LESSON 2a: CELL MEMBRANE STRUCTURE Flashcards by Miss Bambi

-Gateway of the cell
-Acts as boundary
-Controls what enters and exits the cell
-regulate chemical composition
-Maintains homeostasis

Cell Membrane

How well did you know this?

Not at all

Perfectly

The cell membrane
is _______ and
allows a
unicellular
organism to
move

flexible

How well did you know this?

Not at all

Perfectly

Studies of the_______________ provided the first evidence that biological membranes consist of lipid bilayers

red blood cell plasma
membrane

How well did you know this?

Not at all

Perfectly

Plasma Membrane models

Sandwich Model
Unit Membrane Model
Fluid-Mosaic Model

How well did you know this?

Not at all

Perfectly

-2 layers of globular proteins with phospholipid inside to make a layer
and then join 2 layers together to make a channel for molecules to pass

Sandwich Model

How well did you know this?

Not at all

Perfectly

Proponent of Sandwich Model

Danielli and Davson

How well did you know this?

Not at all

Perfectly

-Outer layer of protein with phospholipid bilayer inside,
-believed all cells same composition,
-does not explain how some molecules pass through or the use of
proteins with nonpolar parts
-used transmission electron microscopy

Unit Membrane Model

How well did you know this?

Not at all

Perfectly

Proponent of Unit Membrane Model

Robertson

How well did you know this?

Not at all

Perfectly

Phospholipid bilayer with proteins partially or fully imbedded, electron
micrographs of freeze-fractured membrane

Fluid Mosaic Model

How well did you know this?

Not at all

Perfectly

Proponent of Fluid Mosaic Model

Singer and Nicolson

How well did you know this?

Not at all

Perfectly

How did they examine the plasma membrane under SEM?

1) Rapidly freeze specimen
2) Use special knife to cut membrane in half
3) Apply a carbon + platinum coating to the surface
4) Use scanning electron microscope to see the surface

How well did you know this?

Not at all

Perfectly

According to the electron micrograph which membrane model is
correct?

Fluid-Mosaic Model

How well did you know this?

Not at all

Perfectly

The lipids in a membrane are organized into a _____________

liquid crystalline lattice.

How well did you know this?

Not at all

Perfectly

The lattice becomes a _____________ at
the transition temperature

frozen crystalline gel

How well did you know this?

Not at all

Perfectly

The Plasma Membrane is composed of two layers of lipids. Why is this important?

This allows the membrane to repel too much water around it to prevent the cell to burst.

How well did you know this?

Not at all

Perfectly

-plasma membrane has consistency of olive oil at body temperature,
due to unsaturated phospholipids.
-phospholipids and proteins move around freely within the layer, like it’s a
liquid

Fluid

How well did you know this?

Not at all

Perfectly

plasma membrane has consistency of olive oil at body temperature,
due to ______________

unsaturated phospholipids

How well did you know this?

Not at all

Perfectly

– proteins form a collage that differs on either side of membrane
and from cell to cell (greater than 50 types of proteins)
-proteins span the membrane with hydrophilic portions facing out and
hydrophobic portions facing in.
-mosaic pattern produced by scattered protein molecules when membrane
is viewed from above.

Mosaic

How well did you know this?

Not at all

Perfectly

Hydrocarbons are tightly packed

Gel phase- Low temperature

How well did you know this?

Not at all

Perfectly

Bilayer “Melts”, movement is allowed

Higher temperature-moves to fluid state

How well did you know this?

Not at all

Perfectly

Formation of sphere is _____________

energetically favorable

How well did you know this?

Not at all

Perfectly

a harsh ionic detergent

SDS

How well did you know this?

Not at all

Perfectly

a gentler non-ionic detergent, are
commonly used solubilizing agents

Triton X-100

How well did you know this?

Not at all

Perfectly

A Scheme to Study a
Membrane Protein

-Solubilization,
-Purification, and
-Reconstitution in Liposomes

How well did you know this?

Not at all

Perfectly

Membrane Proteins Can Be Solubilized by _________ That Disrupt the Membrane

Detergents

*Most of the lipids and some proteins drift _________ on either side.

laterally

Phospholipids _________ switch from one layer to the next.

do not

The lipids and proteins in the cell membrane are not fixed in position but _________ moving

constantly

The ________ move laterally within the cell membrane –lateral diffusion

proteins

While the ______ can move both laterally and rotate 360 degrees – flip-flop diffusion

lipids

Cholesterol Affects fluidity: At Body Temp

- it lessens fluidity by restraining the movement of phospholipids; -also reduce permeability to small mol

Cholesterol Affects fluidity: colder temp

maintains fluidity by not allowing phospholipids to pack close together.

