Chapter 6b-f, Cellular Membrane Flashcards
Functions of Cellular membrane and it's components
What is the boundary that separates the living cell from its surrounding
The plasma membrane
What is special about the plasma membrane?
It exhibits selective permeablility.
Selective permeabilty:allows some substances to cross it more easily than others
What is the basic scturcutre of the cell memebrane?
The phospholipid bilayer
If poreins and carbohydrates are part of the membrane compostion, making it a what?
Mosaic
What force does phospholipid use between the fatty acid tails of one another
van der Waal forces
Are membrane lipids able to move in plane of the membrane
Yes, that makes the membrane more fluid and dyamic
What is most of the movement found on the lipid/protein layer of the membrane
Lateral movements, but some movements vertically (flip-flop) traversely across the membrane
Why are flip-flop movemnets way less frequent if thye cytoplasmic and extracellular sides are polar?
Difficult to cross the hydrophobic inner layer if surroundings is polar, the hydrophillic head must cross the hydrophobic layer which is difficult
Which plasma membrane componetn can be either found on its surfrace or embedde in the membrane structure?
Proteins
What are the types of membrane proteins? Where are they located?
Peripheral Proteins: bound to the surface of the membrane.
Integral Proteins:penetrate the hydrophobic core.
Transmembrane Protein: Integral proteins that span the membrane.
How cna the proteins be anchored in the lipid bilayer
Thep ortein can contain both hydrophillic and hydrophobic amino acids. Which allows the protein to slot it’s self into the membrane, allowing it to anchor its self to both polar and non polar regions of the membrane
What are the 6 functions of the membrane proteins
1.Transportation
2.Enzymes
3.Receptors
4.Cell-Cell recognition
5.Intercelluar Joining
6. Attachment Proteins
Describe the six functions of membrane proteins
1.Transportation
-Channel and carriers allow substances to move through the plasma membrane
2.Enzymes
-Increases/speeds up the speed of the reaction
3.Receptors
-Able to detect signaling molecule such as a hormone, or a neurotransmitter and binds to signaling molecule and undergoes signal transduction
4.Cell-Cell recognition
-Can invovle proteins and carbohydrates, An example is a chain of carbohydrates used to be detected as a tag. Specific proteins can recognize this “tag” and signal a specific reponse/interaction
5.Intercelluar Joining
-Can hold cell together. Such as tight junctions
6. Attachment Proteins
-hold the cytoskelton to the associated extracellular matrix
-Extracellular matrix is formed by collagen and other proteins. Parts of this matrix can bind to attachment proteins
These attachment proteins then bind to the cytoskeleton on the other side, creating a thrid but firm structure. Cytoplasm is then supported by cytoskeleton and outside with extracellular matrix.
What are the functons of carbohydrates in the cell membrane
Bonding covalently to proteins or lipids to form (Glyoproteins and Glyolipids)
Located on the exteral side of the plasma membrane and varies in size amoug species,individuals and even cell types in a indvidual
Carbohydrates plays an imporant role in cell-cell recognition
Cells recognize each other by binding to the surface molecules, often carbohydrate, on the plasma membrane.
What is permeability refer to?
To the rate of passive diffusion of molecules across the membrane
What is the fluditiy of the cell?
Fluidity refers to the ability to move molecules in the membrane, and the viscosity of the cell membrane.
How can the fluidity and permeabiltiy of the plasma membrane change?
It can change depending on its compostion and the enviorment.
Can be affected by the diffusion of proteins and other molecules inside cells, thus affecting their function.
This property can be affected by phospholipid strucutre,cholesterol compostion in the membrane and the tempature
Membrane fluidity can affect membrane permeability
What plays a huge impact on membrane permeability
Transport proteins associated with the membrane
What is the function of cholesterol in animal cell membranes
At warm temperatures, cholesterol decreases membrane fluidity by restraining the movement of phospholipids.
At cool temperatures, cholesterol increases membrane fluidity by preventing phospholipids from packing tightly
Acts as “buffer”
What is the polarity of Cholesterol
Cholesterol is amphipathic: has a hydrophillic hydroxyl group and a hydrophobic region of interconnected carbon rings
How do fatty acids effect membrane fluidity?
