Module 2 Flashcards
what does a TEM do?
electrons transmitted through specimen and focused to create a 2D image
what does an SEM do?
electrons sent across surface and reflected ones collected. lower resolution, but makes 3D images
what is an artefact?
a visible structural detail caused by processing of the specimen
where are ribosomes produced?
nucleolus
describe the structure of the mitochondria
double membrane, inner membrane is folded to form cristae, interior fluid called cristae. Has its own DNA
what does the cytoskeleton do?
maintains shape and stability of cell. Holds organelles in place, and causes movement of cell/organelle
what is the cytoskeleton made of?
Microfilaments for cell movement and cytokinesis,
Microtubules, can move organelles and creates spindle fibres
Intermediate fibres for mechanical strength
what arrangement do flagella and cilia have?
9+2 arrangement
what do cilia do?
Beat in a rhythmic manner to create a current to move things
what does SER do?
lipid and carbohydrate synthesis, and storage
what does RER do?
synthesis and transport of proteins, has ribosomes
where can you find ribosomes?
free in cytoplasm, on RER, in mitochondria, in chloroplasts
Describe the process of releasing proteins from the cell
proteins synthesized on RER
packaged into transport vesicles
move towards Golgi via vesicles
vesicles fuse with Golgi
proteins structurally modified by Golgi
proteins travel to cell surface membrane via vesicles
vesicles fuse with membrane and proteins released by exocytosis
what does the Golgi apparatus do?
modifying proteins and ‘packaging’ them into vesicles
describe cellulose cell wall function
gives shape, defense mechanism, and supports both cell and plant when membrane presses against it
what is the function of the vacuole?
generate turgor pressure
how is DNA stored in prokaryotes?
free, in one supercoiled chromosome
what are prokaryotic cell walls made of?
peptigoglycan
describe differences in ribosome sizes
eukaryotes have 80S, prokaryotes have 70S
which biological molecules contain nitrogen?
proteins and nucleic acids
what elements do lipids and carbohydrates contain
carbon, oxygen, hydrogen
what are polar molecules?
molecules with regions of negativity and positivity
describe the properties of water
High boiling point
ice is less dense than water, so floats
adhesion and cohesion
high specific heat capacity
describe how being a solvent makes water useful
acts as a medium for reactions, and can transport dissolved compounds
why is water a good transport medium?
due to capilliary action, and as it is a solvent
why is water being a coolant helpful?
because it can help maintain a constant temperature in an environment due to its high specific heat capacity, allowing enzyme controlled reactions to occur
why is water a good environment for fish to live in?
Because it is very stable. ice floats and creates an insulating layer to maintain stable temperature. the surface tension can also hold some insects
what is sucrose made of?
glucose and fructose
what is maltose made of ?
two alpha glucose
what is lactose made of?
galactose and glucose
what is starch made of?
amylose and amylopectin
describe the structure of amylose
many alpha glucose joined by 1-4 bonds, creating a helix which more is compact and less soluble than the glucose used to make it
describe the structure of amylopectin
mostly 1-4 bonds, but some 1-6 bonds that causes branching. this makes it very compact, and free ends mean glucose can be quickly added/removed.
is glycogen structurally similar to amylose or amylopectin
amylopectin, but with even more branches
how is cellulose formed?
with alternating alpha glucose molecules, creating a straight chain. cellulose is insoluble
how do you test for reducing sugars?
add sample and benedicts reagent
mix and heat in boiling water for 5 mins
should turn red
how to test for non reducing sugars?
boil sucrose(most common one) with HCl, will break down into fructose and glucose, both reducing sugars
how do you test for starch?
iodine solution will turn blue/black
why don’t lipids and water mix?
lipids are non polar
what are the bonds between glycerol and fatty acids called?
ester bonds
what’s the difference between saturated and unsaturated fats?
saturated have no carbon double bonds, whereas unsaturated have some, causing ‘kinks’. these mean they can’t pack as tightly, so are likely to be oils.
describe the structure of a phospholipid
charged phosphate head replaces a fatty acid chain.
what is a sterol?
a lipid that has a polar(hydrophilic) -OH group and the rest of the molecule is hydrophobic
list 8 lipid roles
membrane formation energy storage electrical insulation thermal insulation cushioning for vital organa hormone production waterproofing buoyancy
how do you test for lipids?
mix with water, then ethanol, and shake. look for white emulsion on the top
what is the bond between two amino acids called?
peptide bond
what is an amino acid chain called?
polypeptide
describe the primary structure of proteins
the sequence in which amino acids are joined
describe the secondary structure of proteins
hydrogen bonds may form within amino acid chain, pulling it into an alpha helix shape. they can also form a beta-pleated sheet.
describe the tertiary structure of proteins
the folding of proteins into its final shape
what interactions between R-groups can occur in the tertiary structure?
hydrophilic/phobic
hydrogen bonds
ionic bonds
disulfide bridges, only in cysteine
describe the quaternary structure of proteins
association of additional proteins called subunits
which R-groups will be on the inside/outside of proteins
hydrophilic ones will be on the outside and hydrophobic on the inside, because the are made in the aqueous cytosol
what is a globular protein?
a compact, water soluble protein that is roughly spherical.
what type of protein is insulin?
