IB Topic 2

Cells

Cell Theory

A. There are 3 main points

1. All living organisms are composed of cells.

2. Cells are the smallest unit of life.

3. All cells come from pre-existing cells

Cell theory: history and evidenceA. The discovery of cells is linked to

technological advancements (microscopes)

B. 1590-Jansen developed the compound microscope (it had two lenses)

C. 1665-Robert Hooke discovered the cell

1. Looking at cork

2. Thought the cells looked like chambers

3. Called them ‘cells’, as in jail cells

D. 1675-Leeuwenhoek discovered unicellular organisms

E. 1838-Mathius Schleiden

discovered all plants are

made of cells

F. 1839-Theodore Schwann

discovered all animals are

made of cells

G. 1855-Rudolph Virchow discovers all organisms are made of cells

**organism=any living thing

Characteristics of Life1. Order (organization) – from small to large

-Ex: Organelles make up cells.

Cell make up tissues.

Tissues make up organs.

Organs make individuals.

2. Metabolism- organisms take in and release energy

3. Response (to the environment)- response to stimuli

4. Growth and development-heritable programs of DNA direct growth and development (change in one’s shape during life)

Examples:

5. Homeostasis-organisms have regulatory mechanisms to maintain their internal environments

Examples: body temperature

blood sugar

osmoregulation

6. Reproduction-the ability to reproduce ones own kind

-This follows the theory of biogenesis (life only comes from life)

7. Evolutionary adaptation-life evolves as a result of interaction between organisms and their environment

***Any organism (single cell or multi-cell) that is considered alive must exhibit all of these characteristics.

Multicellular organismsA. Multicellular organisms show emergent

properties

B. Emergent properties arise from interaction of the components

*The whole is greater than the parts (Ex: a heart cannot function without the whole body)

*A single cell can do nothing on its own, but when you put all of the cells together they can perform many functions

Multicellular organisms and differentiation

A. Multicellular organisms differentiate to carry out specialized functions

B. All cells originated from the same place and all carry the genetic information to perform any function (your toe cell could have been a brain cell)

C. In each cell there is only a small amount of activated genetic material

Ex: All cells have the genes for taste. The only cells with activated ‘taste’ genes are on your tongue.

D. Cell differentiation is determined by a cells position relative to the others and chemical gradients

E. Stem cells retain the capacity to divide and have the ability to differentiate along different pathways

Stem Cells

1. Have ability to reproduce and differentiate

2. Embryo cells all start out as stem cells

3. Valuable for scientific research

4. May be able to differentiate stem cells to desired cell type

5. These may replace damaged cells

Example of stem cell differentiation

Homework-Outline one therapeutic use of stem cells for humans or some other

animal.

DO NOT USE WIKIPEDIA AS YOUR RESOURCE!!

You may use any government or university website. Their websites generally end

in .edu or .gov.

Viewing Cells1. Light microscopes allow us to:

-see color images

-have a larger field of view

-prepare samples easily

-observe living and non-living material

**We cannot see most cell organelles

2. Electron microscopes allow us to:

-see more detail because they have a higher resolution

Comparing microscopesLight microscopes

Electron microscopes

Focus beams Lenses electromagnets

Resolving power 200 nm 0.2 nm

Color No staining required/can see color

Requires metal dyes/black and white only

Object Alive or dead Dead only

Expense High school range/cheap

Universities/high cost

Microscope Vocabulary

1. Resolution-describes clarity of pictures

-higher resolution = more detailed pictures

-human unaided resolution= 0.1mm (anything further apart than 0.1 mm is viewed as two objects)

2. Magnification-makes objects larger

3. An increase in magnification may reduce the resolution

Calculating Linear Magnification

A. The formula-

Magnification = size of image

size of specimen

B. Example-the object is magnified by two

This is the magnified image.

This is the original object.

Diameter of the image=4cmDiameter of the specimen=2 cm Find the magnification.

C. Scale bars - lines added to micrographs of drawing to help show the actual size of structures

Ex.

