Mod 11-13

What are the 4 common structural features of a cell?

1. plasma membrane

2. nucleus

3. organelles

4. cytoskeleton

What occurs in and around the structures of a cell?

biochemical processes

human cell

What kind of cells are human and animal cells?

eukaryotic

What are eukaryotic cells?

Cells with a nucleus and membrane-bound organelles.

What kind of cells are bacteria cells?

prokaryotes

What are the 6 organelles?

1. nucleus

2. mitochondria

3. endoplasmic reticulum

4. lysosomes and peroxisomes

5. Golgi complex

6. cytoskeleton

What structures are associated with the plasma membrane?

1. lipid bilayer

2. membrane proteins

3. glycocalyx

4. diffusion and transport

plasma membrane

what is the plasma membrane?

The outer boundary that encloses the cell and separates it from its environment.

What molecule is the plasma membrane made out of?

phospholipids

The plasma membrane is composed of a …

lipid bilayer

lipid bilayer

What is a continuous and sealed plasma membrane?

the cell is surrounded by an unbroken, fluid barrier that isolates the cells contents from the environment

What does a continuous and sealed plasma membrane restrict?

exchange of polar compounds

What is the external leaflet of plasma membrane?

the half of the membrane that faces the extracellular environment

What is the internal leaflet of the plasma membrane?

the side of the membrane that faces the cytoplasm

What is the fluid mosaic model?

The cell membrane dynamic and flexible with embedded proteins.

How can proteins and lipids move within the membrane and what does it describe?

they can move laterally in the plane of the membrane; they are not fixed in place

fluid mosaic model

What is the major plasma membrane phospholipid?

phosphatidylcholine

What is another name for phosphatidylcholine?

lecithin

What is sphingomyelin a constituent of?

glycosphingolipids

What are glycosphingolipids?

membrane lipids made of a carbohydrate chain attached to a ceramide backbone.

What do glycosphingolipids do in the cell membrane?

Anchor the membrane and display carbohydrate molecules on the cell surface.

what is an overall function of glycosphingolipids?

cell signaling

What is the function of cholesterol in cell membranes?

aids in membrane fluidity

What are the lipids composing the plasma membrane?

1. phosphatidylcholine

2. sphingomyelin

3. cholesterol

Where does cholesterol fit in the membrane?

In gaps between phospholipids created by cis unsaturated fatty acid tails.

What does cholesterol prevent in colder/denser membranes?

from becoming brittle and inflexible

what does cholesterol prevent in warmer/flowing membranes?

from becoming too liquid and shapeless

cholesterol in the membrane

what are the 3 types of proteins in the plasma membrane?

1. integral proteins

2. peripheral membrane proteins

3. lipid-anchor proteins

Where can you find integral proteins in the cell membrane?

everywhere, they span the membrane

what are integral proteins partially composed of (1)?

amino acids with hydrophobic side chains

What are integral proteins partially composed of (2)?

amino acids with hydrophilic side chains

What do integral protein do?

Span the plasma membrane and interact with the lipid bilayer.

What do integral proteins (2) do?

interact with the aqueous environments

What do integral proteins functions as?

• channels

• transporters

• receptors

• structural proteins

integral proteins

What are peripheral proteins involved in?

Anchors membrane to the cytoskeleton.

What do peripheral proteins provide?

mechanical support

What are peripheral proteins bound by?

Weak electrostatic interactions with the surface of the lipid bilayer.

What are peripheral membrane proteins attracted to?

phospholipid heads

What do peripheral membrane proteins form interactions with?

integral proteins

What is the function of lipid-anchored proteins?

anchors proteins in place to serve specialized functions

How do lipid-anchored proteins form?

a lipid is covalently attached to a protein, anchoring it to the cell membrane.

proteins on cell membrane

How can you describe the glycocalyx relative to the plasma membrane?

the carbohydrate outer layer

How much weight does the glycocalyx account for the plasma membrane?

2-10%

What is the glycocalyx composed of?

Oligosaccharides extending from the outer leaflet of the lipid bilayer.

