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Cell Membrane and Tonicity: A Comprehensive Worksheet, Exams of Molecular biology

Cell Membrane & Tonicity Worksheet Composition of the Cell Membrane & Functions The cell membrane is also called the PLASMA membrane and is made of a phospholipid BI-LAYER. The phospholipids have a hydrophilic (water attracting) HEADS and two hydrophobic (water repelling) TAILS. The head of a phospholipid is made of an alcohol and GLYCEROL group, while the tails are chains of FATTY ACIDS. Phospholipids can move SIDEWAYS and allow water and other NON-POLAR molecules to pass through into or out of the cell. This is known as simple PASSIVE TRANSPORT because it does not require ENERGY and the water or molecules are moving WITH the concentration gradient. SKETCH AND LABEL a phospholipid coloring the heads red and the tails blue. Another type of lipid in the cell membrane is CHOLESTEROL that makes the membrane more fluid. Embedded in the phospholipid bilayer are PROTEINS that also aid in diffusion and in cell recognition. Proteins called INTEGRAL proteins go all the way through

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Cell Membrane & Tonicity
Worksheet
Composition of the Cell Membrane & Functions
The cell membrane is also called the PLASMA membrane and is made of a
phospholipid BI-LAYER. The phospholipids have a hydrophilic (water
attracting) HEADS and two hydrophobic (water repelling) TAILS. The head
of a phospholipid is made of an alcohol and GLYCEROL group, while the
tails are chains of FATTY ACIDS. Phospholipids can move SIDEWAYS and
allow water and other NON-POLAR molecules to pass through into or out of
the cell. This is known as simple PASSIVE TRANSPORT because it does
not require ENERGY and the water or molecules are moving WITH the
concentration gradient.
SKETCH AND
LABEL a
phospholipid
coloring the
heads red and the
tails blue.
Another type of lipid in the cell membrane is CHOLESTEROL that makes the membrane
more fluid. Embedded in the phospholipid bilayer are PROTEINS that also aid in diffusion
and in cell recognition. Proteins called INTEGRAL proteins go all the way through the
bilayer, while PERIPHERAL proteins are only on one side. Large molecules like
PROTEINS or carbohydrates use proteins to help move across cell membranes. Some of
the membrane proteins have carbohydrate PARTS attached to help cells in recognize
each other and certain molecules.
List 4 functions of the cell or plasma membrane:
a. CELL SIGNALING
b. SELECTIVE TRANSPORT
c. EXCRETION OF WASTES
d. STRUCTURAL SUPPORT
Correctly color code and identify the name for each part of the cell membrane.
Letter Name/Color Letter
Name/
Color
__ A ___
Phospholipid bilayer (no
color) __ H ___
Peripheral protein
(red)
__ B ___ Integral protein (pink) __ I ____ Cholesterol (blue)
__ F ___ Fatty acid tails (orange) __ C___
Glycoprotein
(green)
__ G ___ Phosphate heads (yellow) __ E ___ Glycolipids (purple)
Match the cell membrane structure or its function with the correct letter from the cell membrane diagram.
Letter Structure/Function
Lette
r Structure/Function
__ G ___ Attracts water __ F__ Repels water
__ I ___
Helps maintain flexibility of
membrane _G&F Make up the bilayer
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Cell Membrane & Tonicity

