1 - CELL AND MOLECULAR BIOLOGY Flashcards
define electronegativity
ability of an atom to attract electrons
what are the 3 main type of chemical bonds
ionic
covalent
hydrogen
what are ionic bonds?
transfer of electrons between atoms of differing electronegativity
the one with a higher electronegativity, takes the electrons
what are covalent bonds?
sharing of electrons
atoms can be single/double/triple -bonded
what are non-polar covalent bonds?
equal sharing of electrons between two atoms of similar electronegativity
what are polar covalent bonds?
unequal sharing of electrons between two atoms of differing electronegativity
FORMS A DIPOLE!!
what are van der waal interactions?
weaker and more transient than hydrogen bonding. more of an interaction which gets stronger, the larger the molecule is
what are hydrogen bonds?
weak interaction between a hydrogen (attached to a highly electronegative atom) and a negatively charged atom of another molecule (F, O, N)
what are the 5 most important properties of water?
it’s a good solvent
it has a high heat capacity
ice floats. water expands as it freezes and becomes less dense
it has strong cohesion/surface tension. its strong cohesion between H2O molecules produces high surface tension
it has adhesion. adheres to unlike objects - water sticks to skin/glass
why is water a good solvent?
the dipoles (the slight positive and negative charges) of H2O break up charged ionic molecules, by disrupting the attractive forces between the atoms of that molecule
this makes it easier for water to dissolve substances
why does water have a high heat capacity?
due to the hydrogen bonds between water molecules which require (the absorption) heat to break
what is heat capacity?
the amount of heat needed to change the temperature of a substance by 1 unit (e.g. 1 degree)
why does ice float?
water expands as it freezes and becomes less dense
the H-bonds become rigid and forms a crystal that keeps molecules separated. their attractions arrange them into fixed positions
why is there strong cohesion between water molecules?
due to H2O’s ability to form hydrogen bonds - and the extremely electronegative oxygen and the comparatively positive hydrogen
why does water possess the adhesive property?
due to H2O’s polar nature, it can also attract “unlike” structures. it’s attracted to substances with charges
what are minerals?
inorganic ions the body needs to function
can be found intracellularly and extracellularly
what are vitamins?
organic molecules the body needs to function
what are the (2) major categories of vitamins? when consumed in excess, where are they stored?
fat-soluble
- deposited in body fat; overconsumption can lead to toxic levels in the body
water-soluble
- excreted in the urine
what is vitamin B? describe it
a water-soluble vitamin
8 types of vitamin B
vitamin B usually functions as coenzymes or their precursors in metabolic processes – also important in blood synthesis
what is vitamin C? describe it
a water-soluble vitamin
vitamin C is necessary for synthesizing collagen, an important structural protein, thus a deficiency in vitamin C can lead to scurvy (if the collagen structure is less stable, we get weakened connective tissues)
what are the (2) important water-soluble vitamins?
B and C
what are the (4) important fat-soluble vitamins?
A, D, E, and K
what is vitamin A? describe it
a fat-soluble vitamin
important for:
- vision (visual pigmentation)
- epithelial (skin) maintenance
what is vitamin K? describe it
a fat-soluble vitamin
important for blood clotting. it produces proteins involved in the process
what is vitamin D? describe it
a fat-soluble vitamin
regulates calcium and phosphorous levels by promoting its absorption from the intestine
synthesized by the skin in the presence of sunlight
what is vitamin E? describe it
a fat-soluble vitamin
an antioxidant which prevent cell damage by neutralizing free radicals which (highly unstable unpaired electrons which can destroy cells)
what are the key properties of hydroxyl (OH) groups?
polar and hydrophilic
generally a strong base. but can be acidic depending on conditions
what are the key properties of carboxyl (COOH) groups?
polar, hydrophilic, weak acid
what are the key properties of amino (NH2) groups?
polar, hydrophilic, weak base
what are the key properties of phosphate (PO4 -3) groups?
polar, hydrophilic, acid
what are key properties of carbonyl (C=O) groups?
polar and hydrophilic
what are key properties of methyl (CH3) groups?
non-polar and hydrophobic
what are the 3 disaccharides you need to know for the exam? list what monosaccharides are combined
sucrose: glucose + fructose
lactose: glucose + galactose
maltose: glucose + glucose
in a disaccharide, what joins the two monosaccharides?
