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!

Get a grip!

Activities

1. We will observe how humans use their hands. Do we hold all objects in the same way?

Different ways that of holding different objects with one hand:

• wrap fingers around object
• using 2 fingers (thumb and index finger) to pick up items
• grabbing --> using the whole palm
• use of three fingers (thumb, index and middle)
• 2 palms adjacent to each other (scooping motion OR balancing) 
• using hand and arm (hug)

2. Reach out one of your hand to hold an object that you can wrap your hands around. Observe how you are holding the object. Record these observation in detail both in words and also in a drawing. 

This is my drawing of me holding a pencil.

I used my thumb, index finger, middle finger and ring finger to grasp the pencil and loop around it, trying to support the pencil.

3. After watching the video, Observing Primates, I observed the following about how the gorilla moves about using their arms, legs, hands and feet.

• When walking, 

1. their hands are partially clenched, knuckles touching the ground.
2. hunched back
3. arms are bent at a certain angle

• Generally,

1. their feet look like hands (big toe is very far apart from the other 4 toes)
2. long arms that are longer than their legs

4. Questions on how primates move. 

1. Wouldn't their knuckles hurt hurt when they walk?
2. Why must they walk with their hands and legs instead of just their legs? 
3. Why do they pump/hit their chest?
4. Why a large space between 1st toe and the rest?
5. Do they swing on trees?
6. Why are their arms longer than their legs?
7. Why is the skin so rough/horny? 

Is it Alive - Observation of Substances on Wet Cotton Wool

Part 3

Table 3

Substance A, B and C (clockwise) after 10 minutes

Substance D after 10 minutes

Substance E after 10 minutes

Substance A, B and C (anti-clockwise) after 24 h

Substance B after 24 h

Substance E after 24 h

Substance A after 36 h

Substance B after 26 h

Substance C after 36 h

Substance D after 36 h

Substance E after 36 h

Is it Alive - Observations of Substances in Glucose

    Part 2

Substance A and B at 0 minutes

Substance C and D at 0 minutes

Substance E at 0 minutes

Substance A, B and C after 10 minutes

Substance D and E after 10 minutes

Is it Alive - Observation of Substances in Water

 Table 1 

1. Label the tube A, B, C, D and E.
2. Carefully transfer 1 spatula full of each of the substances A, B , C, D and E into the respective test tube. 
3. Add 3ml of water to each of the tube. Mix well using the wooden splinter.
4. Start your stopwatch.
5. Observe. Write your observations in table 1. Take readings if you have to.
6. After 10 mins, record the observation again.
7. What is your inference for each of the substance? Is there any evidence of life?

Pictures taken from Park Jiwon at 

Source: http://parkjiwon24106biologyjournal.blogspot.sg/ 

Substances A, B, C, D and E (from left to right) at 0 minutes

Substances A, B, C, D and E (from left to right) at 10 minutes

Is it Alive - Liquids Chosen

Three different types of liquids - water, glucose and salt water are also provided to test the reactions of the substances to these liquids. 

Why were these liquids chosen? 

Water: 

The substances may also breathe. If air bubbles are seen coming out from the water, this proves that the substance might be breathing. If the water level decreases, it also means that the substance is a living thing as it needs water to survive. 

Glucose:

The substance might take in the glucose and reproduce, therefore proving that it is a living thing.

Salt Water: 

The substance may need salt water to survive.

Is it Alive? - Physical Appearances

Physical Appearance of Substance A, B, C, D and E

Living Things

Characteristics of Living Things 

1. Need air, food and water.
2. Responds to changes.
3. Able to move by themselves.
4. Able to grow, reproduce and die. 

Conditions needed to support life

1. Warmth

2. Shelter

3. Air

4. Sunlight