Homeostasis Passive Transport

​Lesson Objectives

Explain active transport and its role in homeostasis.

Describe how active transport uses ATP energy to move molecules.

Explain the sodium-potassium pump and its function

Multiple Choice

What is homeostasis?

• Homeostasis is the maintenance of stable internal conditions in an organism.
• Homeostasis is the ability to adapt to external environments.
• Homeostasis is the process of aging in organisms.
• Homeostasis refers to the growth of an organism.

Open Ended

What are the three types of solutions

Match

Match the following forms of passive transport.

• diffusion of water from high to low

• movement of material from high to low

• a transport protein moves materials from high to low

Osmosis

Diffusion

Facilitated Diffusion

• Osmosis

• Diffusion

• Facilitated Diffusion

Labelling

Label each type of passive transport

Drag labels to their correct position on the image

Diffusion

Facilitated Diffusion

Cellular Transport and Active Transport

Multiple Choice

What is passive transport?

• Passive transport is the movement of substances across a cell membrane without the use of energy.
• Passive transport is the movement of substances against their concentration gradient.
• Passive transport only occurs in plant cells.
• Active transport requires energy to move substances across a cell membrane.

Active Transport: is the movement across a cell membrane against the concentration gradient, requiring energy (ATP).

• Moves molecules from low to high concentration (against the gradient)

• Requires cellular energy (ATP)

Involves transport proteins and specialized pump

​Active Transport

Open Ended

• How does active transport differ from passive transport?

The sodium-potassium pump is an essential active transport mechanism in animal cells.

• Pumps sodium (Na⁺) ions out of the cell and potassium (K⁺) ions into the cell

• Maintains resting membrane potential needed for nerve signaling

• Uses ATP to move ions against their gradient

​Sodium-Potassium Pump

• Bulk transport processes like endocytosis and exocytosis move large molecules across the cell membrane.

• Endocytosis: Cells engulf large molecules, forming a vacuole

• Exocytosis: Vacuoles fuse with the membrane to release contents outside the cell

• Used for large molecules that cannot pass directly through the membrane

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​Bulk Transport

​

Endocytosis: is a cellular process in which a cell takes in large molecules or particles from the extracellular environment by engulfing them with its membrane

Steps in Endocytosis

1. Invagination: The cell membrane folds inward to form a pocket around the material.

2. Engulfing: The pocket deepens, surrounding the material entirely.

3. Vesicle Formation: The membrane closes around the material, pinching off to form a vesicle inside the cell, enclosing the ingested material.

Allows cells to remove pathogens, bring in nutrients, and adjust their response to external signals, all contributing to cellular and overall organism homeostasis.

​​Endocytosis

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• Exocytosis is the process by which cells transport materials from inside the cell to the extracellular environment by fusing a vesicle with the cell membrane

• Steps in Exocytosis

1. Vesicle Formation: Inside the cell, substances are packaged into vesicles, which are small, membrane-bound sacs. These vesicles often come from the Golgi apparatus, where materials are processed and packaged.

2. Vesicle Transport: The vesicle moves toward the cell membrane, traveling along the cytoskeleton (using energy).

3. Fusion with the Membrane: When the vesicle reaches the cell membrane, it fuses with it, opening the vesicle to the outside of the cell.

4. Release of Contents: The vesicle’s contents are released into the extracellular space, and the vesicle membrane becomes part of the cell membrane.

• Exocytosis is vital for maintaining stable conditions in the cell and the organism as a whole. It allows cells to communicate and respond to changes in their environment, remove toxins, and secrete important molecules

Exocytosis

Multiple Choice

What is the purpose of the Sodium Potassium Pump?

• To maintain the electrochemical gradient by transporting sodium out and potassium into the cell.
• To transport calcium ions out of the cell and Transport DNA through out the cell

• To facilitate the movement of glucose into the cell and transfers iron and sodium into the bloodstream

• To generate energy for cellular respiration.

​Active transport is critical for various biological processes.

• Root hair cells in plants absorb minerals from the soil using active transport

• Kidney cells regulate ion balance by reabsorbing essential ions

• Villi in the intestines use active transport to maximize nutrient absorption

​Examples of Active Transport in Cells

Multiple Choice

What is the difference between active and passive transport?

• Active transport uses energy; passive transport does not.
• Passive transport requires energy; active transport does not.
• Active transport occurs only in plants; passive transport occurs in animals.
• Active transport moves substances down their concentration gradient; passive transport moves them against it.

​Freshwater Fish:

• Live in hypotonic environments (water concentration is higher outside their bodies than inside).

• Use active transport to expel excess water and conserve salts.

• Their kidneys filter water efficiently, and gills absorb salts from water.

• Saltwater Fish:

  • Live in hypertonic environments (water concentration is lower outside their bodies).

  • Drink seawater and excrete excess salt through specialized cells in their gills.

  • Kidneys are adapted to retain water and excrete concentrated urine.

• Example:

  • Salmon can live in both freshwater and saltwater. Their osmoregulatory

system changes when they migrate between the two environments

​Osmoregulation in Fish