General Biology - ULTIMATE FLASHCARD REVIEWER FOR TERM 1 EXAMINATION

What is the plasma membrane primarily made of?

A phospholipid bilayer

Why is the plasma membrane described as "fluid"?

Because its molecules can move sideways

Why is the plasma membrane described as a "mosaic"?

Because it looks like a patchwork of different molecules

What does "selectively permeable" mean for a membrane?

A membrane that controls what enters and leaves the cell

What is the benefit of the membrane being selectively permeable?

It allows needed substances to enter and prevents harmful substances from entering

How thick is the plasma membrane?

About 8 nanometers

How many plasma membranes would it take to equal the thickness of a sheet of paper?

About 8000

In what decade did scientists first find evidence that every cell is surrounded by a plasma membrane?

The 1890s

What was not yet known about the plasma membrane in the 1890s?

Its structure

In what year was the chemical composition of the plasma membrane discovered?

1915

What class of molecules was the plasma membrane found to be made of in 1915?

Lipids (fats)

Who proposed the sandwich model of the plasma membrane?

Hugh Davson and James Danielli

In what year was the sandwich model proposed?

1935

In the sandwich model where is the phospholipid bilayer located?

In the middle/center

In the sandwich model

what surrounds the phospholipid bilayer?

Who proposed the Fluid Mosaic Model?

S. Jonathan Singer and Garth L. Nicolson

In what year was the Fluid Mosaic Model proposed?

1972

How are proteins arranged in the Fluid Mosaic Model compared to the sandwich model?

Proteins are embedded within the membrane rather than forming layers on the outside

What is the main function of phospholipids in the plasma membrane?

They form the main fabric of the membrane

What is the function of cholesterol in the plasma membrane?

Cell insulation

What is the function of proteins in the plasma membrane?

Transport of substances through the membrane and cell recognition

What is the function of carbohydrates in the plasma membrane?

Cell recognition

What energy source is required for carbohydrate-related membrane processes?

ATP (energy from glucose)

What is cell transport mechanism?

The movement of different molecules in and out of the cell

Does passive transport require ATP?

No

Does active transport require ATP?

Yes

In passive transport which direction do molecules move relative to concentration?

From high to low concentration gradient

In active transport which direction do molecules move relative to concentration?

From low to high concentration gradient

What is simple diffusion?

The movement of molecules directly across the phospholipid bilayer without proteins or channels

Does simple diffusion require ATP?

No

In simple diffusion which direction do molecules move?

From high concentration to low concentration

Does simple diffusion need specialized proteins or channels?

No

Give an example of a respiratory gas that crosses the membrane by simple diffusion.

Oxygen (O2)

Why is oxygen important in simple diffusion?

It binds hemoglobin and is essential for cellular function

Give an example of a gas removed from the body via simple diffusion.

Carbon dioxide (CO2)

What process produces carbon dioxide that is removed via diffusion?

Aerobic respiration

What are steroid hormones derived from?

Cholesterol

Name three examples of steroid hormones that cross membranes via simple diffusion.

Testosterone

Besides sex hormones what other steroid-derived molecule crosses membranes via simple diffusion?

Vitamin D

Do steroid hormones require ATP or channel proteins to cross the membrane?

No

Do lipid-soluble drugs require ATP or carrier proteins to cross the membrane?

No

Name examples of lipid-soluble drugs that cross membranes without channel proteins.

Antibiotics

What are the two parts of a phospholipid molecule?

A phosphate head and fatty acid tails

Are the phosphate heads of a phospholipid polar or nonpolar?

Polar (hydrophilic)

Are the fatty acid tails of a phospholipid polar or nonpolar?

Nonpolar (hydrophobic)

What is the relationship between surface area and rate of diffusion?

Higher surface area leads to a higher rate of diffusion

What is a concentration gradient?

How solute particles move through a gas or solution from high to low particle number

What is the relationship between membrane thickness and rate of diffusion?

A thicker membrane results in a slower rate of diffusion

What is the relationship between molecule weight and rate of diffusion?

Heavier molecules diffuse more slowly

What is facilitated diffusion?

Passive movement of molecules across the membrane using channels or proteins

Does facilitated diffusion require ATP?

