Biology Test 2nd Test

What is the definition of metabolism?

the totality of an organisms chemical reactions

-all reactoins interescet via metabolic pathways

What is the definition of metabolic pathways

molecule is altered in a series of steps to produce a product

Each step is catalyzed by a specific enzyme, a

macromolecule that speeds up a specific reaction

What is the definition of Anabolism?

energy requiring

Ex. Protein synthesis

from amino acids

What is the definition of catabolism?

energy capturing (break things) example: cellular respiration

What is the definition of energy?

the capacity to casue change to rearragne matter

-do work

What is the definition of kinetic?

when energy is associated with motion

What is the definition of thermal?

associated with the movement of moelcule’s

What is the definition of heat?

transfer of thermal energy

What is the definition of Potential?

energy that is not kinetic

What is the definition of chemical?

potential energy

available for release in a chemical reaction

What metabolism is about?

taking energy in one

form and transforming it into another form.

What is the definition of the Second Law of Thermodynamics?

every energy transformation increases the entropy (randomness) of the universe

the free-energy change

of a reaction tells us

whether or not the reaction occurs spontaneously

Biologists follow the energy and entropy what is that?

(order/disorder) changes during chemical reactions

to determine whether they require an input of

energy or occur spontaneously

What is the definition of Gibbs free energy?

G, can be simplified and

referred to as free energy

What is the definition of Free energy?

is the portion of a system’s energy

that can do work

The ΔG

for a process can be used to determine

whether it is spontaneous or not

note on the aG

– ΔG is negative for all spontaneous processes

– ΔG is zero or positive for nonspontaneous processes

traingle G (two things)

whether a reaction

will occur

spontaneously, and

thus release

energy

or

if a reaction

requires energy to

be put into the

system for it

proceed.

What is the definition of endergonic?

is a chemical process that absorbs energy from its surroundings and has a positive change in Gibbs free energy (Δ G > 0). [1, 2]

What is the definition of exergonic?

reaction is a chemical or physical process that releases free energy into its surroundings. [1, 2]

ATP powers cellular work by

coupling exergonic reactions to endergonic reactions

What three type of main work does a cell do?

-Chemical work: pushing endergonic reactions

-Transport work: pumping substances across

membranes against.

-Mechanical work: beating cilia or contracting muscle

cells.

Cells manage energy resources to do work through

energy coupling, the use of an exergonic process

to drive an endergonic one

Most energy coupling in cells is mediated by

ATP

What do Enzymes speed up?

metabolic reactions (lowering energy barriers)

Spontaneous (exergonic) reactions do not need ? and a example

added energy, but they can be slow enough to be

imperceptible.

– For example, the hydrolysis of sucrose to glucose

and fructose is spontaneous

What is the definition of Enzymes?

speed up metabolic reactions by lowering energy barriers

At room temperature…

a solution of sucrose in sterile water would sit for years without appreciable hydrolysis

What are the six steps of Enzyme substrate complex (6):

1. substrates enter active site

2. substrates are held in active site by weak interactions

3. the active site lowers ea

4. substrates are converted to products

5. products are released

6. active site is available for new substrates

Enzyme activity can be affected by general

environmental factors such as?

– temperature

– pH

-can also be affected by chemicals that specifically

influence the enzyme

What are the Effects of Temperature on enzyme?

Each enzyme has an optimal temperature at which it catalyzes its reaction at the maximum possible rate

What is the definition of Mitochondria?

break down glucose to generate ATP (and CO2 and H2O) to use in cellular metabolism for anabolic reactions.

What is the definition of Chloroplasts?

use solar energy to generate ATP to produce glucose (to

store energy)

How is the chemical energy stored in food used to generate atp, the molecule that drives most cellular work?

Cells convert the chemical energy in food into adenosine triphosphate (ATP) through a metabolic process called cellular respiration. [1, 2]

What is the definition of Catabolism?

• Processes that

degrade compounds

to release energy

• By oxidizing organic

fuels

What is the definition of Anabolism?

