AP Bio Unit 3 Flashcard Examples

The back of the card will have a practical example of the definition of term.

First Law of Thermodynamics/Law of Conservation of Energy

Take a ball on top of a hill. Even though it is initially still, it still has maximum potential energy. When it starts rolling down the hill, its potential energy is converted into kinetic energy as it gains speed, demonstrating that energy cannot be created or destroyed, only transformed.

Entropy

A solid’s molecules are tightly packed together in an orderly fashion, so they have low ______. A gas’s molecules are highly dispersed and move in a disorderly manner, so they have high ______.

Second Law of Thermodynamics

In cellular respiration, in the process of breaking down molecules, some energy is lost as heat, thus dispersing some energy and increasing entropy. This also shows that reactions are never 100% efficient.

Exergonic reaction

Cellular respiration releases energy as it breaks down glucose and does not require an external input of energy to occur. Therefore, \deltaG > 0.

Endergonic reaction

Photosynthesis requires energy from sunlight in order to occur and consumes that energy as it converts carbon dioxide and water into glucose and oxygen. Therefore, \deltaG < 0.

Transition state

When you mix vinegar and baking soda, the molecules form a temporary arrangement of atoms before the reaction proceeds. This arrangement represents a high-energy state that occurs right before the transformation of the reactants to sodium acetate, carbon dioxide, and water.

Activation energy

In that reaction between the baking soda and vinegar, it needed _______ energy by absorbing heat in order for the transition state to form.

Enzyme

The hydrolysis of maltose would take billions of years without the help of maltase produced by our digestive systems, which catalyzes the reaction. The transition state would basically never form without maltase to lower the activation energy needed.

Enzyme specificity

Like many other enzymes, lactase can only break down lactose and nothing else.

Substrate

Same thing as a reactant but in terms of enzyme reactions. When amylase catalyzes the breakdown of starch, starch is the ______ in this reaction.

Active site

Starch binds to amylase on a special region of the enzyme where it perfectly fits, as the region is specifically made for starch.

Induced fit

Starch doesn’t perfectly fit into amylase initially, but amylase changes it shape so starch can be accommodated.

Cofactors/coenzymes

DNA polymerase, which synthesizes DNA strands during DNA replication, requires magnesium ions (Mg2+) to stabilize its structure and maintain a functional conformation in its active site.

Factors affecting reaction rates in enzymes: temperature

Many enzymes in humans work best at the average body temperature of 37 C, but they can start to denature at 40 C. This is why mild fevers (37-39 C) can help the body fight infection without damaging the enzyme's functionality, and can even speed up reaction rates, but high fevers above that are dangerous to the body.

Factors affecting reaction rates in enzymes: pH

Acidosis is a life-threatening condition where the pH of the blood falls below 7.35. This is dangerous because it leads to the denaturation of many enzymes involved in important biochemical processes, disrupting normal function.

Factors affecting reaction rates in enzymes: substrate & enzyme concentration

If you take piece of fruit

Allosteric sites and inhibitors

The activity of PFK-1, an enzyme involved in glycolysis, is stopped when ATP binds to part of it (not the active site). This is done to regulate the enzyme's activity in response to sufficient energy availability within the cell and to conserve glucose.

Competitive inhibition

People with high cholesterol are prescribed statin drugs to inhibit HMG-CoA reductase, an enzyme crucial for cholesterol synthesis. Statin molecules closely resemble the reductase, so they are able to bind to the active site and prevent substrate binding.

Photosynthesis part 1: light reactions

How those little cyanobacteria filled our atmosphere with oxygen

Step 1: Photons from the Sun hit their chloroplasts, activating its chlorophyll and exciting the electrons in it.

Step 2: Water molecules are split, releasing oxygen as a byproduct and providing electrons to replace those lost by chlorophyll. Repeat this over tons of time and with tons of cyanobacteria and you get a blue sky.

Step 3: Electrons from that water travels down the electron transport chain (ETC) to create a proton gradient that produces ATP and NADPH for the Calvin cycle.

Photosynthesis part 2: Calvin cycle (dark reactions)

How those little cyanobacteria thrived on just carbon dioxide

Step 1: CO2 from the atmosphere is converted to a 3-carbon sugar called G3P through a series of enzymatic reactions.

Step 2: The G3P can then be used to form glucose and other carbohydrates, which provides energy for the cyanobacteria. ADP and NADP+ are regenerated and return to the light-dependent reactions.

Chloroplast pigments

Chlorophyll a: The primary pigment in cyanobacteria, which is why it’s called blue-green algae. It is also found in all other photosynthetic plants and algae.

Chlorophyll b: Many, but not all plants and algae contain this in lower amounts than chlorophyll a, but in yellow-green algae, it is more abundant. Yellow-green algae is able to thrive in the shade due to its ability to capture a broader spectrum of light wavelengths.

Carotenoids: Autumn leaves are warm colors because chlorophyll breaks down in response to reduced light in order to prevent the formation of free radicals from inefficient photosynthesis. This reveals orange-ish hues in the leaves.

C3 vs C4 plants

Wheat and rice use the Calvin cycle directly for carbon fixation, and this means they mainly grow in colder, wetter regions like Europe. Maize and sugarcane, utilize an additional pathway to concentrate CO2, enhancing photosynthesis efficiencies in hot, dry environments, which is why they're often cultivated in tropical regions.

Aerobic respiration

How your body produces energy during cardio exercise

Step 1: The carbs you ate before your workout got broken down to glucose, and that glucose is broken down into pyruvic acid, ATP, and NADH. This is called glycolysis

Step 2: Pyruvic acid is taken to the powerhouse of your cells and is converted into acetyl-CoA. CO2 is released, which you exhale.

Step 3: The Krebs (citric acid) cycle has the acetyl-CoA converted into ATP, NADH, and FADH2 through a series of reactions, producing more energy.

Step 4:

Anaerobic respiration

Why you feel that burn and tiredness after sprinting