The Planar Rings of Cholesterol Make the Membrane More _____, ___________, and ___________

-Rigid -Less Permeable -Resistant to Low Temperature Crystalization

Major component of animal cell

Cholesterol

Cholesterol is not found in _________, how ever it has ______ that perform the same function.

-Plant Membrane -Sterols

Cholesterol has same molar amounts as _____________

Phospholipids

Heat produces motion of acyl side chains this resulted to change from solid to ___________ transition.

Fluid

By change in solid to fluid state, ________ in the plane bilayer is made possible

Lateral Diffusion

Classification of Membrane Proteins

-Peripheral Proteins -Integral Proteins -Transmembrane Proteins

are proteins that dissociate from the membrane following treatments with polar reagents that do not disrupt the phospholipid bilayer.

Peripheral membrane proteins

can be released only by treatments that disrupt the phospholipid bilayer.

Integral membrane proteins

span the lipid bilayer with portions exposed on both sides of the membrane

Transmembrane proteins

Types of Membrane Proteins

1. Transport Proteins (Channel and Carrier) 2. Cell Recognition Protein 3. Receptor Protein 4. Enzymatic Protein 5. Intercellular Junction Proteins 6. Attachment Proteins

-channel for lipid insoluble molecules and ions to pass freely through

Channel Protein

An inherited disorder that is caused by faulty Cl- channel creating a collection of thick mucus in the airways and in pancreatic and liver ducts

Cystic Fibrosis

– bind to a substance and carry it across membrane, change shape in process

Carrier Proteins

The inability of some persons to use energy for ___________ has been suggested as the cause of their obesity.

Sodium-Potassium Transport

Bind to chemical messengers (Ex. hormones) which sends a message into the cell causing cellular reaction

Receptor Proteins

Some types of _____ result not because the body does not produce enough growth hormone but because the plasma membrane growth hormone receptor is faulty.

Dwarfism

Carry out enzymatic reactions right at the membrane when a substrate binds to the active site

Enzymatic Proteins

____________ releases toxin that interferes with the proper functioning of adenylate cyclase which is involved in ATP metabolism resulting to severe diarrhea.

Cholera Bacteria

Glycoproteins (and glycolipids) on extracellular surface serve as ID tags (which species, type of cell, individual). Carbohydrates are short branched chains of less than 15 sugars

Cell Recognition Proteins

The ______________ are different for each person, so organ transplant are difficult to achieve. When this is introduced and considered foreign the WBC (responsible for immunity) attacked it .

MHC (Major Histocompatibility Complex) Glycoproteins

Attach to cytoskeleton (to maintain cell shape and stabilize proteins) and/or the extracellular matrix (integrins connect to both)

Attachment Proteins

– protein fibers and carbohydrates secreted by cells and fills the spaces between cells and supports cells in a tissue. -can influence activity inside the cell and coordinate the behavior of all the cells in a tissue

Extracellular Matrix

Bind cells together

Intercellular Junction Proteins

Types of Cell Junctions

1. Tight Junctions 2. Desmosomes 3. Gap Junctions

* Transmembrane Proteins of opposite cells attach in a tight zipper-like fashion * No intercellular space, No leakage Ex. Intestine, Kidneys, Epithelium of skin -bar the movement of dissolved materials from the lumen through space between epithelial cells.

Tight Junctions

Long rows of tight junction protein form a ___________.

Complex meshwork

* Cytoplasmic plaques of two cells bind with the aid of intermediate filaments of keratin * Allows for stretching * Ex. Stomach, Bladder, Heart

Desmosomes

* Channel proteins of opposite cells join together providing channels for ions, sugars, amino acids, and other small molecules to pass. * Allows communication between cells. * Ex. Heart muscle, animal embryos

Gap Junctions

Example of Mobility of Membrane Proteins

1. The fusion of human cell and animal cell. 2. After 40 minutes of incubation, the human and mouse protein spread out forming uniform distribution and no separation.

Many Membrane Proteins Move _____ in the Plane of the Membrane

Freely

________ membrane proteins have this freedom of motion

Not all

Can Establish the Rate of Membrane Component Movement

Fluorescence Recovery After Photobleaching (FRAP)