The CellBiology Unit Chapter 2

pg 266 - 295 Addison-Wesley Science 10 Text

Key Concepts• By the end you will be able to:

– Describe the function of cell organelles in a cell, in terms of life processes, and use models to explain these processes and their applications

Student Learning Outcomes

• Describe the cell as a functioning open system that acquires nutrients, excretes wastes, and exchanges matter and energy

• Identify the structure and describe, in general terms, the function of the cell membrane, nucleus, lysosome, vacuole, mitochondrion, endoplasmic reticulum, ribosomes, chloroplast and cell wall, where present, of plant and animal cells

1. All life forms are made from cells

2. Cells only arise from pre-existing cells

3. The cell is the smallest form of life

Two Types of Cells• Prokaryotic Cells

pro beforekaryo nucleus

• Eukaryotic Cellseu truekaryo nucleus

Prokaryotic Cells• Lack an organized nucleus contain nucleoid

– This is where the genetic material is localized• No membrane surrounding nucleoid or internal

structures• Most organelles are lacking• Functions of life are carried out in the cytoplasm

Prokaryotic Cells• Cell wall is present• Genetic material is

DNA• Division via binary

fission• Group includes

bacteria and blue-green algae

Eukaryotic Cells

• Contains a nucleus as well as distinct organelles• DNA is enclosed in a nuclear envelope• Cell division by the process of mitosis• Includes plants, animal cells, fungi and protists

Plant & Animal Cells

• Plant cells rigid cell wall, chloroplasts & large vacuoles

• Animal cells centrioles

The Cell is an Open System• Matter and energy are

exchanged with the environment– Think of an ancient

fortressed town -enclosures in place so threats would be kept out, but supplies and materials could get in

– Also anything built within the town could be transported out

Cell Structures & Their Functions

Cell Functions• Life processes must

occur within specialized structures called organelles– Intake of nutrients– Movement– Growth– Response to stimuli– Exchange of gases– Waste removal– Reproduction

Cell Membrane

• The protective barrier for the cell– Allows transport of needed materials in & waste out– Cell-to-cell interaction & communication– Recognition of molecules

• Phospholipid bilayer with embedded cholesterol, glycoproteins, and integral & peripheral proteins

Nucleus

• Organelle that contains the DNA (genetic material of the cell) and directs all cellular activity– Surrounded by nuclear envelope– Pores allow for transport of materials

Cytoplasm

• Gel-like substance inside the cell membrane– Contains nutrients required by cell to carry on life

processes– Substance which organelles are suspended– Physical nature allows for movement cytoplasmic

streaming

Cell Wall

• Found in plants, bacteria, some protists & fungi

• Is the rigid frame around the cell that provides strength and support

Chloroplasts• Found in plants and

some protists• Contain chlorophyll• Site of photosynthesis

– Conversion of solar energy into chemical energy

6H2O + 6CO2 + energy 6O2 + C6H12O6

Vacuoles/Vesicles• Membrane-bound

structures which store nutrients, products of secretions, and fats– In plants, central

vacuole is for water storage

– Swell to give cell turgor, increasing pressure and firmness

Endoplasmic Reticulum• Series of interconnected

tubes that branch from the nuclear envelope– Materials can be

transported through these tubules

• Rough ER - has ribosomes attached to it, associated with protein synthesis

• Smooth ER - associated with fat & oil production

Ribosomes• Dense-looking granules formed of two parts• May be attached to endoplasmic reticulum or be

free in the cytoplasm• Site where amino acids are assembled into

proteins

Lysosomes• Membrane-bound

sacs from where digestion can occur

• Various roles include– Defense against

bacteria– Destruction of

damaged cell organelles

– Controlled digestion of certain tissues during development

Golgi apparatus• Composed of flat,

disc-shaped sacs involved in secretions

• Receives substances from ER, packages them for transport out of the cell

Mitochondria

• Rod-like structures where chemical energy in sugars is converted to energy the cell can use

• Process called cellular respiration6O2 + C6H12O6 6H2O + 6CO2 + energy

Escherichia coli (E. coli)