glycosidic linkage
briefly describe the reactions of dehydration synthesis and hydrolysis
monomers combine together to form polymers via dehydration synthesis. water is formed during this process.
polymers are broken down to form monomers via hydrolysis. water is consumed
in a polymer, how are bonds broken and formed?
formed: dehydration synthesis; water is formed as by-product
broken down: hydrolysis; water consumed
this applies to all polymers, regardless of it’s a glycosidic linkage, a phosphodiester bond, or a peptide bond.
what are the (2) types of glycosidic bonds?
alpha and beta
determined by the -OH groups of the sugars
describe the alpha-glycosidic bond
between 2 alpha-monosaccharide molecules
the -OH groups forming the bond are both pointing down
describe the beta-glycosidic bond
between an alpha and a beta-monosaccharide molecule
the bond is between an -OH pointing down and an -OH pointing up
what are considered to be under carbohydrates?
saccharides, starch, glycogen, cellulose, chitin
how are starch and glycogen similar and different?
both are polymers of alpha-glucose molecules (thus, have alpha-glycosidic bond)
they differ in their polymer branching and where they are found
glycogen has more branching
glycogen found in animal cells and starch found in plant cells
where is starch found? what’s its function?
in plant cells
stores energy
where is glycogen found? what’s its function?
found in animals
stores energy
how does one differentiate between alpha and beta monosaccharides?
if the OH on the anomeric carbon is pointing DOWN, it’s alpha
if the OH on the anomeric carbon is pointing UP, it’s beta
describe cellulose
a polymer of beta-glucose
a structural molecule for walls of plant cell and wood
describe chitin
a polymer of beta-glucose that’s attached to a nitrogen containing group: (n-acetylglucosamine)
a structural molecule found in fungal cells and insects’ exoskeleton
how are cellulose and chitin similar?
they are both comprised of beta-glucose molecules (but chitin also includes N-molecules)
thus, they both use beta-glycosidic bonds
can humans digest glycosidic linkages?
our digestive system can digest only alpha-glycosidic linkages
they can’t digest beta-glycosidic linkages
- cows have bacteria in their gut that produces the enzymes that can break down beta-glycosidic linkages
what are the macromolecules (polymers) and their monomer components?
carbohydrates (aka polysaccharides): monosaccharides
lipids: a bit complicated, but generally composed of hydrocarbons - lipids are not really considered polymers but are macromolecules
proteins (aka polypeptides): amino acids
nucleic acids (DNA/RNA): nucleotides
briefly describe lipids. what bonds are seen in lipids?
long hydrocarbon chains that are non-polar and hydrophobic
they are not considered polymers bc they are not made of repeated units
covalent bonds between the hydrocarbons
what are the general functions of lipids?
insulation: preserves heat
energy storage: energy reserves we can burn when needed
endocrine molecules (steroid hormones)
structural (phospholipids and cholesterol are key components of the cell membrane)
what are triglycerides (triacylglycerols)
consists of 3 fatty-acid chains attached to a glycerol backbone (3 carbons). the fatty acids can be saturated or unsaturated
body converts calories it doesn’t need right away to triglycerides which are then stored in fat cells. later, hormones release them for energy (in between meals)
differentiate between saturated and unsaturated fatty acid chains
saturated has no double bonds which lead to straight chains. these straight chains can stack densely and form plaques - bad for health
unsaturated has double bonds which lead to kinks in the chains. they stack less densely - good for health. can be cis/trans
what are phospholipids (diacylglycerols)?
2 fatty-acids and a phosphate group (w/ +R) attached to a glycerol backbone
major component of cell membranes
they are amphipathic: has both hydrophilic and hydrophobic properties
- hydrophobic tail: fatty acids
- hydrophilic head: glycerol and phosphate group
what are steroids? what are considered steroids?
contains 3 six-membered rings and 1 five-membered rings (4 rings in total)
e.g. hormones and cholesterol
what’s the most common precursor to steroid hormones?
cholesterol
what are waxes?
esters of fatty acids and monohydroxy alcohol
used as protective coating of skin and exoskeletons
what are carotenoids?
