The Cell and Its Environment

Fall 2010

What is a cell?A cell is the basic unit of living things.Some living things are composed of only

one cell and are called UNICELLULAR organsims.

Organisms that have many different cells are called MULTICELLULAR organisms.

Homeostasis – Maintaining a BalanceCells must keep the proper

concentration of nutrients and water and eliminate wastes.

The plasma membrane is selectively permeable – it will allow some things to pass through, while blocking other things.

What is the function of a cell?* All living things obtain energy different

ways through the processes of photosynthesis or respiration.

Since organisms must use energy there are certain things that have to get into and out of the cell to enable the organism to use or convert energy.

Materials that must be able to move INTO ANIMAL cells:1.Oxygen2. Water3. Particles of food4 Minerals and vitamns

for proteins(K, Na, Fe)

Materials that must be able to move OUT of ANIMAL cells:

1. Carbon dioxide2. Waste materials

Materials that must move INTO PLANT cells:

1. Sunlight2. Water3. Carbon dioxide

Materials that must be able to get OUT of PLANT cells:

OxygenWaste products

What lets stuff in and out of the cell?

Cell MembraneDefinition- a membrane that controls how

materials move into or out of a cell. It acts as a gatekeeper to allow things in and out of the cell.Cell

Membrane

Overview

Cell membrane separates living cell from nonliving surroundings thin barrier = 8nm thick

Controls traffic in & out of the cellselectively permeableallows some substances to cross more easily than

othershydrophobic vs hydrophilic

Made of phospholipids, proteins & other macromolecules

What is a cell membrane?Cell membranes are the outside covering of a

cell that allows things in and out of the cell. Cell membranes are composed of 3 things:1. double layer of phosolipid molecules (fats)2. Proteins – moves large molecules.3. carbohydrate chains4. cholesterol

3 Types of Membrane ProteinsTransport large charged molecules!!

1.Receptor Proteins: Determine what particles can pass through the membrane.

2. Enzymes: Serve as enzymes (may speed reactions).

3.Transport proteins:moves substances across the membrane.

This moves K, Na, Fe, Water, amino acids any charged particle.

Phospholipids – allows not charged small particle through!

Fatty acid

Phosphate

Fatty acid tails – hydrophobic

Phosphate group head - hydrophilic

Arranged as a bilayer

Aaaah, one of those

structure–functionexamples

Why does the phosolipid align in 2 layers?

Phosphate head – hydrophilic because it is charged opposite of water and they attract each other. They will be on the outside touching the Water.

Fatty acid tail – hydrophobic because it has no charge and is repelled by water that is charged.They are pushed way from water and align onthe inside.

Molecules that can move through phosolipid part of membrane

Oxygen, carbon dioxide !! ANY PARTICLE THAT IS SMALL AND NOT CHARGED!!!

ttp://www.teachersdomain.org/asset/tdc02_int_membraneweb/

Any particle that is charged cannot move through membrane because of lipid charged tails.

Function of Carbohydrates in Membrane

Attached to the membrane’s proteins act as identification tags. This allows cells to tell each other apart. A heart cell will have different carbohydrates than a heart cell.

Function of cholesterol in Cell Membrane

Cholesterol strengthens the cell membrane.

Outside of cell

Inside of cell (cytoplasm)

Lipid Bilayer

Proteins

Transport Protein Phospholipids

Carbohydratechains

Structure of the Cell Membrane

Go to Section:

Animations of membrane

structure

How does stuff get in and out of the cell?The cell membrane is what allows stuff in

and out of the cell. The membrane is selectively permeable.

Selectively permeable-Definition- means that some substances

can cross the membrane while others cannot.

Proteins

This model

describes the

structure of the

cell membrane!!

Polar heads love water & dissolve.

Non-polar tails hide from water.

Carbohydrate cell markers

Fluid Mosaic Model

How do phosolipids control what can pass through Membrane?

