Biology Chapter: Movement of Molecules

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Questions and Answers

What is the main characteristic of passive transport?

It requires energy input from the cell.

It allows molecules to move without energy input. (correct)

It occurs against the concentration gradient.

It only transports water molecules.

What factors influence the rate of diffusion?

Pressure, membrane thickness, and ionic strength

Temperature, pressure, and concentration gradient

Size of molecules, concentration gradient, and temperature (correct)

Molecular weight, pH, and presence of channel proteins

Which best describes osmosis?

The movement of molecules via carrier proteins.

The diffusion of water across a selectively permeable membrane. (correct)

The active transport of solutes against their gradient.

The diffusion of nutrients across a membrane.

What distinguishes active transport from passive transport?

Active transport requires energy, while passive transport does not. Signup and view all the answers

What type of protein helps molecules cross the membrane without using energy in facilitated diffusion?

Carrier proteins Signup and view all the answers

Which of the following statements about enzymes is true?

Enzymes can speed up reactions by lowering activation energy. Signup and view all the answers

What can happen to an enzyme if the temperature exceeds its optimal range?

The enzyme becomes denatured. Signup and view all the answers

How does substrate concentration affect enzyme activity?

Increasing substrate concentration increases activity until saturation. Signup and view all the answers

What is the function of channel proteins in facilitated diffusion?

To create a hydrophilic pore for specific molecules. Signup and view all the answers

Which method of transport includes actions such as pinocytosis and phagocytosis?

Bulk transport Signup and view all the answers

What is the primary function of competitive inhibitors?

They resemble the substrate and compete for the active site. Signup and view all the answers

Which mechanism involves the end product of a metabolic pathway inhibiting an earlier enzyme in that pathway?

Feedback inhibition Signup and view all the answers

What role does the active site of an enzyme play?

It is the region where the substrate binds. Signup and view all the answers

How does non-competitive inhibition affect enzyme activity?

It binds to a different site and changes the enzyme's shape. Signup and view all the answers

Which statement best describes allosteric regulation?

It modifies the enzyme's shape, impacting its activity. Signup and view all the answers

What happens during the induced fit model of enzyme activity?

The enzyme changes shape to fit the substrate more tightly. Signup and view all the answers

What is the significance of lowering activation energy in a chemical reaction?

It allows reactions to occur more easily and faster. Signup and view all the answers

Which component in enzyme nomenclature typically indicates an enzyme's function?

The suffix '-ase' at the end of the name. Signup and view all the answers

What is a characteristic of enzyme activity that is regulated through allosteric sites?

Binding at allosteric sites can either inhibit or activate enzyme function. Signup and view all the answers

Which type of inhibition does not directly compete with the substrate for the active site?

Non-competitive inhibition Signup and view all the answers

Study Notes

Movement of Molecules

Passive transport: Movement of molecules across a membrane without energy input. This includes diffusion and osmosis.
- Diffusion: Molecules move from an area of high concentration to an area of low concentration. The rate of diffusion is affected by factors like temperature, concentration gradient, and the size of the molecules.
- Osmosis: The diffusion of water across a selectively permeable membrane. Water moves from a region of high water potential to a region of low water potential. Important in maintaining cellular homeostasis.
Active transport: Movement of molecules across a membrane requiring energy input (usually ATP). Moves substances against their concentration gradient.
- Examples: Sodium-potassium pump, endocytosis, exocytosis.
- Importance: Essential for transporting substances needed by the cell against concentration gradients, like nutrient absorption and removal of waste products.
Facilitated diffusion: Molecules move down their concentration gradient with the help of transport proteins embedded in the cell membrane. This is a type of passive transport, needing no energy.
- Carrier proteins: Bind to molecules and change shape to move them across the membrane.
- Channel proteins: Create a hydrophilic pore for molecules to pass through. Typically specific for the type of molecule they transport.
Bulk Transport: Large particles and macromolecules are transported across the membrane.
- Endocytosis: Plasma membrane surrounds the substance and forms a vesicle/vacuole to bring it into the cell. Includes phagocytosis (cell eating) and pinocytosis (cell drinking).
- Exocytosis: Substances are discharged from the cell by fusing vesicles with the plasma membrane. Excretion of waste or release of hormones.

Enzymes

Biological Catalysts: Speed up chemical reactions in living organisms without being consumed in the process.
Specificity: Each enzyme is highly specific for a particular substrate. Active site that is shaped to fit with the substrate and catalyzes the reaction.
Factors Affecting Enzyme Activity:
- Temperature: Optimal temperature exists for each enzyme, where activity is highest. Too high can denature enzymes.
- pH: Each enzyme has an optimal pH range. Changes greatly affect enzyme shape and activity.
- Substrate Concentration: Increasing substrate concentration increases enzyme activity until the enzyme becomes saturated.
Enzyme Inhibitors: Substances that reduce enzyme activity.
- Competitive inhibitors: Resemble the substrate and compete for the active site.
- Non-competitive inhibitors: Do not resemble the substrate, bind to a different site (allosteric site), causing the enzyme to change shape, and affecting function.
Enzyme Regulation: Controlling the rate at which enzymes work.
- Allosteric regulation: Molecules bind to regions other than the active site, affecting enzyme shape and activity.
- Feedback inhibition: The end product of a metabolic pathway inhibits the enzyme earlier in the pathway, preventing overproduction.
Enzyme Structure:
- Active site: Region on the enzyme that binds to the substrate.
- Substrate: The molecule that the enzyme acts upon.
- Product: The resulting molecules formed during the reaction.
Induced Fit: Enzyme changes shape slightly when substrate binds, forming a tighter interaction for maximum efficiency.
Naming Conventions:
- Often end with "-ase" like amylase, lipase, catalase.
Activation energy: Enzymes catalyze reactions by lowering activation energy - the energy needed for the reaction to begin.

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Description

This quiz focuses on the movement of molecules across membranes, exploring passive transport methods such as diffusion and osmosis, as well as active transport processes that require energy. Test your knowledge on how these mechanisms contribute to cellular homeostasis and nutrient absorption.