fatty acid carbon chain with conjugated double bonds and five/six-membered rings at each end
- includes pigments which produces colour in plants/animals
subgroups: carotenes and xanthophylls
what are porphyrins? give 2 examples
4 joined pyrrole rings
often complexes with a metal in the center
- Fe in hemoglobin (from transporting O2)
- Mg in chlorophyll (for absorbing light)
what are adipocytes?
specialized fat cells
major energy storage site in the body
what are glycolipids?
similar to phospholipids, but instead of a phosphate group, they have a carbohydrate group
what are lipoproteins?
bc lipids are insoluble, lipoproteins are used to transport lipids in the blood
lipoproteins are a lipid core surrounded by phospholipids (lipid bilayer) and apolipoproteins
how does the cell membrane maintain its fluidity in different temperatures?
by changing membrane fatty acid composition
the cell membrane becomes more rigid in cold weather. to avoid rigidity, the cell membrane has cholesterol (prevents tight packing of phospholipids) and mono/polyunsaturated fatty acids incorporated into the membrane which increases fluidity
the cell membrane becomes more fluid and flexible in warm weather. to prevent itself from collapsing, cholesterol is added to restrict movement. the fatty acids become more saturated, allowing it to densely stack itself, increasing rigidity.
describe the general structure of an amino acid
a amino group, carboxyl group, a hydrogen group, and a R-side chain linked to an alpha-carbon
what functions do proteins have?
structural (e.g. collagen)
mechanical/movement (e.g. actin/myosin)
enzymes
hormones (e.g. insulin)
antibodies
fluid balance
acid-base balance - pH (albumin)
channels/pumps
transport (e.g. hemoglobin which moves oxygen)
storage (e.g. casein which stores amino acids in mammalian milk)
what do enzymes do? what do they not do?
catalyze reactions in both forward and reverse directions – lower the activation energy required for a reaction, accelerating the rate of the overall reaction.
they do not change the spontaneity of a reaction or the equilibrium
they have varying function based on pH and temp
what determines the efficiency of an enzyme?
temperature (it can cause denaturation), the ideal temperature for enzymes can vary. but as you raise temperature, you generally see an increase in enzyme activity and reaction rate due to the increase in kinetic energy, having molecules bounce around more quickly. BUT, if temperature raised too high, the enzyme will denature and lose its function
pH (it can cause denaturation), the ideal pH for enzymes vary
- e.g. pepsin prefers low pH
- urease and trypsin prefer moderate pH
substrate and enzyme concentration
presence/absence of inhibitors
what does amylase do?
catalyzes reaction that breaks the alpha-glycosidic bonds in starch
all enzymes are considered proteins, except..?
RNA enzymes / ribozymes / riboenzymes
what type of proteins are there?
storage, transport, enzymes
what are cofactors?
non-protein molecules that assist enzymes, usually by donating or accepting some component of the reaction, such as electrons or functional groups
some bind reversibly or some permanently
what’s a holoenzyme?
cofactor + protein
what’s a apoprotein/apoenzyme?
when an enzyme is not combined with a cofactor but requires it for activity
what’s a coenzyme?
an organic coenzyme, like vitamins
enzymes can also be inorganic (like metals, Fe2+ or Mg2+)!
can be categorized into prosthetic group (bind covalently) and cosubstrates (bind reversibly)
in regards to enzymes, what’s a prosthetic group?
if a cofactor is covalently or tightly bound to an enzyme
what are simple proteins?
proteins formed entirely of amino acids
what are the (2) types of simple proteins?
albumins & globulins: functional proteins that act as carriers or enzymes
scleroproteins: fibrous proteins with a structural function (e.g. collagen)
what are conjugated proteins?
a simple protein linked to a non-protein
what are (5) types of conjugated proteins?
lipoprotein: bound to a lipid
mucoprotein: bound to a carbohydrate
chromoprotein: bound to a pigmented molecule
metalloprotein: protein complexed around a metal ion
nucleoprotein: contains histone or protamine, linked to a nucleic acid
what are the different levels of protein structures? describe them
primary: sequence of amino acid, connected by peptide bonds
secondary: the 3D shape from hydrogen bonding between the carboxyl and amino groups of amino acids, side-by-side (involves the peptide backbone)
tertiary: 3D structure mainly from non-covalent interactions between the R-groups of amino acids
quaternary: 3D shape of a protein that is a grouping of 2 or more, separate peptide chains
how is the primary structure of a protein determined?
