Are we ready to learn about cell transport?

Cell Transport uses the features of the cell membrane to transport molecules in and out of the cell

Cell Membrane

Cell (Plasma) Membrane Function Helps cells maintain homeostasis by controlling what substances pass through its membrane “Selective Permeability” This enables cells to have a constant internal environment despite changing external conditions

Cell Membrane Structure Plasma (cell) membrane is comprised of phospholipids polar heads and non- polar tails proteins embedded in the membrane

Fluid Mosaic Model The cell membranes can be considered a two-dimensional liquid all lipid and protein molecules diffuse freely This is known as the “Fluid mosaic” model

Why transport is needed… To stay alive, a cell must exchange materials such as food, water, & wastes with its environment Cells can die waiting for food to enter or become toxic and die because it took to long for the wastes to exit! These molecules must cross the cell membrane to enter & exit the cell

Small molecules (water, oxygen, carbon dioxide, glucose) can move in & out freely without using ATP via Passive Transport Larger molecules (lipids, polysaccharides, proteins) need energy (ATP) to pass through the cell membrane via Active Transport

Overview of Cell Transport Passive Transport No energy needed HIGH -  LOW concentration 1.Diffusion 2.Osmosis 3.Facilitated diffusion Active transport Energy needed (ATP!!!) LOW-  HIGH concentration 1.Membrane pumps 2.Endocytosis 3.Exocytosis

Identify the Carrier or Transport Proteins in the Cell Membrane below:

Passive Transport

PASSIVE TRANSPORT Does NOT require energy (ATP) to work Molecules move “downhill” from a HIGH to a LOW concentration 1. Diffusion 2. Osmosis = diffusion of water 3. Facilitated diffusion (proteins embedded in cell membrane act as channels or carriers to help molecules move across membrane)

Diffusion movement of molecules from an area of HIGH concentration to an area of LOW concentration No energy needed Molecules passively move due to the concentration gradient always seeking homeostasis (dynamic equilibrium) High Conc >Low Conc.

Diffusion

Diffusion of polar molecules across the cell membrane:

Diffusion

Osmosis This is a water specific process (diffusion of water) Osmosis is the movement of water across the membrane from a HIGH concentration to a LOW concentration Isotonic, Hypertonic, & Hypotonic Solutions

Solute + Solvent = Solution Solute (ice-tea mix) + Solvent (water) _____________________ Solution (ice-tea drink)

Osmosis

Isotonic Solution Concentration of solutes is the same inside & outside the cell Water moves into & out of cell at an equal rate so there is no net movement of water Animal cells do best in isotonic solutions

Hypertonic Solution Solute concentration outside the cell is higher (less water outside cell) Water diffuses out of the cell until equilibrium is reached Cells will shrink & die if too much water is lost Plant cells become flaccid (wilt): Plasmolysis

Hypotonic Solution Solute concentration greater inside the cell (less water) Water moves into the cell until equilibrium is reached Animal cells swell & burst (lyse) if they take in too much water: Cytolysis Plant cells become turgid (rigid) due to water pressing outward against cell wall Turgor pressure in plant cells helps them keep their shape…so Plant cells do best in hypotonic solutions!

Plant Cells in 3 types of Solutions:

Plant Cell in Hypotonic Cell (Preferred)

Animal Cell in a Hypotonic Solution

Facilitated Diffusion Transmembrane proteins embedded in the membrane help the molecules move across the membrane Does not require energy (ATP)

Facilitated Diffusion:

Active Transport: always active….

The cell uses energy (ATP) to transport molecules across the membrane Molecules must move “uphill” against a gradient from a LOW to a HIGH concentration 3 Types 1. Membrane pumps 2. Endocytosis 3. Exocytosis Active Transport

Active Transport: Protein Pumps Proteins embedded in the cell's lipid bilayer Acts as a pump to transport molecules across the membrane The Na/K pump is a common pump that works in the neuron (brain cell) to pump Na and K across membranes

More Active Transport!!! Endocytosis - cell takes in large particles by engulfing them –Food –Nutrients Exocytosis – cell gets rid of particles, opposite of endocytosis –Waste –Enzymes –Hormones –Antibodies

Endocytosis cells absorbing materials from the outside by engulfing them with a part of their cell membrane Large molecules can pass through the plasma membrane via Endocytosis endocytosis is the opposite of exocytosis

Endocytosis Phagocytosis “cell eating” Pinocytosis “cell drinking”

Exocytosis cell releases large molecules through its membrane Membrane-bound vesicles move to the membrane where they fuse with the plasma membrane In protozoans (unicellular organisms) exocytosis may serve the function of eliminating waste products and other molecules not needed by the cell in multicellular organisms exocytosis is used to secrete enzymes, hormones, & antibodies

Endocytosis & Exocytosis

Exocytosis

Exocytosis & Endocytosis

Emily Exocytosis says to study!!!

Cell Transport Review

Review: Active vs. Passive Transport

Quiz Time!

Cell Transport Quiz: In the following pictures, tell: A. What type of transport (passive or active) is shown B. What each type is specifically called

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Ready for more?

11.Diffusion and osmosis are processes in which particles move randomly across the plasma membrane. What type of movement are diffusion and osmosis? a. endocytosis b. active transport c. passive transport d. exocytosis

12. Besides phospholipids, what other substances make up the plasma membrane? a. Co-factors b. vitamins c. proteins d. Nucleic acids

13. Which of these is NOT a function of the cell wall in plants and algae? a. Using glucose to make ATP so that the plant cell can metabolize b. making sure the plant cell does not burst c. support d. protection

14. What is the outer boundary of a cell that encloses the cell's contents? a. the plasma membrane b. the cell wall c. the nuclear membrane d. the vesicle

15. In phagocytosis and pinocytosis, the plasma membrane brings in materials by forming what? a. vesicle b. Golgi Apparatus c. transport protein d. cell wall

16. Why are some particles (amino acid chains and complex sugars) able to cross the plasma membrane by passive transport? a. because they use osmosis b. because they use carrier proteins c. because they use endocytosis d. because they use exocytosis

17. What type of monomers make up the molecules that are embedded in the cell membrane? a. lipids b. amino acids c. glucose d. glycerol

18. Tell whether the following transport methods are active or passive: a.Channel proteins helping a large molecule pass b. osmosis c. Facilitated Diffusion d. Exocytosis e. Na/K membrane pump