In which cells is the glycocalyx dense?

endovascular cells and BBB cells

What are the 3 function of the glycocalyx?

1. to protect the cell from digestion

2. restrict uptake of hydrophobic compounds

3. serve as cell-recognition molecules

How can you describe the glycocalyx?

dense, gel-like network that serves as a physical barrier around the cells

The glycocalyx serves as a barrier against …

vascular permeability

The glycocalyx plays an essential role in what?

Preventing interstitial edema during intravascular volume expansion (e.g., fluid resuscitation).

What can large volumes of administered fluids do?

damage the endothelial glycocalyx, increasing vascular leak into the interstitial space.

What are critical illnesses often accompanied by?

glycocalyx degradation

what is glycocalyx degradation caused by?

inflammatory reaction, hypo perfusion, and shock

What can glycocalyx degradation contribute to?

poor prognosis in critically ill patients

The type of fluid used during resuscitation may …

be beneficial or harmful to the endothelial glycocalyx

Which fluids are better for the glycocalyx?

albumin and FFP

Which fluids are harmful to the glycocalyx?

NS and LR

Fluid administration is …

not without consequences

What properties of the plasma membrane restrict flow in and out of cell?

its hydrophobic and isolating nature

What is simple diffusion?

molecules can move freely from areas of high concentration to low concentration

How can you describe simple diffusion?

passive; no energy expenditure

Which molecules can cross the cell membrane through simple diffusion?

lipid soluble compounds:

• O2

• CO2

• steroidal hormones

How can you describe facilitated diffusion?

passive; no energy expenditure

What does facilitated diffusion require?

a transport protein such as an enzyme

How does facilitated diffusion work?

A transport protein binds a molecule, changes shape, and moves it across the membrane.

what are gated proteins?

transmembrane protein that regulates the flow of ions and molecules into the cell

get checked at the gate

transmembrane proteins that form pores where ions can travel down their gradient

What state can transport proteins be in?

open or closed state

what are the 3 types of gated channels?

1. voltage-gated channels

2. ligand gated channels

3. phoshorylation-gated channels

Where are voltage gated channels found?

in nerve cells

Voltage gated channels are …

open or closed based on voltage changes across the membrane

What do ligand channels open or close in response to?

the binding of a specific molecule at a binding site

in ligand channels, what does binding of a specific molecule do to the channel?

changes conformation of the channel

What do phosphorylation-gated channels require?

activation by way of phosphorylation

Why are phosphorylation-gated channels still considered passive?

even though 1 ATP is required to turn on the channel, that ATP activated the channel and allows a lot of molecules to be transported

What kind of protein does active transport need?

a transport/carrier protein

In active transport, where are substances carried?

low concentration to high concentration

active transport requires …

energy expenditure

What are the 2 types of active transport?

1. primary active transport

2. secondary active transport

What is primary active transport?

directly uses energy from ATP hydrolysis to move molecules and ions across the membrane against their concentration or electrical gradient.

What is an example of primary active transport?

sodium-potassium pump

What kind of port is the sodium-potassium pump?

antiport

What is an antiport?

moves two different molecules across the cell membrane in opposite directions

is the sodium-potassium pump and important example of primary active transport?

yes!

How does the sodium-potassium pump work?

at the expense of 1 ATP, 3 Na+ ions are pumped out of the cell while 2 K+ ions are pumped into the cell against their concentration gradients

sodium potassium pump

what is secondary active transport?

Uses an ion gradient to move another molecule against its concentration gradient.

what is an example of secondary active transport?

sodium-glucose contransporter

What is the sodium-glucose contransporter?

transport of glucose into the cells against (up) its gradient powered by sodium moving down its gradient

What is a symport?

compounds move across a membrane in the same direction

what is an example of symport

sodium-glucose cotransporter

What powers the sodium-glucose cotransporter?

the Na gradient created by the Na-K pump

What powers the transport of amino acids into the cell?

the Na-K pump

What is vesicular transport?

Movement of substances into or out of the cell by vesicles

what is a vesicle?

a membrane bound compartment

What is endocytosis?

transport into the cell