The Liver Cell

Chemical Composition• Major elements making up cell structure:

– Carbon – Hydrogen – Oxygen– Nitrogen

• Organized into 4 major organic compounds– Lipids (fats and oils)– Carbohydrates (sugars, starches, cellulose)– Protein (muscle fibre)– Nucleic Acids (DNA)

Chemical Composition

• Water also major compound– Is the solvent providing environment for

reactions inside and outside of cells• Can find trace elements in tiny

amounts– Zn (zinc)– Mg (magnesium)– Fe (iron)– Mn (manganese)

Chemical Composition

Modeling the Membrane• Sometimes referred to as

the plasma membrane– Consists of a phospholipid

bilayer

Modeling the Membrane• Double layer of lipids with phosphate

group attached– Phosphate faces watery fluids - hydrophilic– Lipids face towards each other - hydrophobic

Modeling the Membrane• Proteins are suspended in the bilayer

– Attach to outside of cell membrane– Attach to inside of cell membrane– Run through the membrane

PERIPHERAL

INTEGRAL

Modeling the Membrane• Cholesterol embedded in phospholipid

bilayer - hydrophobic• Glycoprotein - is a type of protein with

oligosaccharide attached

Modeling the Membrane• Fluid mosaic model

– Proteins are like tiles in a mosaic

– Lipid bilayer is like the grout holding the tiles together

– Each part has role for moving nutrients, gases & wastes in and out

Cell Membrane & Transport RolesSection C 2.2 - pages 274 - 283

Review - Cell Membrane• Cell is an open system what does this mean?

– Nutrients & waste can transport in and out– Barrier against threats– Interacts with surroundings

• Fluid mosaic model what does this mean?– Proteins embedded in phospholipid bilayer– From a top-down view looks like a mosaic piece

Roles of Proteins1. Carriers:

• Bring materials in & out of cell2. Receptors: recognitions of cells

• Involved in cell metabolism• Detection of hormones, viruses, bacteria, etc

3. Adhesion• Link other cells together

Particle Model of Matter1. All matter is made of particles - may be

different in size & composition in different substances

Particle Model of Matter2. Particles are constantly moving or

vibrating• Move least in solids, most in gases• Adding or removing energy will affect

particle movement

Particle Model of Matter3. Particles of matter are attracted to one

another or are bonded together4. Particles have spaces between them

• Smallest in solids (except ice)• Greatest in gases

Diffusion• Natural movement of particles from area

of high concentration to area of low concentration

• End result - state of equilibrium– Particles are still moving but maintain an

overall balanced distribution

Diffusion• Rate of diffusion can be increased by

adding energy & increasing molecular movement

– Ex. by stirring or heating• Process of diffusion will continue even

in absence of added energy

Diffusion• Occurs in cells

– Water is the solvent providing environment for all biological reactions

• Diffusion of water or solutes can occur across cell membrane or within cytoplasm

– Must have a difference between concentrations

Diffusion• Concentration gradient - difference

between areas with two concentrations– Determines the direction water or solutes

will move• In the cell, the cell membrane is the gate-keeper

trying to maintain equilibrium

Diffusion• Movement by diffusion is considered to

be passive transport– Energy input is not required for process to

occur– The energy in the particles is enough for

movement along concentration gradient

Diffusion• The cell needs to keep some substances

out while letting other substances enter• Consider the cell membrane to be

selectively permeable– Will allow certain particles through, but not

others

Diffusion• Semi-permeable membranes are those

which allow certain particles through, but excludes others

– Naturally occurring– Can be synthetic as

well

Diffusion• Passage is determined by

– Size of molecule– Charge on molecule– Solubility in lipids

• In general, particles move from an area of high concentration to an area of low concentration

Drives osmosisand diffusion

Different moleculesor ions move along

concentration gradientindependent of

each other

Involves moleculesor ions of a single type

Must involve different

concentrations in cells

Different concentrationsmust be separated

by a membrane

Concentration Gradient

Osmosis• Refers to the movement of water through

a membrane in response to a concentration gradient– Membrane not permeable to the solute