Worksheet

Composition of the Cell Membrane & Functions The cell membrane is also called the PLASMA membrane and is made of a phospholipid BI-LAYER. The phospholipids have a hydrophilic (water attracting) HEADS and two hydrophobic (water repelling) TAILS. The head of a phospholipid is made of an alcohol and GLYCEROL group, while the tails are chains of FATTY ACIDS. Phospholipids can move SIDEWAYS and allow water and other NON-POLAR molecules to pass through into or out of the cell. This is known as simple PASSIVE TRANSPORT because it does not require ENERGY and the water or molecules are moving WITH the concentration gradient. SKETCH AND LABEL a phospholipid coloring the heads red and the tails blue. Another type of lipid in the cell membrane is CHOLESTEROL that makes the membrane more fluid. Embedded in the phospholipid bilayer are PROTEINS that also aid in diffusion and in cell recognition. Proteins called INTEGRAL proteins go all the way through the bilayer, while PERIPHERAL proteins are only on one side. Large molecules like PROTEINS or carbohydrates use proteins to help move across cell membranes. Some of the membrane proteins have carbohydrate PARTS attached to help cells in recognize each other and certain molecules. List 4 functions of the cell or plasma membrane: a. CELL SIGNALING b. SELECTIVE TRANSPORT c. EXCRETION OF WASTES d. STRUCTURAL SUPPORT Correctly color code and identify the name for each part of the cell membrane. Letter Name/Color Letter Name/ Color __ A ___ Phospholipid bilayer (no color) __ H ___ Peripheral protein (red) __ B ___ Integral protein (pink) __ I ____ Cholesterol (blue) __ F ___ Fatty acid tails (orange) __ C ___ Glycoprotein (green) __ G ___ Phosphate heads (yellow) __ E ___ Glycolipids (purple) Match the cell membrane structure or its function with the correct letter from the cell membrane diagram. Letter Structure/Function Lette r Structure/Function __ G ___ Attracts water __ F__ Repels water __ I ___ Helps maintain flexibility of membrane _G&F Make up the bilayer

__ C &

E ___

Involved in cell-to-cell recognition __ B__ Help transport certain materials across the cell membrane

Transport Requiring Energy What type of transport is represented by the following picture? ACTIVE What energy is being used? ATP In which direction (concentration gradient), is the movement occurring? AGAINST Color the internal environment of the cell yellow. Color and Label the transport proteins red and the substance being moved blue. One type of active transport is called the SODIUM-POTASSIUM pump which helps muscle cells contract. This pump uses PROTEINS to move ions AGAINST the concentration gradient. The protein that is used to pump the ions through is called a TRANSMEMBRANE (INTEGRAL) protein and it changes its SHAPE to move the ions across the cell membrane. Label and color the carrier proteins red and the ions green. TONICITY AND OSMOSIS Part I – Fill in the blanks. A SOLVENT is a fluid in which a substance is dissolved. A SOLUTE is a substance dissolved in a solvent. A SOLUTION is a combination of solute and solvent. The process by which water diffuses across a membrane called OSMOSIS Part II – Look at the solutions illustrated above and fill in the blanks.

  1. Solution B is HYPERTONIC to Solution A. This is because Solution B has a greater concentration of SOLUTES in it than does Solution A. Solution C has no solutes dissolved in it, therefore it is HYPOTONIC to both Solutions A and B.

THEY ARE BOTH SELECTIVELY PERMEABLE BASED ON SIZE OF PARTICLES

  1. Explain the behavior of water molecules in the isotonic solution. WATER MOLECULES WILL MOVE INTO AND OUT OF THE CELL CONTINUOUSLY, HOWEVER, THERE WILL BE NO OVERALL CONCENTRATION CHANGE SINCE THE MOVEMENT SHOULD BE EQUAL.
  2. Does osmosis occur if a cell is placed in an isotonic solution? NO, BECAUSE THERE IS NO CONCENTRATION GRADIENT (AREA OF HIGH TO AREA OF LOW – ISOTONIC IMPLIES EQUAL CONCENTRATIONS)
  3. Why does water enter a cell that is placed in a hypotonic solution? BECAUSE THE CONCENTRATION OF SOLUTE IS LOWER OUTSIDE THE CELL THAN IT IS INSIDE THE CELL, SO THE WATER ENTERS THE CELL TO TRY TO DECREASE/EQUALIZE THE CONCENTRATIONS ON BOTH SIDES OF THE MEMBRANE.
  4. What happens to the pressure inside a cell that is placed in a hypertonic solution? THE PRESSURE DECREASES AS THE WATER LEAVES THE CELL.
  5. What can happen to animal cells when placed in a hypotonic solution? Explain. ANIMAL CELLS IN HYPOTONIC SOLUTIONS CAN RUPTURE AS MORE AND MORE WATER RUSHES INTO THE CELL. PLANT CELLS WILL NOT HAVE THIS ISSUE BECAUSE THE CELL WALL PROTECTS THE PLANT CELLS FROM RUPTURING.
  6. What causes a plant to wilt? PLANTS PLACED IN A HYPERTONIC SOLUTION WILL WILT AS WATER IS REMOVED FROM THEM RESULTING IN PLASMOLYSIS.