homeostasis and cellular transport in Eukaryotic Cells

Plasma Membrane

A selectively permeable phospholipid bilayer forming de boundary of the cells

Substances that enter and exit

Including Ions, Proteins, Molecules, Solutes and liquids.

Two Layers

Of lipid molecules sheets

Hydrophilic

Each lipid has a sheet, with water-attracting side.

Hydrophobic

Water-repeling Side

Double-layer System

Allows the membrane to be selectively permeable

Hydrophilic & Hydrophobic disposition

Hydrophobic tall facing the interior Hydrophilic heads face the exterior and the cytoplasm

Selective Permeability

Allow several types of transport

Fluid Mosaic Model

Most common existing hypothesis of a cell membrane organization

The fluid aspect of the membrane is

The phospholipids are held together by hydrophobic interactions

The hydrophobic interactions of a membrane are

Much weaker than covalent bonds.

The membrane is made of

Different proteins clustered in groups and embedded in the fluid matrix of the lipid layer

Integral proteins and peripheral proteins are

Two mayor populations of proteins in the cell membrane

Integral proteins are called too…

“Transmembrane” Proteins because often span the entire membrane

The hydrophilic region of this proteins are…

In contact with the water in both sides of the membrane

The hydrophobic regions is

Between the lipids layers

What is the most important role of the proteins of membrane?

Transport

Description of the transport of proteins of membrane

Shuttle molecules and ions in and out of the cell

Function of proteins peripheral (aren’t a part of the cell membrane)…

These proteins add structure to the cells by binding with fibers

Another function of peripheral proteins are

They also serve like attachments site for enzymes or as cell-recognition site

Other componentes of the membrane mosaic

Carbohydrates or sugar molecules

Whit who bond the carbohydrates of membrane

Bond with either lipids or proteins of the cells membrane

Specialized sites on the cell surface

The carbohydrates bond with the lipids or the proteins form this sites that allow cells to recognize each other

What may do the carbohydrates of membrane?

Carbohydrates can tell the difference between body cells and foreign invaders

At the membrane level which of these proteins , carbohydrates or lipids simulates the immune system?

Carbohydrates

Passive transport

The movement of substances across a cell membrane whiteout the use of energy by the cell

How happen the Passive Transport

Spontaneously & Automatically

What the passive transport rate depends on on?

Permeability of the cellular membrane

Passive transport consists of

-Diffusion

-Facilitated Diffusion

-Osmosis

Diffusion

Movements of molecules from an area of higher concentration to an area of lower concentration

How long diffusion is?

Process continues until the concentration becomes equal throughout a space

Concentration Gradient

When the concentration of a substance on either side of the membrane are drastically different becomes a ….

What influence the concentration gradients

The direction in which a given substance will flow

What direction will a liquid take according to its quantity in two compartments ?

From the compartment with the most liquid to the one with the least

Regardless

Independientemente

Facilitated Diffusion

Involve transport proteins that can function as either channels or carriers .

Why the molecules are unable to pass through the pores of a selectively permeable membrane.

Because are to larges o due to their charge o polarity.

What are Transport Proteins

The Facilitated diffusion involves Transport Proteins, this protein function as either channels or carriers.

Channel Proteins

Molecules through the membrane (pores & channels) big for large molecules o with the polarity to accepts polar or charged molecules.

Carrier Proteins

Embedded in plasma membrane, this proteins bind to a substance and help it across the membrane. Generally specific for one substance.

What happens at the proteins carrier when insoluble molecules reach their receptors carrier ?

The Proteins undergo structural changes to allow the insoluble molecules to cross the plasma membrane. This process is called Facilitated Diffusion

Osmosis

Is the diffusion of water from areas of high concentration to areas of low water concentration across a selectively permeable membrane.

Diffusion can refer

To any number of particles or molecules.

What do the Osmosis to maintain homeostasis:

Move the water in whatever direction to equalize the concentration of water and any solutes present.

Which are the different types of solutions?

• Isotonic

• Hypotonic

• Hypertonic

Isotonic Solution

The concentration of solutes within and outside the cell is equal. Water is moving across the semipermeable membrane at an equal rate in both directions.

Hypotonic Solution

The concentration of solutes outside the cell is lower than the concentration of solutes inside the cell. Water present outside the cell will move down its concentration gradient into the cell.

What can case a hypotonic Solution over the cell?

The cell will Swell o even Burst if the process occurs in excess.

Hypertonic Solution

The concentration of solutes outside the cell is higher than the concentration of solutes inside the cell. Water will move down its concentration gradient into out of the cell, causing the cell to Shrink.

The Osmotic Pressure is caused by…

Difference in water concentration within and outside of the cell.

-Diffusion

-Facilitated Diffusion

And Osmosis are forms of passive transport

Meaning they requiere No Energy

Active transport occurs …..

When cells must use energy to move molecules, ions, proteins, liquids or solutes into regions that already have a high concentration of these substances.

Why is different Passive Transport and Active Transport

The first one the substances follow their concentration gradients. While the second one the cells use Energy to move substances against their concentration.

Why is importan the Active Transport?

To Mantain a Membrane Potential

Membrane Potential

Voltage Difference , between one side of the selectively permeable membrane and the other.

The Membrane Potential is the Difference on (Voltage) on the Cells

The Difference between the two sides typically falls between -40 and -80 millivolts.

How is the charges observed inside the cel.

Cells typically are more negative on the inside than the outside. Due to a higher concentration of a negative ions.

How Active Transport Contributes with the Membrane Potential ?

By Pushing Ions and other molecules against their gradients.

Mention some tiles of gradients

• Chemical Gradient

• Electrical Gradient

• Electrochemical Gradient

What is the Electrochemical Gradient ?

Are the Combined Effects of electrical and chemical effects

Electrochemical Gradient Means..

Means that Electrical and the Chemical Gradient have and effect on the movement of substances.

Which direction can Encourage the Chemical & Chemical gradients?

Could be in the same direction or they may negate (one gradient opposed another)

How is the interaction between the Active Transport & the Electrochemical Gradient

By expending energy in the form of Adenosine Triphosphate

ATP

Electrical Gradient

Is the difference in the concentration of electrical charges on either side of a membrane.

Sodium-a Potassium Puno

This one facilitates active transport and regulates internal cellular physiology by monitoring the levels of of sodium and potassium ions.

Why are important sodium & potassium in the cell.

Both are integral to optimal functioning within the cell, to metabolic functions, and to signal transmission.

The Sodium-Potassium pump works to keep

The concentration of Potassium inside the cell high and the concentration of Sodium inside the cell relatively low.

How is the concentration of Sodium & Potassium outside the cell.

Potassium = Low

Sodium = High

The Cell remain more negative because of

The Sodium-Potassium pump

Why is important the cell remain Negative

Signal Transmission

1 Phagocytosi

2Pinocytosis

3Receptor-Mediated

Cell Eating

Cell Drinking

Endocytosis