BIOLOGY CHAPTER 7SECTIONS 3-4

SECTION 3CELL BOUNDARIES

Cell (Plasma) Membrane

• All cells have a cell membrane

• Functions: –Controls what enters and

exits the cell to maintain an internal balance called homeostasis

–Provides protection and support for the cell

electron microscope picture of a cell

membrane.

Structure of cell membrane:

Lipid Bilayer - two layers of phospholipids• Phosphate head is polar (hydrophilic = water loving)

• Fatty acid tails non-polar (hydrophobic = water fearing)

• Proteins are embedded in the membrane

Phospholipid

Lipid Bilayer

Proteins

Membrane movement animation

Polar heads love water and interact with it.

Non-polar tails hide from water.

Carbohydrate cell markers

Fluid Mosaic Model of the cell

membrane

MEMBRANE PROTEINS•May go completely across membrane or be on just one side•Functions:–Transport of ions and molecules across

membrane–Provide shape–Allow cell to be recognized (such as by

the immune system)–Signaling molecules (such as hormones)

may attach and cause changes inside cell

• Cell membranes have pores (holes)–Selectively permeable: let some

chemicals through and block others• Small nonpolar molecules such as O2 and

CO2 can go directly through the lipid bilayer• Carrier proteins transport other molecules

and ions

Pore

Outside of cell

Inside of cell (cytoplasm)

Lipid Bilayer

Proteins

Transport Protein Phospholipids

Carbohydratechains

Structure of the Cell Membrane

Animations of membrane

structure

MEMBRANES INSIDE THE CELL

As we have seen, many organelles have membranes:

• Mitochondrion, chloroplast, nucleus (double membranes)

• Endoplasmic reticulum, Golgi, lysosomes, vacuoles

Cell Walls

• Found in plants, algae, fungi, and many prokaryotes

• Surrounds plasma membrane• Main function: provide support

and protection for the cell• Animal cells DO NOT have cell

walls!

1. What is the cell membrane made of?

2. What kind of cells have a cell wall?

3. What does it mean that the cell membrane is selectively permeable?

4. What is the theory that mitochondria and chloroplasts evolved from prokaryotic cells?

5. Which organelle modifies, sorts and packages proteins for storage or export?

6. What 2 things are found in the cytoplasm that construct the cytoskeleton?

7. Which organelle is used during cell division to pull chromosomes apart?

Types of Cellular Transport

• Passive Transport

cell doesn’t use energy

• Active Transport

cell uses energyhigh

low

This will be hard work!!

high

low

Weeee!!!

• Animations of Active Transport & Passive

Transport

Passive Transport

• Cell uses no energy. • Molecules move randomly• Molecules spread out from an

area of high concentration to an area of low concentration.

(high low)• This is referred to as a

concentration gradient.

Three types of passive transport:

1. Diffusion – random movement of particles from high concentration to low concentration. Continues until all molecules are evenly spaced (equilibrium is reached).Molecules will still move but stay spread out.

http://bio.winona.edu/berg/Free.htm

Simple Diffusion Animation

Facilitated diffusion (Channel Protein)

Diffusion (Lipid

Bilayer)

2. Facilitated Diffusion - diffusion of specific particles through transport proteins found in the membrane • Transport proteins

are specific – they “select” only certain substances to cross the membrane

• Transport larger or charged molecules

Carrier Protein

A B

• http://bio.winona.edu/berg/Free.htm

Two types of facilitated diffusion

• Channel proteins - form a hole across membrane. Ex. - aquaporin lets water through

• Carrier proteins - flip back and forth, allow something to bind on one side and then get released on the other. Ex. - glucose transporter

Aquaporin (water channel)

Although water can penetrate through the membrane, some cells need pores to make it go faster.

http://www.rsc.org/chemistryworld/Issues/2003/November/theflow.asp

Glucose transporter (carrier-type transport)

cc.scu.edu.cn

high concentration

to a low concentration

Cell Membrane

Glucosemolecules

Passive Transport: 2. Facilitated Diffusion

Transport ProteinThrough a

Cellular transport from aHigh

Low

• Channel Proteins animations

•Water moves freely through membrane.

•Solute (green) cannot move across.

Osmosis animation

3.Osmosis: diffusion of water through a selectively permeable membrane from high to low concentrations

Active Transport (Low High)

•Cell uses energy (ATP) to do this

•Actively moves molecules or ions to where they are needed

•Movement from an area of low concentration to an area of high concentration

•Three Types:

Types of Active Transport1. Ion pumps and molecular pumps -transport proteins that require energy to do work•Example 1: sodium/potassium pump – move Na+ out and K+ in. Uses chemical energy of ATP

Sodium Potassium Pumps (Active Transport using proteins)

hyperphysics.phy-astr.gsu.edu

• Example 2: sodium-linked glucose transport in intestine and kidney. Sodium moves from high concentration outside to low inside (releasing energy); this is coupled to glucose going from low to high (requiring energy).

classes.midlandstech.edu

Types of Active Transport

2. Endocytosis: taking bulky material into a cell • Uses energy (ATP)• Cell membrane folds

around food particle to form a vesicle

• May form food vacuole and digest food

Two Types of Endocytosis:• pinocytosis: liquids• phagocytosis: solids

EXTRACELLULARFLUID Pseudopodium

CYTOPLASM

“Food” or other particle

Foodvacuole

1 µm

Pseudopodiumof amoeba

Bacterium

Food vacuole

An amoeba engulfing a bacterium viaphagocytosis (TEM).

