Chapter 5 - Membrane Structure Flashcards
What is selective permeability?
Selective permeability is easy permeability for some but not all substances.
Why is selective permeability important to cells?
It allows them to control what substances go in and out during chemical exchanges
What does amphipathic mean?
Has both a hydrophilic and hydrophobic side
T or F: The tails of a phospholipid are hydrophobic
True
What is the role of cholesterol in the cell membrane?
Provides fluidity - restricts movement at high temperatures so they stay together, hinders close phospholipid packing at cold temperatures - keeps it from becoming a gas/being too fluid or from solidifying
Cells can change the ratio of saturated to unsaturated fatty acid tails in their phospholipid bilayers based on their environment. how is this good?
they can maintain the optimal amount of membrane fluidity - if it’s too cold, add more unsaturated, if it’s too hot, add more saturated
Why add saturated fats in hot weather?
They can pack together more tightly because of their lack of a double bond, so they can solidify more easily and aren’t excessively fluid
Why add unsaturated fats in cold weather?
They can’t pack together as tightly because they have a double bond between carbons, forming a kink. This means they don’t solidify as easily.
What does a glycoprotein look like and do?
It’s on the extracellular part of the bilayer and it looks like a super dead tree. It’s used for cell to cell signals, identification, and form holding cells together
What does an integral protein look like/do?
It allows the passage of hydrophilic substances into the bilayer. It has hydrophobic and hydrophilic regions to keep it stuck in there and allow hydrophilic stuff to pass through.
What does a peripheral protein look like/do?
It’s kind of a blob that’s stuck onto the phospholipid bilayer. It supports, communicates, has enzymes, and plays a role in molecule transfer.
What does cholesterol in the phospholipid bilayer do?
It maintains fluidity
What do the phospholipids in the phospholipid bilayer look like and do?
o== they are amphipathic and make up the bilayer and make it semipermeable and protect the cell
What does the hydrophilic region of the phospholipid bilayer do?
Defense, cell comms, lets them not be like “ew get away from me” in an aqueous environment, electrostatic interactions with water
What does the hydrophobic region of a phospholipid bilayer do?
good pbarrier for charged and polar substances because they can’t pass through easily
Why are some regions of membrane proteins hydrophilic and hydrophobic?
corresponds with bilayer + stuff it’s transporting
Describe the transport function of a membrane protein.
Moves charged particles in and out of the cell, is specific
Describe the enzymatic activity function of a membrane protein.
catalyzes chemical reactions
describe the signal transduction function of a membrane protein.
has a binding site with complimentary shape with a chemical messenger like a hormone - may make the protein change shape to send message inside by binding to a cytoplasmic protein (I just know this will be your favorite card, sarah)
describe the cell to cell recognition function of membrane proteins
they’re like id tags where they’re recognized by membrane proteins of other cells, but they’re kinda short lived.
describe the intercellular joining feature of membrane proteins
membrane proteins of adjacent cells may hook together in various kinds of junctions (gap or tight) and it holds cells together and is less short lived
Describe the attachment to cytoskeleton and ECM function of membrane proteins
Elements of the cytoskeleton may noncovalently bond to membrane proteins. this helps maintain cell shape, stabilizes their location, and can coordinate extra and intra cellular changes.
Where are phospholipids made?
Endoplasmic reticulum (i would say smooth)
What is the process for getting membrane parts made and to the membrane?
membrane components synthesized in er (both), transported to golgi apparatus, modified, transported to plasma membrane in vesicles (which have their own plasma membrane lol) and are secreted into the plasma membrane.
Why can oxygen and carbon dioxide diffuse easily through the lipid bilayers while glucose and water need to use proteins to cross the cell membrane?
Oxygen and CO2 are small and nonpolar. Glucose and water are hydrophilic and polar, so they get repelled by the tails. Also glucose is kinda big.
What channel protein transports water?
Aquaporin
Describe a channel protein.
Channel proteins act as a tunnel that molecules like water can use to pass through a membrane. They have hydrophilic channels (though that might depend on what it’s transporting). Sometimes they’re gated, sometimes not.