Globular protein. being water soluble helps it be transported in the blood
what is a conjugated protein?
a protein with a non protein prosthetic group.
what type of protein is hemoglobin?
conjugated protein
what type of protein is catalase (not enzyme)
conjugated protein
what are fibrous proteins?
long, insoluble molecules. They are very organized, and not folded
describe the structure of keratin
fibrous protein in hair, skin and nails. Has lots of cysteine, causing disulfide bridges. more disulfide bridges= tougher material
what is elastin?
fibrous protein found in blood vessels and alveoli. can freely stretch, and cause elastic recoil
what is collagen?
fibrous protein found in skin, tendons, ligaments and nervous system. used as a connective tissue.
what is a nucleotide made of?
pentose sugar
phosphate group
nitrogenous base
how are nucleotides joined together?
nucleotides are joined to form polynucleotides by phosphodiester bonds.
what are pyrimidines?
the smaller bases, Thymine and Cytosine
what are purines?
The bigger bases, Adenine and Guanine
what does antiparallel mean?
The two strands run in opposite directions
what type of base is Uracil
pyrimidine (replaces Thymine)
describe DNA replication
DNA Helicase unzips DNA by breaking H bonds
Free DNA nucleotides pair up with the complimentary base pairs by forming hydrogen bonds
The new nucleotides are joined by DNA polymerase via phosphodiester bonds
One strand is new and one is old, and so is called semi-conservative replication
what is a gene?
The section of DNA that codes for a whole protein
what does it mean for the genetic code to be universal?
It is the same for all organisms
What does it mean for the genetic code to be degenerate?
Multiple codons can code for the same amino acid
describe the process of transcription
DNA is ‘unzipped’ by DNA Helicase
Free RNA nucleotides base pair with complimentary bases on antisense (template) strand
p
Phosphodiester bonds formed by RNA polymerase
mRNA leaves nucleus and DNA reforms
Which strand contains code for the protein?
The sense strand (5’ to 3’) contains the code for the protein, so the antisense strand (3’ to 5’) is the one that binds with RNA, so the mRNA has the same sequence as the sense strand
describe the process of translation
mRNA binds to ribosome
complimentary tRNA anticodon binds, carrying amino acid
another tRNA molecule corresponding to the next codon binds, only two tRNAs can bind at the same time
the amino acids are joined by a peptide bond via peptidyl transferase
the ribosome moves along the mRNa chain, releasing the first tRNA
sequence is repeated until polypeptide formed
describe the structure of tRNA
a folded strand of RNA that is folded so that an anticodon is at one end. The anticodon binds to the complimentary mRNA codon. tRNA carries a corresponding amino acid
What is ATP used for?
synthesis
transport
movement
describe the structure of ATP
nucleic acid with adenine (base), ribose sugar and 3 phosphate groups
how is energy released from ATP?
phosphate group is broken off by addition of water, leaving inorganic phosphate and ADP.
what are the properties of ATP
small- easily moves in and out of cells
water soluble- many processes happen in aqueous conditions
releases enough energy for reactions to occur, but so much that it is lost as heat
easily regenerated with energy
what type of protein is an enzyme?
globular protein
what is the induced fit hypothesis?
The idea that the active site slightly changes shape as the substrate enters. This puts strain on the substrate, helping to lower the activation energy
What is an intracellular enzyme?
enzymes that act within cells. Catalase is an example
What is an extracellular enzyme, and why are they important in digestion?
enzymes that act outside cells. They are important because nutrients are often polymers such as proteins and polysaccharides. They must be broken down into smaller molecules to enter through the cell surface membrane
how is starch broken down?
Starch is broken down into maltose by maltase(disaccharide)
Maltose is broken down into glucose by maltase
What enzyme breaks proteins into smaller peptides?
Trypsin
How does temperature affect enzyme activity?
As temperature increases, so does kinetic energy, causing more enzyme substrate complexes to form. This increases rate of reaction. However, if temperature exceeds an optimum level, the enzyme will denature, and activity will rapidly decrease as the active site will no longer be complimentary
what is Q10?
