Process of Life: DIffusion and Osmosis

Diffusion

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration. 

Keywords: diffuses, concentration, gradient 

Concentration: amount of substance (mass g/kg) / volume of fluid (cm³/ ml) 

The change in concentration between two regions is known as the concentration gradient.

High concentration: amount of substance (higher), volume of fluid (low) 

Low concentration: amount of substance (low), volume of fluid (high) 

Factors of diffusion:

• Temperature
• Size of particles: The bigger the size of the particles, the slower the rate of diffusion.  
• Concentration gradient: The larger the concentration gradient, the faster the rate of diffusion. 

Example

Sugar molecules diffuses down the concentration gradient from Point A to Point B. 

Applications of Diffusion

1. Chemical substances must be able to move from one place to another in order to keep the living organisms alive and growing.
2. For example, food substances that were absorbed need to
   • move from one cell to another
   • move in & out of the cell
   • move from one part of the cell to another
   
   Other examples of diffusion in Biology include:
   - Movement of carbon dioxide during photosynthesis
   - Movement of oxygen and carbon dioxide in animals
   
   Conclusion

• Diffusion is an important process where substances are moved waithout use of energy (passive process).
• It is the net movement of particles (or moelcules; or ions) from a region of higher concentration to a region of a lower concentration. 
• Thus the movement is down a concentration gradient. 

Osmosis

Osmosis is the net movement of water molecules down the concentration gradient through a partially permeable membrane. 

• Water moves freely through pores in the partially permeable membrane
• Solute(green)too large to move across the membrane. 

Concentration = amount of solute / volume of solvent (water) 

Since water potential is a measure of the tendency of water molecules to move from one area to the another, 

We can also define osmosis as the net movement of water through a selectively permeable membrane from a region of higher water potential to a region of lower water potential.

Osmosis in animal cells 

Animal Cells 

• structure is simple
• cytoplasm is surrounded by a partially permeable membrane 

If places in a hypertonic solution (solution has a higher concentration of solutes than the cytoplasm) higher solute concentration (low water potential) -> water leaves the cell by osmosis -> cell loses colume and shrinks (crenates: means that the animal cell shrinks in volume. only used for animal cells!) 

• Water loss only ceases if the concentration of the cytoplasm rises to that of the surrounding solution. -> water leaves the cell by osmosis (no more water loss from the cell : no net movement of water seen) ONLY water loss is ceased, but osmosis still occurs. This is because the concentration of the cell and the surrounding is the same, therefore the cell would have to lose anymore water molecules. 

If places in a hypotonic solution (solution has a lower concentration of sloutes than the cytoplasm- high water potential) water enters the cell by osmosis -> since the cell membrane cannot resist expansion, the cell eventually bursts (cytolysis) 

The Plant Cell 

• each plant cell contains a large central vacuole which contains a solution of salt sugars and ions, is bound by a partially permeable membrane 

If placed in a hypotonic solution, (solution has a lower concentration of sloutes than the cytoplasm- high water potential) water enters the large vacuole by osmosis -> vacuole swells, pushing the cytoplasm against the cell wall -> pushing the inelastic cell wall resists expansion and the cell becomes rigid, or turgid. It can be described as in a state of turgor.  

Young plants, which have little woody tissue, rely on turgor for support against wind and gravity. 

If places in a hypertonic solution (solution has a higher concentration of solutes than the cytoplasm) water leaves the cell by osmosis -> the cytoplasm and vacuole shrinks, pulling the cell membrane away from the cell wall -> the cell is now plasmolysed or is in a state of plasmolysis, The tissue becomes flaccid.

This tissue is flaccid

cell is plasmolysed, tissue is flaccid

PLASMOLYSIS VS CRENATION 

Isotonic Solution

An isotonic solution has the same concentration of solutes as cytoplasm.

No net movement of water molecules into or out of the cell 

Therefore, cells neither shrinks nor expands when put into an isotonic solution. 

What type of solution are these cells in?

                      hypertonic          isotonic                hypotonic 

                 hypertonic       isotonic          hypotonic 

Class Discussion - Cells

Red blood cells

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Function

• The red blood cell delivers oxygen to body tissues via blood flow through the circulation. They take up oxygen in the lungs or gills and release it while squeezing through the  body’s capillaries.

