Unit 4: Cell Processes Flashcards
what is metabolism
all of the enzyme-catalysed reactions in a cell
anabolic vs catabolic reactions
anabolic: putting molecules together, forming bonds, condensation reaction, requires energy (i.e. photosynthesis)
catabolic: big molecules to smaller molecules, breaking bonds, hydrolysis, release energy (i.e cell respiration)
structure of an enzyme
globular protein, soluble, folded into specific shapes, determined by amino acid sequence, has an active site for catalysis
induced fit model
active site will change shape to fit substrate, affecting bonding in the substrate –> releases products, active site returns to original shape
Role of molecular motion and substrate-active site collisions in enzyme catalysis
inc. temp and conc. inc. collision rate
molecules must be correct orientation when they collide with the active site of an enzyme
Relationships between the structure of the active site,
enzyme–substrate specificity and denaturation
denaturation: permanent change to the 3d structure of the enzyme
measurements in enzyme-catalysed reactions
change/time
examples of intra and extra cellular enzyme-catalysed reactions
intracellular = glycolysis and Krebs cycle
extracellular = chemical digestion
why is heat energy generated by the metabolic reactions?
energy transformation is not 100% efficient, so some energy is lost as heat
heat generation can be by: shivering, fat burning
cyclical vs linear pathways in metabolism
cyclical: Krebs cycle & Calvin cycle
linear: glycolysis
explain non competitive inhibition and allosteric sites
non competitive inhibition = substance (allosteric inhibitor) binds to the allosteric site, changing the shape of the active site and making it impossible for the substrate to bind
explain competitive inhibition
competitve inhibition = a competitor with a similar shape binds to the active site, preventing substance from binding
i.e. statins
adding competitive inhibitor = reduce rate, but reaches maximum
non competitive inhibitor, increases conc. of substrate will not increase reaction rate
what is feedback inhibition
the final product becomes a non-competitive inhibitor of the first enzyme in the chain, preventing unnecessary build up of the final product
i.e. threonine to isoleucine
(“3,9 to iso lucy ne”)
Mechanism-based inhibition as a consequence of chemical changes to the active site caused by the irreversible binding of an inhibitor
binds irreversibly to an amino acid somewhere in the chain, causing permanent change to the active site and rendering the enzyme permanently useless
i.e. penicillin inhibits an enzyme in bacteria = antibacterial
stops transpeptidase
what is ATP
molecule that distributes energy within cells
is a nucleotide
adenosine triphosphate
characteristics =
- bond between second and third phosphate group can be broken to release energy
- can be regenerated
- soluble and stable in water
- cannot cross membranes
what life processes within cells receive energy from ATP
active transport, synthesis of macromolecules and movement of cell components (mitosis) or locomotion
energy transfers during interconversions between ATP and ADP
energy released when 3rd phosphate group broken off, forms A-P-P (adenosine diphosphate) or ADP
energy is required to regenerate ATP
what is cell respiration
Cell respiration is a system for producing ATP within the cell using energy released from carbon compounds
Gas exchange: the process of O2 and CO2 diffusing into and out of cells
Ventilation: mechanical movements that supply fresh air
NOT THE SAME THING
differences between anaerobic and aerobic cell respiration in humans
aerobic: with oxygen
1. Humans: CO2 and H2O
can start from carbohydrates, lipids or amino acids
cytoplasm, then mitochondria
30 ATP produced
anaerobic: with no oxygen
1. yeast: CO2 and ethanol
2. Humans: lactate
start with ONLY carbohydrates
only in mitochondria
2 ATP produced
when do we do anaerobic respiration?
when we need ATP but cannot supply fast enough
–> lactic acid builds up, limiting physical ability to keep going
–> oxygen debt = the amount of oxygen that must be absorbed following anaerobic respiration in order to break down the lactate
what are the variables affecting the rate of cell respiration
- decline in O2 conc.
- decline in glucose conc.
- increase in CO2 conc.
can measure oxygen consumption using an respirometer
controlled variable = temp and pressure
what can you investigate using a respirometer?
–> different organisms
–> different temperatures
–> different respiratory substances
explain the transformation of light to chemical energy when carbon compounds are produced in photosynthesis
chemical energy can be in the form of carbs, lipids, proteins, nucleic acids.
this energy transfer is vital for most ecosystems
conversion of CO2 to glucose in photosynthesis
photolysis = using light energy to split water
using hydrogen obtained by splitting water
what is a byproduct of photosynthesis
O2 and glucose
O2 changed the composition of the Earth’s atmosphere
how to separate photosynthetic pigments?
chromatography
Rf value = distance of pigment/distance of solvent
absorption of specific wavelengths of light by photosynthetic pigments
pigments can absorb certain wavelengths of light.
the wavelengths that the pigments reflect are what we see
absorption and action spectra: see C1.3.5 on iPad
Techniques for varying concentrations of carbon
dioxide, light intensity or temperature experimentally to
investigate the effects of limiting factors on the rate of photosynthesis
see diagrams 1.3.7
example of experiment = pondweed experiment
describe the aim of CO2 enrichment experiments
a means of predicting future rates of photosynthesis and plant growth
hypothesis: rising CO2 levels will increase photosynthesis rates
FACE (free air carbon dioxide enrichment experiment)
- observing: plant growth, limiting factors of photosynthesis, effects on other parts of the ecosystem
