Ch 5 Flashcards
What does it mean to be amphipathic and give an example
Both hydrophobic and hydrophilic regions
Ex: phospholipids + membrane proteins
What are lipid rafts
Proteins associated in specialized patches of lipids
Membranes are held together mainly by __
Hydrophobic interactions
Fluid mosaic model function
Acts for passage of things into and out of cell and communication between cells
Some proteins are immobile; what does immobile mean?
Attached top cytoskeleton or extracellular matrix
Membrane fluidity depends on __
Temp and saturation of fatty acid chains
Difference between unsaturated tails and saturated in membrane fluidity
Unsaturated = prevent packing
Saturated = tails pack together
Function of cholesterol in fluidity
Reduces fluidity at high temperature
Decreases temp for solidification
Fluidity Modulation: At lower temperatures, cholesterol prevents the fatty acid chains of phospholipids from packing too closely together, thus maintaining fluidity. At higher temperatures, it can help to restrain excessive movement, preventing the m
How do lipid composition vary with colder and higher temp
Colder = more unsaturated phopholipids
Higher = unique lipids which decrease fluidity
Embedded at least partially in hydrophobic region ___
Integral proteins
Bound to the surface of the membrane
Peripheral proteins
Membrane protein functions (6)
- Intercellular joining
- Attach to cytoskeleton and extracellular matrix
- Enzymatic activity
- Signal transduction
- Cell-cell recognition
- Transport
Short branched carbohydrate chains used to create
Glycoplipids and glycoproteins
Glycolipid and glycoproteins functions
- Sort cells into tissues and organs
- Recognition of self vs non-self: immune system
Membrane layers differ in (2 things)
- Lipid composition
- Direction of inserted proteins
Where and when is the arrangement of membrane lipids and proteins determined
During synthesis in the ER and GA
Selective permeability meaning
Allow passage of some substance, but not others
Is it easy for nonpolar molecules to dissolve in lipid bilayer and why
Yes
Nonpolar molecules share similar chemical properties with the lipid tails of the phospholipids, allowing them to integrate seamlessly into the bilayer. T
How are ions and polar dissolve in lipid bilayer
Water crosses slowly and larger molecules even more slowly
Meaning of passive transport
DOES not use energy
How does substance concentration move in passive transport
High concentration to low
What is the difference between diffusion and osmosis
Diffusion = movement of particles
Osmosis = movement of water
Dynamic equilibrium meaning
Equal movement in either direction across membrane
How does the movement of diffusion differ from osmosis in regards to concentration gradient
Diffusion = move from high to low region
Osmosis = move from high (low solute) water to low (high solute) water concentration
Tonicity meaning
Ability of soln to cause cells to gain or lose water
Tells us what happens to cell when they are put in different solution
3 diff solution in tonicity
- Isotonic
- Hypertonic
- Hypotonic
This solution means the outside solution has the same amount of stuff (like salt) as the inside of the cell. Water moves in and out equally, so the cell stays the same.
Isotonic solution
outside solution has less stuff than the inside of the cell. Water moves into the cell, making it swell like a balloon, and it might even burst!
Hypotonic solution
When water moves out of the cell, cell volume decreases (shriveling, what is this process called
Crenation in RBCs
solution has more stuff than the inside of the cell. Water moves out of the cell, causing it to shrink like a raisin.
Hypertonic soln
What is this process called, when water enters cell and cell volumen increases = cell burts/lysess
Hemolysis
Osmoregulation meaning and examples
Ability of cells to protect themselves from extreme water loss/gain
Paramecium
Contractile vacuoles
What is turgor pressure
When cells with walls exert pressure back against water trying to move into a cell
Facilitated diffusion is aided by )___ and what does it mean
Transport proteins
Span memb to allow passage of polar and charged molec and ions
S
T or f, facilitated diffusion is not passive transport
False, it is bcs no energy input
___ channel that allows passage of polar and charged molec
Hydrophilic channel
__ channel that allow passage of specific ions
Ion channel,
what are carrier proteins and give one example
Bind to specific molec, ion, change shape and release on other side of the membrane
Ex: glucose transporter
What is membrane potential caused by and what is its function
By uneven distribution of anions (-) and cations (+)
This favours passive transport of cations into the cell and anions out
Electrochemical gradient is determined by
Both chemical gradient (concentration) and membrane potential (electrical)
Active transport meaning + characteristics
Moves substance against concentration gradient
1) involves carrier proteins
2) uses energy
A type of transport protein that produces voltage across a membrane as it moves ions
Electrogenic pump
Give 2 examples of electrogenic pump
- Sodium potassium pump in animals
- Proton pump in other organisms
Proton pump movement
Moving against chemical and electrical gradient
Pumps hydrogen from internal to external
Creating higher positive charge outside the cell
Cotransport meaning
Couples the transport one substance down its electrochemical gradient and one against
why is it called cotransport
Gradient created by hydrogen pump is often coupled with a transported for larger biomolecules
T OR F: bulk transport does not need active transport
False
Meaning of bulk transport + give 2 examples
Movement of large quantities across the membrane in vesicles (rather membrane proteins0
1) endocytosis
2) exocytosis
What is exocytosis and where is it formed
Contents released to external space
= vesicles move to cell membrane, merge with it and release contents outside the cell
Formed in golgi apparatus
Endocytosis meaning and give 3 kinds
Formation of vesicles from cell membrane for extracellular substances (bring materials into the cell)
1. Phagocytosis
2. Pinocytosis
3. Receptor-mediated
Phagocytosis function
Cell engulf (eat) external particle by extending pseudopodium around it
Pseudopodium wrap around entire particle creating a food vacuole
In phagocytosis, where does food vacuole fuse to
Fuses to lysosome to digest contents
Pinocytosis meaning
Form of internalization in which vesicles are filled with extracelullar fluid
Cell “gulps” up fluid
Coated with proteins
Specialized form of pinocytosis which is specific to a certain substance is called
Receptor-mediated endocytosis
How does receptor mediated endocytosis work
Protein receptors bind to substance and are then internalized into the vesicle
Two major divisions of cell signalling
1) direct cell contact (local)
- inhibits growth of cells (contact inhibition)
- recognition of cell surface molecules (ex: immune system)
2) chemical signalling (local or long distance)
Long distance signaling uses __
Hormones
2 forms chemical signaling works
1) a chemical signal in extracellular fluid interacts w/ receptor of target cell
2) a chemical signal enters the cell and interacts w/ intracellular receptor
3 stages of cell signalling and give its brief meaning
1) reception: binding of chemical signal to receptors
2) transduction: series of stacking of chemical rxn
3) response: action that happens in the target cell
Molecule which binds to another molecule in reception
Ligand
Ligand binding results in __
Receptor activation & induction of a cascade of cellular events
Where is intracellular receptors located
In the cytoplasm or nucleus of the target cell
How does intracellular receptors work
by receiving signals inside the cell, interacting with DNA, and regulating gene activity to produce a specific response.
= acts as transcription factors and carry out transduction part of the pathway
How does signal transduction work and what step is this and what does it allow
2nd step
= this turns signal into a form that create specific cellular response
= allows
A) amplification
B) coordination
C) control of signal
Signal transduction involves the work of __ (3)
- Protein kinases
- Protein phosphatases
- Secondary messengers
What does cellular response cause
- Activation or deactivation of one or more cellular processes
What does cellular response regulate
Regulate
1) protein synthesis ( growth factors)
2) protein activity (metabolic enzymes)
