Membrane transport Flashcards
What does the phospholipid bilayer descibe?
The arrangement of cell membranes into a hydrophobic region and hydrophilic regions.
What is the hydrophobic layer of the cell membrane made of?
Amino acid chains (fats)
What is the hydrophilic layer made of?
Phosphorus molecules.
What are integral membrane proteins? Are they polar or not?
Integral membrane proteins are proteins that traverse the full thickness of the phospholipid bilayer. They have some hydrophilic (polar) and hydrophobic (non-polar) regions.
What are the proteins attached to the edges of the phospholipid bilayer?
Peripheral proteins
Give some examples of peripheral proteins.
a receptor on the cell surface or an enzyme facing the cytoplasm
What are cytoskeletons made of?
Fibers in the cytoplasm.
What is the sugar coating or carbs located on the outside of a cell called? What is its purpose?
It is called the glycocalyx. It allows cells to recognize each other.
What does cholesterol do? What happens when there is too much of it in a cell?
Cholesterol helps maintain structure and reduce fluidity. Too much cholesterol can make cells lose their felxibility.
Define a junction.
Modifications of the plasma membrane that perform important functions.
What are the 3 types of junction?
Tight junctions, desmosomes, Gap junctions.
What are tight junctions good for? How are they described?
Tight junctions are fusion of adjacent membranes. They prevent the passage of molecules.
What are desmosomes? What are the three parts of a desmosome that help it function?
Desmosomes are anchoring junctions. The two membranes are bound together by linker proteins, held in place by plaques (thicker plates of cell membrane), which is supported by keratin filaments inside the cytoplasm.
What is a gap junction molecule called?
A connexon
What junctions are electrically exciteable?
Gap junctions.
List the 6 functions of these membrane proteins.
- Transport
- Enzymatic activity
- Receptors for signal transduction
- Intercellular joining
- Cell-cell recognition
- Attachment to extracellular membrane
Define interstitial fluid
It is a filtrate of blood that contains salts, sugars, amino acids, vitamins, hormones, and gases.
What three things must a cell do to maintain homeostasis?
Extract materials from outside the cell, keep materials inside the cell, and discard waste from inside the cell.
What are the three types of passive transport?
Simple diffusion, facilitated diffusion, and Osmosis
What are the three influencers of diffusion?
- The concentration gradient
- Molecule size
- Temperature
What types of molecules take part in simple diffusion?
Lipid soluble molecules.
In what direction do molecules move in simple diffusion?
Down the concentration gradient.
What are the 4 characteristics of facilitated diffusion?
- There are specific transporters for simple molecules.
2, It does NOT require ATP - It is limited by carrier/channel saturation.
- It moves down the concentration gradient.
What are the two types of facilitated diffusion?
Channel mediated and carrier mediated.
When will a molecule by carrier mediated?
When the molecule is too large to go through a channel.
What is a common molecule that is carried into the cell in facilitated diffusion?
Glucose
Why may cell membrane channels be specific?
Pore size and the amino acids might be polarized.
What are leaky channels?
Channels that are always open.
What are three characteristics of channel mediated transport?
It can be inhibited, show saturation, and is specific to groups of ions/ ions.
What is osmosis?
The diffusion of water towards areas of lower water concentration.
What are aquaporins?
Channels on cells that can transport water.
What is the definition of osmolarity?
It is the concentration of solute particles.
What is the definition of tonicity?
The ability for a solution to change a cell shape when bathed in solution.
When is a solution hypertonic? What will happen to a blood cell in hypertonic solution?
Hypertonic solution has a lower water concentration, and will cause a red blood cell to shrivel up.
What kind of solution will water move out of?
It will move out of a relatively hypotonic solution.
What is it called when the inside and outside of a cell have the same water/solute concentration?
Isotonic.
Out of ionic and molecular bonds, which molecules will have greater osmotic power?
Dissociated ionic bonds will have greater osmotic power.
how many mosm of tonicity will a 1M glucose solution have?
1mosm
how many mosm of tonicity will a 1M NacL solution have? Take in Na dissociates into a 1+ ion and Cl dissociated into a 1- ion.
2mosm
what is the percentage of saline in isotonic solution?
0.9% NaCl is isotonic saline
What are the two reasons active transport may take place?
- The substance is too large for pores and is lipid insoluble.
- Ions or molecules are moving against the concentration gradient.
Do active transport systems require a specific carrier?
Yes
What are the two types of coupled active transport system?
Symports and Antiports
What is the difference between a symport and an antiport?
A symport moves substances in the same direction, an antiport moves things in different directions.
What is the difference between primary and secondary active transport?
Primary active transport uses ATP to run a pump to maintain a concentration gradient. Secondary AT is a passive diffusion, but is facilitated by a pump on another region of the cell membrane.
What is the ratio of sodium to potassium movement in the NA/K/ATPase pump?
3 Na+ ions leave and 2 K+ ions enter the cell for every cycle.
What is vesicular transport?
The movement of substances in vesicles.
Explain the difference between exocytosis and endocytosis?
Exocytosis is the movement of substances out of the cell, endocytosis is the movement of substances into the cell.
When vesicles approach the cell membrane in exocytosis, what happens to the cell membrane? What are the recognition molecules called on the vesicle vs the cell membrane?
The vesicle membrane fuses into the cell membrane. V cells are on the vesicle and recognize T cells on the PM.
During endocytosis, what happens to the surface area of the receiving cell membrane?
It engulfs the particles then pinches off, losing surface area.
Where does phagocytosis happen? What does it describe?
Phagocytosis is the endocytosis of bacteria, debris, etc. By phagocytes
What is “cell drinking” (the endocytosis of substances dissolved in fluid)?
Pinocytosis
What is the type of endocytosis that deals with hormones, enzymes, and important macros? Hint: The PM has special receptors.
Receptor-mediated endocytosis.
What do neurons do?
