Cell Memebranes T4 Flashcards
Most fluid CSM
- Increase prop of phospholipids w/ unsaturated fatty acid chains = kinks prevent closer packing + maintaisn membrane fluidty to maintain movement of subst across membrane
- Double bonded
- Increase Temp
3.Chosterol - C=C in fatty acid chains
Least fluid CSM
- Increase in proportion of phospholipids w/ saturated fatty acid chains
- Increase proportion of longer fatty acid chains
- Less C=C in fatty acids chains
As fluidity of CSM decreases, what transport least effected?
- Active transport
Why is dye evenley distributed in lipid belayer?
- Protein molecules in outer layer of CSM + those which span bilateral MOVE FREELY between phospholipid molecules.
Cells w highest proportion of single membrane bound structures?
- Goblet cells
Increase x bond helps to increase fluidity?
- C=C (carbon to carbon double bond)
- unsaturated fatty acids = bend fatty acid chain
- less tightly packed + less IMF between mols = MORE FLUID
Which sequence leads to viruses invading cell
- binding to glycoprotein receptor & endocytosis
Roles of cholesterol, glycoproteins, phospholipids and proteins
- regulates membr fluidity + converted to steriod H
- Cell recognition
- Seperating dissolved proteins
- Transporting ions through membranes
FLUID MOSIAC MODEL
- Fluid
- Phospholipid molecules differ
- Protein molecules scattered
- Different protein molecules
- pattern produced when scattered proteins arrange themselves in the CSM (when viewed from above)
Why are channel proteins IMPT in movement of water through CSM? (6m)
- Water mols are polar
- Few polar mol pass through phospholipid belayer
- Hydrophobic core
- Channels through X are hydrophilic
- increases permeability of membrane to water
- protein has quat ss + globular
- hydrophilic parts of protein face aqueous enviornemt
Endocytosis occur @ CSM (6m)
1 Attachment of bacteria to receptors
2 ability to attach to antibody (bound to antigen on bacterium)
3 infolding/invagination
4 membrane engulfs
5 form round bacterium
6 fusion —> formation of vesicle
Explain how features of phospholipids form a layer
- Polar
- Attracted to water/aqueous environment
- H+ bonding (polar head faces water)
- Non- polar/hydrophobic tails
- Repelled/away from water/aqueous environment
Role of channel proteins - 4m + description
- intergral intrinsic membrane protein (exterior hydrophobic)
- Channel allows polar/water soluble mols
- forms hydrophillic pores across membrane
- hydrophilic mol to pass through membranes
- facilitated diffusion + AT
- cellular recognition
Why don’t Ca+ ions pass though phospholipid biller- 3m
- Ca+ hydrophilic/ not lipophillic or lipid soluable
- Ionic
- Phospholipid belayer is hydrophobic
Describe how Ca+ ions move across membranes-5m
- Active transport
- Ca+ ions moved against their conc gradient
- Carrier protein
- Ca+ ions combine w/ binding site
- Carrier protein —-> conformational change/ATP
Describe function of lysosomes destroying bacteria
- lysosomes fuse w/ vesicles
- Form secondary lysosomes
- Lysosomes contain enzyme catalyse/digestion/hydrolysis
- Phospholipid/nuclei acid
- Peptide/ester bond
Functions of CSM
- Facilitated diffusion
- Endocytosis/excosytosis
- Cell recognition
- Barrier to polar molecules
How X ions + non polar move in CSM
- Active transport
- Carrier protein
- Pumped against conc gradient/low to high using ATP
- Binding to receptor site/conformational change
Describe how proteins become denatured @ high temp + leads to damaged CSM/
- Loss of tertiary SS// loss of AS shape/denatured
- Loss of globular structure
- Breakage of ionic/hydrogen/hydrophobic bonds
- Loss of function of membrane proteins
- Transport of polar molecules impaired
- Disrupts interaction between protein + phospholipid belayer
- Membrane becomes leaky/less partially permeable
Bulk transport vs exocytosis
- movement of large molecules s e.g proteins, polysaccharides, endocytosis/exco
- ATP needed for process
-1. Vesicle containing mol moves toward CSM
- membrane of vesicles fuses w CSM
2. Membrane engulfs mol inward
3. Membrane pinched off
4. ATP required
Suggest and explain what would happen to bacteria placed in solution w/ water potential more negative than cell?
