Understanding CellsA. History of the Microscope microscopes :

an object

Make objects larger than they are

Allow us to see objects that can’t be seen with our eyes

1845

anything that will magnify

the inventor of the first microscope is debatable

– Zaccharias and Hans Janssen (Holland) produced a crude microscope

used a 2 lens system

– Galileo (Italy) built a crude compound

microscope

– Anton Van Leeuwenhoek (Holland) built a simple single lens microscope first person to see unicellular

movement

1595

1609

1600’s

– Hooke (England) built a compound microscope 3 lens system

– Hillier and Prebus (U of T Canada) built first electron microscope

– first scanning electron microscope

1665

1930’s

1940’s

B. Types of Microscopes

Are early microscopes

Consist of a lens

1. Simple Microscopes

2. Compound Microscopes

are = still focused when objectives are switched

single

parfocal

There are 2 types of compound microscopesa. Research

b. Dissecting

1. research microscope Has

has a rotating nosepiece with Uses transmitted light (passes through specimen Creates an image

Are used to look at

specimens

magnifies up to

one ocular

3 objective lenses

400 X

inverted

transparent

2. dissecting microscope has

has Has 2 light sources top

& bottom

two eyepieces ( binocular)

1 rotating objective

Creates a image

virtual

Uses incident light (light reflected off the specimen

Are used to look at

Magnify specimens up to 30 X

solid objects

Parts of a Microscope

Part Function

Ocular (eyepiece) is the lens you look throughmagnifies the object 10 X

Objective Lenses Magnify the object;

Revolving Nosepiece Contains 2 – 4 objectivesRotates enabling different lenses to be used

Course Focusing Knob Is used to focus the object on LOW POWERIt moves the stage up and down

Fine focusing Knob makes the image clearer

Iris diaphragm regulates the amount of light reaching the slide

Stage Platform to hold slide

Image Magnification

• Is the magnification you are using when viewing a specimen

• It is created by both the objective & ocular

Formula:Image Magnification = ocular x objective low: 10 X =

medium: 10 X =high: 10 X =

40 X100 X400 X

4 X10 X40 X

Example 1:A student is viewing a specimen on low power. What is the image magnification?

Ocular = 10Objective = 4

Image Magnification = Ocular x Objective

Image Magnification = 10 x 4 = 40

Example 2:A student is viewing a specimen on high power. What is the image magnification?Ocular = 10Objective = 40

Image Magnification = Ocular x ObjectiveImage Magnification = 10 x 40 = 400

Image

• It is what you see• Is created using light

(transmitted or incident)• There are two types:

• Virtual• Inverted

A. Virtual

The the same Produced by a Created using incident light;

reflects off the specimen

image is as it really is

dissecting microscope

B. Inverted

The image is upside down & backwards

Produced by a research microscope Created using transmitted light;

passes through the specimen

Field of View the of the specimen that you

see

Conversion:

field of view

measured in

amount

microns µ (1 106 m)

1mm = 1000 µm It is less withhigher magnifications

the field of view as magnification

low power 4 X 4000 µm

medium power 10 X 1500 µm

high power 40 X 400 µm

decreasesincreases

Drawing Size

1. draw the specimen

2. measure the widest part in mm

3. convert mm to microns (1000 m = 1 mm)

45mm = 45000

Estimation of Actual Size

• Estimate how many specimens fit across the field

actual size = field diameter

fit number

actual size

= 4000 µ 4 = 1000 µ

• Divide the field of view by that number

Scale used to compare diagram size with actual

size of the specimen measure drawing diameter with a ruler

then convert to microns

scale = actual size drawing size

eg) 1 : 50 000 1 : 0.1

on diagram real life on diagram real life

really big things

really small things

D. Electron Microscopes too large, complex and expensive for a

school to use uses a instead of a light wave

focus by adjusting electromagnets

no images since color requires light

able to see great detail

images are called

termite head

beam of electrons

color

micrographs

Ebola virus

Transmission Electron Microscopes beam of electrons

stained tissue imbedded in plastic

Advantages: and the internal detail of the cell can be seen

Disadvantages: and the specimen must be

passes through

very high magnification (100,000 to 1,500,000 X), high resolution

2-D, black and whitedead

human eyelashes

Scanning Electron Microscopes scans the of the specimen

image is produced by the electrons being onto a screen which can be manipulated for a 3-D view often coats the specimen with gold for a sharper image