Describe a carrier protein.
Carrier proteins change shape to let contents in or out and can act as barriers since they don’t let things just go whooshing on through.
How do ions like H+ get through the membrane?
Active transport with a protein because there is no way in heck that charge will be allowed by the tails.
Define diffusion
net movement of particles form an area of high to low concentration down the concentration gradient
define concentration gradient
a region of space over which the concentration of a substance changes (high and low)
define passive transport
a substance diffuses down its concentration gradient across a membrane
define osmosis
net movement of water from an area of higher water potential/lower solute concentration to an area of lower water potential/high solute concentration - diffusion but water
define isotonic
solution with same concentration of solute and water (as whatever you put in it, not like 1 part solute to 1 part water)
define hypertonic
solution with a high solute and low water concentration
define hypotonic
a solution with a high water and low solute concentration
define turgid
sturdy/stiff - this is what happens when the vacuole pushes against the cell wall, causing high turgor pressure.
define flaccid
floppy and limp - the cytoplasm and vacuole start pulling away from the cell wall (membrane comes too) and turgor pressure decreases
define plasmolysis
wilting - the cytoplasm and vacuole really pull away from the cell wall and there’s practically no turgor pressure.
What happens to a plant and animal cell in a hypotonic solution?
Plant cell - turgid because turgor pressure is high and the cell wall is pushed against.
Animal cell - lysed (burst) and spherical before that because there’s too much water inside and no cell wall to hold it in
What happens to a plant and animal cell in an isotonic solution?
Animal cell - bioncave/perfectly happy if not a blood cell because water goes in and out at the same rate
Plant cell - flaccid (but not that flaccid) because there isn’t enough water in that thing to keep turgor pressure up
What happens to a plant and animal cell in a hypertonic solution?
Plant cell - gets plasmolyzed because too much water is leaving and the cell membrane (and everything inside) is pulling away from the cell wall
Animal cell - gets cretnated/shriveled because not enough water
What prevents lysis in plant cells?
cell walls
What prevents lysis in freshwater protista LIKE THE PARAMECIUM???
ALL HAIL PARAMECIUM
They have a contractile vacuole that pumps out water from the PARAMECIUM’s body
Describe facilitated diffusion and give examples
Molecules diffuse across the phospholipid membranes with the assistance of channel and carrier proteins. For example, water uses facilitated diffusion with aquaporins.
Would CO2 use facilitated diffusion to leave a cell?
No. It’s small and nonpolar and can diffuse through the membrane without a protein.
How is ATP used in active transport?
Energy in the form of ATP is expended to move a substance against their concentration gradient
Describe the sodium potassium pump.
3 sodium ions pumped out with atp! This makes it want 2 potassium ions pumped in without the need for more ATP! I know we established that these proteins are specific so it’s pretty cool! Here’s the even cooler part! Sodium wants to go in bc gradient and charge difference, but potassium’s gradient and charge difference conflict! So, it follows the ion charge until the concentration is REALLY strong! Then, it kinda stops moving (or goes in and out at the same rate) and establishes the K+ equilibrium potential! (which is sometimes the membrane potential)
How is glucose transported through a membrane?
Facilitated diffusion with carrier protein
How is water transported through a membrane?
Facilitated diffusion with channel protein
How is sodium transported through a membrane?
active transport with a carrier protein (some need energy and shouldn’t quite be thought of in the same way as others)
How is oxygen transported through a membrane?
Simple diffusion
Describe exocytosis
vesicle that wants to leave cell gets transported to the edge, fuses to it, opens up, lets the stuff out, and joins the membrane or pinches off and leaves.
Describe endocytosis
Includes phagocytosis (big) and pinocytosis (small) - stuff outside membrane comes close to cell membrane, membrane invaginates (makes dimple), pinches it off with stuff inside with the help of specialized proteins, and then the particles make their way into the cell in their brand new vesicle.
Are endocytosis and exocytosis active or passive?
Active - require energy
What is cytosol?
Cytoplasm goo.
