UNIT THREE

BIOLOGYAREA OF STUDY #1: MOLECULES OF LIFE

EXAM REVISION LECTURE

CHP 3: BIOCHEMICAL PROCESSES

CHP 3 TOPIC 1: ENERGY IN CELLS

Living organisms require energy in the form of organic compounds to survive”Heterotrophs: (= other feeding)

– Rely on an external energy source– Uses organic matter from dead and living organisms or their products to obtain carbon

Autotrophs: (= self feeding) – build organic compounds from simple inorganic compounds such as carbon dioxide and water.– Use an external source of energy, usually the sun, to build organic compounds.

Reactions in Cells• occur in the cytosol and cell organelles• some total of a cells reactions is called cellular metabolism

Anabolic (Endergonic) Reactions: Catabolic (Exergonic) Reactions

• energy taken in (cell must expend energy in process)• example: building of macromolecules; synthesis of ATP • reduction reactions are endergonic• controlled by enzymes

• energy is released (net gain)• most not spontaneous and require ‘activation energy’ (from ATP for example) • oxidation reactions are exergonic• examples: cellular respiration, ATP into ADP + Pi

Topic CHP3.1 Questions:1. Which of the following are heterotrophs? (circle) pigeon, amoeba (single celled

protistan), yeast, algae, mushroom, horse2. What percentage of energy is transferred to chemical energy from one trophic level

to the next (on average)? _____________3. What happens to the rest of the energy?4. What is the primary source of all energy?5. Reduction reactions involve the removal of oxygen from organic compounds or the

addition of electrons (i.e. H+). Reduction reactions are: endergonic/ exergonic6. Give an example of a reduction reaction? ___________________7. Oxidation reactions involve the addition of oxygen (or the removal of electrons

from) a substance. Give an example of an oxidation reaction? ____________________

CHP 3 TOPIC 2: ATP

ATP- Energy Currency• The immediate source of energy is the molecule ATP (remember: Coenzyme!)• ATP: Adenosine Triphosphate• Portable energy source that moves about the cell to where its needed (used within 1minute)

• ATP is synthesized from ADP + Pi. The process of synthesizing ATP is called phosphorylation.

• Most ATP is produced in the mitochondria of eukaryotic cells• At sites where energy is required ATP breaks down to form ADP + Pi (Pi is inorganic)• Energy is released for: anabolic reactions; cell growth; tissue repair; movement;

reproduction; active transport; active secretion• Energy required to build up (anabolic/ endergonic reaction)- glucose etc

6

CH

N

C

CC

NH2

N

HC

NN

C

CC

C

O

C

O P O P O P O CH2

O O O

O- O- O-

-

H H

OH OH

H

ATP (Adenosine Triphosphate)

3 phosphate groups

Base (adenine)

Ribose

Topic CHP3.2 Questions:1. What is a coenzyme?2. The addition of Pi to ADP is known as: _________________________3. ADP is: organic/ inorganic4. Pi is : organic/ inorganic5. Name one enzyme responsible for the production of ATP: ___________________6. How many phosphate atoms does ADP have? 7. What kind on bonds connect the phosphates together? ____________________

CHP 3 TOPIC 3: CELLULAR RESPIRATION

• Glucose (C6H12O6) is broken down to release energy• in the presence of oxygen, most cells carry out aerobic respiration• aerobic respiration occurs in three stages: glycolysis, krebs cycle, electron transport chain• aerobic respiration takes place in the mitochondria

Mitochondria• are membrane bound organelles suspended in the cytosol of eukaryotic cells• are the site of some stages of aerobic respiration•(double membrane bound!): have an outer membrane and a highly folded inner membrane, called cristae• fluid inside called matrix • contain respiration enzymes on the internal membranes • are the production site of most ATP• occur in larger numbers in cells with a higher energy requirement

Pyruvate (3 carbon molecule is converted to a 2 carbon molecule, Acetyle coenzyme A prior to stage 2 – Krebs Cycle. Carbon Dioxide is formed from this oxidation reaction.