How much the rate of reaction increases with a 10 degree increase in temperature. It is often taken as 2 for most enzyme controlled reactions
how does pH affect enzyme activity?
A small variation will slightly denature the enzyme and therefore reduce activity, but if returned to normal levels, the enzyme will become renatured. A more significant variation however, will permanently denature the active site of the enzyme, and therefore reduce enzyme activity
How does increasing substrate concentration change enzyme activity
The rate of reaction will increase as more enzyme-substrate complexes can be formed. However, if all active sites are saturated, a new Vmax will not be formed as substrate concentration is no longer the limiting factor
How does increasing enzyme concentration change enzyme activity ?
The rate of reaction will increase as there is more active sites in a given area, leading to more enzyme-substrate complexes. The Vmax will also increase, as there will be more free active sites. This is until substrate concentration becomes a limiting factor
What is a competitive inhibitor, and how do they work?
A molecule that has a similar shape to the substrate, and so can also bind to the active site. Therefore, the enzyme cannot catalyse the reaction as enzyme-substrate complexes cannot be formed
how do competitive inhibitors affect rate of reaction?
The rate of reaction will decrease. However, the Vmax can still be reached when the substrate concentration far outweighs the inhibitor concentration
How do non-competitive inhibitors work?
The inhibitor binds to the allosteric site
This changes the tertiary structure of the enzyme, meaning the substrate cannot bind to the active site, reducing the rate of reaction. Increasing substrate concentration will increase the rate of reaction, The same Vmax will not be reached. They can be both reversible and irreversible
what is end product inhibition?
When the product of an enzyme controlled reaction inhibits the enzyme that produced it. It is a form of negative feedback, and is a control mechanism for the reaction, as to not make excess products and waste resources.
what is a cofactor?
An additional component to an enzyme that helps to catalyse a reaction. Many come for vitamins and minerals
What is a coenzyme?
An organic cofactor
What prosthetic group in the context of enzymes?
A cofactor that is a permanent feature of the enzyme.
What is precursor activation?
Many enzymes, such as those that can cause damage, must be controlled and only activated under certain conditions. This is done by causing a conformational change in the active site, which can be done by either:
adding a cofactor
the action of another enzyme (protease)
change in condition (temperature/pH)
What is compartmentalisation?
The formation of sperate membrane bound areas in a cell to allow different conditions for different reactions to happen simultaneously
what do channel proteins do?
provide a hydrophilic channel that allows diffusion of things like ions
what do carrier proteins do?
can allow both active transport and diffusion. Often involves the changing of shape.
what do glycoproteins do?
involved in cell signaling as a receptor for chemical signals
what do glycolipids do?
they are antigens that can be recognised by the immune system as either ‘self’ or ‘non-self’
what does cholesterol do?
regulates fluidity
How does temperature effect membrane structure?
makes the membrane more fluid, and it will eventually lose structure. This increases permeability. Carrier and channel proteins can also be denatured, affecting permeability.
How do solvents affect membrane structure?
solvents that are less polar than water will dissolve membranes, disrupting cells. This makes the membrane more fluid and therefore more permeable.
What is diffusion?
the net movement of particles from a region of high concentration to a low concentration
what factors affect rate of simple diffusion?
temperature
concentration gradient
what factors affect rate of diffusion across a membrane?
surface area
diffusion distance
temperature
concentration gradient
what is facilitated diffusion?
diffusion across a membrane through channel proteins. This allows polar/charged molecules to pass through. It can also involve carrier proteins. More protein channels increases the rate of facilitated diffusion
What is active transport?
The movement of molecules against a concentration gradient, requiring energy/ATP
describe the process of active transport using carrier proteins
Molecule binds to receptor on carrier protein
ATP binds to carrier protein and is hydrolysed
The energy released causes a conformational change in carrier protein
Molecule released into cell
Phosphate recombines with ADP to form ATP
carrier protein returns to its original shape
what are the two types of bulk transport?
Endocytosis and exocytosis
what are the two types of endocytosis?
Phagocytosis (solids)
pinocytosis (liquids)
describe the process of exocytosis
vesicles move towards and fuse with the cell surface membrane. the contents of the vesicle are released outside the cell.
describe the process of endocytosis
cell surface membrane enfolds a material until the membranes eventually fuse, forming a vesicle. The vesicle moves off into the cytoplasm
what is water potential?
