) (CGRECMSSE)
- Highly COMPLEX and ORGANIZED.
- Activity controlled by a GENETIC program.
- Can REPRODUCE—make copies of themselves.
- Assimilate and utilize ENERGY.
- Carry out many CHEMICAL reactions (enzymes).
- Engage in MECHANICAL activities.
- Respond to STIMULI.
- Capable of SELF-REGULATION.
- They EVOLVE.
What Does it Take to Make a CELL ? (3)
- information
- chemistry
- compartments
Two MAIN cell types:
Prokaryotic and
Eukaryotic Cells
The _____ is a dynamic INFORMATION system
GENOME
Cell function is dependent on ______ reactions occurring in _______
CHEMICAL, COMPARTMENTS
what are viruses?
Viruses are macromolecular packages that can function and reproduce only within living cells.
Outside of cells, viruses exist as
inanimate
particles called VIRIONS.
Structure of viruses (3)
- Protein coat (capsid) that
surrounds nucleic acid - Enclosed in a protein-
containing membrane
(enveloped) or not (naked
or unenveloped) - Nucleic acid either RNA or DNA; encodes viral
proteins
– Thus, either RNA or
DNA viruses
Two main types of viral life cycle:
NON-LYTIC (also known as LYSOGENIC)
LYTIC
NON-LYTIC (also known as LYSOGENIC)
– Viral nucleic acid is replicated in the host; viral proteins produced
– Virus reproduces without destroying the host cell
LYTIC
– Production of virus particles ruptures (and kills) host cell (e.g.,
bacteriophages; ebola virus)
how do RNA Vaccines work?
tricking the body’s cells into producing a fragment of a virus, an antigen, from an RNA template
Main factor that determines what cell type a virus can infect
surface expression of a specific surface protein
Functions of Biological Membranes (6)
1) Define cell boundary
2) Define enclose compartments
3) Control movement of material into and out
of cell / organelles
4) Allow response to stimuli
5) Enable interactions between cells
6) Provide scaffold for biochemical activities
Phospholipid Structure
- Phospholipids consist of a glycerol backbone bound by:
– Two non-polar fatty acyl
molecules (“fatty acid chains”)
– A polar head group linked by a phosphate residue
Lipid molecules, like phospholipids, spontaneously aggregate to bury their _____ in the interior and expose their _____ to water
hydrophobic tails, hydrophilic heads
Where does phospholipids of membranes come from?
- Synthesis occurs in a multistep process at the interface of the cytosol and outer endoplasmic reticulum membrane
Membrane Proteins (3)
INTEGRAL, PERIPHERAL, LIPID-ANCHORED
INTEGRAL membrane proteins…
span the lipid bilayer
PERIPHERAL membrane
proteins associate with…
the surfaces of the lipid bilayer
LIPID-ANCHORED proteins attach to…
a lipid in the bilayer
Integral Protein Functions: (3)
1) Transport of nutrients and ions.
2) Cell-cell communication (gap junction)
3) Attachment
Biological Membranes are: (3)
- Stable
- Flexible
- Capable of self assembly
Membranes also have unique features: (2)
- Different membranes contain different types of lipids and proteins, giving them different functions.
- Differences between cells as well as within organelles
within a cell.
The inner membrane of mitochondria contains a ______ concentration of protein necessary for electron transport chain and ATP synthesis.
very high
Myelin sheath simply consists of layers of
_____ wrapped around the a neuron’s axon.
plasma membrane
Myelin sheaths have ____ of protein.
low amounts
Biological membranes are symmetrical or asymmetrical?
asymmetrical
Two leaflets have distinct lipid composition in many plasma membranes, the
outer leaflet contains…
glycolipids and glycoproteins
Temperature is an important variable affecting the fluidity
of biological membranes:
* Warming _____ fluidity
* Cooling ___ fluidity
increases, decreases
Membrane fluidity is determined by the nature of ____ in membrane
lipids
- Unsaturated lipids ___ fluidity
- Saturated lipids ___ fluidity
increase, decrease
In response to changes in temperature, lipid composition of membranes can be changed by:
1) desaturation of lipids
2) exchange of lipid chains
BALANCE between ordered (rigid) structure and disordered structure
allows: (3)
- Mechanical support and
flexibility. - Membrane assembly and
modification. - Dynamic interactions between
membrane components
Cholesterol acts as a _____ regulator of membrane fluidity
bidirectional
- At high temperatures, cholesterol _____ the membrane and _____ its melting point
- At low temperatures, it ____ and prevents them from ______
stabilizes, raises, intercalates between the phospholipids, clustering together and stiffening.