- Cell cytoplasm/contents shrink
- Plasmolysis occurs/CSM peels away from Cell wall
- Movement of water out via osmosis
- Down water potential gradient/ high to low water potential
Low water potential = more negative
High water potential = more positive
Osmosis in plant cell: placed in pure water/negative water potential
- Plant cell placed in pure water/dilute solution
- Water enters plant via osmosis through ppm
- Pure water/dilute solution = high water potential than cell ‘(more NEG)
- As water enters vacuole of cell —> Vol of cell increases
- Expanding protoplast pushes against cell wall + pressure increases in cell
- In elastic cell wall prevents cell lysis in hypotonic sol
- Plant cell fully inflated w water—-> turgid fully
Osmosis Plant cells: concentrated solution
- Plant cell placed in concentrated solution w/ low water potential
- Water leaves vacuole cell via osmosis through ppm —-> vol of cell decreases
- Protoplast shrinks + no pressure exerted on cell wall
- Protoplast continues brining + pulls away from cell wall
- Plasmolysed/Plasmolysis - hypertonic solution
Osmosis Animal cell: Concentrated solution w lower water potential than cell
- Placed in conc sol w lower water potential then cell
- water will leave cell through ppm via osmosis
- Cell will shrink + shrivel up —>crenation/crenated
- Occurs in hypertonic environment, cell has lower solute conc
Animal cell:Isotonic
- Cell placed in isotonic environment/cell has same sol conc
- Movement of water in and out of cell occurs at same rate (no net movement of water)
- No change to cells
Cell signaling definition
- Molecular mechanism by which cells detect and reason to external stimuli, including communication between cells.
Example of ligand
- Hormone glucagon (released from pancreas) or adrenaline from adrenal glands.
Transport mechanism across CSM for oxygen
- Passive/simple diffusion
Transport mechanism for glucose,AA,ions,water
- facilitated diffusion
Protein involved in passive process =
- channel
- carrier (both)
Protein involved in active process =
- Active transport driven pumps/ sodium potassium pump
- Cotransporters
NO Protein involved and passive process=
- Osmosis/diffusion
NO protein involved in active process=
- Endocytosis/excoytosis/pinocytsosis
Name and explain the process by which water moves into the lumen
- osmosis
- increasing solute conc in lumen lowers water potential
- water moves from a higher to lower water potential down water potential gradient
Describe correct sequence of events in cell signaling pathway
- Protein receptor conformational change
- G-Protein activation
- Enzyme catalyses reaction
- 2nd messenger production
carrier proteins//intrinsic protein
- require energy
- go against the concentration gradient
- take substances from outside and pumps it inside or vice versa
- used for active transport
- interior = hydrophillic
Factors affectiong the rate of diffusion
STEEPNESS OF CONCENTRATION GRADIENT
TEMPERATURE
SURFACE AREA
NATURE OF MOLECULES/IONS
Water potential Ψ + factors affecting
-tendency of water to move out of a solution
-pure water has 0
-solutions have a negative Ψ
-how much water is in solution compared to the amount of solutes
-how much pressure is applied to it (by cell wall)
do plant cells and prokaryotes have cholesterol in their membranes?
plant cells have very little and prokaryotes do not, they both have another compound which does the same thing
how do glycolipids and glycoproteins stabilise the membrane structure?
