Cell Structure and Function

Definition of CellA cell is the smallest unit that is capable of

performing life functions.

RECALL... Levels of Organization!

Why do we call them cells?

• In 1665, Robert Hooke was the first to view cells from cork (dead plant material).

• He called them “cells” because they looked like tiny rooms.

What is the Cell Theory?1. All living things are composed of

cells

2. Cells are the basic units of structure and function in living things.

3. New cells are produced from existing cells.

Why Cells are Important?• What happens inside cells causes us to

be who we are.

What is it that is found inside of all cells???

• All diseases start at the level of the cell.

• All growth and life starts from a single cell.

• Cell specialization: allows cells to perform different functions in multicellular organisms

GENES!! (DNA/RNA)

2 main types of cells

1. Prokaryote:

ex. Bacteria

2. Eukaryote: ex. Plant, Animal, Fungi, Protist

HOW DO PROKARYOTES DIFFER FROM

EUKARYOTES?

1.) No Nucleus

2.) DNA floats in cytoplasm

3.) Flagella

Flagella

As we discuss the differences between Eukaryotic and Prokaryotes fill in your venn diagram.

Eukaryotes Prokaryotes

both

What Makes Prokaryotic Cells Different?

ONLY WRITE THE UNDERLINED WORDS

• Much smaller

• Less complex (SIMPLE)

• No nucleus

• Circular DNA that is found free floating in the cytoplasm

• NO membrane bound organelles found in the cytoplasm

• Always has a cell wall

What Makes Eukaryotic Cells Different?

ONLY WRITE THE UNDERLINED WORDS

• Much larger

• Much more complex• Contain a nucleus to house the genetic material (DNA)

• Linear DNA packaged into chromatin found inside the nucleus

• Contains MEMBRANE BOUND organelles-specialized structures in the cytoplasm

• Not all have a cell wall

Examples of MBOs

• Nucleus

• Smooth endoplasmic reticulum

• Rough endoplasmic reticulum

• Golgi apparatus

• Lysosome

• Mitochondria

• Centrioles

• Vacuole

• Chloroplast

*Ribosomes are NOT membrane bound so can be found in both types of cells*

Characteristics Shared (BOTH)

ONLY WRITE THE UDNERLINED WORDS IN VENN DIAGRAM

• same basic functions

• Plasma membrane to control what enters and leaves the cell

• “Filled” with cytoplasm

• Contain ribosomes to make protein

• Contain Nucleic Acids (DNA/RNA)

Eukaryotic Cells

What does size have to do with it?• Prokaryotic cells are much smaller than

eukaryotic cells. Why?– Smaller surface area to volume allows nutrients to

easily and quickly reach inner parts of the cell.

– No specialization because they are UNICELL ; one cell must be able to do all life functions

– Eukaryotic cells are larger and can not pass nutrients as quickly. They require specialized organelles to:

• carry out metabolism

• provides energy

• transport chemicals throughout the cell

About Cell Membranes

1.All cells have a cell membrane

2.Functions:

a.Controls what enters and exits the cell to maintain an internal balance called homeostasis

b.Provides protection and support for the cell

TEM picture of a

real cell membrane.

3.Structure of cell membrane

Lipid Bilayer -2 layers of phospholipidsa.Phosphate head is polar

(water loving)

b.Fatty acid tails non-polar(water fearing)

c.Proteins embedded in membrane

Phospholipid

Lipid Bilayer

4. Cell membranes have pores (holes) in ita.Selectively permeable: Allows some molecules in

and keeps other molecules outb.The structure helps it be selective!c. The plasma membrane is describe as a Fluid Mosaic

Model because of how it is arrange and there are PORES in between the phospholipids.

Pores

Proteins

Membrane

movement

animation

Polar heads

love water

& dissolve.

Non-polar

tails hide

from water.

Carbohydrate cell

markers

Fluid Mosaic

Model of the

cell membrane

Purpose of Cell TransportCells must move materials across the membrane in

order to maintain homeostasis

– Nutrients/ Oxygen must be able to easily move into the cell– Wastes/ Carbon dioxidemust be able to easily

move out of the cell

Molecular Movement

• All the substances important to life are

almost always part of a solution.

• Solute: The substance dissolved in the

solvent

Ex. Sugar, salt, starch

• Solvent: dissolves the solutes

Ex. Water is the universal solvent of most

solutions involved in cellular activities.

