B2.1 (Cell Membrane Transport) Flashcards
Define polar
has a charge
Why is oil hydrophobic like a cat
Because it is non-polar and water is polar
Why is the phospholipid head exposed to the water outside of the cell
Hydrophilic because polar
What is the difference between micelle and liposome?
Micelle - 1 layer
Liposome - double layer — BIlayer
What is the integral protein
The protein that penetrates from the outside to a bit of the inside
What is the peripheral protein according to the model?
The one on the surface — “peripheral”
What is the yellow thing attached to the phospholipid tail in the Fluid - Mosaic Model?
Describe integral proteins on terms of location type and polarity
Polarity hydrophobic - non polar.
Location: embedded in the hydrocarbon chains in the center of the membrane (the layer of hydrophobic tails)
- Because phospholipids contain long hydrocarbon chains so that they could be polar (?)
- Integral proteins extend across the two phospholipid layers OR into one of the two — either way, they’ll have to reach the tails.
Type: Transmembrane (like transitioning between membrane layers) because they extend across the membrane with hydrophilic parts projecting through the regions of phosphate heads on either side
- Because they meet the second layer of the phospholipids — they touch the surface.
Describe peripheral proteins on terms of polarity and location
- Hydrophilic
- Hence, they are on the surface of the membrane
- Location: NOT embedded/integrated WITHIN the membrane because they are attached to the surface of integral proteins — their attachment is often reversible
What is the purpose of protein on terms of TRACIE.
- Transport: acts as a channel/passage (protein channels) way for non-polar molecular to enter the hydrophilic/polar heads
- The two types of protein transport:
- the molecule can pass through without ATP = facilitated transport = PROTEIN CHANNELS
- with ATP = active transport = protein pumps
- Receptors
How does the cholesterol connect to the phospholipid
hydrophilic head to hydrophilic head, hydrophobic tail to hydrophobic tail
Describe how the cholesterol affects the membrane’s fluidity
Function 1: Reduces membrane fluidity by restricting the movement of phospholipids and other molecules
- when subjected to high temps, the phospholipid tails may move and cause a higher but more unstable state of membrane fluidity. Cholesterol “fills in the gap” or acts as a “buffer” to maintain membrane fluidity
Function 2: increases flexibility by restricting the regular packing of the hydrocarbon tails of phospholipid molecules.
- Why?: It prevents tails from crystallizing and thus the membrane from behaving like a solid
- This is due to if the cell membrane is lowered in temperature, the phospholipids will not move and come packed together. The cholesterol then makes the cell membrane more flexible/fluid by giving them space.
-> Function 1 and 2 pertain the cholesterol occupying the phospholipid tail
Function 3: reduces the permeability to hydrophilic/water soluble molecules and ions such as sodium and hydrogen
- cholesterol is non-polar with a hydrophilic head (ig so it could be attached to the phospholipid head for the functions?)
Define diffusion
The molecules move to high to low concentration with no usage of ATP
Define osmosis
diffusion of water
Explain phagocytosis
Purposes: to let bigger molecules in, can also be for letting things inside the cell
- why also bigger molecules?: Because there may be some molecules that the proteins cannot let pass due to their size.
Process: The cell membrane surround the molecule in a vacuole and the lysosome uses digestive enzymes either to kill it or to break it down into smaller molecules that could enter the cell
Explain “monotopic” and “polytopic”. Give what types of proteins are under each.
Polytopic - poly = many, topic = surfaces.
- For proteins that touch many surfaces: Integral ONLY
Monotopic - mono = only, topic = surface
- For proteins that just touch a single surface: Polytopic AND/OR Peripheral proteins
- REMINDER: Polytopic does run across the two layers BUT they do not necessarily touch all 2 surfaces.
Describe glycoproteins
Definition: Proteins that HAVE oligosaccharide chains attached (“oligo” = few and “saccharides” = sugar)
Purpose: Cell recognition by immune system (detecting if the substance entering is harmful or not to the cell) and hormone receptors (i.e. the R in TRACIE)
Describe the anatomy of a cholesterol
Explain the membrane’s fluidity and why it is important to regulate the fluidity
Highlights:
Characteristics of membrane fluidity:
- Hydrophobic tail like liquid but hydrophobic head like solid.
- Therefore, not sure if the membrane is truly solid or liquid but it is fluid
Why is it important to regulate the fluidity:
- flexibility/mvmt.
- permeability
Outline the similarity and difference between phagocytosis and pinocytosis (DOUBLE CHECK)
Similarities
- lets substances in or out of the cell
Differences
- pino. = liquid
- phago = solids like pathogens
Outline the similarities and differences between active and passive transport
Similarities
- They transport thongs in and out of the cell
- Both use proteins
Differences
- (Passive and under it, the facilitated): Needs no energy — protein channel
- (Active) - needs energy/ATP (aka the energy currency) — protein pump (bc remember it changes the shape of the passage way like a pump?)
What is the difference between plasma and cell membrane?
Outline the composition of a phospholipid (ADD DRAWING)
1.) Phosphate head
- polar
2.) Fatty acid tail
- non-polar
How to find the SA:V ratio of a cube
Divide the surface area by the volume.
**SURFACE AREA of a cube **: 6a^2 where a = length of one side of the cube
**VOLUME of a cube **: V = a^3 where a = length of one side of the cube.
Are lipids proteins or fats
fats
Why do the mitochondria and chloroplasts react to antibiotics
Because they were prokaryote cells (the Endosymbiotic Theory)
Draw a phospholipid bilayer (add photo)
- tails should be thin
- heads should be close
What are the lipid components
- fatty acid
- glycerol
Define the main characteristic of fluid and give examples
a substance that has no fixed shape and things can move around in it
e.g.: cell membrane.
