Unit 3:Movement in and out of Cells

The History of the Cell Theory (p 172)

•Compound Light microscopes

•Invented by Anton van Leeuwenhoek

•1500 x

•Electron microscopes

•Scanning electron microscope (SEM,扫描电镜 )

•Surface of 3D objects

•Transmission electron microscope (TEM, 透射电镜 )

•Inside a cell

•Scanning Tunneling microscope (STM)

•Viewing atoms

The History of the Cell Theory

Robert Hooke- first to use the word “cells”

The Cell Theory:

1. All organisms are composed of one or more

cells.

2. The cell is the basic unit of structure and

organization of organisms.

3. All cells come from preexisting cells.

Two Basic Cell Types Two Basic Cell Types

ProkaryotesProkaryotes::

Cells that do not contain any Cells that do not contain any

membrane-membrane- bound organellesbound organelles

- no nucleus, mitochondria, goli, etc..- no nucleus, mitochondria, goli, etc..

Most Most unicellular unicellular (one cell) organisms; (one cell) organisms;

bacteriabacteria

Two Basic Cell TypesTwo Basic Cell TypesEukaryotesEukaryotes::

Cells that Cells that do do contain membrane-contain membrane-

bound organelles bound organelles (nucleus)(nucleus)

Most Most multicellularmulticellular ((many cellsmany cells))

organisms;organisms; plants, animals, etc. plants, animals, etc.

Some unicellular organism too; algaeSome unicellular organism too; algae

Prokaryote Vs. Prokaryote Vs. EukaryoteEukaryote

Prokaryote Eukaryote

No membrane-bound organelles

Membrane-bound organelles

No nucleus Nucleus

Small (0.001-0.01 mm) Large (0.01-0.1mm)

Small Ribosomes Large Ribosomes

Small, normally circular DNA

Large, chromosome DNA

Review Organelles• Cell labeling practice sheet

Cellular TransportCellular Transport• Cells must move things inside and

outside to maintain homeostasis

• What might they need to take in:

– Food molecules

– Signals

– Ions

• What might they need to release:

– Waste material

– Proteins

– Signals

Cellular TransportCellular Transport• 2 Types of transport:

1)Passive Movement

– Does not require the cell to

use energy to move

2)Active Movement

– Does require the cell to use

energy

– Cell uses energy units

(ATP)

Passive Movement: Passive Movement: DiffusionDiffusion

• Diffusion movement of molecules

from areas High concentrations to

areas of Low concentrations; down a

concentration gradient

• Food coloring in water, sugar in water,

fart fills a room, etc…

• Where does the energy come from for

this movement?

– Kinetic energy in molecules

(random movement)

Passive Movement: Passive Movement: DiffusionDiffusion

• What is the barrier that surrounds all

cells?

– Plasma membrane

• Why can the plasma membrane let in

some material and not others?

– It is partially (selectively) permeable

• What materials do you think can

diffuse into and out of a cell

membrane?

– O2, CO2, Water, etc…

Diffusion FactorsDiffusion Factors• What factors should effect diffusion rate?

1) Distance traveled membrane is thin;

cells are tiny

2) Strength on concentration gradient

3) Surface area of membrane folding of

membranes increase surface area

4) Temperature higher temp= faster

random motion

5) Size of molecule smaller molecules

move faster

Passive Movement: Facilitated Diffusion

• Facilitated diffusion diffusion through a protein

channel or carrier protein that is specific for 1

type of substance (Na+, Cl-, glucose, etc…)

• Still follow concentration gradient

• Can become saturated meaning the movement

is at its maximum rate and can not go any faster

Passive Movement: Passive Movement: OsmosisOsmosis• The diffusion of water across a selectively

permeable membrane（选择 is called

osmosis

• H2O is small enough to fit between

phospholipids but moves very slow, why?

– Hydrophobic center of membrane pushes

it back

• Aquaporins transport channels just for

H2O

Solutions: Solutes and Solutions: Solutes and SolventsSolvents

• Solute the material that dissolves

(disappears into) the solvent

– Salt in salt water

• Solvent the material that breaks apart

and dissolves the solute

– Water in salt water

• Soluble a solute that CAN dissolve in a

solvent

– “like dissolves like”

– Sugar dissolves in water

– Fat CANNOT dissolve in water

Osmotic Pressure:• Movement of water can increase and decrease

pressure inside the cell

• Hypotonic Solution

– concentration of solute is low (high H2O) on the

outside and high (low H2O) on the inside of the

cell

– Water moves into the cell causes it to swell

(best for plant cells)

– High Water Potential (water leaves solution)

– Turgid pressure keeps plants upright

Osmotic Pressure• Hypertonic Solution

– concentration is high (low H2O) on the

outside and low (high H2O) on the inside

– Low Water Potential (water enters

solution)

– Water rushes out of the cell causing it to

shrink

– Plasmolysis shrinking inside plant cells

Osmotic Pressure• Isotonic solution

– concentration inside and outside

the cell are equal (equilibrium)

– Movement of water in and out of

the cell is at equal rates; best for

animal cells

Active Movement• Energy is required to move molecules

AGAINST their concentration gradients

• ATP must be used to make carrier proteins

(pumps) move molecules to the other side

• Cell uses active transport to create

concentration gradients to be used later

by passive transport; nervous system

Active Movement: Large Particles

• Endocytosis

– Cell folds around large particle and

pulls it in; plasma membrane

makes vacuole

• Exocytosis

– Vacuole fuses with plasma

membrane and release large

particles

Know The Difference!

Homework• Read p. 26-33• Questions on p. 27, 29,

31, 33, and 34• Quizlet Unit 3 Vocab• Vocab books for 3.1-3.4• Lab reports on egg and

plant osmosis