- project into the aqeuous enviornment and form hydrogen bonds with water
- glycolipid= hydrophillic carbohydrate chain (made of monosaccharides)
what is glycolax?
sugary cell coating formed by carbohydrate chains on glycoproteins and glycolipids
- made of glycoprotein = ANIMAL CELLS
- made of glycolipids = PLANT CELLS
IMF interactions that drives bilayer formation when phospholipids added to water
- H+ stronger than IMF —> more energy needed to overcome bonds
- phospholipid CANNOT replace H+ w water lost due to lipid insertions
- Water makes cage like structure around lipid = bad as reduces freedom of water mol + number of H+
- forcing lipids into bilayer reduces this effect
Why would phospholipids dissolve in ethanol
- ethanol is mols hydrophobic chain + hydrophillic (OH) polar group
- phospholipid contain hydrophobic and hydrophillic parts = dissolve in ethanol
stem cell signalling
- Undiffrentiated
- exposed to chemical e.g hormone
- produces transcription factor
- binds to promotor region w/ DNA
- switches gene on + transcription
- Mrna leaves nucleur pore to ribosome for translsatoion = protein/polypeptide syntheized
- cell speciliased
Cell signalling: PEPTIDE
- PH binds to protein receptor on glycoprotein
- PH cannot cross membrane - hydrophilic
- Protein receptor undergoes a conformational change
- Activating G protein = releasing chemical activating enzymes in the membrane
- 2nd messanger//cAMP activates enzyme cascade
- amplifying signa; + where inactive enzymes become activated
-small product = transcription factor + squeeze though nucleur pore entering nucleus
Transcription factor movement
Binds to promotor region on DNA strand
- w/ rna polymerase
- forming transcription initation complex
- switching gene on by allowing transcription
- mrna produced + leaves through nucluer pore to cytoplasm –> bind to ribosome for translation
Cell Signalling: STERIOD HORMONE
- diffuses across membrane- hydrophobic
- binds to specific receptors in cytoplasm
- transcription factor
- forming transcription initiation complex
- switching genes on by allowing transcription
- mRNA produced + leaves through nuclear pore to cytoplasm –> bind to ribosome for translation
suggets how oestrogen causes breast cancer
- Oestrogen is SH affecting transcription
- binds to receptor in cytoplasm of target cells = transcription factor –> oestrogen recptor complex
- TF binds to promotr region that regulates cell division w/ RNA polymerase binding to PR
- transcriotion initation complex
- gene switched on = oncogene
- trnscritption = mrna produced + leaves via nucleur pore to cytoplasm
- binds to ribosome for translation = tumor
2 mol combing w cholestrol to form LDLs
- protein + lipids
Hypertonic condition
- More solutes outside the cell than inside
Isotonic
- Equal conc of solutes outside + inside the cell
Hypotonic
Fewer solutes outaide the cell than inside
Secondary AT
- AT of ions outside cell
- Creation of gradient across the membrane
- Ions move down conc gradient releasing energy (KE)
- Energy produced drives another mol to move from low to high concentration
- Electrochemical gradient needed
- Same direction, Secondary AT -** symport **
- Opposite direction- Antiporter
Primary AT
- Primary AT requires energy from ATP hydrolysis
- ATP→ ADP + P (breaking off end phosp group) release energy
- Moving Na+ out of the cell and K+ into the cell (Sodium potassium pump)
- Na+ low inside cell, K+ high inside cell
- Requires ion pump
- 3 Sodium out and 2 Potass in
Passive diffusion
Simple diffusion
FD w Carrier + channel protein
All cells share 4 components:
Plasma memb
Ribosomes
Cytoplasm
DNA
Which condition will result in more uptake of glucose into the intestinal cells after 90 minutes and why?
- 10 mM glucose + NaCl
- 10 mM glucose Na+ free
- Glucose uptake into intestinal cells occurs via SGLT1
- which relies on sodium to transport glucose against its conc gradient
-
Condition (10 mM glucose + NaCl) will result in more glucose uptake, as sodium is present to facilitate active transport.
2.** Condition (10 mM glucose, Na⁺ free)** will result in less uptake because the sodium-dependent mechanism won’t function efficiently.
What do you predict will be the concentration of glucose in the intestinal cells after 90 minutes in each condition?
- 10 mM glucose + NaCl
- 10 mM glucose Na+ free
- with sodium present, the SGLT1 cotransporter actively accumulates glucose against its conc gradient= increasing the intracellular glucose conc above the extracellular conc
- Without sodium, glucose uptake relies on passive transport mechanisms = equilibrates glucose conc across the memb.
- So the intracellular glucose conc will be closer to the extracellular conc in condition 10 mM glucose, Na⁺ free.