surface

reflected off the surface

Advantages: black and white image of the surface of a specimen

Disadvantages: specimen must be although recently there has been a form that uses living material

high magnification (300,000 X),3D

dead

E. Confocal Laser Scanning Microscope (CLSM)

in the 1980’s the use of a laser beam and computers made it easier to view specimens

image is of a very thin section with high resolution which is stored in the computer and can be combined to produce a 3D image that can be manipulated in every direction

living, transparent

F. Imaging and Staining Techniques - essential to see details

most cells are colourless when light passes directly through them in brightfield microscopy

can be used that attach to different parts of the cell, and therefore the image

unfortunately, stains kill the cells

eg) iodine, methylene blue

contrast

stainsimproving the contrast

– ability to distinguish between that are very close together, in other words, of the image

for a standard light microscope

light microscopes have limited resolution because when light is focused into smaller diameters, the image becomes blurred

resolutiontwo structures

clarity

0.2 µm

– a technique used to localize substances in cells

fluorescent substances are attached to molecules in cells

they then in the presence of ultraviolet light

Cell during mitosis

fluorescence microscopy

glow

G. Cell Research at the Molecular Level due to advances in technology, we are able

to see great detail at the molecular level of cells now have other microscopes that can see in even more detail than the SEM and TEM:

atomic force microscope (AFM)

scanning tunneling microscope (STM)

silicon atoms magnified 1 000 000 000 X

surface of a plastic ID card

Gene Mapping DNA found on the chromosomes within the

nucleus of the cell directs the activities of the cell the produced a so that all gene locations are known…this may allow scientists to manage such as

can also use to manipulate plant genes to produce plants that are (many ethical issues involved)

genetic map of humansHuman Genome Project

disease-causing abnormalitiescancer

pest and drought resistant

Cell Communication cells are (

both move into and out of the cell) from one cell travels through the and attaches to specific receptors on other cells (like a lock and key)

the then change shape and allows functions to occur

open systems matter and energy

messenger moleculesbloodstream

receptors

H. Development of Cell Theory

• is the idea spontaneously from

Spontaneous generation

non-living matter

that life can emerge

• It was an idea that continued to thrive from 1500s to the mid 1800s

• It was disproved by:1. Francesco Redi2. Louis Pasteur

1. Francesco Redi - 1668• Questioned the idea that maggots could

appear spontaneously from raw meat• Had 3 jars that contained raw meat:

• 1 open to the air• 1 completely sealed• 1 covered with gauze (contains tiny

holes)• Result = Only the one did

have flies

closed not

Needlham’s Experiment

Belief: boiling destroyed microorganisms Needham’s Experiment: put boiled chicken

broth into a sealed flask In theory, no microorganisms should exist But …microorganisms still appeared?!? Spontaneous generation remained popular…

they ignored contact with air

Spallanzani’s Work

Spallanzani’s belief: microbes in the air inside the flask got into the broth

The test: remove the air from the flask and then seal in the boiled chicken broth

Result: nothing grew in the chicken broth!

Why is Spontaneous generation is still popular?!?

2. Louis Pasteur - 1864

Conducted experiment using broth and flasks

He boiled the broth & put it in an s-shaped flask

After some time he removed the s-shaped flask

Result = Swan neck let in & there was

growth but removal of neck produced mould

S shaped

no air no mould

S-shaped neck a llows air butstops microorganism anddust

Variables in Experiments

Represent conditions that occur in an experimentThere are 3: Controlled variable Manipulated variable Responding variable

1. Controlled Variable Are the in an

experiment that for each trial

E.g. the temperature in the room

conditions remain the same

2.Manipulated Variable

  Are the in the

experiment E.g. amount of light

 

condition(s) that are changed

3. Responding Variable

• Is (what happens)