If cholesterol is added to a crystalline gel membrane, fluidity will…
increase
If cholesterol is added to a liquid crystal membrane, fluidity will…
decrease
Membranes are composed of
LIPID BILAYERS
Amphipathic
having both hydrophilic and hydrophobic parts
______ are main structural components of biological membranes
PHOSPHOLIPIDS
Cells with different functions have…
membranes with different protein compositions
The transmembrane domain (TMD): (3)
- Is an α helical peptide sequence that is largely hydrophobic (uncharged) and spans the membrane; consists of amino acids with hydrophobic side chains
- Is permanently attaches the protein to the PM.
- Can facilitate protein-protein interactions
α helices
_____ molecules cross membranes relatively easily
Small, uncharged
Four basic mechanisms for moving molecules across membranes
1) Simple diffusion
2) Diffusion through a channel
3) Facilitated diffusion
4) Active transport
Passive movement
- Moves from a HIGH to a LOW concentration
- DOES NOT require energy
____ are specific water channels
AQUAPORINS
Channels are formed by
____ that line an aqueous
pore
integral membrane proteins
Channels are particularly effective for…
small,
charged molecules (ions)
Ion channels are often…
gated
Two types of Gated Ion Channels
1) Voltage-gated channels
2) Ligand-gated channels
Voltage-gated channels respond to…
changes in charge across membrane
Ligand-gated channels respond to…
binding of specific molecule on its surface
Binding of a ligand produce ____ in the structure of the receptor/channel
conformational change
Compound binds specifically to integral
membrane protein called a…
facilitative transporter
Most animal cells import glucose from the
blood into cells via a…
facilitative transporter
steps of glucose transporter (4)
1) Transporter ready to accept glucose molecule
2) Glucose is accepted by transporter
3) Intracellular side of transporter opens
4) Glucose is released and cycle repeats
The concentration gradient of one molecule is used to transfer a second molecule in opposite directions
Antiporter
Active transport:
- Compound binds specifically to integral
membrane protein called an ACTIVE TRANSPORTER. - Change in the conformation of the
transporter caused by the hydrolysis of an ATP molecule allows molecules to be released on other side of the membrane. - Using this mechanism, compounds can move
against a concentration gradient
Tetrodotoxin (TTX) and curare are toxins that interfere with…
movement through ion channels
Proteoglycans
proteins with chains of polysaccharides
Functions of the ECM (4)
(CCCB)
- Cell adherence
- Communication between cells
- Cell shape
- Serves as barrier
Anchor membrane proteins (e.g., integrins) assists in: (2)
- Tissue formation and coordinated cell function
- Communication between cells
Membrane proteins play a major role in signal
transduction by converting an ____ signal into ____ signal
extracellular, intracellular
Signal transduction allows cells to rapidly
respond to events happening in their
environment: (5)
- Grow
- Divide
- Survive (or not)
- Move
- Differentiate (i.e., time to change
Three stages to signal transduction
1) Binding of ligand to receptor
2) Signal transduction via second messengers like cAMP, calcium, or G-protein
3) Cellular response: cellular growth, cell division, store glucose
molecules as glycogen
____ is an enzyme that will release glucose units
Phosphorylase-P
Aerobic respiration:
converts in presence of oxygen energy stored in food molecules (e.g., glucose) into chemical energy stored in ATP.
Photosynthesis:
building carbohydrates using energy from sunlight
and CO2
Outer Mitochondrial Membrane (OMM) contains:
(2)
- many enzymes with diverse metabolic functions
- porins, which are large channels permeable (passive diffusion) to many molecules when opened (e.g. ATP, sucrose)
Inner Mitochondrial Membrane (IMM):
- High protein: lipid ratio (3:1)
- Double-layered folds are called cristae
- Rich in a phospholipid called cardiolipin
The mitochondria also has two aqueous compartments:
- Intermembrane space separates OMM and IMM
- Matrix
Matrix:
a high protein content, gel-like consistency space containing mitochondrial ribosomes and mitochondrial genome
Cellular respiration involves a series of ____ reactions.
catabolic
Substrate-level phosphorylation:
Hydrolysis reaction releases enough energy to drive phosphorylation of ADP to ATP
Oxidative phosphorylation:
Chemical energy of organic molecules is transferred to electron carriers that is used to create an electrochemical gradient that can power ATP synthesis
which phosphorylation produces more ATP
Oxidative phosphorylation (88%)
Coenzymes acting as electron carriers can exist
either as:
1) Oxidized—can accept electrons
2) Reduced—can donate electrons when
returning to their oxidized state
Mitochondria Oxidative Phosphorylation steps (2)
1) Generate an electrochemical gradient
2) Proton movement down electrochemical gradient to power ATP synthesis
Photosynthesis can be divided into…
light-dependent reactions and light- independent reaction
Light-Dependent Reactions occur in
thylakoid membrane
Light-Independent Reactions occur in
stroma of chloroplasts
Apoptosis is Initiated by
intracellular stimuli like genetic damage, hypoxia, or virus infection
“Killer” proteins like ____ causes change in mitochondria membrane
potential and to the leak of ____
Bax, Cytochrome c
Key elements of vesicle trafficking to a compartment:(4)
- Movement of vesicle.