• Biosynthetic

processes

• Assemble subunits of

macromolecules

Organic molecules have potential energy

– Arrangement of electrons in bonds between atoms

– Compounds can participate in exergonic reactions –

acting as fuel

Enzymes help degrade complex organic molecules to…

simpler molecules

Complex molecules..

have a lot of potential energy

Simpler molecules…

less potential energy

What are the Two Main Pathways of cellular respiration?

1. Respiration (aerobic or anaerobic)

2. Fermentation – substrate-level

phosphorylation (no electron transport chain)

The breakdown of organic molecules is…

exergonic

What is the definition of Aerobic respiration?

consumes organic molecules and oxygen (as a terminal electron acceptor) and yields ATP

What is the definition of Anaerobic respiration?

is similar to aerobic respiration but consumes compounds other than oxygen (different terminal electron acceptor)

What is the definition of Fermentation?

is a partial degradation of sugars does not require an

electron transport chain (ETC)

How are molecules broken down?

redox

• Transfer of e- from one reactant to another

• Oxidation is the loss of e-

• Reduction is the gain of e-

Oxidation of Organic Fuel Molecules

During Cellular Respiration

• Although carbohydrates, fats, and proteins are

all consumed as fuel, it is helpful to trace cellular

respiration with the sugar glucose

Molecules with a lot of hydrogen…

are great fuels

molecules with a lot hydrogen is transferred to…

oxygen, electrons move to a lower energy state, releasing energy

Energy is not…

released all

at once!

Glucose is broken down

in a…

series of steps

Electrons travel with a

proton (H+), but not

directly to…

O2

What is the definition of a Coenzyme?

electron receptor/carrier

Stepwise energy (electron) release

• One Step

– Exergonic reaction

– Releases large amount

of energy

• Heat and light

• Explosion

• Electron Transport

– Fall of electrons in small

steps

– Energy stored to make

ATP

The Stages of Cellular Respiration: A Preview

• Harvesting energy from glucose by cellular

respiration has three stages

1. Glycolysis - breaks down glucose (6C) into two

molecules of pyruvate (3C)

2. Pyruvate oxidation and the citric acid cycle

complete the breakdown of glucose to CO2

3. During oxidative phosphorylation the electron

transport chain and chemiosmosis facilitate

synthesis of most of the cell’s ATP

Glycolysis harvests chemical energy by…

oxidizing glucose to pyruvate

Glycolysis – Sugar Splittin

• In the cytosol

• Glucose (6C) is broken down into two 3-C sugar

molecules, eventually to pyruvate

What are TWO PHASES of glycolysis?

– Energy Investment: cell spends ATP

– Energy Payoff : ATP and NADH are produced by

substrate-level phosphorylation

What is Oxidative vs. substrate-level

phosphorylation?

• The process that generates almost 90% of the

ATP is called oxidative phosphorylation

because it is powered by redox reactions

• Some ATP is also formed in glycolysis and the

citric acid cycle by substrate-level

phosphorylation

What is the definition of Substrate-level phosphorylation?

Substrate-level phosphorylation occurs when an enzyme

transfers a phosphate group directly from a substrate to

ADP

What is Pyruvate oxidation – in mitochondria?

• 2 membranes

• Smooth outer membrane

• An inner membrane

folded into cristae

• Two compartments:

intermembrane space and

mitochondrial matrix

• Some metabolic steps of

cellular respiration are

catalyzed in the

mitochondrial matrix

• Cristae: large surface

area for enzymes that

synthesize ATP

Review

• What molecule do we start with?

• Why is it important that this process have many steps?

• What do redox reactions have to do with this?

1. What molecule do we start with?

We start with glucose (a 6-carbon sugar molecule) if you are discussing cellular respiration.

• Note: If your class is currently focusing specifically on the citric acid cycle (Krebs cycle), the starting molecule for that specific phase is Acetyl-CoA.

2. Why is it important that this process have many steps?

It allows the cell to release and capture energy controlled and efficiently, rather than all at once.

• Prevents cell damage: Releasing all the energy from glucose in one single step would release too much heat, essentially burning and destroying the cell.