• E.g. the plant with no light dies

the response

the cell was discovered by while he was examining under his microscope

the (which disproves spontaneous generation) proposed by in says that: 1. all living things are

2. all life functions takes place in cells, making them the

3. all cells come from

NOTE: do not fit this category, they are not considered living or non-living

Robert Hookecork

Cell Theory Schleiden and Schwann1839

made of cells

smallest unit of life pre-existing cells

viruses

The Cell Theory

I. The Cell cells carry on all life processes including:

7. reproduction

6. waste removal

5. exchange of gases

4. response to stimuli

3. growth

2. movement

1. intake of nutrients

Nucleus control centre of the cell surrounded by nuclear envelope

(semipermeable double membrane)

the nuclear envelope is perforated by pores which allow the entry and exit of certain large macromolecules and particles

contains DNA (deoxyribonucleic acid), which is found in chromosomes and carries genetic information

nucleolus is a small part that stores ribosomal RNA

Cell Membrane protective barrier for the cell

semipermeable (allows needed materials into the cell and waste materials out)

not rigid; very fluid

type of protein molecule varies with the membrane

Cytoplasm gel-like substance (mostly water)

includes everything between the nuclear membrane and the cell membrane

contains nutrients needed for cellular activities

has specialized organelles with specific functions

network of fibres extending throughout the cytoplasm

used for support, motility and regulation

contain microtubules, microfilaments and intermediate filaments

Cytoskeleton

provide the cell with energy (ATP) Mitochondria

called the “Power house” of the cell

sugar is burned and O2 is used up

number of mitochondria in a cell is directly related to its level of metabolic activity

ex. muscle cells have lots of mitochondria

contain some DNA and can divide

site where protein is produced (protein synthesis)

Ribosomes

take amino acids and make proteins

free ribosomes are suspended in cytosol

bound ribosomes are attached to the outside of the endoplasmic reticulum or nuclear membrane

flat disc-shaped sacs (cisternae)

Golgi Apparatus (Bodies)

store substances from the endoplasmic reticulum, such as proteins which will be secreted for use outside the cell

produces carbohydrates

carries out intracellular digestion

Lysosomes

contains strong digestive enzymes that break down macromolecules

eg) food

fuse with vesicles made by phagocytosis

nickname “the suicide sac”

eg) white blood cells have lots of these

extensive network of membranes accounting for more than half of the total membrane in the cell

Endoplasmic Reticulum

transport system of tubes which connect all parts of the cell

responsible for transporting proteins which are the building blocks of the cell

rough ER

ribosomes attached to it protein synthesis (secretory proteins) membrane factory for the cell

smooth ER

no ribosomes attached associated with fat, oil, steroid

production

eg) sex hormones contain enzymes that detoxify drugs

stores calcium ions which are used for muscle motion

storage place for food, water, or wastes

Vacuoles and Vesicles

surrounded by a membrane

vesicles transport substances through the cell

found in plant cells and some algae contains chlorophyll for photosynthesis

Chloroplasts

chlorophyll produces a green colour

contain a small amount of DNA and can divide

found only in plant cells and some protists and fungi

Cell Wall

rigid wall for protection and support and prevent excessive uptake of water

primary cell wall is developed first with the secondary (more rigid) cell wall developing later

made of cellulose

**Note: the cell still has a cell membrane

Cell Part City Structure

Cell membrane Nucleus Mitochondria Lysosomes Ribosomes Golgi Bodies Vacuoles Endoplasmic Reticulum Chloroplasts DNA Chromosomes

City Limits City Hall Power Plant Garbage Trucks, Recycling Butcher, Bakery, Carpenter, Butcher shopSafeway, IGA, Brick, MallsStreets, Rivers Green houseOriginal Blueprints of city Library