Fatty acids vary in length of hydrocarbon chains as well as in the number and location of double bonds
Which membrane is more fluid? One with short or long fatty acid chains and why?
Short fatty acids create less thick plasma membrane than longer fatty acids chains. They also have less van der Waal forces between the hydrophobic tails.
Which membrane is more fluid? One with saturated or unsaturated fatty acid chains and why?
Unsatured fatty acids chain are more fluid due to more space betwen the chains, less dense overall and thus becomes more fluid
What has a direct impact on membrane permeabiltiy?
Transport proteins have a direct impact on membrane permeability because they facilitate the diffusion of hydrophilic substances and large molecules
What is diffusion?
Diffusuion is the tendency for molecules to spread out evenly to the available space.
How does diffusion work?
It is the diffusion of the population of molecules that may exhibit a net movement in one direction.
Movement is from higher to lower concentration / along the concentration gradient
It is a dynamic equilbrium, many molecules cross both ways. Overall is no movement
What substances would easily pass though the lipid bilayer of the plasma membrane?
Hydrophobic/non polar and small molecules like O2 and CH4
Big molecules with hydrophillic functional groups or Ions will not travel through like Sucrose or Salts
Water does not count, it does passively diffuse into the cell, but not at a rate that is needed. Uses proteins to move the water
What are the types of diffusion?
Simple diffusion:no transport protein is invovled, Small hydrophobic molecules usually cross the membrane through passive diffusion. Ex: O2,CO2,CH4
Facilitated diffusion:transport proteins speed and/or allows the movement of molecules across the membrane. Ex:Glucose
What are transport proteins and what are the two kinds?
Channel proteins have hydrophilic channels that certain molecules or ions can use as a tunnel.
Carrier proteins bind to the molecules and changes the shape to shuttle them across the mumbrane.
Transport proteins are proteins that help faciliate transport across the membrane when there are natural restrictions.
What is passive transport? What are the three examples?
Passive transport is defined as the movement of molecules across a selectively permeable membrane without the use of energy.
Includes simple diffusion, facilitated diffusion and osmosis.
Simple diffusion and facilitated diffusion refer to the movement of solutes. Solutes diffuse down (or with or along) their concentration gradient (so substances move from an area of high concentration to an area of low concentration).
What is osmosis?
Osmosis is the diffusion of water across a selectively permeable membrane. Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration.
How is water moved through the membrane?
Moves across the membrane slowly. Use Aquaporins (channels) in the membrane. (small pores or openings for water molecule)
What is tonicity?
The ability of a solution to cause a cell to gain or lose water comparatively.
What are the three tonics?
Isotonic: solutions have equal solute concentration comparatively
Hypertonic: solutions have higher solute concentration comparatively
Hypotonic: solutions have lower solute concentration comparatively
What happens with a cell without a cell wall when placed in an isotonic, hypotonic and hypertonic solution in relation to the cell’s intracellular environment?
Isotonic: No net water movement across the plasma membrane (cell remains the same)
Hypotonic: Cell gain water (cell lyses/grows until bursts)
Hypertonic: Cell loses water (shirvels/crenates)
How do cell waters maintain water balance?
A plant cell in a hypotonic solution swells until the wall opposes uptake: the cell is now turgid(firm)
If the cell and its surroundings are isotonic, there is no net movement of the water in the cell; the cell becomes flaccid and limp
In a hypertonic environment, plant cells lose water; eventually, the membrane pulls away from the wall, a usually lethal effect called plasmolysis
What is active transport?
Active transport moves substances against their concentration gradient
This requires energy, usually in the form of ATP
Active transport is performed by specific carrier proteins embedded in the membrane
Active transport allows cells to maintain concentration gradients that differ from their surroundings.
What is secondary active transport?
Active transporters can drive the transport of molecules through a different transporter through the creation of an electrochemical gradient
What is an electrochemical gradient and how can it be achieved
ECG is the gradient of charge and concentration of compounds between the inside and outside of the cell. Formed from chemical carriers
Can be achieved with the help of carriers and ATP, creating a charge disparity between the outside and inside of the cell.