The hydrophobic tails will not let any substance pass through that has a charge(ion)(hydrophilic).Only substances that are not charged (hydrophobic)can pass through. If they cannotpass through the membrane, then they must go through the must get in another way.

Fluid Mosiac Model of Cell MembraneFluid Mosiac Model of Cell Membrane

This model describes the structure of the cell membrane because it acts likes a liquid. 1.The cell membrane is flexible not rigid. The phosolipids move from side to side.

2.There are so many molecules that make up the membrane that it looks like a mosiac.

Outside of cell

Inside of cell (cytoplasm)

Lipid Bilayer

Proteins

Transport Protein Phospholipids

Carbohydratechains

Structure of the Cell Membrane

Go to Section:

Animations of membrane

structure

Cell Transport

To understand cell transport, you must understand how molecules move.All molecules move. Even solids vibrate.Most of the cell environment is liquid.Molecules want to reach EQUILIBRIUM!Equilibrium – equal amount of molecules

everywhere(across cell membrane).

Diffusion

Movement of molecules moving from an area of higher concentration to an area of lower concentration.

Example: air freshener, perfume, food cooking, food coloring in water.

Increase temperature; increase rate of diffusionDiffusion occurs in liquids and gases.

Which direction will molecules flow?

Concentration Gradient

Difference in concentration of molecules that makes the molecules move. They move from highest level to the lowest level.

The greater the difference the faster the molecules move.

Concentration Gradient

Diffusion video

http://video.search.yahoo.com/search/video;_ylt=A0SO8ZpVTNdMKS8AS3H7w8QF;_ylu=X3oDMTBncGdyMzQ0BHNlYwNzZWFyY2gEdnRpZAM-?p=diffusion&ei=utf-8&fr2=tab-img&n=21&tnr=21&y=Search

How does stuff get in and out of the cell?

Substances that move into and out of a cell do so by means of one of two processes: PASSIVE TRANSPORT or ACTIVE TRANSPORT.

Types of Cell Transport

No Energy EnergyPassive Transport Active Transport

Diffusion

Faciliated diffusion(osmosis)

Bulk transportendocyotsis

exocytosis

Passive Transport

http://video.search.yahoo.com/search/video;_ylt=A0PDoX1LTNdMKyoAZayJzbkF?ei=UTF-8&p=passive%20transport&fr2=tab-img&fr=The Cell and Its Environment 2010.ppt

Passive Transport

Definition: is the movement of dissolved materials across a cell membrane without using the cells energy.

Energy required: NOType of Transport: PASSIVEDiffusion or facilitated diffusion(osmosis)

Passive Transport

Diffusion – passive transportDefinition: is the process by which molecules

move from an area of higher concentration to an area of lower concentration(liquids or gases).

Ex: If a bacteria lives in a pond, the water in the pond contains oxygen molecules. The area inside the bacteria cell has a lower amount of oxygen than the pond. So, the oxygen molecules outside of the cell will freely move into the cell.

Diffusion CONT’D

Energy required: NOType of Transport: PASSIVE

Faciliated Diffusion- Type of Passive TransportMovement of molecules across the cell

membrane but using a carrier molecule(protein)

NO ENERGY Follows the same rules as diffusion but

these molecules cannot slip through the phosolipid tails.

Osmosis – facilitated diffusion

Definition: is the diffusion of water molecules across a selectively permeable membrane(sometimes uses carrier protein).

-Many life processes require water, therefore; all cells must have the appropriate amount of water in them to function.

Energy Required: NOType of Transfer: PASSIVE

Osmosis – Type of Faciliated DiffusionMovement of WATER across the cell

membrane. Cells are 75 – 90 % water so osmosis is an important process.Water molecules will continue to move

until EQUILIBRUIM is reached.NO ENERGY NEEDED!!

Click on link below to see the flow of water during osmosis.

http://people.eku.edu/ritchisong/RITCHISO/osmosis3.gif

What Makes Water Move?

