BIO U3 AOS2

photosynthesis

process where plants and other photosynthetic autotrophs use energy from sunlight to produce glucose (energy)

enzymes

biological catalysts which increase the rate of a chemical reaction without being used up in the process

substrate

the biological molecule that is being acted upon by an enzyme

active site

location on an enzyme that the substrate binds to and undergoes a chemical reaction

product

what is produced at the end of the reaction

cofactors

molecules that bind to the active site and assist the enzyme in its activity (they do this by helping the substrate fit into the active site better)

Adenine Triphosphate (ATP)

acts as a coenzyme; binds to the active site and converts into ADP once a reaction has taken place (loses a phosphate)

purpose of photosynthesis

process in which plants and other photosynthetic species use energy from sunlight to produce glucose (energy)

anabolic reactions

building complex molecules from simple molecules

• requires energy

• photosynthesis is anabolic

factors affecting photosynthesis

light intensity, temperature, carbon dioxide concentration

cellular respiration

process where organisms break down glucose for energy (ATP) required for biochemical reactions

catabolic reaction

breaking down complex molecules into simple molecules

• releases energy

• cellular respiration is catabolic

factors affecting cellular respiration

glucose availability, temperature, oxygen concentration

endergonic

a chemical reaction requiring energy

exergonic

a chemical reaction that releases energy

factors affecting enzyme activity

• changes in temperature

• pH

• concentration

• competitive/non-competitive inhibition

enzyme activity is dependant on:

• temperature

• pH

• substrate concentration

• enzyme concentration

effect of temperature on enzyme activity

as temperature increases, there is an increase in the rate of reaction until the protein becomes denatured

effect of pH on enzyme activity

enzymes have an optimal pH at which they work best at. variation in pH levels from optimum values can lead to alterations in ionic bonding, reducing activity of the enzyme or shutting it down completely

denaturation

loss of enzyme structure due to the breaking of bonds upon heating, irreversibly changing the shape of the active site

effect of substrate concentration on enzyme activity

as the substrate concentration increases, so does the rate of reaction, until it has reached a saturation point (when all enzymes are being used).

• The rate of reaction progressively tapers off until all the active sites of the enzyme molecules become occupied.

effect of enzyme concentration

an increase in enzyme concentration is expected to produce a continual increase in reaction rate

• enzymes are not consumed in reactions so they are needed in small amounts only

• this may differ if the substrate concentration becomes a limiting factor

competitive inhibition

molecules that bind to the active site of an enzyme, preventing the substrate from binding. If more substrate is added, this overcomes competitive inhibitors

non-competitive inhibition

molecules that bind to another place on the enzyme, referred to as the allosteric site. This changes the conformation of the active site, preventing the substrate from binding

what is regulation of biochemical pathways necessary for?

• preventing waste, which would occur if pathway products were made in excess of what the cell requires

• preventing build-up in cells of products to potentially harmful levels

• preventing the depletion of substrates

allosteric regulation

when a regulator binds to a specific site on an enzyme (not its active site) and this binding produces a change in the enzyme’s shape, affecting its activity

• not permanent, can be reversed

allosteric inhibitors

produces a change in shape of the enzyme which stops enzyme activity

allosteric activators

binding produces a change in the shape of an enzyme which increases enzyme activity

regulators

molecules that bind at a site other than the active site to modulate enzyme activity

• allosteric inhibitors/activators

feedback inhibition

when the end-product of the metabolic pathway inhibits the enzyme that catalyses the first step in a pathway

specificity

refers to how enzymes only allow certain substrates to bind

(1) light-dependant stage

• occurs in the thylakoid/grana

• energy from the sun is used to split water, H2O, into oxygen (which gets released into the env.) and H+ (which is used to load NADP+ and ADP)

inputs of light dependant stage (1)

• 6H2O

• NADP+

• ADP + pi

outputs of light dependant stage (1)

• 6O2 + H+

• NADPH

• ATP

light-independant stage (2)

• occurs in the stroma

• energy from NADPH and ATP are used to fix carbon dioxide into glucose

carbon fixation

converting CO2 into glucose

inputs of light independent stage (2)

• 6CO2

• ATP

• NADPH

outputs of light independent stage (2)

• glucose

• ADP

• NADP

rubisco

enzyme in the Calvin’s Cycle (light independent stage) that helps bond carbons together to make glucose

light compensation point

the point at which the rate of photosynthesis is greater than the rate of cellular respiration

limiting factors of light compensation point

• temperature

• light intensity and colour

• CO2 concentration (input)

• water availability (input)

plant gas exchange

CO2 and O2 and water vapour are released and absorbed into plants through pores called stomata, which can open and close

photorespiration

at high temps, rubisco uses oxygen as a substrate, rather than co2, disrupting the calvin cycle

C4 photosynthesis

photosynthesis stages occur in two different cells

• light dependant occurs in mesophyll cells → pep carboxylase combines CO2 and PEP sugar to form malic acid (pep carboxylase only has CO2 as a substrate)

• calvin’s cycle occurs in bundle sheath cell → from malic acid to glucose. malic acid is converted into pyruvate and CO2, which rubisco uses to create glucose

→ C4 photosynthesis makes rubisco more likely to accept CO2 rather than O2 due to the processes happening in two different cells

when does rubisco preferentially bind to CO2?

