Unit 1 notes from textbook + slides Flashcards
What is cell theory?
1)all organisms are made up cells
2)cells come from pre-existing cells
3) the cell is the fundamentak unit of life
Characteristics of prokaryotes
bacteria and archea
small
lack a nucleus
have a nucleoid
cell wall
first forms of life
circular chromosome
carry additional DNA in the form of plasmids
Characteristics of eukaryotes
animals, plants, fungi, protists
have a nucleus
extensive internal compartmentalization
big
membrane bound organelles
linear chromosomes
what do all cells have?
all cells have a cell membrane or plasma membrane that controls the exchange of material with the environment
characteristics of DNA
double helix
stores information
characteristics of proteins
molecules that provide structure
internal architecture
shape
ability to move
various chemical reactions depends on proteins
polymers of amino acids
transcription definition
the synthesis of RNA from a DNA template, describes the copying of info from one form into another
translation definition
the synthesis of proteins from an RNA template, this process converts info in the language of nucleic acids to info in the language of proteins
central dogma of biology
DNA to RNA (mRNA messenger) to proteins
gene definition
the DNA sequence that corresponds to a functional product such as a protein
DNA replication definition
allows genetic information to be passed from cell to cell or from an organism to its progeny
mutation definition
error in DNA during replication or damage from the environment
metabolism definition
chemical reactions by which cells convert energy from one form to another and build or break down molecules, harness energy from the environment
characteristics of viruses
cannot function on their own, but require a host cell to reproduce
when a virus infects a host cell, it co-opts the cellular machinery to make copies of itself
it infects the host cell by binding to the cell’s surface, inserting its genetic material into the cell
In bacteria, why does translation occur very quickly?
because there is no nuclear membrane that seperates DNA from the surrounding cytoplasm, transcribed mRNA is immediately translated into proteins by ribosomes
what is the cell wall made up of?
peptidoglycan polymer made of sugars and amino acids
how do photosynthetic bacteria gain CO2?
by diffusion of CO2 from the environment into the cell
why is it easier for a small cell to allow for diffusion?
has more surface in proportion to its volume and the interior parts of a small cell are closer to the surrounding environment than those of a larger cell, small enough for molecules to diffuse into the cell’s interior
endomembrane system
network of membranes that allow for the cell to continue functioning even as it changes shape
endocytosis definition
the cytoskeleton and membrane system enable eukaryotic cells to engluf molecules or particles; including other cells
phagocytosis definition
form of endocytosis in which eukaryotic cells surround food particles and package them in vesicles that bud off from the cell membrane
exocytosis definition
molecules or cytoplasmic waste formed within the cell is packaged in vesicles and moved to the cell surface for removal
what must be true in order for a cell to divide successfully?
must be large enough to divide into two and contribute sufficient nuclear and cytoplasmic components to each daughter cell
how do prokaryotic cells reproduce?
via binary fission
a cell replicates its DNA, increases in size and divides into two daughter cells (receive one copy of the replicated parental DNA)
how do eukaryotic cells reproduce?