sequence of nucleotides in the mRNA determine the sequence of amino acids
what are the types of secondary structures of proteins?
alpha-helix
beta-sheet
when talking about the non-covalent interactions that hold the tertiary structure of a protein together, what does it include? (5)
hydrogen bonds
ionic bonds
hydrophobic effect/interaction: R-groups push away from water
disulfide (covalent interaction, an exception): between cysteines
van der waals forces
what are the (3) main protein categories?
globular
structural/fibrous
membrane
describe globular proteins
water soluble
mainly tertiary structures
diverse range of functions
enzymes are globular !!
describe structural/fibrous proteins
not water soluble
mainly secondary structures
long polymers
function: to maintain/add strength to cellular/matrix structures
e.g. collagen or keratin
describe membrane proteins
not water soluble
includes proteins that function as membrane pumps, channels, or receptors
what is protein denaturation?
when a protein reverts back to its primary structure
give (4) examples of denaturing agents
temperature, pH, UV light/chemical, and salt concentrations
a protein’s function is determined by what?
its overall shape! aka 3D structure
when denatured, it won’t be able to function properly
can protein denaturation be reversed?
generally irreversible, but in some cases, can be reversed by removing the denaturing agent
what does protein denaturation imply about the protein’s information?
all information needed for a protein to assume its folded, functional (native) form is encoded in its primary structure
differentiate between protein denaturation and digestion
denaturation reverses a protein to its primary structure
digestion eliminates all protein structures, including primary
what are the functions of nucleic acids?
to encode, express, and store genetic information
how are the strands of DNA connected?
via base pair
hydrogen bonds that occur between nucleotides on opposite strands
how are nucleotides bonded?
phosphodiester bond between the phosphate group of one nucleotide and the five-carbon sugar of another
describe the structure of nucleotides
nitrogenous base, a five-carbon sugar, and a phosphate group
differentiate between nucleosides and nucleotides
a nucleoside does not have a phosphate group
nucleotide: nitrogenous base, sugar, phosphate group
nucleoside: nitrogenous base, sugar
- e.g. “adenosine” instead of “adenine”
what are the nitrogenous bases for DNA and RNA?
DNA: guanine, cytosine, adenine, thymine
RNA: guanine, cytosine, adenine, uracil
in DNA and RNA, which nitrogenous base pairs with what? and how many bonds? what does that implicate
GCAT -> GC AT
guanine and cytosine - 3 hydrogen bonds
adenine and thymine - 2 hydrogen bonds
since G and C have more hydrogen bonds, they require a higher (melting) temperature to break
the same goes for RNA, just replace thymine with uracil
which of the nitrogenous bases are purines? pyramidines?
purines: guanine, adenine
pyrimidines: cytosine, thymine, uracil
differentiate between the structures of DNA and RNA
DNA: GCAT
RNA: GCAU
DNA: has deoxyribose sugar (missing an O on C2). it’s double helix, with 2 strands that are anti-parallel (both run 5’ to 3’ but in opposite directions)
RNA: has ribose sugar. USUALLY single stranded
in regards to DNA, why is the direction called “ 5’ to 3’ “ ?
phosphate is attached to C5 of the deoxyribose sugar and the OH group is attached to C3
looking at DNA we see that the phosphate (at C5) begins the sequence and the OH (at C3) ends it
what is chargaff’s rule?
the number of purines = the number of pyrimidines because they are base paired
A + G = T + C
A = T
G = C
describe the discovery of the cell. who? how?
robert hooke was the first to discover cells when he looked at a piece of tree bark under a microscope and observed the cell walls of dead plant cells
a decade later, van leeuwenhoek enhance the magnification of microscope lenses and was the first to observe living cells
what does the Cell Theory state (3+4=7)?
all living organisms are composed of 1 or more cells
the cell is the basic unit of function, structure, and organization in all organisms
all cells come pre-existing, living cells
NEW TENANTS FROM THE MODERN INTEPRETATION OF THE CELL THEORY:
activity of an organism depends on the total activity of independent cells (each cell contributes to the overall activity of an organism)
energy flow occurs within cells (cells have a functional metabolism)
cells carry hereditary information
all cells have similar basic composition among similar species
what characteristics are shared by all cells?
