Exam #2 - chapter 3-6 Flashcards
Exam #2 Material
define denaturation
protein loses structure and function
things that cause denaturation
- pH
- temp
- ionic concentration of solution (salt concentration)
lipids
- insoluble in water
- high proportion of nonpolar C-H bonds cause the molecule to be hydrophobic
- fats, oils, waxes, some vitamins
Fats
triglycerides
* composed of 1 glycerol and 3 fatty acids
trans fat: produced industrially
unsaturated fat
1 or more double bonds
* low melting point
* plant origin
* liquid at room temp
saturated fat
no double bonds between carbon atoms
* higher melting point
* animal origin
* solid at room temp
phospholipids
composed of:
- glycerol
- 2 fatty acids (nonpolar tails)
- a phosphate group (polar head)
forms all biological membranes, life wouldn’t exist without this
micelles
lipid molecules orient with polar (hydrophilic) head toward water and nonpolar (hydrophobic) tails away from water
phospholipid bilayer
more complicated structure where 2 layers form:
- hydrophilic heads point out
- hydrophobic tails point inward toward each other
cell size and what affects rate of diffusion
- small due to a reliance on diffusion of substances in and out of cells
rate of diffusion is affected by: - surface area available
- temp
- concentraion gradient
- distance
microscope resolution
minimum distance two points can be apart and still be distinguished as two separate points
2 types of microscopes
- Light
- use magnifying lenses with light
- compound and dissection scopes - Electron
- use beam of electrons
- SEM: scanning e- microscope
- TEM: transmission e- microscope
structural similarities of cells
- Nucleoid or nucleus where DNA is located
- Cytoplasm
- semifluid matrix of organelles and cytosol - Ribosomes
- synthesize proteins - Plasma membrane
- phospholipid bilayer
prokaryotic cells
- don’t have nucleus; DNA is in nucleoid
- simplest organisms
- cell wall is outside of plasma membrane
- contain ribosomes (not membrane bound organelles)
- 2 domains: archaea and bacteria
- cell wall is what gives it the structure
bacterial cell walls
- composed of peptidoglycan
- protects the cell, maintains its shape, and prevent excessive uptake or loss of water
- susceptibility of bacteria to antibiotics often depends on the structure of the cell walls
- archaea lack peptidoglycan
flagella
- present in some prokaryotic cells
- used for locomotion
- rotary motion propels the cell
eukaryotic cells
- possess a membrane-bound nucleus
- more complex than prokaryotic cells
- possess a cytoskeleton for support and to maintain cellular structure
animal vs plant cell
plant cells have the following:
* central vacuole
* cell wall
* chloroplast
nucleus
- most eukaryotic cells possess a single nucleus
- nucleolus: region where ribosomal RNA synthesis take place
- nuclear envelope:
– 2 phospholipid bilayers
– nuclear pores: control pasage in and out
ribosomes
- cell’s protein synthesis machinery
- found in all 3 domains
- ribosomal RNA (rRNA): protein complex
- protein synthesis requires messengar RNA (mRNA) and transfer RNA (tRNA)
- ribosomes may be free in cytoplasm or associated with interal membranes
endomembrane system
- series of membranes throughout the cytoplasm
- divides cell into compartments where different cellular functions occur
rough endoplasmic reticulum
- attachment to ribosomes to the membrane is what gives it a rough appearance
- synthesis of proteins to be secreted, sent to lysosomes or plasma membrane
smooth endoplasmic reticulum
- relativley few bound ribosomes
- variety of functions: synthesis, store Ca2+
- ratio of RER TO SER depends on the cell’s function
golgi appartus
- flattened stacks of interconnected membranes (golgi bodies)
- functions in packaging and distribution of molecules synthesized at one location and used at another within the cell or even outside of it
- Cis and Trans faces
vesicles
transport molecules to destination
lysosomes
- membrane-bounded digestive vesicles
- arise from golgi apparatus
- enzymes catalyze breakdown of macromolecules
- destory cells or foregin matter that the cell has engulfed by phagocytosis
microbodies
variety of enzyme-bearing, membrane-enclosed vesicles
Peroxisomes
- contain enzymes involved in the oxidation of fatty acids
- H2O2 produced as by-product – rendered harmless by catalase
vacuoles
membrane bounded structures in plants and animals
3 different types of vacuoles:
1. Central vacuole in plant cells
2. Contractile vacuole of some protists
3. Storage vacuoles
mitochondria
- found in all types of eukaryotic cells
- bound by membranes
– Outer membrane
– Intermembrane space
– Inner membrane has cristae
– Matrix
have their own DNA adn their own ribosomes
chloroplasts
- Organelles present in cells of plants and some other eukaryotes
- Contain chlorophyll for photosynthesis
- Surrounded by 2 membranes
- Thylakoids are membranous sacs within the inner membrane
Grana: are stacks of thylakoids - Have their own DNA
endosymbiosis
One cell, a prokaryote, was engulfed by and became part of another cell, which was the precursor of modern eukaryotes
- Mitochondria and chloroplasts
cytoskeleton
Network of protein fibers found in all eukaryotic cells
- Supports the shape of the cell
- Keeps organelles in fixed locations
Dynamic system – constantly forming and disassembling
3 types of fibers
**Microfilaments (actin filaments)
**
- 2 protein chains loosley twined together waith each part being largest of the cytoskeletal
Microtubules
- Largest of the cytoskeletal elements
- Hollow tubes
**Intermediate filaments
**
- Between the size of actin filaments and microtubules
centrosomes
Region surrounding centrioles in almost all animal cells
Microtubule-organizing center
- Can nucleate the assembly of microtubules
Animal cells and most protists have centrioles – pair of organelles
Plants and fungi lack centrioles
movement within cells
- Actin and microtubules are important for movement within cells.