Molecular MovementFactors that affect the rate of diffusion:

1. concentration (higher=faster)

2. temperature (warmer=faster,

colder=slower)

3. pressure (high pressure=faster)

Concentration = amount of material in an areaDraw a higher concentration of solutes inside the cell than outside the cell.

Draw a lower concentration of solutes inside the cell than inside the cell.

How would these cells go back into homeostasis?

Types of Cellular Transport

Passive Transport

cell does NOT use energy1. Diffusion

2. Facilitated Diffusion

3. Osmosis

Active Transport

cell DOES use energy1. Protein Pumps

2. Endocytosis

3. Exocytosis high

low

This is

gonna

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 highconcentration to an area of low concentration.

• (HighLow)• Moves with the concentration

gradient

Passive Transport:1. Diffusion

1. Diffusion: random movement of particles from an area of high concentration to an area of low

concentration.

(High to Low)

• Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note:molecules will still move around but stay spread out.

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

Simple Diffusion

Animation

2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane

a. Transport Proteins are specific – they “select” only certain molecules to cross the membrane

b.Transports larger or charged molecules

Facilitated

diffusion

(Channel

Protein)

Diffusion

(Lipid

Bilayer)

Passive Transport:

2. Facilitated Diffusion

Carrier Protein

A B

• http://bio.winona.edu/berg/Free.htm

3.Osmosis: diffusion of water through a selectively permeable membrane

• Water moves from high to low concentrations

•Water moves freely

through pores.

•Solute (green) too

large to move across.

Osmosis

animation

Passive Transport:

3. Osmosis

Hypotonic Solution

Hypotonic: The solution (environment) has a lower

concentration of solutes and a higher concentration of

water than inside the cell. (Low solute; High water)

Result: Water moves into the cell from solution: Cell

swells and bursts open (cytolysis)!

• OsmosisAnimations for

isotonic, hypertonic, and hypotonic

solutions

Hypotonic: freshen that lettuce!

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 out of the cell into the solution:

Cell shrinks (Plasmolysis)!

• OsmosisAnimations 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)

• OsmosisAnimations for

isotonic, hypertonic, and hypotonic

solutions

What type of solution are these cells in?

A CB

Hypertonic Isotonic Hypotonic

Osmosis Video Osmosis Rap

Active Transport

•cell uses energy

•actively moves molecules to where they are

needed

•Movement from an area of low concentration

to an area of high concentration (Low High)

•Molecules go against the concentration

gradient

3 Types of Active Tranport

1. Protein Pumps

2. Endocytosis

3. Exocytosis

Types of Active Transport

1. Protein Pumps -

transport proteins that

require energy to do

work

•Example: Sodium /

Potassium Pumps

are important in nerve

responses.

Sodium

Potassium Pumps

(Active Transport

using proteins)

Protein changes

shape to move

molecules: this

requires energy!

Types of Active Transport

• 2. Endocytosis: taking bulky

material into a cell

• Uses energy

• Cell membrane in-folds around food particle

• “cell eating”

• forms food vacuole & digests food

Ex. This is how white blood cells eat bacteria!

Endocytosis by white blood cell

Types of Active Transport

3. Exocytosis: Forces material out of cell in bulk• membrane surrounding the

material fuses with cell membrane

• Cell changes shape –requires energy

• EX: Hormones or wastes released from cell

Endocytosis &

Exocytosis

animations

Endo and Exocytosis (~at 1:13 mark)

Exocytosis and Endocytosis

Exocytosis – process of a cell releasing materials (exiting)

Endocytosis – process of cell taking materials in (entering)Exocytosis

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 protest, like paramecium, has contractile vacuoles

that collect water flowing in and pump it out to prevent

them from over-expanding.

•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.

The process in which the movement of materials across a membrane from low to high concentration requiring energy is ____.A. passive transportB. diffusionC. active transportD. facilitated diffusion

A. B.

C. D.

• Which one is different?

• How is it different?

• Does ACTIVE transport require ENERGY?

• Does passivetransport require energy?

Cell Transport Concept Map Name Date

Cell transport involves the

exchange of molecules

through the

Against the

concentration gradient

(low to high)

Down the

concentration gradient

(high to low)

requires small molecules move

through

examples

moved by

Small molecules

move through

Larger molecules

move through

of water

also called

large molecules

transported by

in out

Example: Example:

Word Bank: Facilitated Diffusion Cell Membrane (2X) Osmosis

Active Transport ATP Energy Food/Bacteria Proteins (2X)

Passive Transport Glucose/Amino Acids/Ions Endocytosis

Diffusion Wastes/Secretions Exocytosis