CHP 3 TOPIC 3: CELLULAR RESPIRATIONAerobic Respiration

Step/ Process Location Products

GlycolysisGlucose, a 6 carbon molecule is spilt into two pyruvate (3 carbon molecule).Energy is released. Energy is used to form ATP and NADH

in the cytosol of cells 2 ATP molecules2 NADH molecules which can be used later to produce more ATP2 Pyruvate (3Cs) formed

Intermediate molecule formed: Acetyl Coenzyme A (a 2 carbon molecule) see next slide!

Krebs CyclesEach pyruvate is broken down to produce 3 molecules of C02 . 2 ATP and loaded (H+) acceptor molecules formed

in the inner compartment of mitochondria

2 ATP molecules8 NADH loaded acceptors2 FADH2 loaded acceptors

6 C02

Electron Transport (Chain)(H+) Electrons from the loaded molecules of NADH and FADH2 are transferred to oxygen to form water and produce 32 ATP

on the inner membranes of mitochondria

32 ATP molecules in most cells(34 ATP in some cells)

6H20

RESPIRATION CYTOPLASMGLYCOLOSIS HAPPENS HERE!

MITOCHONDRIARESPIRATION HAPPENS IN THIS

ORGANELLE!

PROTEINSCARBS

(SUGARS)

AMINOACIDS

FATS(LIPIDS)

GLUCOSEC6H12O6

ACETYL-CoA

PYRUVICACID

GLYCOLOSISIN CYTOPLASM NO OXYGEN!

KREBS CYCLE AND

ELECTRONTANSPORT

MAKES36 ATPS

MAKES2 ATPS

O2 ENTERS HERE

CO2 IS RELEASED

ATP TOTALS

GLYCOLOSIS=2

Krebs + ETC =36

minus 2

Overall =36!

Remember: Aerobic Cellular Respiration

C6H12O6 +

GLUCOSE

6O2

OXYGEN

6CO2 +

CARBON DIOXIDE

6H2O + ENERGY

WATER

36 – 38 ATP

CHP 3 TOPIC 3: CELLULAR RESPIRATIONAnaerobic Respiration: is an energy releasing cellular reaction which does no require oxygen

in animal cells (anaerobic glycolysis): Glucose + 2 ADP + 2Pi 2 ATP + lactic acid• does not require oxygen• is a series of reactions in the cytosol• transfers some of the chemical energy in glucose to chemical energy in ATP• glucose is converted to pyruvate which in turn is converted into lactate• acceptor molecule (nad) used in process of converting pyruvate• produces a net gain of two atp molecules for each glucose molecule• produces waste called lactate• lactate is toxic and in excess causes pain and fatigue in the tissue.

• in plant cells/ yeast (fermentation) Glucose + 2 ADP + 2Pi 2 ATP + ethanol + CO2• anaerobic Respiration in yeasts is called Fermentation.

Anaerobic Vs Aerobicreading page80 (Table 3.2)

Anaerobic Aerobic

Oxygen not required Oxygen required

Rapid ATP Production Slow ATP Production

Mammals sustain over a short period (60 secs)

Sustain indefinitely

Less efficient energy transfer More efficient energy transfer

2 mole of ATP produced per 1 mole of glucose used

36 mole of ATP produced per 1 mole of glucose used (some 38)

Various waste products: lactic acid, water (Humans)Ethanol, CO2 (Yeasts)Butyl alcohol (bacteria)

Waste Products:CO2 and water

Biozone: Page 50

Topic CHP3.3 Questions:1. Chemical formula for a glucose molecule: _______________________2. Chemical formula for aerobic respiration: _____________________________3. In the absence of oxygen most cells carry out: __________________ respiration4. Aerobic respiration takes place in which organelle: ________________________5. True/ False: only animal cells aerobically respire6. True/ False: anaerobic respiration only occurs in the absence of ozygen7. The fluid inside the Mitochondria is called what: ________________8. The three stages of aerobic respiration (in order) include: ___________________,

_____________________, & ___________________________9. Loaded acceptor molecules involved in aerobic respiration include: ______________,