- Movement often requires the use of ATP
- Some cells crawl using actin microfilaments to “push” the cell membrane forward
flagella
9 + 2 arrangement of microtubules
Not like prokaryotic flagella
Microtubules move past each other and this leads to undulation of the flagella
Surrounded by the plasma member with cytoplasm inside
Cilia are shorter and more numerous
extracellular matrix (ECM)
- secrete an elaborate mixture of glycoproteins into the space around them
- form a protective layer over the cell surface
- integrins link ECM to cell’s cytoskeleton
- animal cells lack cell walls*
glycolipids
most tissue-specific cell surface markers
MHC proteins
recognition of “self” and “nonself” cells by the immune system
3 types of cell connections
- Tight Junction
- Adhesive Junction
- Communicating Junction
plasmodesmata
allows direct communication of molecules between adjacent plant cells
membrane structure
- phospholipids arranged in a bilayer
- globular proteins inserted in the lipid bilayer
- Fluid Mosiac Model: mosaic of proteins floats in or on the fluid lipid bilayer like boats on a pond
4 structures of cellular membrances
- phospholipid bilayer
- transmembrane proteins
- interior protein network
- cell surface markers
membranes and microscopes
both TEM and SEM are used to study membranes
phospholipids
structure: - glycerol
- 2 fatty acids
- phosphate group
spontaneously forms a bilayer
(fatty acids on the inside, phosphate on both surfaces)
environmental influences on the membrane
- saturated fatty acids make the membrane less fluid than unsaturated fatty acids
- warm temps make the membrane more fluid than cold temps
- lipid conpositiion of the ER membrane, golgi stack, & plasma membrane are distinct
6 functions of membrane proteins
- Transporters
- Enzymes
- Cell-surface receptors
- Cell-surface identity markers
- Cell-to-cell adhesion proteins
- Attachments to the cytoskeleton
peripheral proteins
anchoring molecules attach membrane protein to surface
anchoring molecules modified with lipids
- Nonpolar regions that insert into the internal portion of the lipid bilayer
- Chemical bonding domains that link directly to proteins
integral membrane proteins
- span the lipid bilayer (transmembrane proteins)
- Transmembrane domain
membrane proteins
pores
Extensive nonpolar regions within a transmembrane protein can create a pore through the membrane
passive transport
the movement of molecules through the membrane in which:
- No energy is required
- Molecules move in response to a concentration gradient
diffusion
- the movement of molecules from high concentration to low concentration
- will continue until the concentration is the same in all regions
major barrier
Major barrier to crossing a biological membrane is the hydrophobic interior that repels polar molecules but not nonpolar molecules
facilitated diffusion
- Molecules that cannot cross membrane easily may move through proteins
- Move from higher to lower concentration
Channel proteins: Hydrophilic channel when open
Carrier proteins: Bind specifically to molecules they assist - Membrane is selectively permeable
ion channels
- Allow the passage of ions
- Gated channels: open or close in response to stimulus (chemical or electrical)
**3 conditions determine direction:
**- Relative concentration on either side of membrane
- Voltage differences across membrane
- Gated channels – channel open or closed
osmosis
net diffusion of water across a membrane toward a higher solute concentration
* cytoplasm of the cell is an aqueous solution
- water is a solvent
- dissolved substances are solutes
osmotic concentration
- Hypotonic solution has a lower solute concentration
- Hypertonic solution has a higher solute concentration
-
Isotonic solution has the same concentration
* aquaporins facilitate osmosis
maintaining osmotic balance
- some cells use extrusion in which water is ejected thru contractile vacuoles
- isomotic regulation involves keeping cells isotonic with their environment
- plant cells use turgor pressure to push cell membrane to cell wall
active transport
- Requires energy – ATP is used directly or indirectly to fuel active transport
- Moves substances from low to high concentration
- Requires the use of highly selective carrier proteins
3 carrier proteins used in active transport
uniporters: move 1 molecule at a time
symporters: moves 2 molecules in the same direction
antiporters: move 2 molecules in opposite directions
Sodium-Potassium Pump
- direct use of ATP for active transport
- low internal Na+ and high K+ concentration
- uses antiporter to move 3 Na+ out of the cell and 2 K+ into the cell
coupled transport
- indirect use of ATP
- uses the energy released to supply energy to active transport of a different molecule
- symporter is used
- Glucose-Na+ symporter captures the energy from Na+ diffusion to mvoe glucose against the concentration gradient
countertransport
move material in opposite directions
bulk transport: endocytosis
- movement of substances into the cell
- phagocytosis: cell takes in particulate matter
- pinocytosis: cell taken in only fluid