• Passive transport• Movement from high concentration to low

concentration

Osmosis - Hypotonic • “hypo” means under

– Lower concentration of solutes in solution than in the cell

– Water will enter the cell

Osmosis - Hypertonic • “hyper” means over

– Higher concentration of solutes in solution than in the cell

– Water will leave the cell

Osmosis - Isotonic • “iso” means equal

– Equal concentration of solutes in solution and in the cell

– Water will leave the cell and enter the cellno net movement of water but is in equilibrium

Facilitated Diffusion• Substances soluble in water but not lipids

need some way to cross the cell membrane– Use of proteins embedded in membrane

• Channel proteins• Carrier proteins

Facilitated Diffusion• Channel proteins

– Create pores or channels in membrane• Small, water-soluble particles are able to move

through• Movement in response to concentration gradient

Facilitated Diffusion• Carrier proteins

– Able to attach to larger molecules not capable of diffusing across membrane on own

– Changes shape and physically moves molecules across and into cells

Facilitated Diffusion• Movement in response to concentration

gradient but needs protein facilitator– Forms of protein-mediated passive transport,

as no added energy is required

Active Transport• Transport via protein carrier will, in some

cases, require energy input– Moving against concentration gradient– From areas of low concentration to areas of

high concentration• Carrier proteins work almost like a pump

Active Transport• Energy needed comes from substance

called adenosine triphosphate, ATP

Endocytosis• Use of vesicles, sacs surrounding large

particles– Usually small and temporary

• When feeding (example: amoeba), comes across food particle, and engulfs it using the cell membrane: ENDOCYTOSIS– Pinches off and membrane then encloses

particle within it

Exocytosis• Use of vesicles, sacs surrounding large

particles– Usually small and temporary

• Moves to the plasma membrane & fuses– Ruptures, releasing contents into

surroundings

Check & ReflectPage 283

#2, 3, 5, 6, 7, 10

Application of Cellular Transport

• Industrial use of synthetic cell membranes which mimic natural function– Known as membrane

technologies– Pharmaceutical research

uses understanding of cell membrane proteins to develop new drug therapies

Membrane Proteins & Disease

• New discoveries focus on receptor or recognition proteins– May be able to produce a “lock-and-key” model to prevent

viruses to enter cell• Ex. HIV viral research

– Single out defective cells, not healthy ones using recognition proteins

• Ex. Cancer drugs

Protein Hormone Transport• Ex. Insulin - small protein

produced in pancreas– Secreted into bloodstream,

binds with membrane receptors

– Receptor sites including liver, muscle and fat

• Binding stimulates movement of glucose, which is used to produce energy

Dialysis• Two types of dialysis

– peritoneal dialysis – hemodialysis

Reverse Osmosis• Desalination removing salt from sea water to

make it suitable for drinking– Move water through series of smaller and smaller

filters• Requires pump activity against concentration gradient• Active transport

Surface Area to Volume RatioSection C 2.4 - pages 289-293

YOU NEED A CALCULATOR!!!

Is Bigger Better?• Why are cells so small?• Wouldn’t it be better if cells grew bigger?

– Then you would only need a few hundred cells instead of trillions

• Let’s consider this …

Time for Math … • Ability to transport material in and out is critical

– Must be kept at a maximum• If cells become larger, the volume increases

– Thus more molecules will need to be transported– The distance they must travel will also increase

• Surface area will also need to increase!!

• Get out your calculators!! Let’s calculate this …

• Surface area to volume ratio calculated by:

Shape & Size of Organisms• Amount of surface exposed to environment is

crucial– SA determines opportunities for transport of materials

Maximizing Potential• Cells must have greatest SA:V

– Maximizes efficiency & promotes survival– Distance any molecule must travel is not too far

