Theme 1:Introduction to Molecular and Cellular Biology Flashcards
what is the mature cell wall is composed of?
The mature cell wall is composed of layers of peptidoglycan connected to each other
how does the cell wall get a ridgid mesh like structure
repeating disaccharide units bound together by glycosidic bonds between the sugars and layers of peptidoglycan connected by peptide bonds between the amino acid side chains give result in a rigid, mesh-like structure,
how does the cell wall get ridity and strength
repeating disaccharide units bound together by glycosidic bonds between the sugars and layers of peptidoglycan connected by peptide bonds between the amino acid side chains give result in a rigid, mesh-like structure., which gives the cell wall rigidity and strength.
what bond is between amino acid side chains?
peptide bonds
what are the Antibiotics that target the cell wall
b-lactams
Glycopeptides
what do b lactams do?
b-lactams bind directly to transpeptidase enzyme and inhibit its function (cross linking of peptide side chains)
what do glycopeptides do?
Glycopeptides bind to peptide side chains of NAM and prevent transpeptidase from cross linking
what is in a gram negative outer membrane?
Phospholipid-Lipopolysaccharide (LPS) bilayer
(extra lipid layer - mechanism of the Gram stain)
Cytoplasmic membrane is composed of a phospholipid bilayer – no polysaccharide
Hence the CM and OM are chemically very different
what is the major function of OM
structural
what is he composition of OM
Phospholipid layer similar to CM + Lipopolysaccharid
what does a lipopolysaccarcharide contain
- lipid A
- core polysaccharide
- O-specific polysaccharide
what is the outermembranes most important biological properties?
its toxicity to animals
what does the outermembrane, specifically lp0s, of pathogenic gram negative bacteria represent
an important virulence determinant
what is immunogenicity of lps associated with?
with the polysaccharide components
what is toxicity in the outer membrane associated with?
lipid component (lipid A)
what is required for toxicity in the outer membrane
both lipid component A and polysaccharides components in vivo
when only is pls released in large amounts?
when cells lyse
how does a large amount of lps accure when cells lyse in vivo?
Autolysis of the bacteria,
External lysis mediated by immune system,
Phagocytic digestion of bacterial cells by immune cells
what is the role of lps in virulence?
LPS (Lipid A portion) binds to LPS binding protein in the blood
LPS-LPS binding protein binds to macrophage (phagocytic white blood cell) receptor
Macrophage activation
Produces defence proteins and chemicals called cytokines and chemokines (Interleukins, tumour necrosis factor, PAF)
Promote inflammation and activate host defences
What is inflammation?
Localised protective response
Increased dilation and permeability of blood vessels
Allows defence chemicals and immune cells enter infected tissue
Pathogen and infected tissue are destroyed and removed
what happens during respiratory distress?
Increased blood vessel permeability
Fluids enter air spaces of the lungs
Impaired gas exchange
“Drowning”
how can plant tissues and organs be ditinguised?
- the sources
- the sinks
- vascular tissues (exchanges of resources)
what do sinks do in regard to plants?
Sinks need to receive organic resources from the sources
what are sources in regards to plants?
- mature/largely grown leaves
what parts of the plant are sinks?
- meristems
- young leaves
- stems
- roots
- fruits/flowers
- storage organs
what ensures the survival of the plant or new progeny?
- fruits/flowers
- storage organs
in a plant there is a constant movement of resources. explain this.