It is determined by the type of surroundings the cell is placed that determines the concentration gradient

Solution: mixture in which molecules of one substance are evenly dispersed.

Solvent: substance that makes up the greatest part of the solution.(usually water)

Solute: substance dissolved in the solvent.(K, NaCl, O Na, Amino acids)

Types of solutions cell can be placed

IsotonicHypertonicHypotonic

IsotonicConcentration of solutes are EQUAL

inside and outside the cell.Why do they give a person who is

dehydrated a saline(minerals and salt) drip(IV) vs. distilled 100% water.

Hypertonic

Solutes on the outside of cell is higher. Water leaves cell

This is why slugs shrivels up with salt.Animals that leave in salt water have

adaptations to deal with the salt in the water.

This is why you do not drink salt water.How will road salt affect roadside plants?

Hypertonic Solution

Cells are shrinkingbecause moresolute outside so water leaves cell.

Hypotonic

Concentration of solute is greater inside the cell so water moves in.

Animal cell will burst.Plant cells fill vacuole creates RIGOR!This is what causes plant to stand up.

Hypotonic Solution

Hypotonic Blood Cells

What do cells look like when they have too much or too little water?

Video – diffusion, osmosis & solutionshttp://video.search.yahoo.com/search/

video;_ylt=AgiX5UpIi9KIAFvWdkNyYsubvZx4?p=diffusion&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-701

Facilitated Diffusion CONT’D

Active Transport

Sometimes cells need materials to flow the opposite direction of the flow of diffusion. In this case the cell would need to use ACTIVE TRANSPORT to carry these materials in and out.

DEFINITON: is the movement of materials a cross a cell membrane against the gradient using cellular energy.

The cell uses its’ energy so the transport proteins “pick up” materials and “carry” them across the membrane.

Examples of substances that are carried in and out of the cell this way are: calcium, potassium, and sodium.

ENERGY REQUIRED: YESTYPE OF TRANSPORT: ACTIVE

Active Transport – the energy changes the shape of the protein to match the molecule

Once the molecule

is through the

membrane the

protein will change

its shape back!

http://video.search.yahoo.com/search/video;_ylt=A0SO8ZrQT9dMlgEAXAD7w8QF;_ylu=X3oDMTBncGdyMzQ0BHNlYwNzZWFyY2gEdnRpZAM-?p=active+transport&ei=utf-8&fr2=tab-img&n=21&tnr=21&y=Search

Bulk Transport – No energy

Particles too large to move through the membrane.(Particle of food, proteins)

2 Types of Bulk Transport1. Endocytosis2. Exocytosis

Steps of Endocytosis1. Molecules move into the cell by the cell

surrounding the particle and forming a vacoule around it.

2.Once vacuole is in cell, lysosomes will place digestive juices in the vacoule and break up the food or particles.

Pinocytosis: liquid is surrounded brought into cell.

Phagocytosis: solids are surrounded and brought into the cell.

SOLID LIQUID

Endocytosis

http://video.search.yahoo.com/search/video;_ylt=A0SO8Z1uUddMelcAfjn7w8QF;_ylu=X3oDMTBncGdyMzQ0BHNlYwNzZWFyY2gEdnRpZAM-?p=endocytosis&ei=utf-8&fr2=tab-img&n=21&tnr=21&y=Search

Steps of Exocytosis

1. Opposite of endocytosis2. Vacoule send to the cell membrane

with waste and particles and ejected out of

cell membrane.

Exocytosis

Exocytosis

http://video.search.yahoo.com/search/video;_ylt=A0SO8ZrfUddMOygAFNj7w8QF;_ylu=X3oDMTBncGdyMzQ0BHNlYwNzZWFyY2gEdnRpZAM-?p=exocytosis&ei=utf-8&fr2=tab-img&n=21&tnr=21&y=Search

Types of Cell Transport

No Energy EnergyPassive Transport Active Transport

Diffusion

Faciliated diffusion

Bulk transport

endocyotsis

exocytosis