- Tethering vesicle to target compartment.
- Docking of vesicle to target compartment.
- Fusion of vesicle and target membrane
Docking of vesicle to target compartment uses proteins called…
SNAREs.
Photophosphorylation creates ____ necessary for
carbohydrate synthesis through ____
ATP and NADPH, Calvin cycle
_____ are ENZYMES (proteases) that activate proteins that
are involved in dismantling the cell
CASPASES
Functions of Smooth ER (SER) (4)
- Lipid synthesis
- Production of steroid and hormones
- Detoxification
- Sequestration (storage) of Ca2+
Functions of Rough ER (RER) (4)
- Synthesis of membrane phospholipids.
- Glycosylation of proteins
- Protein folding — quality control
- Protein synthesis, modification, and transport
where and how does Protein Synthesis occur?
In the cytoplasm, ribosomes synthesize polypeptides from mRNA
Translation is completed in 1 of 2 ways:
FREE or ER BOUND ribosomes.
Ribosomes are targeted to the ER membrane by a specific…
signal sequence
The signal sequence is: (3)
- Located in the amino-terminus (N-terminus)
- Contains several consecutive hydrophobic amino acids
- Directs synthesis to the ER compartmen
Protein moves through channel into ER for…
cotranslational
import
Cotranslational Protein Import steps (4)
- After translation of SIGNAL SEQUENCE, a Signal Recognition Particle (SRP) binds to signal sequence and STOPS the translation
- SRP binds SRP receptor to target the whole translation complex to ER
- SRP is released and ribosome binds to translocon. Once this is done, protein synthesis resumes
- Polypeptide enters the ER (through the translocon) as it is translated. In the end, the signal peptide is cleaved off and chaperone folds the protein
To the plasma membrane via biosynthetic/secretory pathway =
exocytosis
From the plasma membrane → organelle within cell via endocytic pathway =
endocytosis
A protein targeted to the ER lumen, after it is fully synthesized and properly folded, has 1 of 2 options:
Option 1. It is retained in the ER lumen, if that is where it functions.
Option 2. It is transported from the ER to the Golgi complex for further modification and delivered to distal parts of the biosynthetic/secretory pathway
Material moves from ER to Golgi and then to other compartments and the plasma membrane in a
_____ direction.
proximal to distal
_____ acts as a sorting station (i.e., sorts whether proteins should continue on to the next Golgi station or be shipped back to the ER)
cis Golgi network
_____ sorts protein into different types of vesicles—vesicles go to plasma membrane or other intracellular destinations (e.g. lysosomes)
trans Golgi network
In addition to sorting, the Golgi is also involved in synthesis of _____ and specific modification of _____
polysaccharides, proteins and lipids
The transfer of vesicles from ER to Golgi, and between the Golgi sub- compartments, is achieved by ____
coat
proteins
Coat proteins have 2 functions:
- Helps form the vesicle.
- Helps select ‘cargo’
COPI and COPII are _____ that assemble on the
______ of donor compartment membranes at sites where budding takes place
protein complexes, cytosolic surface
COPI-coated vesicles move in____ direction
retrograde
COPII-coated vesicles move in ____ direction.
anterograde
Two-layered coat consists of:
- Clathrin - coat protein
(outer layer) - AP complex = Clathrin
Adaptor Protein complex
(inner layer)
AP/Clathrin-coated vesicles move from ____ to other compartments
trans Golgi network
Lysosomal membrane is
composed of ____ that act as a protective lining next to acidic lumen
glycosylated proteins
Lysosomes Function (2)
- Autophagy
- Degradation of internalized materials
Autophagy:
Normal disassembly of unnecessary or dysfunctional cellular components
Tonoplast:
Vacuolar membrane that contains active transport systems that allows ion and molecule transport
Function of Plant Vacuoles (3)
- Intracellular digestion
- Mechanical support
- storage
Cytoskeleton
Dynamic network of interconnected filaments and tubes that extends throughout the cytosol (and some organelles) of eukaryotes
Functions of the cytoskeleton:
1) structural support
2) spatial organization within cell
3) intracellular transport
4) contractility and motility.