divide the nucleus by mitosis, divide cytoplasm into two daughter cells by cytokinesis
the DNA of eukaryotes is found in the nucleus therefore, cell division requires first the breakdown and then the reformation of the nuclear envelope
environmental conditions that could affect the rate at which a cell can divide
levels of available nutrients
competition
temperature
pH
osmotic pressure
Lag phase definition
adjustment period
individual bacterial cells are growing but not readily dividing
making the tools they need ie. expressing genes that encode for particular proteins like structural proteins, enzymes, integral membrane proteins
no display of a net increase in growth at this phase
exponential phase definition
when bacteria have adapted they maximize all the benefits from the nutrient media
replication occurs
phase where the overall population of cells undergoes binary fission at a constant rate
replication is at its maximum
increases exponentially
stationary phase definition
key nutrients are beginning to deplete therefore, bacteria start to compete for nutrients, metabolic waste products released from the bacterial cells builds up in environment (toxic to bacterial cells)
net zero growth
equal amount of individual cells actively dividing as there are cells that are dying
death phase definition
death of many bacterial cells, more cells are dying than actively dividing
nucleic acids definition
encode and transmit genetic information
polymers of nucleotides
linekd with phosphodiester bonds
carbohydrates definition
provide a source of energy and make up the cell wall in bacteria, plants and algae
polymers of simple sugars
composed of C, H, O usually in the ratio of 1:2:1
major source of energy for metabolism
linked with glycosidic bonds
lipids definition
make up cell membranes, store energy and act as signaling molecules
covalently linked via ester linkage
amino acid structure
central carbon atom (alpha carbon), covalently linked to four groups:
an amino group (NH2)
a carboxyl group (COOH)
a hydrogen atom (H)
an R group or side chain that differes from one amino acid to the next
peptide bond formation
formed between the carbon atom in the carboxyl group of one amino acid and the nitrogen atom in the amino group of the next amino acid
covalent linkage
involves the loss of a water molecule
nucleotide characteristics
contains a 5-carbon sugar, a nitrogen-containing compound called a base and one or more phosphate groups.
sugar for DNA and RNA
deoxyribose (hydrogen on the second carbon), ribose (OH group on the second carbon)
Two types of nitrogen containing bases
Pyrimidine bases: have a single ring and include cytosine and thymine
Purine bases: have a double ring and include guanine and adenine
how are nucleotides connected?
In DNA and RNA, each adjacent pair of nucleotides is connected by a phosphodiester bond, which forms when a phosphate group in one nucleotide is covalently joined to the sugar unit in another nucleotide
how are bases connected?
via hydrogen bonds
Adenine is double bonded to Thymine
Cytosine is triple bonded to Guanine
polysaccharides function
provide long term energy storage (starch and glycogen) or structural support (cellulose in plant cell walls)
how are monosaccharides connected?
building blocks of complex carbohydrates and attached to each other by covalent bodns called glycosidic bonds
formed between carbon one of one monosaccharide and a hydroxyl group carried by a carbon atom in a different monosaccharide molecule
property shared by lipids
all hydrophobic, chemically diverse
fatty acid definition
long chain of carbon atoms attached to a carboxyl group
glycerol defintion
a 3 carbon molecule with OH groups attached to each carbon
fatty acid bonding
the carboxyl end of each fatty acid chain attaches to glycerol at one of the OH groups, releasing a water molecule
saturated vs unsaturated fatty acid
unsaturated: contain double bonds, have a kink at each double bond
saturated: no double bonds, max number of hydrogen atoms attached to each carbon, straight chains
forces between neighbouring fatty acid chains
Van der Waals Forces
because of these forces the melting point of fatty acids depends on their length and level of saturation
increase in length higher melting point
the more kinks, reduces tightness of the molecule, decreases interactions and decreases melting point
hydrophilic
water loving, polar
hydrophobic
water fearing, non-polar
order of strength of bonds
1) covalent 2)ionic 3)Ion-PD 4)Hydrogen bonds 5)PD-PD 6) Ion-ID 7) PD-ID 8) ID-ID
phospholipids properties and structure
glycerol backbone attached to a phosphate group and two fatty acids
phosphate group is hydrophilic because its polar and fatty acid tails are hydrophobic and nonpolar
amphipathic
micelle shape
lipids with bulky heads and a single hydrophobic tail are wedge-shaped and pack into spherical structures called micelles
bilayer shape
lipids with less bulky headgroups and two hydrophobic tails are roughly rectangular form a bilayer
hydrophobic heads are the outside surface, hydrophobic tails inside
liposomes
when phospholipids are added to a test tube of neutral water they spontaneously form spherical bilayer structures called liposomes that surround a central space, resembling a cell
why is the lipid bilayer said to be fluid?
lipid molecules are able to move within the plane of the membrane because of the weak vanderwaal forces that break and reform
different types of membrane proteins and their functions
transporters: moving ions or molecules across the membrane
receptors: allow the cell to receive signals from the environment
enzymes: catalyze chemical reactions
anchors: attach to other proteins and help maintain cell structure/shape
integral membrane proteins definition
permanetly associated with cell membranes and cannot be seperated from the membrane without destroying it
most integral proteins are transmembrane proteins that span the entire bilayer
peripheral membrane proteins definition
temporairly associated with the bilayer or with integral membrane proteins through weak noncovalent interactions, can be removed
what can and can’t move through the bilayer?