bound by plasma membrane: a selective barrier that separate its contents from the outer environment
contains genetic material (DNA)
contains ribosomes: synthesizes functional proteins from genetic material (RNA)
describe the RNA World Hypothesis theory. what does it state/believe? why? backed by what?
suggests that RNA was the precursor of current life (based on DNA, RNA, and proteins)
states that RNA stores genetic information like how DNA does, catalyzes chemical reactions like how enzymes do - a reason behind the belief that RNA played a major role in the evolution of cellular life
also backed by the fact that RNA is more unstable than DNA, due to its extra hydroxyl group which makes it more likely to participate in chemical reactions
what does the Central Dogma of Genetics (a theory) state?
states that information must travel from DNA -> RNA -> protein
cannot travel backwards from protein! information however, can travel back and forth between DNA and RNA in special cases
describe the stereomicroscope. what are the pros and cons?
uses visible light to view the surface of a sample
pros: can view living samples
cons: has low light resolution compared to a compound microscope
describe the compound microscope. what are the pros and cons?
uses visible light to view a thin section of the sample
pros: can view some living samples (single cell layer)
cons: may require staining for good visibility which kills cells - samples that are thin enough don’t require staining
describe phase contrast microscope. what are the pros and cons?
uses light phases and contrast for a detailed observation of living organisms. including internal structures if thin
pro: good resolution and contrast
cons: not ideal for thick samples. produces a “halo” effect around the perimeter of the samples
describe the confocal laser scanning microscope and fluorescence. what are the pros and cons?
used to observe thin slices while keeping a sample intact
pros: can observe specific parts of a cell via fluorescent tagging
cons: can cause artifacts - not naturally present and caused by the process
note: can be used with light instead of fluorescence
what is a common microscopy method used to observe chromosomes during mitosis?
confocal laser scanning microscope and fluorescence
describe scanning electron microscope (SEM)? what are the pros and cons?
shoots electrons across the surface of a specimen, allowing high definition image
pros: view surface of 3D objects with high resolution
cons: can’t use on living samples as the preparation kills samples. preparation is extensive as samples need to be dried and coated. and is costly
describe cryo scanning electron microscope (Cryo SEM). what are the pros and cons?
similar to SEM
pros: sample is not dehydrated, so you can observe samples in their more “natural” form
cons: can’t be used on living samples. samples must be frozen, which might cause artifacts
describe transmission electron microscope (TEM). what are the pros and cons?
electron beams passed thru a thin section of the sample, producing very high resolution 2D images. can see internal structures - not just tissue and cells
pros: can observe very thin cross-sections in high detail, and can observe internal structures with very high-resolution
cons: cannot be used on living samples. requires extensive preparation (samples must be dehydrated, fixed into resin, and sliced into thin sections) and is costly
which microscope has the highest magnification?
transmission electron microscope (TEM)
describe electron tomography. what are the pros and cons?
not a type of microscope, but a technique used to build a 3D model of the sample via TEM (transmission electron microscope) data
pros: can look at objects in 3D and see objects relative to one another
cons: same as TEM cons: cannot be used on living samples. requires extensive preparation and is costly
what is centrifugation?
common technique used to prepare sample for observation or further experimentation
it spins and separated liquified cell homogenates into layers based on density
in centrifugation, what is the order in which cells separate?
most dense to least dense
most dense will pellet to the bottom and so on
in differential centrifugation that deals with organelles, which parts are expected to separate first, to the bottom?
nuclei layer -> mitochondria/
chloroplasts/lysosomes ->
microsomes/small vesicles ->
ribosomes/viruses/larger
macromolecule
differentiate between differential centrifugation and density centrifugation
differential: density, shape, and speed
- spin, separate dense pellet, repeat
density: density
what should be noted about solubility in differential centrifugation?
differential centrifugation forms continuous layers of sediment, where insoluble proteins are found in pellet and soluble proteins remain in the supernatant, liquid above the pellet
differentiate between anabolic and catabolic processes/reactions
anabolic: small molecules assembled into bigger ones – requires energy
catabolic: large molecules broken into smaller ones – releases energy (CATACLYSM LOL!!!!)
what is ATP?
a common source of activation energy
ATP stores its potential energy in the form of chemical energy.
