UNIT 2; section 3 variation in biochemistry + cell structure

in red blood cells

carries o2 around the body

found in a variety of organisms = all vertebrates

large protein , = quarternary structure --- 4 polypeptide chains

each chain has a haem group = contains iron

each molecule of Hb can cary 4 o2 molecules

in the lungs the o2 joins to Hb to form oxyhaemoglobin = ASSOCIATION

near body cells o2 leaves oxyhaemoglobin =  returns to Hb =DISSOCIATION

affinity = tendency a molecule has to bind to o2

Hb's affintity for o2 varies depending on the conditions its in

1 condition that affects it is the po2 = partial pressure of o2

po2 is a measure of o2 conc.

the greater the conc. of dissolved o2 in cells, the higher the po2

as po2 increases = Hb's affinity for o2 also increases
o2 loads onto Hb to form oxyhaemoglobin where theres a high po2= association
oxyhaemoglobin unloads its o2 where theres a lower po2 = dissociation

high po2 in the lungs (alveoli)
when cells repsire they use up o2 = lowers the po2

Alveoli in lungs  -
high o2 conc.
high po2
high affinity
o2 loads
association

respiring tissue -
low o2 conc.
low po2
low affinity
o2 unloads
dissociation

show how saturated the Hb is with o2 at any given partial pressure

the affinity of Hb for o2 affects how saturated the Hb is ;
where po2 is high (in the lungs) , Hb has a high affinity for o2 ,so it has a high saturation of o2

where po2 is low (respring tissues), Hb has a low affinity for o2, so it has a low saturation of o2

saturation of Hb can also affect the affinity = this is why the graph is s-shaped

when Hb combines with the first o2 molecule ,its shape alters = easier for other moelcules to join too

as the Hb starts to become saturated = harder for o2 to join

as a result - the curve has a steep bit in the middle where its really easy for o2 moleules to join + shallow bits at each end where its harder

when the curve is steep , a small change in po2 causes a big change in the amount of o2 carried by the Hb

partial pressure of co2 = measure of the conc. of co2 in a cell

pco2 also affects o2 unloading

Hb gives up its o2 more readily at a higher pco2 = lower affinity

when cells respire they produce co2 = raises pco2
* increases the rate of o2 unloading so the dissociation curve shifts right

saturation of a blood with o2 is lower for a given po2 , meaning more o2 is being released

= the bohr effect

low o2 enviroments -
have Hb with a higher affinity for o2 than human Hb
dissociation curve is further left than ours

high activity levels -
Have Hb with a lower affinity for o2 than human Hb 
as they need their Hb to easily unload o2 
dissociation curve is to the right 

size
small mammals have a higher surface area to volume ratio than larger mammals
^lose heat quickly - high metabolic rate to keep them warm = high o2 demand 
mammals smaller than humans have Hb with with a lower affinity than human Hb - they need to be able to easily unload o2 to meet the demand 
dissociation curve is to the right of ours

nucleus = genetic materail

plasma membrane = holds cell together + controls entry and exit 

cytoplasm = gel like substance where most chemical reactions happen

ribosomes = where proteins are made 

mitochondria = aerobic respiration 

few extra cells 

palisade cell = leaf cell which absorbs light for photosynthesis

rigid cell wall = made of cellulose, it supports and strenthens the cell 

chloroplasts = where photosynthesis occurs

permanent vacuole = contains cell sap + a weak solution of sugar + salts . also pushes the chloroplasts closer to edge so they can absorb light

chloroplasts

double membrane 
thylakoid membranes - stacked to form grana 
grana are linked by lamellae 
stroma is the fluid filled space 

made of lots of monossachrides 
eg. 

cellulose starch glycogen

cell wall in plants 

long unbranched chains of B-glucose 

bonds between sugars are straight - so cellulose chains are straight 

cellulose chains linked by hydrogen bonds - from strong fibres - microfibrils

strong fibres mean cellulose provides structural support for cells

glucose is a monossarchride with 2 forms - alpha and beta

beta glucose is the same as alpha glucose  - EXCEPT the OH and H on the right are swapped around 

alpha glucose reads - HO OH 

beta glucose reads - HO H 

when monossachrides join , a molecule of h2o is released 

bond = glycosidic 

second beta glucose molecule is upside down 
^ this lines the 2 OH groups up so the glycosidic bond is straight 

main energy store in plants
doesnt effect osmosis as it is insoluble = good for storage 
mixture of 2 polyssacrhides of alpha glucose = amylose and amylopectin 

amylose
long unbranched chains of a-glucose
coiled structure due to bonds between the glucose molecules = good for storage 

amylopectin

long branched chain 
side branches allow enzymes that break down the molecule to get at the glycosidic bonds easily = so glucose can be quickly released quickly ie = large s.a.

main energy storage in animals 

polyssachrides of a-glucose

similar to amylopectin - more side branches coming off 
lots of branches means stored glucose can be released quickly 

very compact - so good for storage