• Maximizes ATP production: A step-by-step breakdown allows the cell to harvest energy efficiently, transferring it into smaller, usable packets of ATP and electron carriers (like NADH).

3. What do redox reactions have to do with this?

Redox (reduction-oxidation) reactions are the driving mechanism that moves the energy along.

• Oxidation: Glucose is progressively oxidized (loses electrons and hydrogens) throughout the pathway.

• Reduction: Electron carriers like \(NAD^{+}\) and \(FAD\) are reduced (gain those electrons and hydrogens) to become NADH and \(FADH_{2}\).

• The Goal: These carriers take the high-energy electrons to the Electron Transport Chain, where the energy is ultimately used to mass-produce ATP

Is Glycolysis

endergonic or

exergonic?

• What was the

net gain from

Glycolysis?

• What does ATP

do for a cell?

Glycolysis is an exergonic process overall because it releases energy as glucose breaks down into pyruvate

Net Gain from Glycolysis

• ATP: A net gain of 2 ATP molecules per glucose molecule (2 are invested, 4 are produced).

• NADH: A net gain of 2 NADH molecules.

• Pyruvate: 2 pyruvate molecules. [1, 2, 3]

What ATP Does for a Cell

• Energy Currency: Acts as the primary energy-supplying molecule (adenosine triphosphate) to power cellular work.

• Powers Reactions: Releases energy when a phosphate group is removed (forming ADP), which drives energy-requiring (endergonic) reactions.

• Cellular Transport & Movement: Supplies energy for active transport across cell membranes, muscle contraction, and chemical synthesis

What is Cellular Respiration – Pyruvate Oxidation?

• Links Glycolysis and

Citric Acid Cycle

• Pyruvate (high energy

molecule) enters the

mitochondria

• Oxidized (what does that

mean?)

• Multi-enzyme complex –

catalyzes 3 reactions

– First step where we

see CO2

– NAD+ is reduced

• Product is Acetyl CoA

Cellular Respiration – Citric Acid Cycle

What are the major

inputs?

• What are the major

outputs?

• What is oxidized and

what is reduce

The Citric Acid Cycle (or Krebs cycle) processes acetyl-CoA in the mitochondrial matrix to produce electron carriers and carbon dioxide

Per glucose molecule (two turns of the cycle): [1, 2]

• 2 acetyl-CoA (from pyruvate)

• 6 \(\text{NAD}^{+}\)

• 2 \(\text{FAD}\)

• 2 \(\text{ADP}\) and inorganic phosphate (\(\text{P}_{i}\))

• 2 oxaloacetate (which are regenerated

Major Outputs

Per glucose molecule (two turns of the cycle)

• 4 \(\text{CO}_{2}\) (released as waste)

• 6 \(\text{NADH}\) and \(6 \text{H}^+\)

• 2 \(\text{FADH}_{2}\)

• 2 \(\text{ATP}\) (or \(\text{GTP}\))

• Oxidation and Reduction

  • Oxidized: The carbon atoms originating from the acetyl group of acetyl-CoA are oxidized, releasing carbon dioxide (\(\text{CO}_{2}\)). Intermediates like isocitrate, alpha-ketoglutarate, succinate, and malate lose electrons/hydrogens.

  • Reduced: The coenzymes \(\text{NAD}^{+}\) and \(\text{FAD}\) accept high-energy electrons and hydrogen ions to become reduced into \(\text{NADH}\) and \(\text{FADH}_{2}\)

How many products per cycle Cellular Respiration –

Citric Acid Cycle?

Products per cycle:

3 NADH

1 FADH2

1 ATP

(2 CO2)

Electron transport and oxidative

phosphorylation result in…

most ATP synthesis

Molecules of NADH and FADH2 produced during

glycolysis and the citric acid cycle account for most

of the energy extracted from…

glucose

NADH and FADH2 donate electrons to the electron

transport chain, which….

powers ATP synthesis via

oxidative phosphorylation

What is Cellular Respiration – Oxidative Phosphorylation

-We have generated a total of 4 ATP by SLP.