• In humans, no cell is more than 0.1 mm from a blood-transporting capillary

• Plants utilize xylem and phloem for transport systems

Check for Understanding

• Page 294 Unit C 2.0 Section Review– Complete Questions

• 2, 4, 6, 7, 15, 16, 17, 31, 33

Quiz on Chapter 2 TOMORROW

… Bring a CALCULATOR

PlantsBiology Unit Chapter 3

pg 296 - 333Addison-Wesley Science 10 Text

Cells, Tissues & Systems

• Survival happens when– Needs are met– Challenges in environment are met

• May be dependent on single-cell or interaction of countless cells

Division of Labour• Cells can be specialized for one particular

function– More effective performance– Efficient performance

• Single-celled organisms must be able to multi-task

Size• Surface area to volume ratio restricts size

of unicellular organism • In multi-cellular organisms, internal

structures aid in efficient material exchange

Interdependence of Cells

• When a single-celled organism dies, that is the end of it

• When a cell in a multi-cellular organism dies:– Does not kill entire organism

• However there is a cost

Why do Cells Divide?– To grow new tissues– To repair damaged tissues

• Process is via mitosis– One cell literally divides into two daughter

cells

• Cell division does not occur at the same rate throughout the entire organism– Meristems are growth areas in particular

spots on the plant• Produce root tissue and shoot tissue

Why do Cells Divide?

Multicellular Structure• Living systems made up of many parts

– Cells begin to have specialized functions• Groups of cells performing same function

together are called tissues

Multicellular Structures• When tissues contribute to the same

function they are called organs, and these come together to form systems

Multicellular Structures• In a plant there are

two systems– Shoot system– Root system

The Shoot System• Refers to everything above the ground

– Includes stem, leaves, buds, flowers and fruits

– Also includes tubers• Swollen stems underground that store food, ex.

potatoes

The Root System• Refers to everything that is underground

– Also includes aerial roots, even though these are above ground

Roots and Shoots• Made up of tissues specialized for

different activities– Some examples are gas exchange, transport

of materials, photosynthesis …• These tissues are made up of three main

types of individualized, specialized cells

Dermal Tissue (Epidermis)• Outer layer that covers all herbacious

(non-woody) plants– Generally one-cell layer thick– Duty is exchange of matter and gases into

and out of the plant

Dermal Tissue (Epidermis)• In woody plants, replaced by cork and

bark in secondary growth stage of development

Dermal Tissue (Epidermis)• In the shoot system

– Comprises the stem and leaves• Primarily involved in gas exchange

– Protects from disease– Secretes a waxy substance - cuticle

• Resists attacks from pests• Reduces water loss

Dermal Tissue (Epidermis)• In the root system

– Responsible for the uptake of water & mineral saltsfrom the soil

Ground Tissue• Makes up majority of the plant

– Found as the layer beneath epidermis• Has several important functions

– In the stem provides strength & support– In the roots involved in food & water

storage– In the leaves where photosynthesis occurs

Vascular Tissue• Responsible for the movement of

materials through the plant– Xylem tissue moves water and dissolved

minerals from the roots up the stem to the leaves

– Phloem tissue transports sugars from the leaves to other parts of the plants

Xylem & Phloem

Xylem Tissue• Thick-walled tubes of varying diameter

Phloem• Formed from individual long sieve tube

cells– Have perforated end walls– Continuous ducts

Phloem• Connected to small, nucleated companion

cells– Direct activities

Plant Cell Specialization• Root hairs - responsible for absorption of

water & minerals from soil– Increases surface area for absorption– More water can enter, maximizes osmosis

Plant Cell Specialization• Cuticle - produced by dermal cells of

shoot system– Protects cell from water loss

Plant Cell Specialization• Guard Cells - form tiny pores called

stomata– For gas exchange– Upper epidermis usually fewer stomata than

lower epidermis

Check & ReflectTo be completed for homework

**summative**Pg 302

Q #s 1, 2, 4, 5, 7We will take these up for homework

marks tomorrow first thing

Section C3.2

The Leaf & Photosynthesis

Monocot vs Dicot• Two types of plants

– Monocotyledons• Only one seed leaf in the embryo

(ex corn)– Dicotyledons

• Two seed leaves in the embryo (ex beans)

• Closer comparison of the two

– Monocots tend to have parallel veins while Dicotsusually are netted

Venation

– Monocot floral partsare in multiples of 3

– Dicot floral parts are in multiples of 4 or 5

Flower Parts

– Monocot roots are adventitious

– Dicot roots are bothadventitious and primary

– Monocot vascular bundles are scattered

– In Dicots, the vascular bundles form a ring

Vascular Tissues

What is the Leaf?