Axonemal microtubules
- Highly organized, stable
- Part of structures involved in cell movement
Cytoplasmic microtubules
- Loosely organized, very dynamic
- Located in cytosol
Microtubules Structure
13 protofilaments form longitudinal array creating an hollow cylinder
Heterodimers are aligned in the ___ direction creating ____
same, structural
polarity
The Microtubule-Organizing Center is only found in…
eukaryotic cells.
Microtubule-Associated Proteins (MAPs)
Several different proteins that bind MT
Microtubule-Associated Proteins function
- Modulate assembly, function
- Mediate interactions with other cellular structures
Two major classes of
MAPs
Non-Motor and motor Proteins
MT-Associated Non-Motor Protein function
Control MT organization in cytosol
two types of MT-Associated Motor Proteins
kinesin and dynein
MT-Associated Motor Proteins function (3)
- Use ATP to generate force.
- Can move material along MT track.
- Can generate sliding force between MTs.
Kinesin = ___ end-directed
plus
Dynein= ___ end-directed
minus
Microfiliments have several important functions: (5)
- Maintenance of cell shape
- Cell movement
- Vesicle transport
- Muscle contraction
- Cytokinesis
Actin is the…
central component of MFs
Actin exists in cells either as a ____ or as a ____
monomer, polymer
F-actin microfilaments can be arranged in a loose array network
(meshwork) or tight bundles/cables/fibers. The organization of these
structures is regulated by:
actin-binding proteins
Myosins:
a superfamily of motor proteins associated with microfilaments.
Most myosin molecules move toward the ___ end of microfilaments.
‘plus’
myosin are Divided into 2 broad groups:
1) Conventional myosins
2) Unconventional myosins
Conventional myosins
- Type II
- Primary motors for muscle contraction
Unconventional myosins
- Type I and types III-XVIII
- Organelle / vesicle movement
_____ generate force and contribute to motility in non- muscle cells
Unconventional myosins
Microtubule-based and microfilament-based motors can cooperate in…
intracellular transport
Intermediate Filaments (IF) function
Provide structural support and mechanical strength.
Intermediate filaments
composed of ___ in the cytoplasm are stained red
keratins
ntermediate filaments
composed of ___ in the nucleus are stained blue
lamins
Intermediate filaments are especially abundant in the…
axons of neurons
Nucleus Function (3)
- Storage, replication, and repair of genetic material.
- Expression of genetic material
- Ribosome biosynthesis
Nucleus Structure
Nuclear envelope
* Nuclear membrane
* Nuclear pores
* Nuclear lamina
Nuclear content
* Chromatin
* Nucleoplasm
* Nucleolus
The Nuclear Envelope Structure
2 parallel phospholipid bilayers separated by 10-50nm space
Outer nuclear membrane (ONM)
binds ribosomes and is continuous with rough endoplasmic reticulum
Inner nuclear membrane (INM)
has integral proteins and connects to nuclear lamina
Importance of the Nuclear Envelope (3)
- Separates nuclear content from cytoplasm
- Separates transcription and translation processes
- Selective barrier that allows limited movement of molecules between nucleus and cytoplasm
The Nuclear Lamina
Provides structural support for nuclear envelop
Lamins (intermediate filaments) are found in…
animal cells only
Nuclear lamina is bound to ____ of the nuclear
envelop (NE) by _____
inner membrane, integral membrane proteins
Nuclear Pore
Gateways between cytoplasm and nucleus
The Nuclear Pore Complex (NPC) is:
Composed of nucleoporins (NUPs)—a large family of different proteins
Nuclear Import
Regulated movement of proteins into the nucleus
Nuclear Import requires an:
intrinsic amino acid targeting sequence - Nuclear Localization Signal (NLS)
NLS =
several positively charged amino acids within the protein sequence.
Nuclear Import steps
- Protein with NLS (cargo) interacts with Importin protein in cytoplasm
- Cargo/Importin complex interacts with FG-NUPs at the NPC and enters the nucleoplasm
- Ran-GTP (G-protein) interacts with Importin; cargo dissociates and stays in nucleoplasm
- Ran-GTP/Importin complex exits nucleus through NPC
- GTP hydrolysed to GDP. Importin released in cytoplasm to find new cargo
Nucleolus
Largest structure inside the nucleus of eukaryotic cells.
Primary function of the nucleolus is
biosynthesis of ribosomes.