The Cell as a City

The Chemical Composition of Cell Structures is the major compound found in all

cells cell structures are made up of

organized into 4 major organic compounds

1. lipids -

2. carbohydrates -

3. protein -

4. nucleic acids -

, such as are found in tiny amounts in the solvent

water

carbon, hydrogen, oxygen and nitrogen

fats and oils

sugars, starches and cellulose

muscle fibre

DNA, genetic material

trace elements zinc, magnesium, and iron

Isolating Cell Organelles isolating specific cell organelles allows

researchers to study their

is a process that uses to the organelles

a centrifuge is used to test tubes containing at various speeds

the resulting force separates the cell components by

composition and functions

cell fractionationcentrifugation separate

spindisrupted cells

size and density

Types of Cells

prokaryotes –

eg) bacteria

bacteria

all cells contain a

have a

,

they have a usually very cells

cell (plasma) membrane, cytoplasm (cytosol), chromosomes and ribosomes

do not nucleus or nuclear membranenucleoid region

small

eukaryotes –

eg)

have a and a

generally than prokaryotic cells

nucleusnuclear membrane

larger

plants, animals, fungi, protists

Comparing Plant and Animal Cells

Plants cell membrane &

cytoskeleton made up of

DNA- made of

for cell division

made of cellulose

have which contain chlorophyll for photosynthesis

central vacuoles some plants store

energy in the form of

Animals

for cell division

cell wall chlorophyll

vacuoles and vesicles

may contain in the form of fats

proteins & lipids

sugars, nitrogen bases & phosphate

no centrioles

cell wallchloroplasts

large

starch or oils

SAME

SAME

centrioles

NO

NO

small glycogen or lipids

Animal Cell smooth ER

lysosomes

golgiapparatus

cell membrane

cytoplasm

mitochondrion

centrioles

ribosome

rough ER

nucleus

nuclear envelope

Animal Cell

Plant Cellcell walls

cell membranevacuole

cytoplasm

chloroplasts

mitochondrion

golgi apparatus

smooth ER

ribosome

rough ER

nucleusnuclear envelope

Plant Cell

J. The Cell Membrane all cells have

the cell membrane is which means it allows the passage of

passage depends on of molecule

scientists have developed the to describe the cell membrane

it is made up of:

1. phospholipid bilayer – a where the and are the and

cell membranes

selectively permeable certain molecules

size and charge

double layerphosphate ends face out

attracted to water, lipids (fats) face inrepel water

Fluid Mosaic Model

Phospholipid Bilayer

2. protein channels – found throughout the bilayer and may be

inside attached to the outside (peripheral), or pass all the way through (integral)

Fluid Mosaic Model of the Cell Membrane

both the phospholipids and the proteins can within the membrane

is found packed in the bilayer

migrate and move laterally

cholesterol between phospholipids

the types of lipids in the bilayer determine the of the cell eg)

fats make the membrane more

fats make the membrane more

temperature resistance

unsaturated (kinked)

fluid

saturated (straight)

viscous

different types of cells contain a

the plasma proteins have six basic functions:

different set of proteins

1. transport

2. enzyme activity

3. signal transduction

4. cell-cell recognition

5. intercellular joining

6. stability and maintenance of cell shape

K. The Particle Model of Matter this model is used to understand the types of

transport in cells:

1. All matter is made of however they can be of

2. The particles of matter are

Adding or removing affects the movement of the particles.

They move the least in and the most in

particlesvarying size and composition.

constantly moving and vibrating. solids

gases.energy

3. The particles of matter are to one another or are bonded together.

4. Particles have between them that are smallest in and greatest in (exception – ice). The spaces may be occupied by particles of another substance.

attracted

spacessolids gases

L. Cell Transport there are two methods by which molecules

move into and out of cells:

1. – does require the addition of energy

a) Simple Diffusion

b) Osmosis

2. –requires

c) Facilitated Diffusion

Passive Transport NOT

Active Transport energy

a) Simple Diffusion a is a

molecules naturally move the gradient from concentration to concentration until the concentration is in all areas…called

the flow of in and out of the cell is regulated by the (recall fluid mosaic model) it is caused by the of particles and is passive because is required for it to occur

1. Passive Transport

concentration gradient difference in concentration between two points “down”

high lowequal

simple diffusion

nutrients/wastescell membrane

collisionno extra energy

membranes always allow all kinds of molecules in and out

they can be selective depending on what the cell needs:

1. membranes – allow the passage of molecules

2. membranes – allow the passage of molecules

3. membranes – allow any molecules through

do not

permeableall

semipermeablesome

impermeable do not

all molecules but necessarily at the

diffusion rate is affected by:

1. of molecules – molecules diffuse2. – high temperature

provides more so diffusion occurs

3. – higher concentration means so diffusion occurs

4. through which it travels – solids diffusion more than liquids or gases

diffuse notsame rate

size small faster

temperatureenergy faster

concentrationmore collisions faster

mediumrestrict

b) Osmosis is the diffusion of

across a membrane

it relies solely on the

three situations can arise depending on the tonicity of the cell’s environment:

1. Hypotonic

concentration of water is greater on the

net movement of water is the cell

osmosis watersemipermeable

concentration gradient

intooutside

2. Hypertonic

concentration of water is greater on the

net movement of water is of the cell

3. Isotonic

concentration of water is inside and outside the cell

water moves into and out of the cell at the

outinside

same rate

equal

in animal cells the process of losing water and is called

is the of animal cells

is the of water balance

plants rely on osmosis to regulate the water pressure exerted on the inside of their cell walls…called

without turgor pressure plants

http://www.youtube.com/watch?v=DQuM4BnSRS8

http://www.youtube.com/watch?v=ZsAFEI8IcVU

shrinking

cytolysis swelling and bursting

osmoregulation control

turgor pressure

wilt

crenation

occurs when the cell membrane of a plant cell from the cell wall due to being placed in a environment

before after

plasmolysisshrinks away

hypertonic

is the opposite of plasmolysis…it is the rehydration of a plant cell due to being placed in a environment

deplasmolysis

hypotonic

c) Facilitated Diffusion only matter that is

can pass the lipid bilayer by simple diffusion water soluble particles use the to move across the membrane by

molecules and pass through the pores created by the

molecules are across the membrane by the

molecules are moving the concentration gradient, therefore no extra energy needs to be expended by the cell

soluble in lipidsthrough

protein channelsdiffusion

small ionschannel proteins

big helpedtransport (carrier) proteins

down

protein channel

Active Transport is the movement of

molecules the concentration gradient

it requires two things:

1. transport proteins

2. ENERGY…adenosine triphosphate (ATP)

small particles are transferred using a

in the membrane carries the particle to the

active transportagainst

“protein pump”

carrier proteinother side

one example is the used to keep the concentration of and in the cell

all cells have which is a separation of across their plasma membranes…called the

the cell is charged compared to the cell

ions move with the which takes into consideration the gradient and gradient

sodium-potassium pumpK+ high

Na+ low

voltages,opposite charges,

membrane potential

inside negativelyoutside

electrochemical gradient,concentration

charge

cells use to bring particles cell membrane

and then pinches off to form a around it

the cell can then use the contents where needed cells use to large particles transports via transport vesicles budded off the

the vesicle and the and releases its contents into the both endocytosis and exocytosis in the form of

endocytosis in

engulfs a molecule (nutrient, bacteria etc)transport vesicle

exocytosis remove

wastes and cell products (proteins, hormones)

Golgi apparatus

joins with restores cell membrane ECF

require energyATP

M. Application of Cellular Transport 1. Membrane Technologies industrial use of

to the action of membranes

useful in the study of

study of that bind with specific molecules to bring them into the cell by

syntheticsmimic

receptor proteins

endocytosis

HIV and cancer

focus on of receptor proteins to prevent the virus from getting in

development of drugs that the immune system to cancer cells

develop that target the of cancer

recognition

drugs unique proteins

stimulatedetect and destroy

2. Synthetic Membrane Technology are

surrounded by a identical to the membrane in human cells used to to infected tissues in a

inside holds while the bilayer holds

liposomes fluid-filled sacsphospholipid bilayer

deliver drugscontrolled delivery system

water-soluble medicinefat-soluble medicine

Advantages:

1. liposomes stay in the blood for than medication on its own

2. delivers treatment to no harm to other cells

3. used in to into cancer cells to kill them

longer time

target cells only,

gene therapy inject DNA

liposome releasing a drug

3. Dialysis rids the body of

two types available to people with kidney failure both based on the principles of

a. Hemodialysis must be performed in a

hospital blood is from

the body, cleansed and returned to the body

toxins, wastes and excess fluid

diffusion and osmosis

removed

b. Peritoneal dialysis soft catheter inserted into the

sterile dialysate fluid (mixture of water, glucose, sodium, chloride, etc.) is pumped into the cavity

toxins move down the into the fluid which is then removed from the body

abdominal cavity

concentration gradient

N. Surface Area to Volume Ratio the of membrane (

) around a cell in relation to the of the cell ( ) determines how many molecules (nutrients and wastes) will of the cell

cells divide to maintain a (lots of membrane to low volume)

as a cell grows the SA/V ratio until the cell is no longer efficient…growth then the cell

amount surface areasize volume

pass in and out

high surface area to volume ratio

larger dropsslows

divides

organisms can have to help increase overall SA/V ratio

eg) in lungs – increase SA for O2(g) and CO2(g) diffusion

in small intestines – increase SA for absorption of nutrients

specialized structures

alveoli

villi and microvilli

Example 1

For the following “cell”, calculate the surface area, the volume and the surface area to volume ratio:

10 mm

4 mm

2 mm SA = ( × w × 2) + ( × w × 2) + ( × w × 2)

= (4 mm × 2 mm × 2) + (4 mm × 10 mm × 2) + (2 mm × 10 mm × 2)

= 16 mm2 + 80 mm2 + 40 mm2

= 136 mm2

SA/V = 136/80 = 1.7

V = × w × h = 4 mm × 2 mm × 10 mm = 80 mm3

Example 2

For the following “cell”, calculate the surface area, the volume and the surface area to volume ratio:

SA = ( × w × 2) + ( × w × 2) + ( × w × 2)

= (4 mm × 7 mm × 2) + (4 mm × 10 mm × 2) + (7 mm × 10 mm × 2)

= 56 mm2 + 80 mm2 + 140 mm2

= 276 mm2

SA/V = 276/280 = 0.99

V = × w × h = 4 mm × 7 mm × 10 mm = 280 mm3

10 mm

7 mm

4 mm

O. Single-Celled vs. Multicellular single celled organisms can live

they are quite many

individually or in colonies

small, microscopic

this need resulted in the development of of cells, tissues and systems in animals and plants

once a single-celled organism or colony of single-celled organisms reaches a certain size, it requires a multicellular level of organization

specialization

performs necessary to maintain life of the organism entire cell all functions

performing the same function

eg) red blood cells, dermal tissue

tissues – groups of cells

contributing to the same function

eg) heart

organ – group of tissues

contributing to the same function

eg) circulatory system, root system

system – group of organs

this in larger organisms allows in life processes and therefore

“division of labour”greater efficiency

increases survival

O. Plant Structure, Growth and Development

Shoot system

Root system

A. Plants Organs, Tissues and Cells• plants contain a _________ system (__________) and

a ___________ system (_______________________)• almost all vascular plants rely on both systems to

live• roots receive ______________ and other

_______________________ from __________________________________

• shoot system depends on ____________ and ______________________ absorbed from ___________by roots

shoot above groundroot underground

water minerals the ground

sugar gases the leaves

1. Roots – plant - nutrients and water

2. Leaves – sunlight and gases for photosynthesis

3. Stem – plant- water and

nutrients4. Flower/cones -

Plant Organs

anchor

absorb

collect

support

transports

reproduction

Plant Tissues

1. Dermal Tissue (Epidermis)

outer layer of cells that covers all herbaceous (non-woody) plants

responsible for the exchange of matter and gases into and out of the plant

in woody plants the epidermis of the stem is replaced by cork and bark

protects the plant from disease

2. Ground Tissue

found as a layer beneath the epidermis

provides strength and support (in stem) involved in food and water storage (roots)

location photosynthesis occurs (leaves)

air spaces between cells allow gases to diffuse

3. Vascular Tissue

responsible for transport of materials

contain phloem and xylem tissues that transport water, dissolved minerals and sugars a) Xylem – moves water and dissolved

minerals from the roots up the stem

b) Phloem – transports sucrose and other dissolved sugars from the leaves to other parts

