Exploring Cells and Their Functions

Which of the following statements is true about living organisms?

• All living organisms are made of cells.

• Only multicellular organisms are made of cells.

• Only unicellular organisms are made of cells.

• Living organisms are not made of cells.

Answer explanation

The correct statement is that all living organisms are made of cells. This includes both unicellular and multicellular organisms, as cells are the fundamental units of life.

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DOK Level 2: Skill/Concept

NGSS.MS-LS1-1

What is the primary function of the cell membrane?

• To produce energy for the cell

• To control what enters and leaves the cell

• To store genetic information

• To synthesize proteins

Answer explanation

The primary function of the cell membrane is to control what enters and leaves the cell, maintaining homeostasis and protecting the cell's internal environment.

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DOK Level 2: Skill/Concept

NGSS.MS-LS1-2

Which of the following is a characteristic of all living things?

• They can move independently.

• They are made of one or more cells.

• They can photosynthesize.

• They have a nervous system.

Answer explanation

All living things are characterized by being made of one or more cells, which is fundamental to life. The other options, such as movement, photosynthesis, and having a nervous system, do not apply to all living organisms.

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DOK Level 2: Skill/Concept

NGSS.MS-LS1-1

Which part of the cell is responsible for producing energy?

• Nucleus

• Mitochondria

• Ribosome

• Golgi apparatus

Answer explanation

The mitochondria are known as the powerhouse of the cell because they produce energy in the form of ATP through cellular respiration, making them essential for cellular functions.

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DOK Level 2: Skill/Concept

NGSS.MS-LS1-2

How do sensory receptors in the skin respond to stimuli?

• By sending messages to the brain

• By producing hormones

• By contracting muscles

• By storing energy

Answer explanation

Sensory receptors in the skin detect stimuli such as touch, temperature, and pain. They convert these stimuli into electrical signals that are sent to the brain for processing, making 'By sending messages to the brain' the correct choice.

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DOK Level 2: Skill/Concept

NGSS.MS-LS1-8

Which of the following best describes a tissue?

• A group of similar cells working together

• A single cell performing all functions

• A collection of different organs

• A system of interacting subsystems

Answer explanation

A tissue is defined as a group of similar cells working together to perform a specific function, making the first choice the correct answer. The other options describe different biological structures or systems.

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DOK Level 2: Skill/Concept

NGSS.MS-LS1-3

Explain how the structure of a cell membrane contributes to its function.

• The rigid structure allows for protection.

• The flexible structure allows for selective permeability.

• The thick structure allows for energy storage.

• The transparent structure allows for light absorption.

Answer explanation

The flexible structure of the cell membrane, primarily composed of a phospholipid bilayer, allows it to be selectively permeable, enabling the cell to control the movement of substances in and out, which is crucial for maintaining homeostasis.

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DOK Level 3: Strategic Thinking

NGSS.MS-LS1-2

Develop a model to describe how the nervous system processes information from sensory receptors.

• Sensory receptors send signals directly to muscles.

• Sensory receptors send signals to the brain, which processes and responds.

• Sensory receptors store information for future use.

• Sensory receptors do not interact with the brain.

Answer explanation

Sensory receptors detect stimuli and send signals to the brain. The brain processes this information and generates appropriate responses, making the correct choice "Sensory receptors send signals to the brain, which processes and responds."

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DOK Level 3: Strategic Thinking

NGSS.MS-LS1-8

Use evidence to support the claim that the body is a system of interacting subsystems.

• The body functions independently without interaction.

• The body is composed of isolated organs.

• The body systems work together to maintain homeostasis.

• The body systems compete for resources.

Answer explanation

The body systems work together to maintain homeostasis, demonstrating that they are interconnected subsystems. For example, the respiratory and circulatory systems collaborate to ensure oxygen delivery and carbon dioxide removal.

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DOK Level 3: Strategic Thinking

NGSS.MS-LS1-3

How does the structure of mitochondria support its function in the cell?

• Its large surface area allows for efficient energy production.

• Its small size allows for easy transport within the cell.

• Its rigid walls provide structural support.

• Its transparent membrane allows for light absorption.

Answer explanation

The large surface area of mitochondria, due to their inner folds (cristae), enhances the space available for chemical reactions involved in energy production, making it more efficient.

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DOK Level 3: Strategic Thinking

NGSS.MS-LS1-2