Bio 1500 Exam One
First Homo sapiens
200,000 years ago
First dinosaurs
240 mya
Oldest fossils
3.5 billion years ago
One area in a cell has a higher density of a certain type of molecule compared to a neighboring area. This situation describes:
a concentration gradient
The highest rates of diffusion are associated with
high temperatures large diffusion surface area steep concentration gradient
How does facilitated transport differ from diffusion?
in facilitated transport, the substance passes through a pore, or tunnel, inside other molecules in the membrane
What does it mean if a channel is gated?
sometimes the channel allows molecules to pass through, and sometimes it doesn't
What is diffusion?
the spontaneous movement of molecules away from areas of highest density
What is the difference (or relationship) between the terms diffusion and osmosis?
they both function in the same way, but osmosis refers specifically to the diffusion of water molecules
After molecules have moved around until there is no longer a concentration gradient, how do the molecules behave?
they continue moving, but their density remains relatively even throughout the space
Bacterial Photosynthesis
2,700,000,000 years ago
Earth formed
4.6 billion years ago
First Insects
480 mya
Cretaceous Extinction
66 million years ago;
What benefit do cells obtain by using facilitated transport instead of simple (=unfacilitated) diffusion to move material across a membrane?
Some molecules have positive and negative regions (i.e. polarity) that prevent them from moving easily through the membrane; facilitated transport overcomes this problem
Which three of the following are types of transport proteins?
channel proteins aquaporins carrier proteins