Metabolism, Enzymes, Respiration and photosynthesis

Question 1

What is the catabolic pathway?

Answer 1

Break down of complex molecules into simpler molecules. Degrative. Releases energy eg cellular respiration

Question 2

What is the anabolic pathway?

Answer 2

Builds complex molecules from simpler ones. Constructive (biosynthetic), requires energy eg synthesis of proteins from amino acids

Question 3

What is exergonic?

Answer 3

Net release of free energy.without addition of energy. Negative delta G, spontaneous or energetically favourable, moves towards equilibrium and final state has less free energy than initial state/ reactants

Question 4

What is endergonic?

Answer 4

Absorbs free energy/requires input of energy. Positive delta G, nonspontaneous or energetically unfavourable, moves away from equilibrium and final state has more free energy than initial state/reactants

Question 5

What is an enzyme and what does it do?

Answer 5

Is a macromolecule that acts as a catalyst by speeding up reactions without being consumes. Mainly proteins although ribosomes can also act as enzyme. Speeds up metabolic reactions by lowering activation energy barriers specific for reactions they catalyse.

Question 6

What is the activation barrier?

Answer 6

The energy required to start the chemical reaction

Question 7

How does the activation barrier work?

Answer 7

It orientates substrates correctly. Active site of substrate is specific so must match
Straining substrate bonds. Substrate being flexed to fit active site
Providing a favourable microenvironment with correct temp/pH. optimal temp for enzymes to work
Covalently bonding to substrate

Question 8

How is enzyme so specific?

Answer 8

It is specific to certain substrates and binds to substrate at active site only

Question 9

What are the 6 stages of the induced fit model?

Answer 9

1. Substrates enter active site;enzyme changes shape such that its active site enfolds the substrates (induced fit)
2. Substrates held in active site by weak interactions such as hydrogen bonds and ionic bonds
3. Active site can lower Ea and speed up a reaction
4. Substrates are converted to products
5. Products are released
6. Active site is available for new substrate molecules

Question 10

What affect does temperature have on enzymes?

Answer 10

They are affected by the environment and can operate optimally at certain temperatures or pH

Question 11

What can activate enzymes?

Answer 11

Cofactors (non protein enzyme helpers) and coenzymes (organic factors)

Question 12

What can inhibit enzymes?

Answer 12

Competitive inhibitors (bind to the active site of an enzyme, competing with the substrate) and Non competitive inhibitors (bind to another part of an enzyme changing its function)

Question 13

What is ATP?

Answer 13

The powerhouse of cell, couples endergonic and exergonic reactions to drive metabolic processes

Question 14

What is each step of a metabolic pathway catalysed by?

Answer 14

A specific enzyme

Question 15

What are the components of ATP?

Answer 15

Adenosine tri-phosphate (3 phosphates, ribose sugar and nitrogenous base-adenine)

Question 16

What breaks ATP bonds and what occurs when broken?

Answer 16

Broken by hydrolysis to yield ADP + pi + energy

Question 17

Where does aerobic respiration occur and what is facilitated by?

Answer 17

Occurs in mitochondria and facilitated by enzymes. The enzymes are located in the mitochondrial matrix and the inner membrane

Question 18

What are the 4 shapes of proteins?

Answer 18

Primary, secondary, tertiary and quaternary

Question 19

What is the shape of an enzyme?

Answer 19

Is globular in shape and changes shape to fit to protein

Question 20

How does aerobic respiration work?

Answer 20

Consumes organic molecules and oxygen and yields ATP, water and energy in the form of ATP and heat

Question 21

What are the 3 stages of respiration?

Answer 21

Glycolysis, citric acid cycle and electron transport chain/oxidative phosphorylation

Question 22

How does glycolysis work?

Answer 22

Breakdown of glucose to pyruvate, occurs inside the mitochondrion and produces a small amount of ATP and electron carriers NADH

Question 23

How does the citric acid cycle work?

Answer 23

Pyruvate is transformed into acetyl Co-A (CO2 is produced) and enters the citric acid cycle where some ATP, NADH and FADH2 carriers are produced

Question 24

How does the electron transport chain/oxidative phosphorylation work?

Answer 24

Electron carriers from glycolysis and CAC enter the electron transport chain where they are passed through a series of molecules (mostly proteins and cytochromes) which will accept and donate electrons. Electrons are passed to oxygen forming water. At the same time, the electron transport chain causes H+ (protons) from the matrix to the intermembrane space creates an electrochemical gradient and the H+ pass back. through the membrane via ATP synthase. At this point ADP + Pi forms ATP

Question 25

How can ATP be generated without oxygen?

Answer 25

By ethanol fermentation (alcohol, pyruvate- CO2=acetylaldehyde which reduced to ethanol) or lactic acid fermentation (direct reduction from pyruvate to lactate, no release of CO2)

Question 26

What is photosynthesis and where does it occur?

Answer 26

Converts solar energy to chemical energy, providing food. Occurs in the chloroplast in plants, algae, some protists and prokaryotes

Question 27

What does the chloroplast contain?

Answer 27

Contains stroma (a dense interior fluid), chlorophyll (green photosynthetic pigment) which is in the membranes of the thylakoids (connected sacs in the chloroplast). Grana is thylakoid sacs and stroma

Question 28

What is the chemical formula for photosynthesis?

Answer 28

6CO2 + 12H2O + light energy -> C6H12O6 + 6O2 + 6H2O

Question 29

What does chloroplast do in photosynthesis?

Answer 29

Splits the H2O into H and O and incorporates the electrons of hydrogen into sugar and releases O2 as by product

Question 30

What occurs in the light reaction in photosynthesis?

Answer 30

It occurs in thylakoids. Splits H2O, reduce NADP+ and NADPH and generates ATP from ADP

Question 31

What occurs in the calvin cycle in photosynthesis?

Answer 31

Occurs in the stroma. Froms the sugar from CO2 using ATP and NADPH. Carbon enters the cycle as CO2 and leaves as a 3 carbon sugar (glyceraldehyde-3-phosphate) which can be stored as starch or exported as sucrose

Question 32

What are the 2 photosystems and what occurs here?

Answer 32

PSII and PSI. A photon of light hits the chlorophyll pigment and electrons flow through the photosystems through an electron transport chain which generates ATP via protons diffusing across the membrane (similar to mitochondrion in respiration)