**You must know how to convert between SI Units to perform a magnification problem correctly!!

Ex: 1mm = 1 x 10-3 m

1 mm

Common SI Unit Conversions

1nm (nanometer) = 1 x 10-9 m

1ųm (micrometer) = 1 x 10-6 m

1mm (millimeter) = 1 x 10-3 m

1cm (centimeter) = 1 x 10-2 m

1m (meter) = 1m

1km (kilometer) = 1 x 103 m

Calculating linear magnification

Calculating linear magnification1. Use a ruler to find the length of the scale bar.

2. Measure the length of the picture using the same unit that you used to measure the scale bar.

3. Divide the length of the picture by the length of the scale bar and multiply by the number in the scale bar.

4. If you did this correctly you should have only one unit left (it should be the unit that was in the scale bar). This is the size of the object in the picture.

6. Once you have the size of the object you can calculate magnification.

7. Divide the measured size of the picture by the actual size of the object and multiply by the scale bar (with units).

8. When you do this be sure your units are the same. When you divide they should cancel out.

9. If you did this correctly, your magnification should not have a unit.

Example:

Go to p. 169 Figure 10.1-C. Calculate the magnification.

1. Length of scale bar = 0.8 cm

2. Length of picture = 5.7cm

3. 5.7 cm x 10.0 μm = 71.25 μm = actual

0.8 cm size of object (photo)

Number given in scale bar of

picture

4. To calculate the magnification you must convert the actual size of the object and the measured size of the photo to the same units (meters are usually the easiest).

5. How it looks:a. 5.7 cm= 5.7 x 10-2m or 0.057 m

(IMAGE SIZE)b. 71.25ųm = 71.25 x 10-6m or 0.00007125 m

(ACTUAL SIZE)*In (a) the decimal was moved to the left

two times (x 10-2) and in (b) the decimal was moved to the left six times (x 10-6)

6. Magnification = 0.057 m =800

0.00007125 m

7. The picture is magnified 800 times.

Assignment

Calculate the magnification for the following images.

1. p. 169 Figures 10.1 d and e

2. p. 860 Figure 43.19

3. p. 921 Figure 46.10

4. p. 114 Figures 7.3 a and b

Limitations to Cell Size

A. Cells cannot grow indefinitely

B. They reach a maximum size and divide.

C. Bigger cells are less efficient.

-They have to transport materials further.

-The smaller the surface area to volume ratio the harder it is for the cell.

D. As surface area increases so does the volume.

E. Volume increases more rapidly than surface area.

F. The rate at which cells can move things in or out depends on the surface area.

G. The rate at which things are used or produced depends on the volume.

H. Example:

SA = 24 in2

V = 8 in32”

2” 4”

4”

SA = l x w x #of sidesV = l x w x h

SA = 96 in2

V = 64 in3

**Volume increases faster than the surface area. In this example the SA increased by 4 and the volume increased by 8.

How Big Is A Cell?OBJECT SIZE

Eukaryotic 10-100 μm

Prokaryotic 1-5 μm

Nucleus 10-20 μm

Chloroplast 2-10 μm

Mitochondrion 0.5-5 μm

Large virus (HIV) 100 nm

Ribosome 25 nm

Cell membrane 7.5 nm

DNA dbl. helix 2 nm

H atom 0.1 nm

Prokaryotic Cells

E. coli

Diagram of a typical prokaryote

Prokaryote organelles1. Cell wall-gives the cell structure and strength

2. Plasma membrane-separates the internal features from the outside environment

3. Cytoplasm-holds cell’s organelles and enzymes

4. Pili-help the cell hold

on to other structures

and aid in movement

5. Flagella-aid in organism movement

6. Ribosomes-make protein from mRNA

7. Nucleoid-area containing naked DNA

8. Slime capsule-a protective barrier around the cell (may help

shield it from

antibiotics)

