Download SI Worksheet 5 Answers

Biology 1
Lecture 6-Membrane and Enzymes
I. Plasma Membrane
1. Draw a small section of the plasma membrane including phospholipids and proteins.
Indicate which region is hydrophilic and hydrophobic also explain what it means to be
hydrophilic and hydrophobic.
Hydrophilic : love water
Hydrophobic: do not love water
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diffusion
osmosis
low
passive transport
phospholipids
active transport
membrane
hypertonic
hypotonic
isotonic
down
exocytosis
endocytosis
tonicity
polarity
hydrophobic
up
hydrophilic
mosaic
bilayer
uptake
processing
transport
equilibrium
gradient
high
2.Use the terms on the left to fill in the blanks in the statements on the right. The terms
can be used more than once or not at all. Terms can be used as singular or as plural
( i.e. “s” at the end)
1.A cells membrane is selectively permeable due to the pore size and __polarity____ of the
molecules.
2.___Passive____ transport is the process of transporting solutes across the plasma
membrane without the use of energy. In this process solutes are going ___down____ their
concentration _____gradient_____.
3. _____Hypertonic______ indicates that the concentration of solute is higher on the outside
of the cell.
4.___phospholipids_____ form a two-layered membrane, known as the __phospholipd____
___bilayer_____.
5. Solutes will move from an area of ___high__ solute concentration to an area of
____low______solute concentration to reach equilibrium. This processes is know as
___diffusion_______.
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Biology 1
6. ____Active___ transport is the process of transporting solutes across the plasma membrane with the
use of energy. In this process solutes are going ___up_____ their concentration ____gradient____.
7. Water moves across the membrane in response to solute concentration inside and outside of the cell by
a process called ____osmosis____.
8. __Tonicity___ is a term that describes the ability of a solution to cause a cell to gain or loss water.
9. ____Exocytosis_____ and ____endocytosis____ transport large molecules.
10. ____Osmosis____ will move water across a membrane _____down_____ its concentration gradient
until the concentration of solutes is equal on both sides of the membrane.
11. _____Isotonic___ indicates that the concentration of a solute is the same on both inside and out of the
cell.
12. ____Hypotonic_______ indicates that the concentration of solute is higher on the inside of the cell.
b. Draw case where you have .3 M glucose outside cell and .5M
inside
3. Indicate which way water will move ( in/ out of
the cell).
Also indicate whether the cell is hypotonic, isotonic, or
hypertonic in relation to the environment.
Water will move inside the cell. Cell is hypotonic to its
environment.
Environment
Water will move out of cell down its
concentration gradient. Cell is hypertonic to
its environment since water is moving out.
There will be no net movement of water because there are equal
concentrations inside and out.The cell is isotonic to its
environment.
Cell
.5 M glucose
!
a. Draw case where you have .5 M glucose inside and outside
the cell. Show how water will move
.9 M
glucose
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Biology 1
4. Indicate the difference between passive transport, active transport and osmosis
Passive transport moves atoms/ molecules across cell membranes , unlike active transport, it does not
require the input of energy. Reason being, atoms/ molecules are moving “down” their concentration
gradient which is favorable (i.e. atoms want to diffuse from an area of high concentration to an area of
low concentration to achieve equilibrium so they have a desire to move “down” their concentration
gradient)
Active transport also moves atoms/ molecules across cell membranes, however it requires the input of
energy. Reason being, the atoms/molecules are moving “up” their concentration gradient which is not
favorable.
^ think of it like the atoms are being forced to move in a direction they do not want to so they
need an extra push in this direction --> energy
Osmosis is the process of water molecules moving from an area of high concentration to an area of low
concentration. Osmosis will move water down its concentration gradient to an area of high solute
concentration.
^ think of it like water wants to “dilute” the solute ( hence why it is a solvent-something that does
the dissolving) so since it wants to dilute the solute it will move to an area with a higher solute
concentration. That way both water and solute can achieve equilibrium!!
5. Explain the process of exocytosis and endocytosis
Exocytosis: when vesicles fuse with plasma membrane to release enclosed contents
Endocytosis: when plasma membrane folds inwards enclosing contents from outside of cell forming a
vesicle
II. Enzymes
1. Circle T/F for the below sentences
a. A single enzyme may act on thousands or millions of substrate molecules per second
b. An enzyme can increase the energy of activation needed to begin a reaction
c. Enzymes are proteins
T
F
F
F
d. A cells environment does not affect an enzymes activity
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T
T
T
F
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Biology 1
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e. Enzyme inhibitors increase an enzymes action
T
F
f. Chemical reactions either release or store energy
T
F
g. ADP is the energy currency of cells
T
F
h. A substrate binds to an enzymes active site
T
F
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