• when carbon dioxide levels in the leaves are high

• oxygen levels are low (water is freely available)

• when temperatures are moderate

c3 photosynthesis

• occurs in the mesophyll

• undergoes photorespiration under hot conditions

PEP carboxylase

an enzyme found in mesophyll cells that combine CO2 to PEP sugar to form malic acid

CAM photosynthesis

separates processes by day and night

• at night: CAM plants open their stomata, allowing CO2 to diffuse into the leaves, which is converted into malic acid & other organic acids and stores it in the vacuole for later use

• during the day: CAM plants do not open their stomata, but they obtain CO2 through the release of organic acids which break down into CO2, therefore entering the Calvin Cycle where rubisco converts it into glucose

purpose of cellular respiration

breaks down glucose to produce ATP

• metabolism

• movement

• active transport

glycolysis (1)

• occurs in the cytosol

• glucose is split into two pyruvate molecules

• net yield of 2 ATP

• aerobic & anaerobic respiration

input: glucose, NAD+, ADP+pi
output: 2 pyruvate, NADH, 2 ATP

Krebs Cycle (2)

• occurs in the mitochondrial matrix

• produces net 2 ATP

inputs: pyruvate, NAD+. FAD+, ADP+pi

outputs: CO2, NADH, FADH2, 2 ATP

Electron Transport Chain (3)

• occurs in the cristae of the mitochondria

• electrons from NADH and FADH2 pass through protein complexes

• the energy released creates a H+ gradient

• H+ flows back through ATP synthase, producing ATP (26-28 ATP)

• oxygen is the final electron acceptor and and combines with electrons and H+ to form water

anaerobic respiration/fermentation

when O2 is unavailable, animal and yeast cells recycle the NAD+ molecules and produce energy quickly

• occurs in cytosol

• glucose and then fermentation

ethanol fermentation

• occurs in cytosol of yeast cells

• plants cannot remove ethanol and it will become toxic & kill the plant

inputs: 2 pyruvate, 2 NADH

outputs: ethanol, 2 CO2, 2NAD+

lactic acid fermentation

• anaerobic pathway in animal cells

• if lactic acid builds up in muscles, it can become toxic

• glucose is converted, via glycolysis, into 2 lactate molecules + yield of 2ATP

inputs: 2 pyruvate, 2NADH

outputs: lactic acid, 2NAD+

factors affecting the rate of cellular respiration

• temperature

• glucose availability

• oxygen concentration

effect of glucose availability on cellular respiration

glucose is an input for glycolysis, therefore, a higher glucose concentration = greater reaction rate. the rate eventually plateaus as enzymes become saturated with glucose

effect of temperature on cellular respiration

as temperature increases, the rate of cellular respiration increases. If temperature is above the optimum level, the rate decreases very quickly due to enzymes denaturing.

effect of oxygen concentration on cellular respiration

oxygen is a substrate for cellular respiration, therefore, higher oxygen concentration = greater rate.

if oxygen isn’t present, anaerobic respiration will take place which produces less ATP (~2 ATP) but is a faster process

traits and techniques that can improve through crispr-cas9

• photosynthetic efficiency

• crop yield

• crop quality

• biotic and abiotic stress resistance

• hybrid breeding

how can crispr-cas9 increase photosynthetic efficiency

CRISPR-Cas9 could be used to reduce rubisco’s ability to bind with oxygen and undergo photorespiration, and instead improve its ability to bind with carbon dioxide, therefore increasing carbon fixation

biofuel fermentation

fermentation of sugars from plants produces ethanol, which can be used as fuel

biofuel

fuel made from organic material (biomass)

first generation biofuels

biofuels which are produced from edible feedstocks

• produced through fermentation

pros of first vs second generation biofuels

• first gen: high energy yields, process of converting it to biofuels is well understood

• second gen: they dont compete with food crops for land, water, and other resources, more environmentally friendly than first gen

second generation biofuels

biofuel produced from non-edible feedstocks

• produced through thermochemical conversion