ATP is an unstable molecule because the 3
phosphates in ATP are negatively charged and repel one another. when one phosphate group is removed via hydrolysis, a more stable ADP molecule results. the change from a less stable molecule to a more stable molecule always releases energy
it provides energy for all cells by transferring phosphate from ATP to another molecule
how is new ATP formed?
via phosphorylation
ADP and phosphate come together using energy from an energy-rich molecule, like glucose
define Km and Vmax in regards to enzymes
Km: “michaelis constant”, represents the substrate concentration at which the rate of reaction is half of the max velocity (rate) of the enzyme, or Vmax
Vmax: max velocity (rate) of the enzyme
what are allosteric enzymes?
they have both an active site for substrate binding AND an allosteric site for binding of an allosteric effector (can be an activator/inhibitor)
they can have multiple sites for regulatory enzymes to bind
what is competitive inhibition? describe Km and Vmax in this situation
substance is an inhibitor (by mimicking the substrate) that binds at the active site, preventing substrates from attaching. this binding is reversible and brief
the effect of competitive inhibition can be combated by increasing concentration of substrate
competitive inhibitors increase Km (bc it directly interferes with how substrates bind) but Vmax remains the same
what is non-competitive inhibition? describe Km and Vmax in this situation
substance inhibits enzyme by binding somewhere other than the active site, allowing the substrate to still bind, but the enzyme’s ability to catalyze a reaction has decreased and reaction doesn’t reach completion (bc the enzyme conformation has changed but the ability of a substrate to bind has not been)
Kmax remains the same but Vmax decreased
what is allosteric inhibition?
substance binds to enzyme (at the allosteric site, affecting the ability of the active site to function) and induces its inactive form
does not follow Km and Vmax trends
what is uncompetitive / anti-competitive inhibition?
when an enzyme inhibitor binds to the enzyme-substrate (ES) complex – preventing the formation of the product
describe the relationship between Km and binding affinity
recall, Km: the substrate concentration at which the rate of reaction is half of the max velocity of the enzyme, or Vmax
Km inversely represents binding affinity
a higher Km = worse substrate binding
lower Km = better substrate binding
Km and binding affinity are both intrinsic properties so increasing/decreasing substate/enzyme concentration doesn’t affect this property
what is cooperativity, in regards to enzymes?
positive cooperativity: phenomenon where an enzyme becomes more receptive to other substrates after binding to a substrate at its active site
negative cooperativity: enzyme becomes less receptive to other substrates after binding to a substrate at its active form
cooperativity isn’t limited to enzymes can also be done by non-enzymes e.g. oxygen in hemoglobin
what are the (3) classifications of membrane proteins?
peripheral: loosely attached to surface of one side of the membrane
integral: embedded in the cell membrane
transmembrane: type of integral; travels all the way through the membrane
what are the (8) types of membrane proteins?
channel proteins
recognition proteins
ion channels
porins
carrier proteins
transport proteins
adhesion proteins
receptor proteins
what are channel proteins?
proteins that provide a passageway through the membrane for hydrophilic (water soluble), polar, and charged substances
can also be done for substances that can normally diffuse, to allow the protein to regulate how much goes in, more quickly, etc (e.g. aquaporins for water)
what are recognition proteins?
type of glycoprotein (has an attached oligosaccharide/carbohydrate) used to distinguish between self and foreign – healthy vs diseased – by immune cells
cell-to-cell recognition
what are ion channels?
used to pass ions across the membrane
they can be open or gated (3 types) so there are 4 types overall
referred to as gated channels in nerve and muscle cells
what are glycoproteins?
play a role in cell-cell recognition; immune cells can check membrane glycoproteins to identify if a cell is foreign or not
cell signaling: glycoproteins can act as receptors by binding to signalling molecules
used in cell adhesion by binding to molecules outside the cell help stabilize them
what are the (3) different types of ion, gated channels?
voltage-gated: responds to difference in membrane potential to open/close
ligand-gated: chemical (signalling molecule) binds to open channel
mechanically-gated: responds to pressure or vibration
AND open channel
what are porins?
allows the passage of certain ions and small polar molecules
increases the rate of water passing in kidney and plant root cells
tends to be less specific: if you can fit through the large passage, you can go through
what are transport proteins?