-Most of the energy is in the electron carriers

-Now we enter the stage with the most energy

generation.

(Reduced molecules contain most of extracted energy)

-the final, most energy-efficient stage of aerobic cellular respiration where cells use oxygen to convert nutrient-derived electron carriers into ATP (adenosine triphosphate), the primary energy currency of the body.

What is Cellular Respiration – Oxidative Phosphorylation?

Electrons from the Reduced electron carriers enter the

Electron Transport Chain

• Proteins embedded in the membrane

– Each with more pull on electrons

• Alternate between Reduced and Oxidized

• Each handoff drops the free energy

Cellular Respiration – Oxidative Phosphorylation

A hydrogen ion gradient

across a membrane is

used to drive ATP

synthesis

Electron Transport Chain: Mitochondria

Comparing eukaryotic ETC to prokaryotic ETC

Bacterial and Archaeal ETCs

• In plasma membrane (no

mitochondria)

• Shorter – fewer components

• Similar ATP synthase

• What are the

most important

parts of each

stage?

1. The Important Parts, Inputs, and Outputs of Each Stage

Cellular respiration happens in four distinct stages.

Stage	Most Important Parts	Inputs	Outputs
1. Glycolysis (Happens in cytoplasm)	• Breaks down glucose. • Does not require oxygen.	• 1 Glucose • 2 \(NAD^{+}\) • 2 ATP	• 2 Pyruvate • 2 NADH • 2 Net ATP
2. Pyruvate Oxidation (Enters mitochondria)	• Converts pyruvate into a usable form for the next cycle. • Releases the first \(CO_{2}\).	• 2 Pyruvate • 2 \(NAD^{+}\) • 2 Coenzyme A	• 2 Acetyl-CoA • 2 NADH • 2 \(CO_{2}\)
3. Citric Acid (Krebs) Cycle (Mitochondrial matrix)	• Fully oxidizes acetyl-CoA. • Heavily loads up electron carriers.	• 2 Acetyl-CoA • 6 \(NAD^{+}\) • 2 FAD	• 4 \(CO_{2}\) • 6 NADH • 2 \(FADH_{2}\) • 2 ATP
4. Electron Transport Chain & Oxidative Phosphorylation (Inner mitochondrial membrane)	• Uses electrons to power an ATP-making factory. • Requires oxygen as the final electron acceptor.	• 10 NADH • 2 \(FADH_{2}\) • Oxygen (\(O_{2}\))	• \(H_{2}O\) (Water) • \(NAD^{+}\) • FAD • ~28 to 32 ATP

What are the

inputs/outputs?

• Inputs (What you need): Food (Glucose) and the air you breathe (Oxygen).

• Outputs (What you make/release): Cellular energy (ATP), plus waste products (Water and Carbon Dioxide that you exhale).

Why NAD+ and FAD+ are Important

NAD+ and FAD+ are critical to cellular respiration because they act as high-energy electron taxicabs.

1. The Pick-up: During the first three stages of respiration, glucose is broken down. NAD+ and FAD+ strip high-energy electrons and hydrogen atoms from the food molecules, turning into NADH and FADH2.

2. The Drop-off: They travel to the final stage (the Electron Transport Chain) and drop those high-energy electrons off.

3. The Purpose: The energy from these dropped-off electrons powers the cellular machinery (ATP synthase) to produce massive amounts of ATP. Without these carriers, the transfer of energy from food to ATP would completely stop.