No

In facilitated diffusion

which direction do molecules move?

What is the key difference between simple diffusion and facilitated diffusion?

Facilitated diffusion requires proteins or channels

What is osmosis?

The movement of water from high concentration to low concentration

What two factors does the movement of water in osmosis depend on?

The concentration gradient of water and the concentration of solute

In osmosis, does water move toward the side with low or high solute concentration?

High solute concentration

What are aquaporins?

Transport proteins that allow water to move across the plasma membrane

What is a leaky channel?

A channel that is always open and allows continuous ion flow

Give an example of an ion that commonly uses leaky channels.

Potassium

Why are leaky channels important in neurons?

They help maintain resting membrane potential

For potassium via leaky channels where is concentration high and where is it low?

High inside the cell, low outside the cell

What triggers a voltage-gated channel to open?

Changes in membrane potential

Give two ions that move through voltage-gated channels in neurons.

Sodium and calcium

For sodium and calcium in neurons where is concentration typically high and low?

High outside the cell, low inside the cell

What is the threshold potential that opens voltage-gated sodium/calcium channels?

-55 millivolts

What happens at the threshold potential in a neuron?

The gate opens

What triggers a ligand-gated channel to open?

Binding of a specific molecule

Where are ligand-gated channels especially important?

At the neuromuscular junction

What molecule triggers the acetylcholine-gated channel?

Acetylcholine

What is the functional role of acetylcholine at the neuromuscular junction?

It triggers action potential for muscle contraction

What triggers a mechanically gated channel to open?

Physical deformation such as pressure

Give an example of a physiological role of mechanically gated channels.

Inducing pain signals from pressure

Which ion is associated with mechanically gated channels in the example given?

Sodium

What happens to a cell's electrical state when a mechanically gated channel opens?

It changes

What is a carrier-mediated channel?

A channel where the protein undergoes a conformational shape change to transport specific molecules

What triggers a carrier-mediated channel to open?

A particular stimulus

Name the transporter proteins used for glucose movement in carrier-mediated transport.

GLUT transporters

Where are GLUT transporters commonly found in the body?

In muscle tissue and throughout the body

What hormone regulates glucose uptake via GLUT transporters?

Insulin

What is the relationship between GLUT transporters

glucose

Which GLUT transporter is described as ubiquitous (found everywhere)?

GLUT1

Which GLUT transporter is insulin-regulated and found in muscle and fat cells?

GLUT4

What disease is linked to impaired GLUT function?

Type 2 diabetes

What is Aquaporin-2 (AQP2) and where is it found?

A channel protein in the kidney collecting ducts that regulates water reabsorption

What hormone controls AQP2 activity?

ADH (antidiuretic hormone)

What condition results from defects in AQP2?

Nephrogenic diabetes insipidus

What is the consequence of nephrogenic diabetes insipidus?

Excessive water loss and dehydration

What is primary active transport?

Movement of molecules against their concentration gradient using ATP directly

What are ATPase pumps?

Membrane proteins that hydrolyze ATP to drive active transport

How many sodium ions does the Na+/K+ ATPase pump move out of the cell per ATP?

3

How many potassium ions does the Na+/K+ ATPase pump move into the cell per ATP?

2

For sodium is concentration high or low outside the cell?

High outside, low inside

For potassium is concentration high or low inside the cell?

High inside, low outside

Name one essential physiological process that depends on the Na+/K+ ATPase pump.

Nerve impulse generation (also cell volume maintenance and resting membrane potential)

What drug class inhibits the Na+/K+ ATPase pump in cardiac therapy?

Digitalis (e.g.Digoxin)

How does insulin relate to the Na+/K+ ATPase pump?

Insulin controls glucose level; a higher Na+/K+ pump activity means more energy

How does thyroid hormone relate to the Na+/K+ ATPase pump?

High thyroid hormone (T3/T4) increases the rate of the Na+/K+ pump

What condition is associated with increased body temperature from thyroid hormone effects?

Hyperthyroidism

What patient population commonly receives Digoxin?

Heart failure patients

What effect does Digoxin have on heart contraction and rate?

It strengthens heart contractions and slows the heart rate