More prokaryote organelles

An electron micrographs of E. coli

** For IB you must be able to identify the structures on a micrograph.

http://www.cellsalive.com/index.htm

Another diagram of a prokaryote

Prokaryote reproduction

1. Most prokaryotes

divide by binary fission

2. Some reproduce by

budding or filamentous

growthhttp://www.bact.wisc.edu/Microtextbook/index.php?module=Book&func=displayarticle&art_id=112

Eukaryote Cells

Animal cell

General Eukaryote Information

1. All eukaryotes have enclosed nuclei and other membrane bound organelles

2. Eukaryotes are true cells (‘eu’ = true)

3. Eukaryotic cells are present in protists, plants, fungi and animal

Homework1. Draw, label and annotate a diagram of a

eukaryotic animal cell

Include:

free ribosomes rough ER

lysosomes Golgi apparatus

mitochondria nucleus

cytoplasm centrioles

cell membrane nucleolus

DNA (chromatin) smooth ER

1. Animal cells have a secretory vesicle

-It secretes glycoproteins that makeup the extracellular matrix

-The extracellular matrix functions in support, adhesion and movement

The Secretory Vesicle

Diagram of a plant cell

Plant Cells

1. Organelles found in plants only:

-cell wall

-chloroplasts-organelle required for photosynthesis

-vacuole-membrane bound sac used for storage of organic compounds

2. More on the cell wall

-Found in all plants and some prokaryotes

-provides rigid support for the cells

-made mostly of cellulose

-plays important role in turgor (hardening of cells by the intake of water)

-prevents cells from taking in too much water

Plant Cells

Homework: Outline the roles of extracellular

components in plants (cell wall) and animals

(extracellular matrix).

Summary of differences between eukaryotes and prokaryotes!

Prokaryotic Cells Eukaryotic cells

small cells (< 5 mm) larger cells (> 10 mm)

always unicellular often multicellular

no nucleus or any membrane-bound organelles

always have nucleus and other membrane-bound organelles

DNA is circular, without proteins (naked)

DNA is linear and associated with proteins to form chromatin

(not naked)

ribosomes are small (70S) ribosomes are large (80S)

no cytoskeleton always has a cytoskeleton

cell division is by binary fission cell division is by mitosis or meiosis

reproduction is always asexual reproduction is asexual or sexual

Cell MembranesA. The Fluid Mosaic Model-model of the

plasma membrane

B. Designed by Singer and Nicolson

C. The model is a mosaic of proteins embedded in a phospholipid bilayer

D. The phospholipid bilayer has two layers of amphipathic lipids

Hydrophilic heads

Hydrophobic tails

E. Amphipathic- has a polar head and a non-polar tail

F. Hydrophilic=water loving (polar)

-found on inner and outer edges of cell membrane

G. Hydrophobic=water fearing (non-polar)

-found inside the cell membrane

Hydrophilic heads

CytoplasmHydrophobic tails

Diagram of cell membrane

H. Lipids can move laterally through the cell membrane

I. Cholesterol molecules found between the phospholipids may reduce fluidity, but prevent crystallization

J. Membranes must be fluid to work

K. Proteins make up the mosaic part of the membrane (3 main types)

L. Integral proteins

-embedded in the membrane (partially or completely

M. Peripheral proteins

-found in hydrophilic areas only

N. Glycoproteins

-proteins within the membrane that have carbohydrates attached to them

O. Protein functions

-antibody recognition -hormone binding sites

-electron carriers

-channels for passive transport

-pumps for active transport

Types of Cellular Transport

A. Types of passive transport include diffusion, osmosis and facilitated diffusion

B. Diffusion-passive movement of particles from and area of high concentration to an area of low concentration

-Particles move down the concentration gradients (high to low)

C. Illustration of diffusion

D. Osmosis-passive movement of water from an area of low solute concentration to an area of high solute concentration

E. Hypertonic solution-high solute/low solvent

F. Hypotonic solutions-low solute/high solvent

G. Isotonic solution-equal solute/solvent

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

Look at the red blood cells, not the black circles.

H. Facilitated diffusion

-involves transport of charged molecules

-does not require energy

-charged molecules must diffuse through special proteins (the cannot diffuse through the cell membrane on their own)

GET YOUR BOOK.