Which stage

produces the

most ATP?

he Electron Transport Chain (along with Oxidative Phosphorylation) produces the most ATP by a landslide. While Glycolysis and the Citric Acid Cycle only yield a meager 2 ATP molecules each, the Electron Transport Chain uses the electrons delivered by NADH and FADH2 to generate roughly 28 to 32 ATP molecules per single molecule of glucose.

review

• Hydrogen moves across membrane, electron on

receptor

• Oxygen is the last electron receptor and

combines with H to make water

Review Cellular Respiration:

• Electron carriers bring e- to

ETC

• H+ ions move across

membrane and set up gradient

• e- move down chain

• H+ moves down gradient

through ATP synthase

• ADP is phosphorylated to

ATP

Photosynthesis feeds the

-biosphere

ex: plants, multicelular alga,unicellular protisits,cyanobacteria,purple sulfur bacteria

The Process That Feeds the Biosphere

• Autotrophs are the producers

• Heterotrophs obtain organic material from other

organisms

Importance of Autotrophs

• Autotrophs: self feeders

– Photoautotrophs – oxidize organic compounds

– Chemoautotrophs – oxidize inorganic compounds

(Hydrogen sulfide, CO2 and Oxygen)

Autotrophs feed Heterotrophs

• ”Other Feeders”

• Most are

completely

dependent on

autotrophs

Photoautotrophs

• Use light energy to drive the synthesis of sugars

(molecules with a lot of potential energy)

• Chloroplasts – in mesophyll

Photosynthesis converts light energy to the

chemical energy of food

Plants and other

photosynthetic

organisms contain

organelles called

chloroplasts

Chloroplast

• Organelle

• Location of

photosynthesis

• Thylakoid

– Membranes –

light reactions

• Stroma – Calvin

Cycle

The Two Stages of Photosynthesis

1. Light-Dependent Reactions

• Location: Thylakoid membranes inside the chloroplast.

• Process: Chlorophyll absorbs sunlight to split water molecules (H₂O).

• Outputs: Produces oxygen gas (O₂) as a byproduct, alongside energy carrier molecules ATP and NADPH. [1, 2, 3, 4]

2. Calvin Cycle (Light-Independent Reactions)

• Location: Stroma (the fluid part of the chloroplast).

• Process: Uses the ATP and NADPH produced in the first stage, along with carbon dioxide (CO₂) from the air, to build sugars.

• Outputs: Produces high-energy carbohydrates like glucose

Light and Energy

• Electromagnetic energy

– Propagates as waves

• Photons interact with leaves like particles

– Each with fixed energy

Light and Energy

• Light is

– REFLECTED

– TRANSMITTED

– ABSORBED

- Chlorophyll

absorbs violet-

blue and red

light

- Reflects or

transmits green

light

Which wavelengths

of light are most

effective in driving

photosynthesis and

why?

The red (600–700 nm) and blue (400–500 nm) regions of the visible light spectrum are the most effective in driving photosynthesis

Excitation of Pigments by Light

• Absorb visible light

• Chlorophyll a – key

in light reactions

• Chlorophyll b

• Carotenoids –

photoprotective

The Two Stages of Photosynthesis

1. Light-Dependent Reactions

• Location: Thylakoid membranes inside the chloroplast.

• Process: Chlorophyll absorbs sunlight to split water molecules (H₂O).

• Outputs: Produces oxygen gas (O₂) as a byproduct, alongside energy carrier molecules ATP and NADPH. [1, 2, 3, 4]

2. Calvin Cycle (Light-Independent Reactions)

• Location: Stroma (the fluid part of the chloroplast).

• Process: Uses the ATP and NADPH produced in the first stage, along with carbon dioxide (CO₂) from the air, to build sugars.

• Outputs: Produces high-energy carbohydrates like glucose

Light Reactions

• Within the membrane of thylakoid

• Light Harvesting Complex

– Pigments – variety - increases

range of wavelengths that will

excite electron

– Photons moved along to excite a

special pair of Chlorophyll a

molecules in Reaction Center

• Reaction Center Complex

– Special pair of Chlorophyll a

– Electron excited to Primary

Electron Acceptor

reaction-center complex

The reaction-center complex is an association of proteins

holding a special pair of chlorophyll a molecules and a

primary electron acceptor

The Calvin cycle uses the chemical energy of

ATP and NADPH to reduce CO2 to

sugar

he Calvin cycle is

anabolic; it builds sugar from

smaller molecules by using ATP and the reducing

power of electrons carried by NADPH

Carbon enters the cycle

as CO2 and leaves as a

sugar named

glyceraldehyde 3-

phospate (G3P)