6: Cell Membranes Flashcards
Module 1, Lesson 6
All plasma membranes contain…
Lipids and proteins
____ are a fundamental structure in plasma membranes.
Phospholipids
____ on the outer surface of the membrane create a sugar coat (glycocalyx).
Carbohydrates
What are the functions of the glycocalyx?
(three)
- Protects the cell
- Helps the cell interact with other cells
- Helps other cells recognize the cell
Phospholipids are composed of a ____ head group and two ____ tails.
Hydrophilic head group
Hydrophobic tails
The tails of phospholipids are long chains of…
Fatty acids
Phospholipids that connect fatty acids to a phosphate group using glycerol are called…
Glycerol phospholipids
True or false:
Cells can control the length of a phospholipid’s fatty acid tail.
True
A fatty acid that contains double bonds is considered…
Unsaturated
A fatty acid that does not contain double bonds is considered…
Saturated
In water, phospholipids associate into structures such as the…
(two)
Micelle and bilayer
A spherical structure where the head groups are on the outside is called a…
Micelle
A continuous sheet with two outside edges made up of head groups is called a…
Bilayer
List the three types of monolayers.
Faces, leaflets, surfaces
Phospholipid bilayers give the cell membrane its property of…
Selective permeability
Which types of molecules can freely cross the plasma membrane?
Small and nonpolar (hydrophobic)
Which types of molecules can only cross the plasma membrane slowly?
Polar, hydrophilic
The ____ model of the plasma membrane visualizes it as a 2D fluid where proteins are either inserted or dissolved.
Fluid mosaic
The two main types of proteins in the plasma membrane are…
Integral proteins and peripheral proteins
____ is a lipid inserted into the bilayer that enhances barrier properties.
Cholesterol
Phospholipids and proteins can diffuse ____ in membranes.
Laterally
Phospholipids and proteins are able to diffuse in membranes due to…
Weak hydrophobic interactions
List three things that can reduce the fluidity of the plasma membrane.
- Lower temperatures
- Longer fatty acid tails
- Saturated fatty acid tails
Cells can reduce the affinity of phospholipids for each other by…
Adjusting the length of the tails or the number of bonds in the tails
Proteins embedded in the phospholipid bilayer are called the…
Integral membrane proteins
True or false:
We can isolate integral membrane proteins without destroying the membrane.
False
Because the proteins are embedded in the bilayer, isolating them requires destroying the membrane.
Proteins that pass through the bilayer and are exposed on each side of it are called…
Transmembrane proteins
Transmembrane proteins with only one transmembrane domain are called…
Single-pass proteins
Transmembrane proteins with multiple transmembrane domains are called…
Multi-pass proteins
Proteins that are attached to lipids or fatty acids are called…
Lipid anchor proteins
Transmembrane proteins and lipid anchor proteins are types of…
Integral membrane proteins
True or false:
A single lipid anchor protein is only found on one side of the bilayer or another.
True
Proteins that are noncovalently bound to transmembrane proteins or phospholipid heads are called…
Peripheral membrane proteins
True or false:
Peripheral membrane proteins can be removed from the membrane without destroying it.
True
True or false:
Membrane faces are asymmetric.
True
The faces of a membrane differ in…
Composition and function
Carbohydrates are only found on the ____ face of the plasma membrane.
Outer
The inner face of the plasma membrane is also called the ____ face.
Intracellular
The outer face of the plasma membrane is also called the ____ face.
Extracellular
____ proteins detect signal molecules and initiate a response.
Receptor
____ proteins allow a cell to be recognized by other cells.
Cell identity
____ promote a specific chemical reaction.
Enzymes
____ proteins help cells attach to one another.
Cell adhesion
____ proteins transmit changes in the cytoskeleton to changes in the membrane.
Cytoskeletal attachment
____ proteins facilitate movement of small molecules across the plasma membrane.
Transport
____ can be used to move molecules across the membrane that cannot cross by themselves.
Transport proteins
Transport proteins are present in both ____ and ____ membranes.
Plasma and organelle
____ create a pore in the membrane to let certain molecules (often ions) cross.
Channel proteins
Channel proteins move molecules using…
Passive transport
Channel proteins that can open or close in response to a signal are called…
Gated channel proteins
True or false:
Some channel proteins will only allow a specific molecule to cross the membrane.
True
____ can use passive transport to carry out facilitated diffusion.
Carrier proteins
Carrier proteins work by…
Bonding to a molecule, then reversing shape to allow it into the cell
True or false:
A single carrier protein can transport multiple types of molecules.
False
Each carrier protein is specific to a certain molecule.
True or false
Carrier proteins can engage in both active and passive transport.
True
Most carrier proteins engaged in active transport are considered…
ATPases
ATPases power movement using energy from…
ATP hydrolysis
____ uses ion gradients as its energy source.
Coupled transport
What are the two types of molecules involved in coupled transport?
Symporters and antiporters
____ move both the ion and a molecule in the same direction.
Symporters
____ move a molecule in the opposite direction from an ion.
Antiporters
Most coupled transporters are located in the ____ and move molecule using the ____ gradient.
Plasma membrane ; sodium
The movement of water down its concentration gradient is known as…
Osmosis
Water molecules will naturally move to an area with…
Higher solute concentration
The force needed to stop osmosis from occurring is called…
Osmotic pressure
A solution in which solute concentration is equal on both sides of the plasma membrane is…
Isotonic
A solution in which there is a greater solute concentration outside the cell is…
Hypertonic
A solution in which there is greater solute concentration inside the cell is…
Hypotonic
In an animal cell in an isotonic solution…
Water goes in and out of the cell at the same rate.
In an animal cell in a hypertonic solution…
Water leaves the cell, causing it to shrivel
In an animal cell in a hypotonic solution…
Water rushes into the cell, causing it to burst
In plant cells, the ____ prevents the cell from bursting.
Cell wall
In a plant cell in a hypotonic solution…
Water pushes the membrane against the cell wall, creating a normal turgid cell
In a plant cell in an isotonic solution…
The cell becomes a weaker (flaccid) cell.
In a plant cell in a hypertonic solution…
The membrane shrinks back from the cell wall, causing the cell to shrivel
Eukaryotic cells can ingest large materials from the extracellular environment using…
Endocytosis
During endocytosis…
The plasma membrane buds inward to collect macromolecules or entire cells
What are the three types of endocytosis?
- Pinocytosis (cell drinking)
- Receptor-mediated endocytosis
- Phagocytosis (cell eating)
Eukaryotes internalize macromolecules and water molecules using…
Pinocytosis
During pinocytosis…
Portions of the membrane constantly bud inward, collecting nearby macromolecules at random.
Eukaryotes are able to recognize and consume specific macromolecules using…
Receptor-mediated endocytosis