Biology Exam 3

ATP structure

• Ribose (sugar)

• Adenine (nitrogenous base)

• Three phosphates

ATP

energy currency of the cell

Phosphorylation

transfer of a phosphate group from one molecule to another

ATP provides energy via

phosphorylation

Phosphorylation =

free energy that can do work

Cellular Respiration

when cells make ATP

• electrons make an H+ gradient across a membrane

ATP synthase

• H+ transport proteins in membrane

• use free energy from H+ moving down concentration gradient to synthesize ATP

ATP is synthesized by…

ATP synthase

Why do we eat food?

• for electrons

• provides mitochondria w/ electrons & H+

Cellular Respiration =

process of stripping electrons from food to make ATP

• Oxidizes macromolecules

Cellular respiration is a …

long series of redox reactions

4 Stages of Cellular Respiration:

1. Glycolysis

2. Pyruvate Oxidation

3. Citric Acid Cycle

4. Oxidative Phosphorylation

First 3 stages of cellular respiration do what?

extract electrons from food and store in NADH & FADH2

Last stage of cellular respiration does what?

uses the stored electrons to help produce ATP

Types of Redox Rxns:

• Oxidation

• Reduction

Oxidation

Loss of electrons

Reduction

Gain of electrons

Reducing Agent

Donates electrons and causes another substance to be reduced

• reagent of oxidation

Oxidizing Agent

Accepts electrons and causes another substance to be oxidized

• reagent of reduction

Cellular Respiration Equation:

C6H12O6 + 6O2 —> 6CO2 + 6H2O + energy

Cellular respiration equation whats being oxidized and reduced?

glucose is oxidized to 6CO2

6O2 is reduced to 6H2O

Cellular respiration is controlled fire because?

Rxn proceeds in a large number of small steps

• energy released a little bit at a time

Electron Carriers

electrons torn from organic molecules are stored by electron carriers

NAD+ =

main electron carrier

NADH carriers electrons to…

the electron transport chain

Electron Transport Chain:

uses electrons to create a H+ gradient

Oxidative Phosphorylation:

Process that generates 90% of ATP

• powered by redox rxns

Substrate-Level Phosphorylation:

• small amount of ATP generated in glycolysis & citric acid cycle

• Occurs when an enzyme transfers a phosphate group directly from substrate to ADP

Glycolysis & Citric Acid Cycle —>

break apart glucose molecule

ALL CO2 produced in cellular respiration is—>

produced by pyruvate oxidation (2co2) & citric acid cycle (4co2)

Main Function of Glycolysis & Citric Acid Cycle:

capture electrons from food ; store as NADH

NADH is used to make ATP by

Oxidative Phosphorylation

ALL O2 is used in …

oxidative phosphorylation

ALL H2O is produced by …

oxidative phosphorylation

Cellular Respiration Part I —>

extracting electrons & protons from food

• glycolysis, citric acid cycle

Most of glucose’s electrons are extracted in…

citric acid cycle

Purpose of Glycolysis & Pyruvate Oxidation:

• prepare glucose for citric acid cycle

• transform glucose into acetic acid in an energized form called Acetyl CoA

Why must glucose be transformed into Acetyl CoA?

Citric acid cycle can only process Carboxylic Acids

Why does cellular respiration start with sugar?

cells make ATP using electrons & protons from food

How do cells make ATP using electrons & protons?

use NAD+ and enzymes called dehydrogenases

Dehydrogenase

rips electrons & protons from food, storing electrons in NADH

Citric Acid Cycle (carboxylic acid cycle):

takes carboxylic acids & chops off CO2

Glycolysis:

breakdown of glucose begins here

Purpose of Glycolysis & Pyruvate Oxidation:

transform glucose into Acetyl CoA

Glycolysis transforms glucose into…

2 Pyruvate molecules

Pyruvate Structure:

a 3 Carbon carboxylic acid

Purpose of Glycolysis:

1. Extract electrons (make NADH)

2. Transform glucose into a carboxylic acid (Pyruvate)

Glycolysis occurs where?

In Cytoplasm

Two Major Phases of Glycolysis:

1. Energy Investment Phase

2. Energy Payoff Phase

Energy Investment Phase

2 ATP are used to split glucose into 2 three-carbon sugar molecules

Energy Payoff Phase

4 ATP are synthesized

2 NAD+ are reduced to NADH

small sugars are oxidized to form 2 Pyruvate & 2 H2O

How many net ATP produced by substrate-level phosphorylation during glycolysis?