What is the Leaf?• Collection of tissues• Main purpose is to support process of

photosynthesis– Dermal, ground & vascular tissues

The Chloroplast• Unique to plants

– Where photosynthesis takes place• Means “putting together with light”

– Identified by their color• Found in ground tissue of leaves and some stems

The Chloroplast• Movement in chloroplasts has given

indirect evident to cytoplasmic streaming

Gas Production• Two important reactions take place in

plants– Produce gases– Are the opposites of each other

Gas Production• Photosynthesis produces oxygen and

glucose• Cellular respiration produces carbon

dioxide and water, plus ATP energy– Plants take in carbon dioxide, but they also

produce carbon dioxide!• Simply take in more carbon dioxide than they produce

Section 3.3

The Leaf Tissues & Gas Exchange

Getting Air In, Without Lungs!!

• Air (gases) can enter cells via passive diffusion– This would take a long time

• Leaf has developed specialized cells to maximize its ability to exchange gases

Dermal Tissue• Epidermis on top and bottom of leaf is

very thin and clear• Tiny openings called stomata are formed

by guard cells– This allows gas to exchange easily

Dermal Tissue• Stomata regulate movement of gases

– Carbon dioxide and oxygen can enter and leave the leaf

• Direction is determined by a concentration gradient

• Majority found on lower surface of leaf

Abscisic Acid• A plant hormone• Mediator in adaption of plant to stress

– Stomata opening and closing are sensitive to abscisic acid

– Rapid onset when water uptake from roots is insufficient to keep up with transpiration

Transpiration• This is the process of water loss through

the stomata

– Film of water is always on cell surface

– Means water is continually being lost by evaporation

– When water is not available, guard cells become limp, closing the stomata

Transpiration– Water enters

root hair cells and moves through cells by osmosis

– Water rises in xylem due to adhesionand cohesion

– Evaporation has a cooling effect

Xerophytes• Xero means dry• Phyte means plant

– Therefore, a xerophyte is a plant able to survive in an environment with very little water

Xerophytes• Adaptations to the habitats can include:

– Reduced leaves• Spines

– Thickened waxy cuticle– Reduced number of stomata– Stomata surrounded by hairs– Water storage tissue– Low growth forms

Ground Tissue

Ground Tissue• Between upper and lower epidermis is the

mesophyll– Two very different types of cells here

• Palisade tissue cells (parenchyma) just below upper epidermis

• Spongy mesophyll tissue (parenchyma) below palisade and above lower epidermis

Ground Tissue• Palisade Tissue

– Long, rigid, rectangular– Tightly packed– Responsible for photosynthesis

• Many chloroplasts found here– Require carbon dioxide, produce oxygen

Ground Tissue• Spongy mesophyll tissue

– Loosely packed, irregularly shaped, less rigid cells

– Increased space allows more gas diffusion• Moves oxygen towards stomata for release• Moves carbon dioxide from the air to the palisade

tissue

Vascular Tissue• Provides leaf with water for transpiration

& photosynthesis– Removes sugars produced in photosynthesis

• Xylem & phloem linked together in a vascular bundle

Gas Exchange• No organs specific for gas exchange -

occurs via diffusion– The leaf is not the only place that gas

exchange occurs– Pores in bark and herbaceous plants are called

lenticels• Provide pathway for gas exchange• Also provide pathway for an opening for

transpiration

Section 3.4Transport in Plants

Cohesion & Adhesion• Water clings to each other, and to other

molecules– Helps aid in transport of water

• Attraction of water molecules to each other is called cohesion

Cohesion & Adhesion• Due to polar nature of water molecules

– Remember, positives and negatives attract• Also means water is attracted to other

molecules– The attraction of water molecules to other

substances is called adhesion

Root Pressure• Rate of transpiration is low• Roots still collecting minerals• Water is forced from higher pressure in

roots to lower pressure in leaves

Water Transport• Transport of water in plants is due to a

combination of factors– Differences in pressure caused by osmosis &

transpiration– See diagram in text on pg 318 for summary

Water Transport• Evaporation of water through stomata or

lenticels creates– Tension (or) transpiration pull– This draws water up xylem to leaves– Then can be moved into ground tissue and

out through stomata• In ideal conditions, water can move 75

cm per MINUTE!!– Very cool …

Tonicity• Tonicity refers to

solutions being hypertonic, hypotonic or isotonic

• When solute concentration around a plant cell changes, there is an effect on the cell