proteins that transport materials across the membrane
they do this by active transport and facilitated diffusion (note that only active transport uses ATP)
what are the types of transport proteins? (2)
carrier and channel
what are carrier proteins?
allows for selective transport across the membrane via integral membrane protein
changes shape (undergoes conformational changes) after binding to specific molecule that enables it to be passed across - also changes shape to release it
what’s the major difference between active transport and passive transport
active transport uses ATP
what are adhesion proteins?
attach cells to neighbouring cells and provide anchors for stability via internal filaments and tubules
what are receptor proteins?
these membrane proteins are binding sites for signalling molecules which then transmit changes to the inside of the cell
what are the (3) major components/properties that contribute to the cell membrane? describe them
phospholipid membrane permeability: allows small, uncharged, non-polar, hydrophobic molecules to freely pass through the membrane. polar molecules may pass through if they’re small and uncharged (everything else requires a transporter)
cholesterol: adds rigidity to the membrane in normal conditions and maintains fluidity at lower temperatures
glycocalyx: carbohydrate coat; covers the outer side of the cell wall (in some bacteria) or plasma membrane (in some animal cells).
what are the functions of the glycocalyx?
glycocalyx: carbohydrate coating on the outer side of the cell wall or plasma membrane
possible functions:
- adhesive capabilities
- barrier to infection and chemical/physical damage OR
- markers for cell-cell recognition
can be found on the inside of blood vessels where it helps to provide a protective barrier and maintains the vascular walls beyond the plasma membrane
what does the glycocalyx consist of?
glycocalyx: carbohydrate coating on the outer side of the cell wall or plasma membrane
consists of glycolipids attached to the cell membrane AND glycoproteins that may serve as recognition proteins
what performs the same role cholesterol does in animal cells’ membranes but in plant cells and prokaryotes?
cholesterol: adds rigidity to the membrane in normal conditions and maintains fluidity at lower temperatures
plant equivalent = sterols
prokaryotes equivalent = hopanoids
what are the (4) main functions of the cell membrane?
acts as a barrier between the inside and outside of the cell
allows for communication with other cells
has selective permeability to regulate transport of substances in and out of a cell
provides structural support and protection
what’s the fluid mosaic model?
a biological term used to describe the cell membrane
fluid: cell membrane components are constantly shifting around - even the phospholipids which frequently rotate and move laterally within the same layer (can even flip vertically into another layer)
mosaic: composed of multiple different parts (phospholipids and proteins)
how are peripheral proteins held in place to a side of the cell membrane? how can this attachment be disrupted?
peripheral membrane proteins are generally hydrophilic and held together by hydrogen bonding and electrostatic interactions
this can be disrupted by changing salt concentration or pH
how can integral proteins be detached from the membrane?
integral proteins are hydrophobic and can be detached using detergent
differentiate between chromatin and chromosomes
chromosomes are tightly condensed chromatin when the cell is ready to divide
how many chromosomes do humans have?
46
23 from their mother, 23 from their father
what’s chromatin?
general packaging structure of DNA around proteins (histones) in eukaryotes
tightness in packaging depends on the cell stage
what’s a histone?
proteins that provides structural support for DNA
what’s a nucleosome?
a unit of DNA wrapped around 8 histones
what’s the nucleolus?
found in the nucleus; the site of ribosome synthesis
briefly describe the process of ribosome synthesis
rRNA synthesizes in the nucleus
ribosomal subunits are synthesized using rRNA and ribosomal proteins (imported from the cytoplasm).
once ribosomal subunits have formed, they’re exported to the cytoplasm for final assembly of a complete ribosome
what is the substitute of cytoplasm in the nucleus? (what’s there instead?)
instead of cytoplasm, the nucleus has nucleoplasm
describe the outer layer of the nucleus and what it uses for transport
the nucleus is bound by a double layer nuclear envelope with nuclear pores for transport (for mRNA, ribosome
subunits, dNTPs, proteins like RNA
polymerase and histones).
the double membrane means it has two phospholipid bilayers
what is the nuclear lamina?
found in the nucleus of eukaryotic cells
a dense fibrillar network (intermediate filaments and membrane associated proteins) that provide mechanical support AND help regulate DNA replication, cell division, and chromatic organization
differentiate between the nucleus and nucleoid
nucleus found in eukaryotic cells
nucleoids found in prokaryotes