2 ATP

Glycolysis does NOT release any…

CO2

Purpose of Pyruvate Oxidation:

• Extract electrons (make NADH)

• Transform pyruvate into another carboxylic acid (Acetyl CoA)

Purpose of Citric Acid Cycle:

• Extract electrons (make NADH)

• Complete the breakdown (oxidation) of the remaining glucose

How many cycles does citric acid cycle turn for glucose? Why?

• Turns twice per glucose

• because 2 acetyl CoA are produced per glucose

Citric Acid Cycle generates…

1 ATP

3 NADH

1 FADH2

(per acetyl CoA)

2 CO2 (waste)

Purpose of Oxidative Phosphorylation:

Use electrons extracted from glucose to make ATP

2 Steps of Oxidative Phosphorylation:

1. Electron Transport Chain

2. Chemiosmosis

1. Electron Transport Chain

Uses electrons from NADH & FADH2 to create a H+ gradient

2. Chemiosmosis

H+ is then allowed to move down its concentration gradient through a large protein complex called ATP Synthase

ATP Synthase =

uses proton motive force of chemiosmosis to make ATP

Protein complexes I, III, IV are …

active transporters (pumps protons)

Protein complex II is…

integral membrane protein (no proton pump)

ATP Synthase is what kind of transport?

passive transport

Electrons in electron transport chain end by what?

electrons that began in food end by reacting with O2 to make H2O

What is the terminal electron acceptor?

O2

ATP Synthase & Chemiosmosis:

H+ moves into binding sites on the rotor of ATP synthase, causing it to spin in a way that catalyzes phosphorylation of ADP to ATP

Chemiosmosis:

the use of free energy in a H+ gradient to drive cellular work

1 ATP synthesized per 4 Protons

10 protons / NADH → 2.5 ATP per NADH

6 protons / FADH2 → 1.5 ATP per FADH2

Does NADH or FADH2 generate more ATP?

NADH → 2.5 ATP

Burning Fat & Protein:

alternative entry points into cellular respiration that bypass glycolysis

Fat Breakdown

supplies molecules that can enter respiration and generate ATP.

Protein Breakdown

supplies carbon-containing molecules, while nitrogen must be processed and removed.

Biosynthesis

intermediates of cellular respiration are used to synthesize fats and monomer

What is the primary product of photosynthesis?

G3P

What if no O2?

Fermentation

Fermentation

allows glycolysis to continue when oxygen is unavailable by regenerating NAD⁺ from NADH.

• Pyruvate oxidizes NADH to produce NAD+

Fermentation Equation

Pyruvate + NADH → Lactate + NAD+

• Net eq.= Glucose → Lactate + 2 ATP

Photosynthesis

captures light energy and stores it in organic molecules.

Where does photosynthesis occur?

Chloroplasts of plant cells

Chloroplast

solar powered chemical factories

• use light to rip electrons from H2O

Chloroplast : Electrons from H2O used to do?

1. make ATP by chemiosmosis

2. Transform CO2 into glucose

Photosynthesis equation is the reverse of?

Cellular respiration

Photosynthesis reactants make what products?

CO2 → C & O of Glucose

H2O → H of Glucose and O2

2 Steps of Photosynthesis:

1. Light Reactions

2. Dark Reactions

Light Reactions

harvest electrons from H2O using solar power to make ATP & NADPH

Light Reactions Location:

Occur in Thylakoids in chloroplasts

Light Reactions have Photosystems II & I that?

• produce ATP & NADPH

• capture & harvest energy from light

Photosystem II (first):

• Light stimulates an electron in chlorophyll to a higher energy state

• this electron excites neighboring chlorophyll molecules

• finally, a central chlorophyll molecule is stimulated & loses its electron

• electron goes through electron transport chain to make ATP

• 
  

• Replacement Electron = electrons stripped from H2O

How is Light Captured?

Excitation of chlorophyll by light

• one electron goes to excited state (unstable)

• electron falls back down and releases energy

• Captured by NADP+

In Chloroplasts excited electrons are captured by…

NADP+

Photosystem I (second):

• same process as Photosystem II

• BUT, replacement electrons come from Photosystem II

Where do the replacement electrons come from in Photosystem I?

electrons from Photosystem II

Where do the replacement electrons come from in Photosystem II?

electrons from H2O

Dark Reactions

Use the Calvin Cycle

Dark Reactions Location:

Occur in stroma of chloroplasts

Calvin Cycle

• Fixes CO2 using Rubisco

• Uses ATP & NADPH from Light Reaction

• Product = G3P

Product of Dark Reactions: Calvin Cycle

G3P

Cell - Cell Communication:

• cells communicate using chemical signals

• chemical signals are synthesized & secreted by a Source Cell

• detected by Receiver Cell

• receiver cell respond to signal