-leaves provide organic compounds, recieve minerals from the roots
storage organs recieve everything
roots provide minerals , recieve organic compounds
what are the same principles that underlie early development in plants and animals?
cell division
patterning and organogenesis
differentiation and growth
what action allows post embryonic organ formation?
meristems
what does the shoot apical meristem make?
stem, leves ,flowers fruit and seeds
what does the root apical meristem make?
primary and lateral roots
what are The tiny leaves that surround the meristem called?
leaf primordia
what are plant organs made from?
meristems
what is the reason for the large diversity in plant organs?
the need to adapt to specific envoirnments
what family are cluster roots found in?
proteaceae
what sort of soil do proteaceae live on?
one of the oldest and poorest and dry soil in the world. it contains v low amounts of phosphorus leaving the plants to mine for it
what are some features of proteaceae?
stomatal crypts and suken stomata
what does photosynethesis do?
converts water and CO2 to sugar molecules which provide energy and carbon for biosynthetic processes
how do sugars provide energy in the dark?
through respiration
is photosynthesis anabolic or catabolic
builds molecules= anabolic
is respiration anabolic or catabolic
breaks down molecules=catabolic
what is an oxidation chemical reaction?
loss of one or more electrons
what is a reduction chemical reaction
gain of one or more electrons
describe the two steps involved in photosynthesis in light stage
(Step 1) Light energy is captured by the light-dependent
reactions of photosynthesis
(Step 2) The captured light energy is used to fix CO2
as carbohydrate in the light-independent reactions of photosynthesis
Light energy is converted into
chemical energy
what reactions occur in light dependant stage ?
light reactions
what reactions occur in light independant stage ?
carbon reactions
what is produced in light dependant stage ?
Splits H2O to produce O2, ATP and NADPH
what are ATP and NADPH necessary for ?
to form sugars and for molecules such as amino acids, sulfur metabolitesetc
what does photolysis mean?
light splitting (of water)
what is the formula for photolysis
2 H2O + photons (light) ―› O2 + 4 H+ + 4 e-
after photolysis what are the h+ and e- used for ?
to produce NADPH and ATP
why do different species of plants use slightly different light wavelengths?
as they contain different types of pigments
what are the 2 major carbohydrates made out of photosynthesis?
Sucrose and starch
what is the principle photosynthetic product?
sucrose as it accounts for most of the CO2 absorbed
what is the role of sucrose in plants ?
important storage sugar
(tap root of carrots and sugar beet (up to 20% dry weight)
and in leaves, eg 25% leaf dry weight in ivy)
major form for translocation of carbon
(from photosynthetic leaves (source leaves)
in germinating seedlings after starch or lipid breakdown)
how are sugars produced in plants ?
by source tissues
in light period
where does translocation occur?
source to sink over short term
from storage tissues to young tissues over long term
what form do many plants store the CO2 that they have fixed?
glucose polymers (starch)
how can starch granules be seen in plant cells
staining them with iodine
name some features of starch
- water insoluable
- size & shape is species specific
when do plants use their leaf starch ?
Leaf Starch is used at night in a way that almost all is consumed during the night, BUT NOT ALL : plants avoid getting hungry
how do plants allow growth at night?
Starch synthesis and degradation are tightly regulated to allow growth at night
during the night what provides energy and building blocks for growth and maintenance in plants?
mitochondria
what is the 2 mechanisms of growth?
division and expansion
what is division in relation to plants?
cells are dividing. Mostly occurs in meristems
what is expansion in relation to plants?
cells are growing and also differentiate. Widespread through tissues in many species
how much do species increase their biomass by typically for most herbaceae species per day?
15-20%
what do most scientists use to measure plant growth?
Relative Growth Rate (RGR), expressed as g.g-1.day-1 or mg.g-1.day-1
RGR = ln(W2)-ln(W1)
t2-t1
how does plant biomass increase
exponentially
what two issues explain largely the tissue, cellular and metabolic complexity of the plants
Plants are sessile: they cannot escape stressful environmental conditions
Most plants are autotrophs: they do not need organic compounds for their subsistance, they make them
what are the roles of a cell wall?
1: maintaining/determining cell shape (analogous to an external skeleton for every cell). It controls the rate and direction of cell growth and regulates cell volume
2: Support and mechanical strength (allows plants to get tall, hold out thin leaves to obtain light)
3: Prevents the cell membrane from bursting in a hypotonic medium (i.e., resists water pressure)
what are the roles of the vacuole?