The amount of pressure exerted by water as they collide with a membrane/container
what is hydrostatic pressure?
pressure caused by an increase in water, and therefore volume, of a solution.
what happens when an animal cell is placed in a solution that is:
Hypertonic
Isotonic
Hypotonic
Water leaves cell and it shrinks (crenation)
No net osmosis, no change
Water enters cell, it swells and bursts (cytolysis)
what happens when a plant cell is placed in a solution that is:
Hypertonic
Isotonic
Hypotonic
Water leaves cell and membrane comes away from the cell wall (plasmolysis)
No net osmosis, no change
Water enters cell, it swells and becomes turgid, with cell membrane pushing against cell wall
What are the three phases of interphase?
G1
S
G2
what happens during G1?
protein synthesis, organelles replicate, cell size increases
what happens during S?
DNA replication
what happens during G2?
cell size increases, energy stores increased and duplicated DNA checked for errors
What is G0?
When a cell leaves the cell cycle, and is no longer dividing
What are the reasons for entering G0?
differentiation
DNA has become damaged
As you age, senescence becomes more common
What are the three checkpoints in the cell cycle?
G1 checkpoint
G2 checkpoint
Spindle assembly checkpoint
What happens during prophase?
chromatin coils and condenses to form chromosomes
nuclear envelope disappears
spindle fibres formed
What happens during Metaphase?
Chromosomes moved to centre of cell by spindle fibres
What happens during Anaphase?
Chromatids separated and pulled to opposite poles
What happens during Telophase?
nuclear envelope reforms
chromosomes begin to uncoil
What happens in cytokinesis is animals?
Cleavage furrow forms around middle of cell membrane and pulled inwards until it fuses around the middle
What happens in cytokinesis in plants?
vesicles assemble in the middle of the cell and fuse with each other and the cell surface membrane, dividing the cell into two. New cell wall then forms over the membrane.
What happens during prophase 1?
nuclear envelope reforms
spindle formation begins
bivalents form
Crossing over!
what happens during metaphase 1?
Homologous chromosomes assemble along metaphase plate
Independent Assortment of Homologous chromosomes
what happens during Anaphase 1?
Chromosomes pulled to opposite poles
What happens during Telophase 1?
nuclear membrane reforms, chromosomes uncoil, then cytokinesis occurs
What happens during prophase 2?
nuclear envelope breaks down and spindle formation begins
What happens during metaphase 2?
Line up on metaphase plate
Independent assortment of sister chromatids
What happens during anaphase 2?
Chromatids pulled to opposite poles
What happens during Telophase 2?
Chromatin formed
nuclear envelope reforms
cytokinesis then occurs, resulting in 4 haploid daughter cells
How are Erythrocytes adapted for their function?
biconcave for increased SA:V
No nuclei for more space for haemoglobin
can squeeze through narrow spaces
How are neutrophils adapted for their function?
Multi-lobed nucleus to squeeze through small gaps
Many lysosomes to attack pathogens
How are sperm cells adapted for their function?
flagellum to swim
many mitochondria to swim
acrosome at head contain digestive enzymes to break down protective layers around egg
How are palisade cells adapted for their function?
contain chloroplasts
rectangular so can be closely packed
thin cell walls, increase carbon dioxide diffusion
large vacuole for turgor pressure
chloroplasts can move in cytoplasm for more sunlight
How are root hair cells adapted for their function?
Long extension which increase surface area
How are guard cells adapted for their function?
Become less swollen when they lose water, so the stomata close and they lose less water
thicker on one side so cell changes shape when volume changes
How is Squamous epithelium adapted for its function?
One cell thick to allow rapid diffusion
found in lining of lungs
How is Ciliated epithelium adapted for its function?
have cilia that move in a rhythmic manner
goblet cells also present, that release mucus to trap any unwanted particles in the air
How is Cartilage adapted for its function?
contains collagen and elastin
prevents bones rubbing and causing damage
How is the epidermis adapted for its function?
single layer of closely packed cells covered in waxy cuticle to reduce water loss
stomata control gaseous exchange
How is xylem tissue adapted to its function?
elongated dead cells strengthened with lignin for structural support
what are the three levels of stem cell potency?
Totipotent- can differentiate to any type of cell
Pluripotent- Can form all tissue types but not an organism
Multipotent- Can form a range of cells within a certain type of tissue
What stem cells are found in the bone marrow?
Haematopoetic stem cells
What are the sources of animal stem cells?
Embryonic stem cells- totipotent at start, pluripotent after a few days
Tissue stem cells- Found in bone marrow and umbilical cord
Where are plant stem cells found?
meristem tissue, found in roots and shoots (where growth happens)
What are the uses of stem cells?
Heart disease Type 1 diabetes Parkinson's Alzheimer's birth defects spinal injuries developmental biology
What ethical issues are there with stem cells?
Destruction of embryos (life begins at conception)
When embryo has rights
Get around this with umbilical cord stem cells but they do not divide well, and Haematopoetic cells are only multipotent
