AP Biology Unit 3

Enzymes

Biological catalysts that speed up reactions, generally proteins.

Substrate

The reactant molecule that binds to the enzyme.

Active Site

The region where the substrate binds to the enzyme.

Activation Energy

The minimum energy required to start a chemical reaction.

Enzyme-Substrate-Complex

A temporary molecule formed when the substrate binds to the enzyme.

Transition State

The highest energy point along the reaction pathway, a brief unstable state between the substrate and product.

Induced Fit Model

States that a substrate binds to an active site and both change shape slightly, creating an ideal fit for catalysis.

Primary Structure

The sequence of amino acids in a polypeptide chain.

Secondary Structure

The local folded structures that form within a polypeptide due to interactions between atoms of the backbone.

Tertiary Structure

The overall three-dimensional shape of the polypeptide, resulting from interactions between the R groups of the amino acids. Includes the active site.

Quaternary Structure

The arrangement of multiple polypeptide chains within an enzyme.

Enzyme Catalysis

The process of enzymes speeding up chemical reactions.

Catalyst

Speeds up chemical reactions without being consumed in the process.

Specificity

An enzymes ability to selectively bind to and catalyze reactions on a specific substrate or set of substrates.

Enzyme Inhibition

When an inhibitor binds to an enzyme and reduces/blocks enzyme activity.

Competitive Inhibition

Competes with the substrate to bind to the active site & blocks the substrate from binding

Non-Competitive Inhibition

Binds to a site that’s NOT the active site.Alters the enzyme’s shape and affects its ability to bind to the substrate and catalyze the reaction.

Allosteric Inhibition

Binds to a site that’s NOT the active site.Alters the enzyme’s shape and affects its ability to bind to the substrate and catalyze the reaction.

Environmental Impacts on Enzyme Function

Environmental factors such as temperature & pH can impact enzyme function, changes in these factors disrupt the enzyme’s structure slowing down its activity and possibly denaturation.These changes can alter the enzyme's active site, affecting substrate binding and overall catalytic efficiency.

Optimal pH

The specific pH level at which an enzyme exhibits maximum activity and catalytic efficiency, as deviations can lead to reduced effectiveness or denaturation.

Optimal Temperature

The temperature at which an enzyme functions most effectively, resulting in the highest reaction rate before denaturation occurs.

Denaturation

The process by which an enzyme's structure is altered, resulting in the loss of its biological activity. This can occur due to extreme temperature, pH changes, or other environmental factors.

Cellular Energy

The energy that cells use to power their various functions and processes. The energy is derived from the breakdown of food molecules and is stored in the form of a molecule known as ATP.

ATP

‘Adenosine Triphosphate’ (ATP) is the primary energy carrier in cells, providing energy for metabolic processes and cellular functions.

ATP→ ADP Cycle

The process by which cells store and release energy. ATP is reduced to ADP+Pi (inorganic phosphate) through hydrolysis and is regenerated back to ATP with energy (through cellular respiration OR photosynthesis).

Energy Coupling

When energy produced by one reaction is used to drive another reaction. This energy transfer allows for cells to do work efficiently and help cause non spontaneous reactions.

Non-Spontaneous Reactions

Doesn’t favor product formation and requires energy input or an external source to proceed

Spontaneous Reactions

Favors product formation under given conditions and doesn’t require energy input. 

Exergonic Reaction

A chemical reaction that releases energy, often in the form of heat, or energy carriers (ATP) and occurs spontaneously.

Endergonic Reactions

A chemical reaction that requires energy in order for it to occur

Laws of Thermodynamics

1st Law - Energy can’t be created or destroyed

Metabolic Pathways

A series of enzyme-catalyzed reactions, converting substrates into products for energy. Can be categorized as ‘catabolic pathways’ or ‘anabolic pathways’ .

Catabolic Pathways

Breaks down complex molecules into simpler ones

Anabolic Pathways

Build up complex molecules from simpler ones.

Photosynthesis

The process of capturing light energy and converting it into chemical energy. Photosynthesis converts CO2+H2O → C6H12O6 + O2. It occurs in the chloroplast and it takes place in two main stages; light independent reactions and light dependent reactions. 

Light-Independent Reactions

• Calvin Cycle’

• Converts CO2 → C6H12O6

• Uses energy stored in ATP & NADPH from the light dependent reactions

• Takes place in the stroma

Calvin Cycle

A series of biochemical reactions in plants that convert carbon dioxide and other compounds into glucose using ATP and NADPH produced in the light-dependent reactions of photosynthesis.

Light-Dependent Reactions

• Converts light into chemical energy

• Occurs in the thylakoid membrane

• Produces ATP & NADPH

Chloroplast

An organelle found in plant cells that’s responsible for photosynthesis. Its structure consists of a double membrane, a internal membrane system (thylakoids), and a fluid-filled space (stroma).

Chlorophyll

A green pigment located in the thylakoid and its function is to absorb/capture light energy and start the process of converting it into chemical energy. It also excites electrons and drives the formation of ATP and NADPH through the Electron Transport Chain.

Electron Transport Chain

A series of 4 protein complexes the couple redox reactions creating an electrochemical gradient that leads to the creation of ATP in a system known as Oxidative Phosphorylation.

Photosynthesis in Prokaryotes

Photosynthesis first evolved in prokaryotic organisms such as cyanobacteria. Around 3 billion years ago they evolved the ability to perform oxygenic photosynthesis and use water as an electron donor.

Binary Fission

A form of asexual reproduction where a bacteria divides into two identical daughter cell

Endosymbiotic Theory

Proposes that certain organelles such as mitochondria & chloroplasts were once free-living prokaryotic cells that were engulfed by an ancestral eukaryotic cell and formed a symbiotic relationship. 

Cellular Respiration

A metabolic pathway that uses glucose to produce ATP. It’s carried out by both prokaryotes and eukaryotes. The process can be divided into three stages: Glycolysis, Krebs Cycle, and Oxidative Phosphorylation. 

Glycolysis

• Occurs in the cytoplasm

• Inputs 2 ATP, 2 NAD+, 1 glucose

• Outputs 4 ATP, 2 NADH, 2 Pyruvate

Krebs Cycle

• Occurs in the mitochondrial matrix

• Inputs 2 Acetyl CoA

• Outputs ATP, CO2, FADH2, NADH

Electron Transport Chain & Oxidative Phosphorylation

• Occurs in the inner mitochondrial membrane

• Inputs NADH, FADH2, O2, ADP, Pi

• Outputs ATP, H2O

• Decouple OP from the ETC generates heat which can be used to regulate body temp

Fermentation

A process that produces energy in the absence of oxygen, glucose and other molecules are broken down to produce. Allows glycolysis to occur without oxygen producing organic molecules such as alcohol and lactic acid as waste products.

Photosystems

Protein complexes in thylakoid membranes that capture light energy for photosynthesis, primarily involving Photosystem I and II. They play a critical role in the light-dependent reactions, facilitating the conversion of light energy into chemical energy in the form of ATP and NADPH.

Photosystem II

This photosystem is the first in the light-dependent reactions. It absorbs light, excites electrons, and transfers them to an electron transport chain. PSII also splits water molecules, releasing oxygen as a byproduct.

Photosystem I

This photosystem comes after Photosystem II in the light-dependent reactions. It absorbs light to excite electrons, ultimately contributing to the production of NADPH.

Fitness