• Structure:

• Biconcave discs, having a depressed center on both sides. (These depressed centers allow the cells to have more cell membrane surface we tend to use the phrase “higher surface area to volume ratio” which can be exposed to diffusing oxygen while transiting the lungs. This structure also allows them to be more flexible when negotiating tight passages.)
• 7.8 micrometers in diameter

• Does not have nucleus and most organelles such as mitochondria to accommodate maximum space for haemoglobin.(the compound that carries oxygen through the body.)
• check this website: http://www.wisc-online.com/objects/ViewObject.aspx?ID=ap14604
• Red blood cells are red only because they contain a (protein chemical ← wrong term.  Haemoglobin is a protein, we don’t call it a protein chemical) called hemoglobin which is bright red in colour
• The main function of the red blood cell is to transport oxygen from the lungs, to the other tissues and cells of the body. The other function of the red blood cell is to partly carry carbon dioxide, which is a waste product of metabolic activities in the body.

Xylem Vessels (Xylem cells)

• Consist of dead hollow cells because the walls are lignified and the cell contents disintegrate. 

• The lignin makes the cell wall impermeable so they are in effect waterproof. It also makes the vessels extremely strong and prevents them from collapsing. They have a wide lumen and are linked end to end to create a long, hollow tube since the end cell walls have one or many perforations in them. 
• This allows the transport of large volumes of water. (The sidewalls have bordered pits (unlignified areas) to allow lateral movement of water ← this point will only be covered at higher levels).
• Xylem vessels are found in angiosperms.

Source:http://au.answers.yahoo.com/question/index?qid=20100710023937AAM9Akd

Intestinal Cells (sometimes known as intestinal epithelial cells)

Location: the small intestines

Structure and characteristics:

• Contain many membrane-bound vacuoles
• Aglycocalyx surface coat contains digestive enzymes. ← no need to know this for now, it is beyond your syllabus
• Microvilli on the apical surface increase surface area ← once again, the portion that is underlined should be re-written as “increase surface area to volume ratio” for the digestion and transport of molecules from the intestinal lumen

The points stated below refers to the functions of the intestine, which are facilitated by the intestinal epithelial cells

• Ion uptake
• Water uptake
• Sugar uptake
• The main function of intestinal cells is associated with secreting digestive juices into the lumen (the inner cavity of an intestine or blood vessel

Root Hair Cell

Structure + Function

1. Elongated structure that protrudes out to the soil
- This is to increase the surface area to volume ratio; thereby increasing the rate of uptake of water from the soil to the cell.

2. Large vacuole

- The root hair cell has a large central vacuole to maximize the amount of water capacity of the cell; thus, the cell is able to absorb and store more water.

3. Cell sap

- The cell sap of the root hair cell has a lower water potential than the water in the soil ← Good. We will learn what is water potential in the later lessons after ecology. Thus, the water from the soil moves into the cell via osmosis.

Read more: http://wiki.answers.com/Q/What_is_the_structure_of_root_hair_cells#ixzz21S1j6XeB

For the points below, it is more of how the various structures in the cell contributes to the function of a cell.  May be said for plant cells in general, and is not specific to only the root hair cell.

4. Nucleus

-Contains contains chromatin material, consisting of the DNA if the cell which is important (inherited by the daughter cells)

5. Plasma membrane

-Controls the movement of substance into and out of the cell and is used for cell identification.

6. Cell Wall

-The cell wall is a strong surface, surrounding the plasma membrane, which protects the cell and give it its shape. It also prevents expansion when too much water enter the cell.

7. Cytosol

-The cytosol is made up of water, salts and organic molecules and many enzymes that speed up reactions. It is important as it suspends the cell organelles within it.

Read more: http://sst-health-science-class-107.blogspot.sg/2010/01/root-hair-cell.html

Differences between Animal and Plant Cells

Plant cells have a central large vacuole while animal cells have many small vacuoles.
Plant cells have a cell wall while animal cells dont.
Plant cells have a fixed shape will animal cells have an irregular shape.
Plant cells have chloroplasts while animal cells do not.

Cell Structures and Functions

Learning outcomes:

•  Explain that the basic unit of all living things is the cell.
•   Identify structure and state the function of the main organelles in the cell such as nucleus, nucleus membrane, chromatin, cytoplasm, vacuole, mitochondria, ER, ribosomes, golgi apparatus, lysosomes, chloroplast, cell wall

Cell Theory

• All living things are made up of cells
• Cells are the smallest working units of all living things
• All cells come from pre-existing cells through cell division

A cell is the smallest unit that is capable of performing life functions.