Tonicity• Plasmolysis shrinking of cytoplasm and

plasma membrane away from cell wall– Due to outflow of water in hypertonic solution– Observed only in cells with rigid cell walls

Sugar Transport• What happens if you removed the

phloem?– Plant would die

• Cells would not be receiving products of photosynthesis

Sugar Transport• Where sugar is manufactured

– The leaf• Called the source

• Where sugar is used or stored– Throughout the plant

• Called the sink

Section 3.5Control Systems

Response to Stimuli• Not as pronounced

as in animals• Do have responses to

specific stimuli– Light– Gravity

Response to Stimuli• Plants grow towards light

– Phototropism– Movement of the plant in response to the

stimulus• Shoots towards light• Roots away from light

Response to Stimuli• Response to gravity• Called gravitropism

– Roots grow towards gravitational force– Shoots grow away from it

Tropisms

Positive gravitropism

GravityRoot

Negative gravitropism

GravityStem

Weak negative phototropism

LightRoot

Positive phototropism

LightStem

TropismStimulusPlant Part

Auxin• Another plant hormone

– Ability to initiate cell elongation response– Discovered by F.W. Went in Holland

Other Control Mechanisms• Respond to touch

– To temperature, chemicals and water– To photoperiod

Angiosperms

• Sketch this diagram in your notes and label:– Testa (seed coat)– Micropyle (ask me!!)– Embryo root (hyopcotyl)– Embryo shoot (plumule)– Cotelydons

Angiosperms• Sketch this diagram in your notes and

label:– Sepals– Petals– Anther– Filament– Stigma– Style– Ovary

Angiosperms• Pollination transfer

of pollen grains (♂gametes) to carpel (♀gametes)

Angiosperms

• Fertilization ♂gametes join with ♀gametes in ovary of plant

Angiosperms

• Seed Dispersal Is covered by a seed coat -usually has some stores of food

• Angiosperm means “enclosed seed”

Germination• Need specific conditions

– Water• should be a moist environment

– Oxygen• plenty of access

– Temperature• usually around 15°C• moderate

Starchy Seed Germination1. Imbibition uptake of water initiates

biological processes2. Gibberellin transport gibberellin levels rise;

carried from embryo away3. Amylase production a starch-digesting

protein enzyme is produced4. Starch digestion starch is converted into

sugars5. Sugar transport Sugar carried from stores to

embryo; provides energy (cellular respiration) for germination to occur

Flowering Plants• Flowering under control of light• Is the length of uninterrupted darkness

critical to flowering

Long-Day Plants• Flowers after day-length increases above a

certain threshold• Only when day length >12 hours (short night)

– Ex. Arabidopsis– Under control of phytochrome and

cytochrome

Short-Day Plants• Flower after day length decrease below a

certain threshold• Long night

– Ex. wheat

Phytochrome

• Blue-green pigment– Active state (Pfr) at sunrise – Inactive state (Pr) at sunset

• Influences seed germination, stem elongation and formation of leaves, flowers, fruits and seeds– Natural sunlight contains more red

wavelengths than far-red– Shade contains more far-red wavelengths

than red wavelengths

Phytochrome

• Pr absorbs red light (650-670 nm) strongly– Once red photon has been absorbed there is a

rapid change to Pfr• Now far-red (705-740nm) preferentially absorbed

Phytochrome

Phytochrome

– Apical meristemsresponsible for plant length

– Found in roots and shoots

– Lateral meristemsresponsible for increase in plant girth