Lecture 18

Question 1

Living cells

Answer 1

are open systems constantly requiring an input of materials from external sources that can yield the energy needed to do work

the work of the cell includes assembling polymers, membrane transport, moving and reproducing

animals can obtain energy to do this work by feeding on other animals or photosynthetic organisms

Question 2

Energy in cells

Answer 2

energy flows into an ecosystem as sunlight and leaves as heat

chemical elements essential to life are recycled

photosynthesis generated O2 and organic molecules are used in cellular respiration

Question 3

Catabolic pathways yield energy by oxidising organic fuels ..

Answer 3

catabolic pathways release stored energy by breaking down complex molecules

anabolic pathways enable cells to reform complex molecules needed by cells

electron transfer plays a major roles in these pathways

these processes are central to cellular respiration

Question 4

Catabolic pathways and production of ATP

Answer 4

the breakdown of organic molecules is exergonic

fermentation is a partial degradation of sugars that occur without O2

aerobic respiration consumes organic molecules and O2 and yields ATP

anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2

Question 5

redox reactions

Answer 5

the transfer of electrons during chemical reactions releases energy stored in organic molecules

this released energy is ultimately used to synthesise ATP

Question 6

the principles of redox

Answer 6

chemical reactions that transfer electrons between reactants are called oxidation-reduction or redox reactions

in oxidation- a substance loses electrons or is oxidised

in reduction- a substance gains electrons or is reduced

the electron donor is called the reducing agent and the electron acceptor is the oxidising agents

some. redox reactions do not transfer electrons but change the electron sharing in covalent bonds

Question 7

oxidation of organic fuel molecules during cellular respiration

Answer 7

during cellular respiration, the fuel is oxidised and O2 is reduced

organic molecules with an abundance of hydrogen are excellent sources of high energy electrons

energy is released as the electrons associate with hydrogen ions are transferred to oxygen, a lower energy state

Question 8

Stepwise energy harvest via NAD+ and the electron transport chain

Answer 8

in cellular respiration, glucose and other organic molecules are broken down in a series of steps

electrons from organic compounds are usually first transferred to NAD+, functions as an oxidising agents during cellular respiration

each NADH represents stored energy that is tapped to synthesise ATP