Cell Biology Discoveries and Applications Flashcards
What do Cell-cell recognition proteins do?
Recognize other cells via a sugar molecule
What do intercellular joining proteins do?
Joins cells to other cells. For example, skin cells
What are the 2 main components of membranes?
Fluid mosaic and phospholipid bilayer
Hydrophilic substances pass through the membrane because the membrane is selectively permeable
Diffusion, facilitated diffusion through proteins, ATP pump (allows to move molecules against concentration)
What separates the cell from its external surroundings?
Plasma membrane
In the early days, why was the existence of the cell plasma membrane debated?
The membrane could net yet be visualized with microscopes.
Some claimed that the protoplasm could just stick together on its own, while others thought that membranes were secondary structures that the protoplasm formed upon contact with its external environment
When did the existence of the plasma membrane become fully accepted?
The beginning of the 20th century
What did Moritz Traube contribute to the acceptance of a cell plasma membrane?
In the 19th century, he perused the idea that there was an outer barrier of the cell.
He created the first artificial semipermeable membrane using droplets of glue in tannic acid.
What is osmosis?
The movement of water through a selectively permeable membrane into a region of higher solute concentration to equalize this concentration on both sides
What is hypertonic, isotonic, and hypotonic in relation to osmosis and blood cells.
Hypertonic: Solution has very high concentration of solute, causing cells to shrink
Isotonic: Solution is balanced with cells
Hypotonic: Solution has very low concentration of solute, causing cells to burst
What suggested that the outer membrane was made of lipids?
Isolated animal cells formed spheres in water
In the 1890s, 2 scientists demonstrated what?
Meyer and Overton shows that lipid-soluble chemicals were able to pass through cell membranes. They concluded that the membrane may be composed of phospholipids and cholesterol
Cell membranes are not like balloons. What do they facilitate?
Environment interaction and communication
What year did the electron microscope show that the cell membrane is a lipid bilayer?
1950s
What attributes of the phospholipid bilayer allow it to maintain a barrier between the internal and external?
Hydrophobic tails and hydrophilic heads
What do cholesterol molecules do in the phospholipid bilayer?
They enable membrane fluidity
In addition to allowing lipids to pass through the cell plasma membrane, ____ are also allowed to pass through
ions
What is membrane potential? When and who was it demonstrated by?
The difference in electric potential between the inside and the outside of a biological cell.
In 1910, Rudolf Hober measured the electrical charge on the inside and outside of cells
How do ions and other molecules move across the cell plasma membrane?
The membrane contains special protein transporters
The plasma membrane contains many embedded _______ and ________ that perform many functions like being receptors and transporters
proteins, molecules
What is the current model that describes a cell membrane?
Fluid mosaic
What makes the membrane fluid mosaid?
Fluid because molecules move freely past one another
Mosaic because of the diversity of molecules in the membrane
When, who, and what demonstrated membrane fluidity?
In 1970, Frye and Edidin labeled 2 cells with dye and watched as the two dye populations mixed
Cell membrane are composed mainly of what?
Lipids and proteins
What do proteins do in the phospholipid bilayer?
Regulate traffic across the membrane and perform other functions
What are two ways substances can move across the membrane?
Passive transport - Requires no energy
Active Transport - Requires energy in the form of ATP
What are 2 ways substances move across the membrane with passive transport? Briefly describe them
Diffusion: Hydrophobic and small uncharged polar molecules diffuse through the lipid bilayer
Facilitated Diffusion: Hydrophobic substances diffuse through the membrane with the assistance of transport proteins
With facilitated diffusion, what are the 2 types of proteins that can help with it? Briefly describe them
Channel Proteins: Leaves an open channel for substances to move through
Carrier Proteins: Can open and close and let through only a little bit of the substance at a time
Describe how active transport works
Transport proteins actively pump substances against the concentration or electrochemical gradients. This requires the input of energy
What is osmosis?
The movement of water across the membrane via diffusion or facilitated diffusion
Nerve cells send what down their axons?
Electrical impulses/signals
At the end of a neuron, electrical signal is converted into what?
Chemical Signal or Neurotransmitter
What is the electrical signal passed down in a neuron caused by? How does the signal move down?
The movement of ions through specific transporter proteins in the membrane. The signal moves down by the controlled opening and closing of ion transport channels. (Na goes in, K is pumped out)
What is chemiosmosis?
The movement of ions across a semipermeable membrane down their electrical and chemical gradient
Who and when proposed the chemiosmotic hypothesis?
Peter Mitchell in 1961
What is the chemiosmotic hypothesis?
The movement of protons (H+) down their electrochemical gradient across a membrane can drive the formation of ATP through ATP synthase protein. Protons can also be used to power the rotation of flagella in bacteria
What is reverse osmosis?
A water purification process that uses a partially permeable membrane to separate ions, unwanted molecules, and larger particles from drinking water
What is reverse osmosis used for?
Water desalination, maple syrup production, low-alcohol beer production, fruit juice concentrate
What happens in Cystic Fibrosis?
Airways accumulate thick mucus, making it difficult to breathe. Recurring lung infections can result in lung scarring
What is Cystic Fibrosis caused by?
Mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. This gene makes the CFTR membrane channel protein that transports chloride ions in and out of the cell
Where the the CFTR protein produced?
Cells that produce mucus, sweat, saliva, tears, and digestive enzymes
Why is the transport of chloride ions important in the CFTR protein?
It helps control osmotic movement of water in tissues
When happens when CFTR is not functional?
Mucus-producing cells produce abnormally thick and sticky mucus, which can obstruct airways and glands. This happens because water moves only into cells due to the osmotic pressure