PHAGOCYTOSIS

PINOCYTOSIS

Pinocytosis vesiclesforming (arrows) ina cell lining a smallblood vessel (TEM).

0.5 µmPlasmamembrane

Vesicle

Types of Active Transport

3. Exocytosis: forces material out of cell in bulk• Membrane surrounding

the material (vesicle) fuses with cell membrane

• Requires energy (ATP)• Ex.: hormones or

wastes released from cell

Endocytosis & Exocytosis

animations

1.Which type of cellular transport requires energy?

2.Which type of cellular transport always goes from high to low concentration?

3.What is the diffusion of water from high to low concentration?

Effects of Osmosis on Life

Water is so small and there is so much of it the cell can’t control its movement through the cell membrane.

Hypotonic Solution

Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (low solute; high water)

Result: Water moves from the solution to inside the cell): cell swells and bursts open (cytolysis)

• Osmosis Animations for isotonic,

hypertonic, and hypotonic solutions

Hypertonic Solution

Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (high solute; low water)

Result: Water moves from inside the cell into the solution: Cell shrinks (plasmolysis)

• Osmosis Animations for isotonic,

hypertonic, and hypotonic solutions

shrinks

Isotonic Solution

Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.

Result: Water moves equally in both directions and the cell remains same size (dynamic equilibrium)

• Osmosis Animations for isotonic,

hypertonic, and hypotonic solutions

What type of solution are these cells in?

A CB

Hypertonic Isotonic Hypotonic

How Organisms Deal with Osmotic Pressure

• Paramecium (protist) removing excess water video

•Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure.

•A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.

How Organisms Deal with Osmotic Pressure

•Salt water fish pump salt out of their specialized gills so they do not dehydrate.

•Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.

SECTION 4. THE DIVERSITY OF CELLULAR LIFE

Organisms are either unicellular or multicellular.

Unicellular organisms include:• All prokaryotes. These are Bacteria and

another domain, Archaea (originally grouped with bacteria)

• Some eukaryotes. Include most of the organisms referred to as protists (such as protozoa and some algae), and some fungi (such as yeast).

Some unicellular eukaryotes

biology.tutorvista.com

Multicellular organisms include:• All plants• All animals• Some protists• Some fungi

Multicellular Organisms

Cell specialization – cells throughout an organism develop in different ways to do different tasks.–Specialized animal cells:

Ex: red blood cells – transport oxygen; muscle cells – movement

–Specialized plant cellsEx.: guard cells – monitor internal conditions

Tissues

Tissue = group of similar cells that share a structure and function

Examples:• muscle tissue• epithelial tissue - sheets that enclose

or line body parts. Ex. - outer layer of skin

• connective tissue - holds organs in place

• nervous tissue

Organs

• Groups of tissues work together to form an organ

• Examples:‒Stomach has

Muscles to mix food and digestive juices

Epithelial tissue to produce acids for digestion

Blood to provides oxygen‒Others: lungs, liver, kidney, thyroid,

muscles, brain

Tissues of the Stomach

bioserv.fiu.edu

Human Organswww.sciencekids.co.nz

Organ Systems

• A group of organs that work together to perform a specific function

• General functions of organ systems:–Exchanging materials with

environment–Transporting materials to and from

cells–Allowing movement–Storing nutrients for later use–Responding to stimuli

Some Human Organ Systems

• Cardiovascular or circulatory system: heart, blood vessels. Distributes blood (with nutrients, gases, immune cells) to all parts of the body.

• Respiratory system: nose, mouth, trachea, lungs. Takes in oxygen, removes carbon dioxide.

www.bupa.co.uk www.lung.ca

Some Human Organ Systems

• Digestive system: mouth, stomach, intestines, liver. Breaks down food to nutrients.

• Endocrine system: pituitary, pancreas, thyroid, thymus, adrenal glands, ovaries, testes. Produce hormones to regulate body functions.

www.womens-health-advice.com

www.encognitive.com

Some Human Organ Systems

• Nervous system: brain, spinal cord, nerves. Coordinates body activities, responds to stimuli

• Reproductive system: male and female sex organs, uterus, mammary gland. Allows for reproduction and growth and development of the child.

askabiologist.asu.edu

www.britannica.com

Some Human Organ Systems

• Urinary system: kidneys, bladder. Removes waste and regulates water balance.

• Muscular and skeletal systems: muscles, bones, tendons, ligaments, joints. Support body and allow movement.

www.naturalhealthschool.com

www.universalmedicalinc.com

Plants also have tissues, organs, and systems

• Vascular tissue forms tube-like structures to transport food, water, and minerals.

• Organized into a vascular system

www.mhhe.com

crescentok.com

• Photosynthesis involves specialized cells and tissues

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