HW 4 Week 5

The lipid:protein ratio in a typical membrane is approximately:

1:1

Cell adhesions are important components of:

Tight junctions

Liver cells respond to epinephrine by:

Breaking down glycogen

What molecule is described in the following passage: "Extracellular matrix (ECM) protein important for structural support; comprised of 3 intertwined polypeptide chains that bundle together to form a rigid macro molecular fiber, the most abundant protein in the body"?

Collagen

The H+ ATPase (aka "proton pump") creates electrochemical gradients across the membranes of plants, fungi and protists. This is an example of:

Direct active transport

After you eat, insulin is secreted by the pancreatic Beta cells into the bloodstream, where it diffuses throughout the body to bind to receptors on target cells, telling them to take up glucose. This mode of signaling is referred to as:

Endocrine

When liver cells produce glucose in response to Glucagon, which is secreted when your blood sugar levels drop below a specific level. What type of transport is most likely responsible for getting the glucose back out into the bloodstream?

Facilitated diffusion

Which NEVER used simple diffusion to pass through the membrane?

Ions

What is NOT a tenet of the fluid mosaic model of the cell membrane?

Membranes are comprised of many lipid rafts floating in a lipid sea.

Which of the following most closely approximates a second messenger?

Na+ ions, which flow into a muscle cell in response to binding of acetylcholine to its receptor, which leads to Ca++ release from internal stores.

What can diffuse most easily through the membrane.

O2

The most fundamental function of the epithelium in animals is to prevent entry of pathogens and toxins from the environment. Which of the following is common to all epithelial cells?

They are held together by tight junctions