Examples of cells: Amoeba proteus, Plant stem, Bacteria, nerve cell, red blood cell

Two types of cells

• Prokaryotic

1.     Do not have organelles (specialized structures in cells) surrounded by membranes

2.     Few internal structures

3.     One-celled organisms eg. bacteria

•  Eukaryotic

1.     Contain organelles surrounded by membranes

2.     Most living organisms eg. Plant, animal, fungi 

Plant Eukaryotic Cell

Animal Eukaryotic cell

Cell Wall

• Most commonly found in plant cells and bacteria
• Surrounds the cell membrane
• Rigid structure that maintains the shape, supports & protects cells
• Permeable to small molecules and small proteins only

Cell Membrane

• Selectively permeable membrane of cell that controls movement of substances in and out of the cell

Inside the cell…

Nucleus

• ·      Contain chromatins that control cell activities
• ·      Chromatin contain DNA which is the genetic material
• ·      DNA contain instructions for traits & characteristics and to carry out the cell’s function
• ·      Separated fro cytoplasm by nuclear membrane       

   Cytoplasm

• Gel-like mixture
• Surrounded by cell membrane
• Contains organelles

Mitochondria

• referred to as the powerhouse of the cell
• the food we eat is transformed into energy (ATP) for the cell and our bodies

Endoplasmic Reticulum 

• An interconected network of tubes and vesicles
• Synthesis of proteins, fats, steroid
• Transports materials around in cell
• Smooth type: Lacks ribosomes
• Rough type: RIbosomes embedded in surface 

Ribosomes

• Each cell contains thousands
• Make proteins
• Found on endoplasmic reticulum & floating throughout the cell

s  Golgi Bodies (smaller versions of the Golgi Apparatus)

•      - Works closely with the ER
•      - Primary function is to process and package complex molecules such as proteins and  fats that are made by the cell
•      - Brings these products to the surface of the cell where they can be secreted
•      other secretions include hormones, antibodies and enzymes

   Lyosome

•  Contain digestice enzymes
•  Digest excess or worn-out organelles, food particles and engulf bacteria or       viruses
•  Also help repair worn-out plasma membrane
•  They also provide sugars, amino acids and bases which are the function of macromolecules
•  Cell breaks down if lyosome explodes

Vacuoles 

•  - Membrane - bound sacs for storage, digestion and waste removal
•  - Central large vacuole-help plant vells matintain shape
•  - Food vacuoles: formed by phagocytosis 
•  - Contractile vacuoles (in freshwater protists): pump excess water out of the cell
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       Chloroplasts

         

         - Usually found in plant cells

         - Contains green chlorophyll

         - Where ohotosynthesis takesm place

         - Converts light energy to chemical energy in glucose

       

       

Harvard VPA - Froggies

Biodiversity

There are 13 billion known species of organisms! And this is only 5% of all organisms that EVER lived! New organisms are still being found and identified.

What is Classification?

1. It is the arrangement of organisms into orderly groups based on their similarities. 
2. Classification is also known as taxonomy. 
3. Taxonomy are scientists that identify & name organisms. 

The benefits of classifying: 

1. An accurate and uniformed way to name organisms
2. Prevents misnomers such as starfish and jellyfish that aren't really fish
3. Uses some language (Latin or Greek) for all names. 

Early Taxonomists

2000 years ago, Aristotle was the first every Taxonomist. 

John Ray, a botanist. 

• 2000 years ago, Aristotle was the first taxonomist.
• Aristotle divided organisms into plants and animals.
• He subdivided them into their habitat.
• John Ray, a botanist, was the first to use Latin for naming. 
• his names were very long descriptions telling everything about the plant. 

Carolus Linnaeus

• Father of taxonomy
• Developed the modern system of naming known as binomial nomenclature
• Two word name (genus and species) --> How "homosapiens" came about! 

Father of taxonomy.

Standardized Naming - Binomial Nomenclature 

• Binomial nomenclature
• genus species
• latin or greek
• italicized in print 
• Captialize genus not species
• underline when writing 

Giant panda!

Polar bear.

Mama grizzly bear and Baby grizzly bear! AWW! <3

Rules for naming organisms

• The International Code for Binomial Nomenclature contains the rules for naming organisms
• All names must be approved by International Naming Congress (International Zoological Congress) 
• This prevents duplicated names

Classification Groups

• Taxon (taxa - plural) is a category into which related organisms into which related organisms are placed
• There is a hierarchy go groups (taxa) from broadest to most specific 
• Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Domains 

• Broadest, most inclusive taxon
• Three domains
• Archaea and eubacteria are unicellular prokaryotes (no nucleus or membrane - bound organelles) 
• Eukarya are more complex and have a nucleus and membrane-bound organelles

Taxons

• Most genera contain a number of similar species with the exception of home that only contains modern humans
• Each successive classification category or taxon contains more different types of organisms than the preceding category

King

Philip

Came

Over

For

Gooseberry 

Soup

Why do we need to classify organisms?

Organisms. 

This small seedling is a living thing too. Don't underestimate it!

Aww a cute puppy! <3

Flowers.

It will be easier to identify them when they are grouped according to their similar and common characteristics or traits because it is more well-organized. It will also be easier to retrieve information when we need to because it is we can find the organisms fast. 

An adorable baby elephant following its mother!