Cell Structure

and Function

Unit 4

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 multicellularorganisms

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

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 nutrientsto 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

Examples of MBOs

Nucleus

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Golgi apparatus

Lysosome

Mitochondria

Centrioles

Vacuole

Chloroplast

*Ribosomes are NOT membrane bound*

Eukaryote

(Eu – True)

Prokaryote

(Pro – No)

• No

Nucleus• Has TRUE

Nucleus• Genetic

Material

(DNA)

• Cell

Membranes

• Cytoplasm

• Ribosomes

• No

membrane

bound

organelles

• Simple,

small

• Membrane

bound

organelles

• Large,

complex

Pro

kary

otic v

s. E

ukary

ote

sSize does

matter!

Which type

of cell is

bigger?

Watch

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

Amoeba Video

Complete Cell Structure Flip

BookWrite the function for each cell organelle

and label pictures

***Major Test Grade: Cell Comparison

Poster

Day 2 Notes: Cell membrane, transport and solutions

• To be a barrier between a cell and its environment

• Allow nutrients and water to enter while removing waste products

• The membrane is selectively permeable (controls

what molecules come in and keeps other molecules out) Ex. Bouncer at a club

Function of the Cell Membrane

Cell / Plasma membrane Function

• Maintains an internal balance inside the cell: Homeostasis

Parts of the plasma membrane• The phospholipid form 2 layers.

• Each layer contains hydrophilic heads (water-loving) and hydrophobic (water-fearing) tails

Parts of the plasma membrane• Carbohydrate chains are at the surface and are

sites where viruses or chemical messengers can attach.

• Proteins will help transport (move) macromolecules (glucose) in & out of the cell.

Transport Protein

Transport Protein

Carb Chain

PhospholipidBilayer

Hydrophobic

Parts of the Cell (Plasma) Membrane

• Phospholipid bilayer • Transport proteins

INSIDE OF 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?

A B Where is there a higher conc.?

Where is there a lower conc.?

What does “B” represent?

Predict what will happen in the diagram?

CA

C

SELECTIVELY PERMEABLE MEMBRANE

PARTICLES WILL MOVE FROM A TO C TO REACH EQUILIBRIUM

Passive Transport-

Passive Transport

– requires NO energy

– Goes from high to low concentration

– 3 main types: diffusion, facilitated diffusion, osmosis

3 Types of Passive Transport1. Diffusion

• Movement of moleculesthrough the cell membrane from high to low conc.

2. Facilitated Diffusion

• Movement of molecules through the cell membrane using transport proteins from high to low conc.

3. Osmosis

• Movement of water molecules through the cell membrane from high to low conc.

Facilitated diffusionWhy?

Diffusion (any particles) or

Osmosis (water only)Uses a TRANSPORT PROTEIN going from H to L concentration

Assessment

When no energy is required for molecules to move through the membrane it is called

A. Active transport

B. Passive transport

Assessment

What transport moves particles into and out of the cell?

A. Osmosis

B. Diffusion

C. Facilitated Diffusion

D. Both B and C

WATER ONLY!

Passive Transport: Osmosis

Osmosis - Movement of water from high to low concentration through a membrane

Water molecule

Solute moleculeEx. sugar

• Water is so small and can easily pass through the membrane so it REQUIRES NO ENERGY (passive transport).

• Water is ALWAYS flowing.

•Water moves freely through pores.

•Solute (green) too large to move across.

Osmosisanimation

Passive Transport: Osmosis

3 types of Osmotic solutions

Remember!

Solution: Mixture of water (solvent) and particles (solutes)

Ex. The environment of the cell is a solution. Blood is a solution.

3 types of osmotic solutions for cells

a. Isotonic

b. Hypertonic

c. Hypotonic

3 types of Osmotic solutions

Isotonic SolutionCell remains same size

• Water moves?

– In and out equally

Where is there more water, cell or environment?

– Equal conc. of water inside and outside of cell

• When you have balance its called?

Homeostasis

Hypotonic Solution ex. distilled waterCell gets BIG- blows up

(Hypo – Hippo)

• Water moves?– Inside the cell

Where is there more water, cell or environment?

• Solution– has more water

• Cell– has less water

Animal cell may LYSIS or BURST

Hypertonic Solution ex. salt solutionCell Shrinks

• Water moves?– Out of cell

What has more water?

• Solution– has less water

concentration

• Cell– has more water

concentrationVideo

Plant will WILT

Osmosis Across Membranes

Questions

• What type of solution is in side A? Hypotonic Solution

• What type of solution is in side B? Hypertonic Solution

• Which way will water move to balance out the tube? Right to left (There is more water)

• Are the black dots moving through the membrane? Yes or no, explain. No, only water is!

Inside CellOutside Cell Inside Cell Inside CellOutside Cell Outside Cell

A B CIsotonic Hypertonic 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 tugor pressure.

•A protist 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.

Osmotic Solutions: Real Life

• If you put salt onto a slug, it dies. Why? Explain using information about the osmotic solutions.

Water moves in or out of cell?

What happens to the cell?

What solution is this?

80% water

20% water

2.Water moves in or out of cell?

What happens to the cell?

What solution is this?

10% salt

90% salt

3.

Water moves in or out of cell?

What happens to the cell?

What solution is this?

17% water

83% salt

6.

Osmotic Problems

Active Transport•cell uses ATP energy

•actively moves molecules to where

they are needed

•Movement from an area of low

concentration to an area of high

concentration

(Low High)

• Goes against the concentration

gradient

3 Types of Active Transport

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!

Types of Active Transport

3. Exocytosis: Forces bulky material out (exit) of cell in membrane surrounding the material fuses with cell membrane

• Cell changes shape –requires energy

• EX: Hormones or wastesreleased from cell

Exocytosis

Exocytosis and Endocytosis

Exocytosis

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?