P. Photosynthesis plants contain chloroplasts that contain

chlorophyll (green pigment)

found in the ground tissues of leaves and sometimes in stems

light energy is absorbed by the chlorophyll and converted into chemical energy and stored in the bonds of the glucose molecules cannot take place in the dark

water + carbon dioxide glucose + oxygen

6 H2O + 6 CO2 C6H12O6 + 6 O2

Q. Cellular Respiration provides the energy of the cell’s life

processes bonds are broken and new compounds formed releasing energy

takes place in the mitochondria takes place all the time in both plants and

animals, but at a much slower rate in plants

glucose + oxygen water + carbon dioxide

C6H12O6 + 6 O2 6 H2O + 6 CO2

R. Leaf Tissues and Gas Exchange guard cells form tiny pores called stomata

that allow gas exchange to happen easily carbon dioxide and oxygen can enter and

leave by diffusion

most stomata are found in the lower epidermis guard cells swell up to open the stomata

potassium ions move in by active transport, and water follows by osmosis

S. Transpiration process of water vapour leaving the leaf

through the stomata controlled by the guard cells

number and appearance of stomata depends on the environmental conditions

eg) hot, dry conditions very few stomata

humid conditions many stomata

Palisade Tissue found just below the upper epidermis

long, rigid, rectangular, tightly packed cells responsible for photosynthesis contain many chloroplasts require carbon dioxide and produce oxygen

Spongy Mesophyll Tissue irregularly shaped, less rigid cells

between the palisade tissue cells and lower epidermis

move oxygen toward stomata for expulsion

move carbon dioxide from the air towards the palisade cells

Cross Section of Leaf Tissue

Cross Section of Leaf Tissue

T. Transport in Plants 4 processes aid in the transport of materials

in plants

1. Cohesion the attraction of water molecules to other

water molecules due to water having a slight positive end

and a slight negative end causes water molecules to hold together

contributing to high surface tension

2. Adhesion the attraction of water molecules to

molecules of other substances

3. Root Pressure dissolved minerals are present in the cells

of the root as a result of active transport, thus producing a higher solute concentration inside the cell

through osmosis, water is drawn into the cells creating positive pressure that forces fluid up the xylem

water is forced from a higher pressure in the roots, toward the lower pressure in the leaves

the evaporation of water through the stomata in transpiration creates a tension or transpiration pull

as each water molecule evaporates, it creates a pull on the adjacent water molecules pulling them up the xylem vessels to the leaves most water is lost through the stomata (evaporation)

the transpiration pull is maintained to continue drawing water up the stem

4. Transpiration

if the temperature is high the rate of evaporation through the stomata will be high and movement through the xylem will be rapid rest of the water is used to produce sugars (photosynthesis)

Tonicity as water enters the plant cells by osmosis,

the cell is said to be turgid

turgidity allows the plant to hold itself up so that it can get sunlight for photosynthesis

it is better for cells to be in a hypotonic environment

U. Control Systems a stimulus is a change in the environment

that causes a reaction in an organism

both plants and animals respond to stimuli

“tropism” refers to the movement of a plant in response to a stimuli

eg) loud noise, bright light

Phototropism plant growth in response to light

the plant tip detects the stimuli and sends a chemical to the area of elongation

auxin is a hormone that promotes cell growth or elongation of cells facing away from the light, causing the leaf or stem to bend toward the light positive phototropism is growth towards the light source

negative phototropism is growth away from the light source

eg) stem, flowers

eg) roots

Gravitropism (Geotropism) plant grown in response to gravity

plants depend on heavy starch particles in specialized cells as indicators of gravity

starch grains shift and settle due to gravity

positive gravitropism is growth towards gravitational pull

eg) roots

negative gravitropism is growth away from gravitational pull

eg) stem

Other Control Mechanisms temperature, chemicals and water

tendrils respond to touch eg) peas

flowering is often a response to the length of darkness that the plant is exposed to

eg) Christmas cactus, poinsettias