Biology Chapter: Cell Transport & Homeostasis

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Questions and Answers

What is the primary role of vesicles in active transport?

To move large particles into or out of the cell and export materials. (correct)

To regulate the concentration of sodium and potassium ions.

To facilitate the movement of small molecules across the cell membrane via diffusion.

To concentrate waste materials outside the cell

Which of the following best describes phagocytosis?

The cell takes up dissolved ions for concentration.

The cell secretes neurotransmitters.

The cell engulfs large solid particles into a vesicle for digestion. (correct)

The cell eliminates waste products.

What type of transport is involved when white blood cells engulf bacteria?

Endocytosis (correct)

Exocytosis

Passive Diffusion

Facilitated Diffusion

Which process describes the cell 'drinking' by engulfing liquids?

Pinocytosis (C) Signup and view all the answers

How does the movement of oxygen and carbon dioxide across the cell membrane classified?

Passive transport (A) Signup and view all the answers

Which of the following processes requires the cell to expend energy?

Active transport (D) Signup and view all the answers

A cell is placed in a solution where the concentration of solutes is higher outside the cell than inside. What type of solution is this, and what will happen to the cell?

Hypertonic; the cell will shrivel (D) Signup and view all the answers

What is the primary role of transport proteins in facilitated diffusion?

To assist molecules that cannot cross the membrane on their own (D) Signup and view all the answers

If a cell membrane is permeable to both water and a solute, during osmosis, what typically happens with the solute?

The solute will also move across the membrane (C) Signup and view all the answers

Which of the following molecules can pass through the cell membrane via simple diffusion?

Oxygen ($O_2$) (B) Signup and view all the answers

According to the content, what does the term 'concentration gradient' refer to?

The difference in concentration of a substance between two areas (D) Signup and view all the answers

When a solution is at 'equilibrium' what does that mean?

The concentration of the molecules are equal across the membrane. (B) Signup and view all the answers

What happens to water concentration in a hypertonic solution, compared to inside a cell?

Water concentration is lower in the solution (C) Signup and view all the answers

What is the primary role of feedback mechanisms in maintaining homeostasis?

To use system outputs to signal changes in input, stabilizing or amplifying responses. (A) Signup and view all the answers

Which of the following best describes a positive feedback loop?

A process where the output of a system intensifies the initial response. (A) Signup and view all the answers

Which characteristic of the cell membrane is most crucial for maintaining cellular homeostasis?

Its selectively permeable nature that controls what goes in and out of the cell. (C) Signup and view all the answers

What types of molecules can easily pass through the cell membrane?

Small, nonpolar, hydrophobic, and/or neutral molecules (A) Signup and view all the answers

Which of the following is an example of negative feedback loop?

The regulation of blood sugar levels by insulin, which reduces high blood sugar back to the normal level. (D) Signup and view all the answers

What is the relationship between stimulus and response related to homeostasis?

A stimulus causes a response, which helps the organism maintain homeostasis. (D) Signup and view all the answers

How does understanding cellular transport help in comprehending homeostasis?

It explains how cells maintain their internal conditions by controlling the movement of substances. (D) Signup and view all the answers

What occurs when a cell is placed in a hypotonic solution?

The cell swells due to water intake. (D) Signup and view all the answers

What does the term 'dynamic equilibrium' mean in the context of homeostasis?

It refers to a stable internal environment through controlled fluctuations within a range. (D) Signup and view all the answers

Which of the following best describes an isotonic solution?

The solution has the same water concentration as the cell's cytoplasm. (D) Signup and view all the answers

When a cell is in a hypertonic solution, what happens to the cell?

It shrinks due to the loss of water. (B) Signup and view all the answers

A cell with 20% NaCl and 80% H2O is placed in an environment of 10% NaCl and 90% H2O. What net movement of water and overall effect on the cell will likely occur?

Net movement of water into the cell, causing it to swell. (A) Signup and view all the answers

A cell with 5% NaCl and 95% H2O is placed in an environment with 15% NaCl and 85% H2O. What effect would you expect to see?

The cell will shrink. (B) Signup and view all the answers

If a cell contains 10% NaCl and 90% H2O, and it’s placed in an environment with the same concentrations, how will the cell be affected?

The cell will remain the same. (D) Signup and view all the answers

What is the key characteristic of active transport using molecular pumps?

It moves molecules against the concentration gradient, requiring energy. (D) Signup and view all the answers

Which process involves the movement of water across a membrane from an area of higher water concentration to an area of lower water concentration?