Can’t: the hydrophobic interior of the lipid bilayer prevents ions and charged polar molecules from moving across it
many are too large to move across
Can: gases and non polar molecules such as lipids can mvoe across the bilayer
small uncharged molecules are able to move through the bilayer to a very limited extent
diffusion definition
the net movement of substances such as ions and molecules from areas of higher to lower concentration
passive transport definition
occurs when molecules move across a cell membrane by diffusion (ie. simple diffusion)
occurs when molecules move passively down a concentration gradient through protein transporters (ie. facilitated diffusion)
two types of membrane transporters
channel proteins: provides an opening between the inside and outside of the cell through which certain molecules can pass, depending on their shape and charge. Some are gated, meaning they can open in response to some sort of signal either chemical or electrical
carrier proteins: binds to and then transports specific molecules. Binding of the transported molecule induces a conformational (shape) change in the membrane protein, allowing the molecule to be transported across the bilayer
two ways water moves through the lipid bilayer
1) passive transport to a limited extent
2) channel proteins called aquaporins, allow water to move much more readily via facilitated diffusion
osmosis
net movement of a solvent such as water across a selectively permeable membrane such as the cell membrane
water moves from regions of higher water concentration to regions of lower water concentration
active transport definition
transport against a concentration gradient
requires ATP to move substances through transport proteins embedded in the membrane
secondary active transport definition
transport against a concentration gradient driven by an electrochemical gradient
primary structure of a protein
the sequence of amino acids in a protein, first level of protein structure, ultimately determines how a protein folds
secondary structure of a protein
interactions between streches of amino acids in a protein form local secondary structures
H-bonds can form between the carbonyl group in one peptide bond and the amide group in another, thus allowing localized regions of the polypeptide to fold, the R groups project outwards from the alpha helix
tertiary structure of a protein
the 3D conformation of a single polypeptide chain, usually made up of several secondary structure elements, results from the interactions between the amino acid R groups, this structure usually includes loops or turns in the backbone that allow R groups to sit near each other in space and for bonds to form
determines the function
denaturation definition
process by which molecules are unfolded and therefore lose their structure
due to chemical treatment or high temperature that disrupts the hydrogen bonds and ionic bonds holding the tertiary structure together
allosteric enzymes definition
enzymes that are regulated by molecules that bind at sites other than their active sites
activity of these enzymes can be influenced by inhibitors and activators
negative feedback definition
the final product inhibits the first step of the reaction
used to maintain homeostasis
what must an organic molecule contain?
at least one C-H bond
what end are amino acids added to?
Carboxyl end
what end are nucleotides added to?
the 5’ carbon of a new monomer is attached to the 3’ carbon of the existing strand or 1st monomer
what end are sugars added to?
4’ end of the incoming monomer is added to the 1’ end of the 1st monosaccharide
graph of facilitated transport
level of glucose inside=level of glucose outside
ie converges to 1
describe the process of macromolecular assembly of proteins in the cell
the process is spontaneous
energetically favorable
delta G<0
folded proteins are more stable
happens due to the hydrophobic effect
nucleoside definition
sugar+base
what is the backbone of DNA?
deoxyribose sugar + phosphate
what two interactions occur between bases?
hydrogen bonds and stacking interactions (help stablize the strands)
what drives the spontaneous formation of the DNA double helix?
the hydrophobic effect
major and minor grooves definition
regions where proteins bind to the DNA
different proteins recognize the different sequences of bases
why can’t ions diffuse through the lipid membrane?
ions in an aqueous solution are usually surrounded by water molecules and are larger called hydration shells