- Containing water in plant cells
- Maintaining internal hydrostatic pressure or turgor within the cell – so allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole
- Maintaining an acidic internal pH\
- Containing small molecules (storage)
- Isolating materials that might be harmful or a threat to the cell,
e. g. glucosinolates in brassicaceae which are defense compounds - Place to degrade unwanted substances
- In seeds, stored proteins needed for germination are kept in ‘protein bodies’, which are modified vacuoles.
where do chloeoplasts within plant cells orginate from?
endosymbiotic event with photosynthetic cyanobacteria
name 3 genomes that plants contain
- nuclear (around 30000 genes)
- chloroplastic (around 100-150 genes)
- mitochondria (around 40 genes
what do chloroplasts and mitochondria reply on to be functional?
nuclear genes
what do the proteins encoded in the nuclear genome allow chloroplasts to do?
fix CO2
where does translation occur?
in the nucleus/cytosol but also in the organelles
where do polypetides encoded in the nucleus stay?
in the cytosol or can be transported to the organelles
chloroplasts – mitochondria
what does a transit peptide allow?
allows polypeptides recognition and transported to the chlorplast
Why more metabolites in plants than animals?
- Plants are sessile and have to cope with their environment: they need a large panel of chemicals
- Plants do not have nerves and use a wide range of chemical signals (for ex. Hormones, but not only) to organise and coordinate their responses between their different organs
- Most plants do not uptake metabolites from their environment: they need to produce all of them
- Plants make photosynthesis, which require a large panel of compounds such as pigments / antioxydants..
what are the two main classes of metabolites?
- primary metabolites
- mostly secondary metabolites
what is primary metabolism
Primary metabolism is about reactions and compounds essential for survival of the plants
Primary metabolism is mostly the same for all plant species
what is secondary metabolism?
Secondary metabolism is not essential for survival of the plants, or more precisely is not essential in optimal growth conditions
Secondary metabolism largely varies from species to species and also within a specie in response to environmental factors(stresses/situations)
Many secondary metabolites have medical applications
Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism
difference between if primary metabolism stopped compared to secondary metabolism
Unlike primary metabolites, absence of secondary metabolites does not result in immediate death, but rather in long-term impairment of the organism’s survivability, fecundity, or aesthetics, or perhaps in no significant change at all.
what are the functions of secondary metabolism?
- defence
- u-v protection and n-storage
- attraction
why are Metabolic pathways are very well coordinated/regulated
Several reasons:
- save energy (many reactions are less costly in the light when they occur in chloroplasts) - co-factors are usually in very low amounts - some intermediates are highly toxic for the cells (reactive oxygen species)
During Nitrate assimilation, Nitrite is very toxic. So Nitrate reductase is very tightly regulated
describe plant mitochondria in comparison to animal mitochondria
1: Very large genome compared to animal, also very variable between species
2. Plant mitochondria have uncoupling protein that allows H+ to diffuse from the intermembrane space back to the matrix: dissipation of excess energy
3. They also have Alternative Oxidase (AOX) which provides alternative route for electrons passing through electron transport chain to reduce Oxygen to water.
3. NAD(P)H dehydrogenases, attached to the outer surface of the inner membrane facing the intermembrane space can oxidize cytosolic NADH and NADPH.
4. Plant mitochondria cannot oxidise fatty acids
what is the main role of respiration?
A main role of respiration is about producing energy for non-photosynthetic cells or in the dark when photosynthesis cannot provide it
what are the other functions of mitochondria apart from the main one?
Glycolysis and The TCA cycle (citric acid cycle) provide the substrates for the synthesis of a large number of amino acids
what are some very important enzymes in the synthesis of amino acids?
amino transferases
name some examples of amnio transferases
glutamate
oxaloacetate
aspartate
alpha-ketoglutarate
how do some aminotransferases generated additional amino acids?
There is also aminotransferases which can transfer NH3+ group from alanine or gutamate to generate additional amino acids
