BASI M01L05 Cell Membranes and Transport

In the lipid bilayer, polar heads face….

outward to an aqueous environment

In the lipid bilayer, non-polar tails face….

away from the aqueous interface

Membrane fluidity increases with…

high temperature and unsaturated fatty acids

Membrane fluidity decreases with….

low temperature and saturated fatty acids

In the common intestinal bacterium Escherichia coli, a decrease in environmental temperature ______ the synthesis of an enzyme that introduces double bonds into the hydrocarbon chains of fatty acids.

increases

Amphibians and reptiles adapt to lower temperatures. These animals can ______ the proportion of cholesterol in the membrane, thereby decreasing the interaction between hydrocarbon chains and reducing the tendency of the membrane to gel.

increase

Integral membrane proteins….

wind in and out of the bilayer

Lipid anchored proteins…

covalently attach to lipid molecules that tether the protein to the membrane

Peripheral membrane proteins….

link to integral membrane proteins or phospholipid head groups

The carbohydrate-rich layer on the surface of cells is called?

cell coat or glycocalyx

The glycocalyx provides which functions?

protection, lubrication, cell recognition, adhesion

What molecules are able to cross the lipid bilayer through simple diffusion (unassisted)?

uncharged molecules like gases (O₂, CO₂, NO) and small polar molecules

Passive transport requires…

no energy

Active transport requires….

energy

In which form of transport do molecules move from high to low concentration?

Passive

In which form of transport do molecules move from low to high concentration?

Active

Channel proteins mediate…

passive transport

Most ion-channels are….

gated

T or F: Channel proteins are not selective.

false

What binds to open the channel in a gated channel protein?

ligands

What binds to open carrier proteins?

solutes

Carrier proteins mediate….

passive or active transport

In primary active transport, energy for movement is derived from…

the breakdown of ATP

In secondary active transport, energy for movement is derived from…

the energy stored in ionic concentration differences between the sides of the cell membrane

Uptake of glucose in the intestinal lumen is mediated by….

Na⁺-dependent glucose transporters

Is the uptake of glucose secondary or primary active transport?

secondary

What allows glucose to enter the cell in the intestinal lumen?

The flow of Na⁺ down its concentration gradient

The Na/K ATPase is an example of….

primary active transport

The Na/K ATPase pumps out ______.

3 molecules of Na

The Na/K ATPase imports ______.

2 molecules of K

The Na/K ATPase creates a ____ on the inner side of the membrane.

negative charge

The GLUT2 carrier protein which transports glucose outside of the cell is an example of…

carrier-mediated passive transport

Which carrier protein(s) are located at the basal membrane?

Na/K ATPase and GLUT2

Which carrier protein(s) are located at the apical membrane?

Na-dependent glucose transporter

A mutation in the CFTR chloride channel can result in…

cystic fibrosis

Cystic fibrosis is the result of….

insufficient hydration of mucus, leading to the build-up of mucus and bacteria in the lungs