- requires energy
bulk transport: exocytosis
- movement of substances out of the cell
- used in plants to export cell wall material
- used in animals to secrete hormones, neurotransmitters, digestive enzymes
- requires energy
define thermodynamics
- branch of chem and physics concerned with energy changes
- cells are governed by the laws of chem and physics
Energy
2 states:
1. Kinetic: energy in motion
2. Potential: stored energy
many forms: mechanical, heat, sound, electric current, light, or radioactivity
heat is the most convenient way of measuring energy
1 calorie = 4.2 joule
1 Calorie = 1,000 calories = 1 kcal
redox reactions
oxidation: atom or molecule loses an electron
reduction: atom or molecule gains an electron, higher level of E than oxidized form
OIL RIG
1st law of thermodynamics
- energy cannot be created nor distroyed
- can only change from one form to another
- total amt of energy in the universe remians constant
- during conversion, energy is lost as heat
2nd law of thermodynamics
- entropy (disorder) is continuously increasing
- E transformations proceed spontaneously to convert matter from a more orded/less stable to less ordered/more stable
free energy
- the amout of energy available to break/form bonds
- G= gibbs free energy = energy available to do work
- H = enthalpy, energy in molecules chemical bonds
- T = absolute temp
- S = entropy, unavilable energy
ΔG = ΔH - TS
ΔG = change in free energy
+ΔG:
- products have more free energy
- not spontaneous, requires input of energy
- endergonic
- ΔG:
- products have less free energy than reactants
- spontaneous
- exergonic
activation energy
- extra energy required to destablilize existing bonds and initiate a chemial rxn
- exergonic rxn’s rate depends on activation energy
- rate can be increased by:
1. Increasing energy of reacting molecules (heating)
2. Lowering activation energy
catalysts
substances that influence chemical bonds in a way that lowers activation energy
Suns impact
- all life gets energy from the sun
- every organism is dependent on a very tiny amt of energy we get from the sun
- stored as potential E in chemical bonds
ATP
- adenosine triphosphate
- Chief “currency” all cells use
Composed of: - Ribose – 5 carbon sugar
- Adenine
Chain of 3 phosphates: - Key to energy storage
- Bonds are unstable
- ADP – 2 phosphates
- AMP – 1 phosphate – lowest energy form
ATP Cycle
ATP hydolysis drive endergonic rxns
- couplet reactions results in net -ΔG
- ATP not suitable for long term energy storage
- ATP -> ADP = 7.3 kcal/mole
ATP -> AMP = 10.3 kcal/mole
*between 1-2 billon ATP’s per minute
enzymes
- most enzymes are protein
- some RNA
- shape of enzyme stabilizes a temporary association between substrates
- enzyme not changed or consumed in rxn
active site
- Pockets or clefts for substrate binding
- Forms enzyme-substrate complex
- Precise fit of substrate into active site
- Applies stress to distort particular bond to lower activation energy
- Induced fit
nonprotein enzymes
2 kinds:
1. intramolecular catalysis: catalyze rxn on RNA molecule itself
2. intermolecular catalysis: RNA acts on another molecule
*important in ribosomoes
define multienzyme complexes
subunits work together to form molecular machine
- Product can be delivered easily to next enzyme
- Unwanted side reactions prevented
- All reactions can be controlled as a unit
enzyme function
- rate of enzyme-catalyzed reaction depends on concentractions of substrate and enzyme
- any chemical or physical condition that affects the enzyme’s shape can change rate of:
- optimum temp
- optimum pH
define Inhibitor
substance that binds to enzyme and decreases its activity
2 types of inhibitors
competitive inhibitor: competes with substrate for active site
noncompetitive inhibitor: binds to enzyme at a site other than active site
- causes shape change that makes enzyme unable to bind substrate
ATP Cycle
ATP hydrolysis drivers endergonic reactions
- not suitable for long term energy
activation energy
amount of energy needed to start a reaction
What is ATP composed of
- 5 carbon sugar ribose
-adenine - chain of 3 phosphates
Allosteric enzymes
enzymes exist in active and inactive forms
- most noncompetitive inhibitors bind to allosteric site (chemical switch on and off)
Allosteric inhibitor
Bids to allosteric site and reduces enzyme activity
allosteric activator
binds to allosteric site and increases enzyme activity
cofactors
-metal ions that are found in the active site participating directly in catalysis
coenzyme
- nonprotein organic cofactor molecule
anabolic reactions
- expend energy to build up molecules
catabolic reactions
- harvest energy by breaking down molecules (cats love to tear apart)
biochemical pathways
reactions occur in a sequence, product of one reaction is the substrate for the next
feedback inhibition
shuts down pathway so raw materials and energy are not wasted
- end product of pathway bind to an allosteric site on enzyme that catalyses
Organism made of small cells has an advantage over an organism composed of smaller fewer cells? (true/false)
True