I. Active Transport

-requires energy

-used when diffusion cannot occur

-substances move up the concentration gradient (move from low to high concentrations

J. The Sodium Potassium Pump

-An example of active transport

-Pumps ions against the gradient

-Translocates three sodium ions out of the cell for every two potassium ions pumped in

-ATP powers the changes in protein structure to transport the ions

-ATP phosphorylation=a phosphate group from the ATP is added to the protein

-When ATP is broken energy is released

-ATP ADP

(adenosine triphosphate adenosine diphosphate)

J. The Sodium Potassium Pump (continued)

Sodium Potassium Pump

Sodium Potassium Pump 2

K. Other forms of cellular transport

1. Endocytosis-when a cell extends its membrane around a substance in order to engulf it

2. There are two types:

-Phagocytosis-when the cell engulfs a solid (‘cell eating’)

-Pinocytosis-when the cell engulfs a fluid (‘cell drinking’)

3. Exocytosis-the excretion of macromolecules by vesicles fusing to the plasma membrane

4. Homework:

Find an animation of each of the following:

-pinocytosis

-phagocytosis

-exocytosis

Send the website URLs to me in an e-mail

K. Other forms of cellular transport

L. Membrane fluidity

A. The cell membrane is highly fluid allowing it to creating vesicles for endocytosis and exocytosis

B. In endocytosis the membrane becomes slightly smaller

C. In exocytosis the membrane becomes slightly larger

D. Animation for endocytosis and exocytosis

ASSIGNMENTDue Tuesday

• Compare osmosis and diffusion.• Compare facilitated diffusion and active

transport.• Compare endocytosis and exocytosis.

Due Wednesday• At home, watch the animations that are in the

notes. (Click on the hyperlinks and watch the videos.)

• Make a list of the ones that helped you the most.

M. Functions of the Golgi apparatus and rER in exocytosis1. Golgi apparatus

-Prepares substances for exocytosis

-Wraps the substances with portions of its own membrane

-Creates a vesicle that will join with the cell membrane to release the materials

2. rough ER-

-Functions in protein transport

-Assists in creating vesicles to move proteins around the cell or out of the cell via exocytosis

-The vesicles created by the rER often fuse with the Golgi appartus

-Eventually, new vesicles may be formed and transported out of the cell

M. Functions of the Golgi apparatus and rER in exocytosis

(continued)

Cell divisionA. The cell cycle consist of the following parts:

1. Interphase (3 stages)

-G1

-S

-G2

2. Mitosis (4 stages)

-Prophase

-Metaphase

-Anaphase

-Telophase

3. Cytokinesis (not truly separate from mitosis)

B. Interphase

1. G1-Characterized by cell growth and

appearance of cell organelles

S-Synthesis of DNA (DNA replication)

G2-Preparation for mitosis

2. DNA is found in the form of chromatin (unraveled)

3. Interphase is an active period

4. Often makes up about 90% of the cell cycle

C. Mitosis

1. Purpose of mitosis is to increase the number of cells without changing the genetic material

2. The daughter cells are identical to the parent cells

3. Mitosis can occur in haploid, diploid or polyploid cells

4. The stages

a. Prophase-

-chromosomes coil

and become visible

-mitotic spindles begin

forming

-centrioles move to opposite poles

-nucleolus disappears

-nuclear membrane disappears

-sister chromatids are joined together

C. Mitosis (continued)

4. The stages

b. Metaphase-

-Chromosomes

move to metaphase

plate

-centromeres attach

to spindle fibers

C. Mitosis (continued)

4. The stages

c. Anaphase-

-sister chromatids separate and move to opposite poles

-chromatids are now considered

chromosomes

C. Mitosis (continued)

4. The stages

d. Telophase-

-chromosomes

arrive at poles

-spindles disappear

-chromosomes become chromatin

-nucleus, nucleolus and nuclear

membrane reappear

C. Mitosis (continued)

D. Cytokinesis

1. Division of the cell (specifically, the cytoplasm)

2. It is hard to distinguish cytokinesis from telophase

1. What is the longest stage of the cell cycle?2. List all steps of the cell cycle in order.3. In what stage of the cell cycle does DNA

replication occur?4. True or false? All new cells are the same as

the old ones.5. Picture6. Picture7. In interphase the DNA is uncoiled. Is the

uncoiled DNA chromatin or chromosomes?8. In what stage of interphase do cell grow and

develop organelles?