______________________10. In glysolysis, one molecule of glucose produces two 3 carbon molecules called: __________ 11. Acetyl Coenzyme A has how many carbons? __________________12. One molecule of glucose produces how many molecules of CO2? __________13. How many molecules of ATP are produced from one molecule of glucose? ____________14. True/ False: Amino acids can be used for cellular respiration15. True/ False: amino acids are converted directly into Acetyl co enzyme A and skip glycolysis16. In the absence of oxygen, through the process of respiration plants convert glucose into

what: ____________________________________-

CHP 3 TOPIC 4: PHOTOSYNTHESIS

Photosynthesis is the conversion of light energy (photons) to stored chemical energy in glucose molecules

• Simple molecules water and CO2 are converted to glucose with oxygen as a waste product• Reaction occurs when chlorophyll (plastid) is present.(carotenoids also absorb blue-violet

light and appear orange yellow or red)• Chlorophyll traps the light energy and converts it to a form of chemical energy (ATP &

NADPH+) which can be used to make glucose• Most plants contain two forms of chlorophyll, chlorophyll a & chlorophyll b, together these

pigments absorb light at the violet/ blue and red ends of the spectrum

violet blue green yellow orange red

Absorption

CHP 3 TOPIC 4: PHOTOSYNTHESIS

Rate of Photosynthesis• influenced by available wave lengths of light• Is also dependent upon light intensity; the stronger the light, the greater the rate• Does not increase indefinitely: at high light intensities is limited by:

• availability of the reactants: CO2 and H2O• availability of enzymes which catalyse the reaction

Process of Photosynthesis• doesn’t take place in all plant cells, even not all leaf cells (i.e. most epidermis cells lack chloroplasts – exception: guard cells)• occurs in a number of steps that can be divided into two stages: light dpendent stage & light independent stage (also referred to as dark stage, although they don’t require darkness, they simply don’t require light!)

Site of Photosynthesis• Chloroplasts

• Stage 1: Grana • Stage 2: Stroma

Granum

Thylakoid Membrane

Thylakoid Space

Site of Photosynthesis

takes place in chloroplast

CHP 3 TOPIC 4: PHOTOSYNTHESISStage/ Description Location Products

Light- dependent ReactionsLight energy is trapped by chlorophyll and used to produce ATP and to split water molecules into H= ions and oxygen. Oxygen given off as waste. H+ ions are taken by acceptor molecules NADP12H2O + light energy 6O2 + 24H+ (as NADPH) + stored ATPRole of ATP Synthase

Within grana (thylakoid membranes)

6 O2 (from the split water molecules; it is released by diffusion into atmosphere)

ATP – net gain of 2

NADPH

Light-independent ReactionsCO2 from the atmosphere is combined with hydrogen (from the loaded acceptor NADPH) to form sugar in a series of reactions known as Calvin cycle. ATP produced in light stage used for thisRole of Enzyme – rubisco, PGAl

In stroma: Glucose C6H12O6

6 H2O

CHP 3 TOPIC 4: PHOTOSYNTHESIS

CHP 3 TOPIC 4: PHOTOSYNTHESIS

• one important product formed in the calvin cycle is PGAL (phosphoglceraldehyde), a compound that contains 3C atoms.

• PGAL can react to form various sugars, including glucose, fructose, sucrose.

• sucrose is the form in which carbohydrates are transported through the phloem.

• Starch (a polysaccharide) is the storage carbohydrate in plant cells.

CHP 3 TOPIC 4: PHOTOSYNTHESIS

Topic CHP3.4 Questions:1. Light energy is also known as what: _____________2. A chemical formula for photosynthesis is: _______ +________ ______ + ________+ ____3. A example of a plastid in plant cells is a: ____________4. Green plants deflect ____________________ coloured light5. The two stages of photosynthesis are: 1. ___________________ + 2.___________________6. Stage 1 takes place in: _____________________ Stage 2 in: _____________________7. True/ False: all plant cells photosynthesise8. CO2 enters a leaf through which key structure: _________________ 9. Loaded acceptor molecules of photosynthesis include: _____________10. Carbon fixation is also known as: _______________________11. PGAL has how many carbons? ___________________

CHP 3 TOPIC 5: STARVATION

• animals require a continuous supply of energy and matter for survival

• when an animal is starved it uses energy from body tissue.

• after glucose is used up, fats and then proteins are used.

• during starvation people use up to 97% of fat tissue, 31% of skeletal muscle and 27% of blood.

• when an animal reaches this stage, it is called autophagia (feeding off self).