Cell Boundaries Part 2

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Information about Cell Boundaries Part 2

Published on February 7, 2008

Author: itamarita1984

Source: slideshare.net

Description

part 2 of cell boundary notes

What happens when we reach equilibrium? Particles continue moving across membrane but in both directions! ***No more changes in concentration

Particles continue moving across membrane but in both directions! ***No more changes in concentration

Problems for diffusion… Things too large Charged molecules Positive/negative Opposites attract but likes do not… These all present serious problems for things getting across membranes…

Things too large

Charged molecules

Positive/negative

Opposites attract but likes do not…

These all present serious problems for things getting across membranes…

If things can cross a membrane we call the membrane PERMEABLE If things canNOT cross a membrane we call the membrane IMPERMEABLE

Biological membranes are… SEMI-PERMEABLE Aka… Selectively permeable Cell membranes are picky

SEMI-PERMEABLE

Aka…

Selectively permeable

Cell membranes are picky

Osmosis Water (H2O) can pass easily through most biological membranes Def: Diffusion of Water through a semi-permeable membrane

Water (H2O) can pass easily through most biological membranes

Def:

Diffusion of Water through a semi-permeable membrane

How Osmosis works… We have water molecules and some other molecules, let’s say sugar If we have more water on one side of the membrane (HIGH conc. of H2O), then the water will diffuse across… Membrane will let water thru but not sugar Water can move back and forth (not sugar)

We have water molecules and some other molecules, let’s say sugar

If we have more water on one side of the membrane (HIGH conc. of H2O), then the water will diffuse across…

Membrane will let water thru but not sugar

Water can move back and forth (not sugar)

Water moves from areas of HIGH conc. To areas of LOW conc. Water moves across till equilibrium is reached Isotonic: when conc. of water = conc. of sugar Hypertonic: “above strength” When we begin with more sugar in water More concentrated sugar solution on side A Hypotonic: “below strength” When we end with less sugar Dilute sugar solution on side A

Water moves across till equilibrium is reached

Isotonic:

when conc. of water = conc. of sugar

Hypertonic: “above strength”

When we begin with more sugar in water

More concentrated sugar solution on side A

Hypotonic: “below strength”

When we end with less sugar

Dilute sugar solution on side A

 

Osmotic Pressure We will discuss later… PLEASE read page 186 This is a confusing concept…

We will discuss later…

PLEASE read page 186

This is a confusing concept…

How do big molecules diffuse across a membrane so quickly if the membrane is selectively permeable?

Facilitated Diffusion What does facilitate mean? Proteins are the extra help “escorts” across the membrane We call these protein channels… Allow specific things thru

What does facilitate mean?

Proteins are the extra help

“escorts” across the membrane

We call these protein channels…

Allow specific things thru

Facilitated Diffusion (continued) FAST SPECIFIC Still diffusion so we only see it from high concentration to low Does NOT require energy

FAST

SPECIFIC

Still diffusion so we only see it from high concentration to low

Does NOT require energy

 

 

What about when we want to go against the concentration? (From low concentration to high?)

What do we need??? ENERGY!!!!

ENERGY!!!!

ACTIVE transport Process that moves molecules against the concentration gradient Requires ENERGY A protein pumps small molecules and ions across a cell membrane against the conc. gradient To pump large molecules and clumps… 2 other processes: Exocytosis Endocytosis The can change shape of membrane

Process that moves molecules against the concentration gradient

Requires ENERGY

A protein pumps small molecules and ions across a cell membrane against the conc. gradient

To pump large molecules and clumps…

2 other processes:

Exocytosis

Endocytosis

The can change shape of membrane

Types of Active transport Molecular Transport When small ions and molecules are carried across membrane Endocytosis Endo- means…. -Cyto- means… -sis mean…. Exocytosis Exo- means…. -Cyto- means… -sis mean….

Molecular Transport

When small ions and molecules are carried across membrane

Endocytosis

Endo- means….

-Cyto- means…

-sis mean….

Exocytosis

Exo- means….

-Cyto- means…

-sis mean….

Molecular Transport Proteins are used to pump small molecules and ions across membrane even against the conc. Gradient The cell devotes a lot of ENERGY to pumping things across membrane Potassium, calcium, and sodium are some things that need to pumped across

Proteins are used to pump small molecules and ions across membrane even against the conc. Gradient

The cell devotes a lot of ENERGY to pumping things across membrane

Potassium, calcium, and sodium are some things that need to pumped across

Endocytosis When cells need to take in large material Process of taking material into the cell by process of infolding, or pockets, of the cell membrane Pocket breaks loose from cell membrane and forms a vacuole inside the cell Two Types… Phagocytosis Pinocytosis

When cells need to take in large material

Process of taking material into the cell by process of infolding, or pockets, of the cell membrane

Pocket breaks loose from cell membrane and forms a vacuole inside the cell

Two Types…

Phagocytosis

Pinocytosis

 

Two types of endocytosis: 1. Phagocytosis “ cell eating” Extensions of cytoplasm surround the particle and package it within a food vacuole Cell then engulfs the package Amoebas 2. Pinocytosis “ cell drinking” When cell needs to take up liquid Tiny pockets in cell membrane form Fill with liquid Then pinch off to form vacuoles inside of cell

1. Phagocytosis

“ cell eating”

Extensions of cytoplasm surround the particle and package it within a food vacuole

Cell then engulfs the package

Amoebas

2. Pinocytosis

“ cell drinking”

When cell needs to take up liquid

Tiny pockets in cell membrane form

Fill with liquid

Then pinch off to form vacuoles inside of cell

 

 

Exocytosis Exo- means… Cyto means… Sis means… When cell releases large amounts of material Excretes stuff Membrane of vacuole surrounding particle inside cell fuses with the cell membrane The contents in vacuole are then forced out of the cell We see this in removal of water by contractile vacuoles

Exo- means…

Cyto means…

Sis means…

When cell releases large amounts of material

Excretes stuff

Membrane of vacuole surrounding particle inside cell fuses with the cell membrane

The contents in vacuole are then forced out of the cell

We see this in removal of water by contractile vacuoles

 

 

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