Osmosis (C) Signup and view all the answers

Study Notes

Cell Transport

Students should analyze the relationships between cell structures and functions to understand cell transport.
Investigations should be conducted to determine the role of cell transport (active, passive, and osmosis) in maintaining homeostasis.

Overview of Homeostasis

Homeostasis is the need of an organism to maintain a stable internal environment.
A dynamic equilibrium is maintained, meaning conditions stay within a range, not always the same.
Examples of internal conditions regulated for homeostasis include pH, temperature, and blood sugar.
Organisms constantly respond to stimuli in the environment to maintain homeostasis.
Stimulus = a change in the environment
Response = a change in the organism as a result of the stimulus.

Feedback Mechanisms

Feedback mechanisms help regulate homeostasis in response to stimuli.
These mechanisms use the output of a system to signal a change in the input, stabilizing or amplifying the system response.
Feedback mechanisms can be positive or negative.

Positive Feedback Mechanisms

In a positive feedback loop, the output intensifies the response.
Examples include:
- Childbirth: hormones, contractions, and pressure increase the response.
- Fruit ripening: ethylene signals surrounding fruit to ripen, accelerating the process.

Negative Feedback Mechanisms

In a negative feedback loop, the output causes a counter-response to return to a set point.
Examples include:
- Body temperature regulation (thermoregulation)
- Water concentration regulation (osmoregulation)
- Blood sugar regulation

Maintaining Homeostasis at the Cellular Level: The Cell Membrane

Homeostasis is maintained from the organ system level down to the cellular level.
The cell membrane plays a crucial role in controlling the movement of things into and out of the cell.

Cell Membrane Permeability

The cell membrane is selectively permeable, meaning it's particular about what enters and exits.
Small, nonpolar, hydrophobic, and neutral substances easily pass through.
Polar and large molecules do not easily pass.

Types of Cell Transport

Cell transport is classified as either passive or active.
Passive transport requires no extra energy.
- Molecules move from an area of high concentration to an area of low concentration (down the concentration gradient).
  - Examples include simple diffusion, facilitated diffusion, and osmosis.
Active transport requires extra energy.
- Molecules move against the concentration gradient (from low to high concentration).
  - Examples include molecular pumps, exocytosis, and endocytosis.

Passive Transport: Simple Diffusion

Simple diffusion is the movement of small, nonpolar molecules across a membrane until equilibrium is reached.
Equilibrium is achieved when the concentration is equal on both sides of the membrane.
Examples include O₂ and CO₂.

Passive Transport: Facilitated Diffusion

Facilitated diffusion uses transport proteins to help facilitate the movement of molecules that can't pass directly across the cell membrane.
Molecules move down their concentration gradient.
Examples include glucose and calcium.

Passive Transport: Osmosis

Osmosis is the simple diffusion of water across a selectively permeable membrane.
Water moves from an area of high water concentration to an area of low water concentration until equilibrium is reached.
High water concentration means low solute concentration
Low water concentration means high solute concentration

Types of Solutions based on Osmosis

Hypertonic solution: Water concentration is lower outside the cell, causing net movement of water out of the cell resulting in cell shrinkage/ shriveling.
Hypotonic solution: Water concentration is higher outside the cell, causing net movement of water into the cell resulting in cell swelling.
Isotonic solution: Water concentration is equal inside and outside the cell, water movement in and out of cell is balanced.

Active Transport: Molecular Pumps

A cell uses energy to pump molecules across the membrane, against the concentration gradient through a protein channel.
This concentrates molecules inside the cell and removes waste quickly.
- Examples include ions such as potassium (K+), chlorine (Cl-), and sodium (Na+).

Active Transport: Vesicles

Endocytosis brings large particles into the cell using vesicles.
- Examples include white blood cells engulfing bacteria
Exocytosis moves large particles out of the cell by using vesicles.
- Examples include nerve cells releasing neurotransmitters.

Types of Endocytosis

Phagocytosis: cell engulfs solids.
Pinocytosis: cell engulfs liquids.

Summary of Transport

A table summarizing different types of transport, examples of substances transported, and their roles in maintaining homeostasis.

Practice Questions

Practice problems related to different types of cell transport.
Examples from the cell and environmental concentrations(e.g., 5% vs 15% solutions).

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Description

Explore the critical concepts of cell transport and homeostasis in this quiz. Analyze how different cell structures contribute to transport mechanisms and learn about feedback mechanisms that maintain internal stability. Understanding these relationships is key to mastering biological principles.