Chapter 7: The Plasma Membrane
Structure and Function exam
review with correct descriptions
2025 newest
plasma membrane structure - Answer surrounds the cell,
contains the organelles, protects and separates the inside of the
cell from the outside, allows and controls the passage of
substances in/out of the cell
selectively permeable - Answer only lets certain substances
in/out of the cell
Has 4 main functions: - Answer 1. physical isolation
2. regulation of exchange
3. communication
4. structural support
,* Regulation of exchange - Answer controls the exchange of
water, *ions, nutrients, wastes, and products* between the cell
and extracellular environment
* Communication - Answer contains membrane bound proteins
that attach to the *cytoskeleton, adjacent cells, and the
extracellular matrix (ECM)*
Membrane structure - Answer All animal cells are surrounded by
a plasma membrane.
Cell membranes are composed of mostly proteins and lipids with
a small amount of carbohydrate:
- proteins: 55%
- phospholipids: 25%
- cholesterol: 13%
- other lipids: 4%
- carbohydrates: 3%
Ratio of protein to lipid varies depending on metabolic activity of
the cell or organelle.
Membrane components - Answer Phospholipids-
in a phospholipid molecule, two of the -OH (hydroxl) groups on a
glycerol are joined to *two fatty acids*. The third -OH joins to a
phosphate group which in turn, to another polar group of atoms
- phosphate and polar groups form a hydrophilic, polar head
, - hydrocarbon chains of the 2 fatty acids form a hydrophobic, non
polar tails
What does polar mean? - Answer the molecule has a positive and
negative charge
- polar molecules like other polar molecules
Phospholipid bilayer - Answer made of TWO layers of
phospholipids
- non polar; fatty acid tails point inward
- polar heads are on either surface
Membrane Steroid Cholesterol - Answer in animal cells,
cholesterol fat that is wedged between phospholipid molecules
act as a *"temperature buffer"*, resisting changes in membrane
fluidity as the temperature changes
- at warm temps, (like 37 C), cholesterol restrains the movement
of phospholipids and reduces fluidity
- at cool temps, it maintains fluidity by preventing tight packing
Membrane carbohydrates - Answer in the external surface,
carbohydrate groups join with lipids to form *glycolipids* and with
proteins to form *glycoproteins*
- these carbohydrate groups serve as a cell identity marker for
cell-cell recognition, a cell's ability to distinguish one type of
neighboring cell form another
Structure and Function exam
review with correct descriptions
2025 newest
plasma membrane structure - Answer surrounds the cell,
contains the organelles, protects and separates the inside of the
cell from the outside, allows and controls the passage of
substances in/out of the cell
selectively permeable - Answer only lets certain substances
in/out of the cell
Has 4 main functions: - Answer 1. physical isolation
2. regulation of exchange
3. communication
4. structural support
,* Regulation of exchange - Answer controls the exchange of
water, *ions, nutrients, wastes, and products* between the cell
and extracellular environment
* Communication - Answer contains membrane bound proteins
that attach to the *cytoskeleton, adjacent cells, and the
extracellular matrix (ECM)*
Membrane structure - Answer All animal cells are surrounded by
a plasma membrane.
Cell membranes are composed of mostly proteins and lipids with
a small amount of carbohydrate:
- proteins: 55%
- phospholipids: 25%
- cholesterol: 13%
- other lipids: 4%
- carbohydrates: 3%
Ratio of protein to lipid varies depending on metabolic activity of
the cell or organelle.
Membrane components - Answer Phospholipids-
in a phospholipid molecule, two of the -OH (hydroxl) groups on a
glycerol are joined to *two fatty acids*. The third -OH joins to a
phosphate group which in turn, to another polar group of atoms
- phosphate and polar groups form a hydrophilic, polar head
, - hydrocarbon chains of the 2 fatty acids form a hydrophobic, non
polar tails
What does polar mean? - Answer the molecule has a positive and
negative charge
- polar molecules like other polar molecules
Phospholipid bilayer - Answer made of TWO layers of
phospholipids
- non polar; fatty acid tails point inward
- polar heads are on either surface
Membrane Steroid Cholesterol - Answer in animal cells,
cholesterol fat that is wedged between phospholipid molecules
act as a *"temperature buffer"*, resisting changes in membrane
fluidity as the temperature changes
- at warm temps, (like 37 C), cholesterol restrains the movement
of phospholipids and reduces fluidity
- at cool temps, it maintains fluidity by preventing tight packing
Membrane carbohydrates - Answer in the external surface,
carbohydrate groups join with lipids to form *glycolipids* and with
proteins to form *glycoproteins*
- these carbohydrate groups serve as a cell identity marker for
cell-cell recognition, a cell's ability to distinguish one type of
neighboring cell form another
