Chapter 3: Biochemical Pathways Flashcards
Define biochemical pathway
- A series of interconnected biochemical reactions (chemical reactions that occur in living things)
State the worded equation for photosynthesis
- Carbon dioxide + water → glucose + oxygen
- Light and chlorophyll above and below the arrow
State the worded equation for cellular respiration
- Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP)
State the role of NADP+ and ADP in photosynthesis
- NADP+ and ADP are coenzymes that are inputs for the light dependent stage of photosynthesis
- NADP+ functions as a carrier of hydrogen ions and electrons in the transfer of energy in photosynthesis
- ADP when combined with Pi produces ATP
State the role of ADP, FAD and NAD+ in cellular respiration
- These are unloaded forms of high energy molecules
- Through cellular respiration, they become loaded and create ATP
- ADP is recycled to generate more ATP
- FAD functions as a carrier/acceptor for electrons to the electron transport chain where they are used to synthesise ATP molecules
- NAD+ is an electron carrier used to temporarily store energy during cellular respiration
State what happens to coenzymes once they have delivered their energy or H+
- They become unloaded and are reused
List the loaded forms of NADP+, ADP, NAD and FAD
- NADP+ → NADPH
- ADP → ATP
- NAD+ → NADH
- FAD → FADH
Explain how temperature affects the rate of enzyme activity
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Low temperatures → less movement
- Collisions between substrate and enzyme molecules are less frequent resulting in a low rate of enzyme activity
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High temperatures → more movement
- Collisions between substrate and enzyme molecules are more frequent resulting in a higher rate of enzyme activity
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Above an enzyme’s optimum temperature → denaturation occurs
- Kinetic energy becomes too high
- The enzyme starts to change shape → active site is disrupted and the enzyme activity quickly drops
- This is irreversible
Explain how pH affects the rate of enzyme activity
- If pH is above or below the optimal pH level the shape of the enzyme’s active site can change preventing the formation of an enzyme-substrate complex
- This causes enzyme activity to decline and eventually stop
Explain how enzyme concentration affects the rate of enzyme activity
- Higher concentration of enzyme will result in a higher rate of enzyme activity, given there is unlimited substrate and optimum conditions (i.e. temperature and pH)
Explain how substrate concentration affects the rate of enzyme activity
- A higher substrate concentration will result in a higher reaction rate, provided there is unlimited enzyme
- With a finite amount of enzyme, the rate of enzyme activity will increase until all the enzymes are working at their maximum rate (then the rate of reaction will plateau)
- In photosynthesis, the active sites of the enzymes that catalyse the reactions that synthesise glucose in the light-dependent reactions all become occupied
Explain how competitive inhibitors reduce the action of enzymes
- Competitive inhibitors have a similar shape to the substrate
- Competitive inhibitors block the formation of enzyme-substrate complex by binding to the active site
- Fewer substrate can bind to enzymes which decreases the rate of reaction
Explain how non-competitive inhibitors reduce the action of enzymes
- The inhibitor binds to a region (allosteric site) other than the active site
- The shape of the active site changes, therefore, the substrate cannot bind
- Rate of reaction is reduced
Explaint the difference between reversible and irreversible inhibitors
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Reversible inhibitors → the inhibitor can dissociate from the enzynme
- Bind weakly (noncovalent)
- Can be competitive or non-competitive
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Irreversible inhibitors → form a covalent bond with part of the enzyme causing a permanent change
- Bond strongly (covalently)
- Normal substrate is permanently blocked from accessing the active site
Define limiting factor
- Limiting factors are environmental conditions that restrict the rate of biochemical reactions in an organism
