1.5 Book Reading

What happens to energy when it’s converted to heat?

It becomes kinetic energy contained in the random motion of atoms or molecules.

Why is heat energy difficult to use for work?

Because it’s the most chaotic form of energy, representing random molecular movement.

What does entropy measure?

The disorder or randomness in a system.

What happens to entropy when energy is converted from one form to another?

Entropy increases.

What type of energy do molecules of food, gas, and other fuels contain?

Chemical potential energy.

How do living cells and automobile engines release energy?

Both break down fuel molecules into smaller waste molecules with less chemical energy, releasing energy for work.

What does a cell contain?

All the machinery needed to carry out life’s functions.

How are living cells described?

Dynamic and constantly performing work.

What law states that energy cannot be created or destroyed?

The law of conservation of energy.

What is the basic process of cellular respiration?

The breakdown of fuel molecules to release energy stored in a usable form (ATP).

What is a Calorie?

The amount of energy required to raise 1 kilogram of water by 1°C (1,000 small calories).

Why are food labels measured in kilocalories?

Because using small calories isn’t practical.

Why can’t fuel molecules like carbohydrates and fats be used directly for energy?

Their chemical energy must first be converted into ATP.

What does ATP stand for?

Adenosine triphosphate.

What makes up ATP?

Adenosine and three phosphate groups.

How does ATP release energy?

When the third phosphate group is removed, releasing energy for cellular work.

What does ADP stand for?

Adenosine diphosphate (two phosphate groups).

How is ATP renewable?

It’s regenerated by adding a phosphate group back to ADP using energy from food.

How many ATP molecules are recycled per second in a cell?

About 10 million.

What is the role of ATP in cells?

It acts like an energy shuttle, transferring energy to where it’s needed for cellular work.

What is passive transport?

Diffusion of substances across a membrane without using energy.

What causes diffusion?

Molecules move from high to low concentration due to random motion.

What happens at equilibrium?

Molecules continue to move but there’s no net change in concentration.

What is facilitated diffusion?

Passive transport through proteins that act as corridors for specific molecules.

What drives passive transport?

The concentration gradient, not cellular energy.

What is a solute?

A substance dissolved in a solvent to form a solution.

What is a solvent?

The liquid in which a solute is dissolved.

What is osmosis?

Diffusion of water across a selectively permeable membrane.

What does hypotonic mean?

Lower solute concentration and higher water concentration; cells gain water.

What does hypertonic mean?

Higher solute concentration and lower water concentration; cells lose water.

What does isotonic mean?

Equal solute and water concentrations; no net movement of water.

What is osmoregulation?

The control of water balance within a cell or organism.

How do animal cells respond in an isotonic environment?

They maintain constant volume; this is their ideal condition.

What happens to animal cells in a hypotonic environment?

They gain water, swell, and may burst (lyse).

What happens to animal cells in a hypertonic environment?

They lose water and shrink (crenate).

How do plant cells respond in an isotonic environment?

They become flaccid (limp) and droop slightly.

What happens to plant cells in a hypotonic environment?

They take in water, become turgid (firm), and this is their ideal state.

What happens to plant cells in a hypertonic environment?

They lose water, the plasma membrane pulls away from the cell wall (plasmolysis), and the cell shrivels.

Why is turgor pressure important for plants?

It helps them maintain upright structure and keep leaves firm.

What is active transport?

Movement of molecules across a membrane using energy, often against the concentration gradient.

How does a cell perform active transport?

By using transport proteins powered by ATP to pump substances across the membrane.

What example shows active transport in animal cells?

Nerve cells pump sodium out and potassium in to maintain proper balance.

What is endocytosis?

The process by which a cell takes in large molecules or particles by engulfing them in its membrane.

What is phagocytosis?

A type of endocytosis where the cell engulfs solid particles or food ("cell eating").

What is pinocytosis?

A type of endocytosis where the cell takes in fluids ("cell drinking").

What is exocytosis?

The process by which a cell exports materials or waste by fusing vesicles with the cell membrane.

What are phospholipids?

The main ingredient in all membranes, forming the phospholipid bilayer.

What are enzymes?

Proteins that speed up chemical reactions by lowering activation energy.

What is activation energy?

The energy required to start a chemical reaction by breaking chemical bonds.

How do enzymes lower activation energy?

By binding to reactant molecules and stressing their bonds to make them easier to break.

What determines which reaction an enzyme promotes?

Its unique three-dimensional shape.

What is the active site of an enzyme?

The region where the substrate binds and the reaction occurs.

What is induced fit?

When the enzyme changes shape slightly to better fit the substrate.

What is an enzyme inhibitor?

A molecule that binds to an enzyme and decreases its activity.

What is metabolism?

The total of all chemical reactions in an organism.

What is a substrate?

The specific reactant an enzyme acts on.

What is lactose?

A disaccharide (a sugar found in milk).

What is lactase?

An enzyme that breaks down lactose into simpler sugars.

What type of enzyme action does lactase demonstrate?

Induced fit, where the enzyme changes shape slightly to fit the substrate.

How do sperm cells obtain energy for movement?

Sperm cells break down glucose through cellular respiration to generate ATP.

How does sperm cell energy relate to the female reproductive system?

ATP gives sperm energy to swim through the female reproductive tract to reach the egg.

What is cellular respiration?

An energy-releasing chemical process that breaks down fuel molecules and stores energy in ATP.

Why is cellular respiration similar to an automobile engine?

Both convert chemical energy in fuel into kinetic energy for work and release heat as waste.

What are fuel molecules?

Organic compounds like carbohydrates and fats that store chemical energy.

Why is heat produced during energy conversions?

Because all energy transformations generate heat as a byproduct.

What is kinetic energy?

Energy of motion.

What is potential energy?

Stored energy due to position or structure.

What is chemical energy?

Potential energy stored in chemical bonds of molecules.

How is chemical energy converted into usable energy?

Through processes like cellular respiration that produce ATP.

What is ATP’s role in active transport?

It provides the energy to move solutes against their concentration gradient.

What is the plasma membrane’s role in transport?

It controls what enters and leaves the cell, maintaining homeostasis.

Why are membranes described as selectively permeable?

They allow some substances to cross more easily than others.

Why do molecules diffuse?

Because they are in constant random motion due to kinetic energy.

What happens when a cell loses water?

It shrinks and its functions may slow or stop.

What happens when a cell gains too much water?

It can swell and burst if no wall prevents expansion.

What type of environment do animal cells do best in?

Isotonic environments, where water movement is balanced.

What type of environment do plant cells do best in?

Hypotonic environments, where turgor pressure keeps them firm.

Why can’t some substances cross the membrane easily?

They are too large or too hydrophilic for the lipid bilayer.

What helps these substances cross the membrane?

Transport proteins, through facilitated diffusion or active transport.

Why are enzymes important for life?

They allow metabolic reactions to occur fast enough to sustain life.

What happens if enzymes didn’t exist?

Reactions would be too slow to support living cells.

How can enzyme activity be affected?

By temperature, pH, and inhibitors.

What happens to enzymes at high temperatures?

They denature, losing shape and function.

What are nanomachines in biology?

Molecular structures (like enzymes) that perform specific functions within cells.

What does "phosphorylation" mean in relation to ATP?

The transfer of a phosphate group from ATP to another molecule, energizing it.