Are protein pumps and channels integral or peripheral proteins?
They are integral because they transport particles in and out of the cell
Give the function of glycoproteins
For communication with other cells and cell recognition by immune system
Describe the model of the Davson-Danielli Model
-
protein-lipid sandwich (double layered — correct but not all)
-> They do not recognize integral nor peripheral proteins. They just sit on top of the phospho heads because they don’t permeate the lipid bilayer
-> Because of this, the proteins coat outer surface
Describe how water moves in osmosis
Along the concentration gradient (meaning in consideration of concentration of solutes)
- low to high
- unlike simple diffusion (high to low,)
Does water have concentration?
No
Define simple diffusion
The movement of molecules from high concentration to low concentration
Outline the different types of passive transport
Simple diffusion, osmosis, facilitated diffusion
Differentiate between facilitated diffusion and simple diffusion
Simple diffusion
- Mvmt. of molecules directly through the lipid bilayer
Facilitated diffusion
- through a protein
-> Thus facilitated
What dictates if a type of transportation is active or passive
The concentration gradient and if they are going against it (active)
-> for active transport: it is like rowing against a lake current
-> for passive transport: it’s like floating along the lake current
What are the core of the membrane and its permeability
hydrophobic hydrocarbon chains (phospholipid tails)
- higher (?) permeability to large and hydrophilic molecules
- low permeability to ions and polar molecules
Why can’t really big molecules pass through the membrane w/o proteins/help?
because the distance between the heads are small
What does the cell need for nutrition (to go in and out)
sugar, amino acids, fatty acids, vitamins
How does oxygen and carbon get inside the cell
They’re small enough to pass through the cell membrane
Why are nutrients sent out the cell?
To send to other cells
Define aquaporins
Protein channels for water
- so ig osmosis is also facilitated diffusion?
- (prob need proteins because of the polar charge whereas the charges of the ones that go through simple diffusion are non-polar)
What are antigens
enemies of the body — harmful to us
- e.g. harmful pathogens like bacteria
Describe bulk transport
Active transportation,
- What does it transport?: transports solids and/or liquids by vesicles at the plasma membrane
- pinocytosis
- phagocytosis
-> endocytosis + exocytosis basically
-> stores things in vesicles + endo + exocyt can take in large quantities or large molecules thus bulk
What do we mean when we say membranes are fluid mosaics
- phospholipid bilayer = fluid portion
- flexible, allowing for cellular shape changes
- proteins attached to cytoskeleton
Describe receptor proteins
- binds to specific external molecule that triggers a change in the cell
- can be integral or peripheral
Describe enzyme protein in the cell membrane
- promotes chemical reactions (make them very fast)
- integral/peripheral
- can be ATP synthase
What are the charges of the molecules that use simple diffusion?
Non-polar
- they get through the phosphate heads (which are polar) through following the concentration gradient (simple diffusion)
Define osmolarity
measure of solute concentration
Define hypertonic
When a solution has high solute concentration
Define hypotonic
Low solute concentration (loses water)
Define isotonic
same solute concentration (no net flow)
Outline the three measurements of osmolarity
Hypertonic, hypotonic and isotonic
Describe carrier proteins [3]
Definition: Integral proteins that facilitate the transport of ions and biomolecules (e.g. sugar) across the cell membrane between cells or organelles
Active or Passive: Can be both.
Process: Molecules bind to the binding site. Then, the protein undergoes a conformational change and then the molecule enters the other side of the membrane (outside or inside the cell)
Differentiate carrier proteins vs channel proteins
Channel proteins have pores but Carrier proteins have binding sites
Give an example of carrier proteins
sodium-potassium pump
Describe what is a voltage-gated channel
Type of channel protein that opens or closes in response to changes in the membrane potential (voltage) of a cell.
- Seen where?: used to generate action potentials in cells such as neurons and muscle cells
- the opening and closing regulated by changes in electric charge (voltage-gated)
Describe gated-ion channels (add photo)
Broad category of channel proteins that open or close accoridng to specific signals
e.g.: voltage-gated channels, thermally gated channels etc
Define symport and antiport
Symport - both molecules move the same direction
Antiport - molecules move in opposite direction
How many sodium and potassium get transported in the sodium-potassium protein
3 sodiums exit, 2 potassium ions enter
creates a stable electrochemical gradient.
WHY DOES SIMPLE DIFFUSION ONLY HAPPEN TO SMALL AND NON-POLAR PARTICLES
Non-polar:
- hydrophobic centre of the membrane bc of the hydrocarbon tail
Small:
space between the phospholipids are small
Describe channel proteins (BOOK)
- lets ions + polar molecules to pass through
- can be diff directions
- usually lets higher -> lower so theres a net concentration, goes along concentration gradient
- facilitated diffusion, passive transpo (no energy expended)
- diameter and chem properties DETERMINE one type of particle to pass through (e.g. sodium ions or potassium ions)
Liquid-ordered phase
Differentiate between carrier proteins, protein pumps and channel proteins
Carrier proteins
- 2 types: active or passive
- has binding sites
- conformational change
Protein Pumps
- kind of carrier protein
-> conformational change
-> active type
Channel proteins
- do not do conformational change
- passive only
- along conc. gradient
What makes protein pumps go thru conformational change?
The hydrolysis of ATP (to ADP + Pi) causes a conformational change in the protein pump
ATP allows the membrane proteins to change shape.
Define conformational change
change in the shape of a macromolecule (e.g. protein)