1. What happens in interphase?

2. What happens in mitosis?

3. What is the first stage of the cell cycle?

4. What is the second stage of the cell cycle?

5. What is the longest stage of the cell cycle?

6. List the steps of interphase (in order).

7. List the steps of mitosis (in order).

8. Draw and label all stages of mitosis.

9. Explain what happens in each step

Comparing cell division in plants and animals

A. Plant cells do not cleave like animal cells.

B. Plant cells do form a cell plate where the metaphase plate was.

C. Both cell types will enter interphase after cytokinesis

D. Cell division hyperlink

Plant Animal

Procedures involving mitosis

A. Growth (when you get bigger)

B. Embryonic development (after the gametes fuse, the cell divides)

C. Tissue repair (when you get a cut or abrasion)

D. Asexual reproduction (bacteria make copies of themselves)

Daughter cells are genetically identical

In mitosis all daughter cells are identical to the parent cell.

They are genetic duplicates and have the same DNA.

DNA is always replicated in S phase of interphase.

There is no recombination or crossing over of genetic material.

Cancer

A. Cancers (tumors) are the result of uncontrolled cell division

B. They can occur in any organ or tissue

C. Causes:

-carcinogens: chemicals that increase the probability of a proto-oncogene mutation (proto-oncogenes control how often a cell divides)

C. Causes (continued):

-Viruses: may cause cancer by injecting their genetic material into the host’s chromosomes

Example: HPV (human papillomavirus) is linked to cervical cancer

-Age: changes required for a cell to become cancerous could take a long time to develop

-cancer is common in older people

-the longer we live the more chances there are for mutations to occur

C. Causes (continued):

-Diet: diets high in animal fat have been linked to cancer

-Environment: sun, asbestos, radiation

-Genetics: family history

D. Types of tumors

1. Benign: non-cancerous tissue caused by excessive cell division

-typically not harmful, unless it becomes significantly large

-weight and size can put pressure on blood vessels, nerves or organs

2. Malignant: cancerous mass of tissue

-cells divide quickly and without order

-can spread to other parts of the body

E. Cancer treatments1. Surgery: remove all cancerous tissue

before it spreads

-best chance for treatment

-only used when cancer is confined to one area of the body (breast cancer/testicular cancer)

E. Cancer treatments (continued)

2. Radiation: use energy to kill cancer cells and shrink tumors

-ionized energy is released in a beam and directed to specific points

-the beam will damage the genetic material of cancerous cells, making it impossible for them to reproduce

-side effects: tiredness, skin reactions

E. Cancer treatments (continued)

3. Chemotherapy: treatment of cancer with drugs (chemicals)

-work by preventing cancer cells from multiplying

-side effects: damage to normal cell

Ex: Hair and sperm producing cells can be damaged (temporarily)

Cancer video

# 18. How cells prevent cancer

A. Tumor suppressor gene

-inhibits cell division

-repairs DNA mistakes

-tell cells when to die (apoptosis)

-about 30 tumor-suppressor genes have been identified

-if they are inactivated cancerous cells may develop

B. Proto-oncogenes-control how often a cell divides

C. Oncogene-mutated forms of genes

-cause cells to grow out of control (leads to cancer)

# 18. How cells prevent cancer

Get an orange book

1. Complete the following assignment.p. 40 #1-2 and 4-6

Miscellaneous

Be sure your have an understanding of the differences between the following terms:

-haploid -centromere

-diploid -centrioles

-centrosome

-chromatin

-chromosome

-chromatid