Plant Cells and Plant TissuesTypes of Plant Cells: Parenchyma Cells. These cells are the most general of plant cells. They consist of thin flexible cell walls. They contain a large central vacuole and can carry out most of the metabolic functions of the plant. Mesophyll cells of the leaf are parenchyma cells. The fleshy tissue of most fruits also contain much parenchyma.

Collenchyma Cells. These cells have a much thicker primary wall than the parenchyma cell. Grouped in strands or cylinders they support young plants.

Sclerenchyma Cells. Function in support of the plant. They contain a thick secondary wall containing lignin. For all intent and purpose these cells function best when dead.

Tracheids. These are water conducting elements. These cells are dead and are found along with vessel elements making up the plants xylem.

Sieve-tubes. These function in carrying food throughout the plant. They are kept alive and nourished by companion cells. These are found in the plants phloem.

Tissue Types: Dermal Tissue. generally a single layer of cells. They are tightly packed and covered with a transparent, waxy, material called the cuticle.

Vascular Tissue. functions in support and transportation of food and water throughout the plant.

Ground Tissue. makes up the bulk of a young plant. It fills the space between the dermal and the vascular tissues.

Systems in Plants

SYSTEMS IN PLANTS :

1. Root Systems: Roots anchor the plant, absorb minerals and water,conduct water and nutrients, and store food. These are two types of root systems. Taproot System: This system consists of a single main vertical root with many smaller side roots. Examples of this type of system are: carrots, turnips, and dandelions. They serve as excellent reserves for food and anchor the plant well. Fibrous System: This system consists of many small lateral roots that spread out just below the soil's surface. The plants containing this type of root system has excellent exposure to water in the soil. It helps anchor the plant and helps prevent soil erosion. Adventitious roots are roots that grow from plant structures other than the roots

2. Shoot System: The shoot system consists of vegetative shoots which produce leaves and floral shoots that end with the flower. Stems contain areas where side branches and leaves develop from. Leaves: Leaves carry on photosynthesis. Their position and shape allow them to absorb the maximum amount of sunlight as possible. The leaf consists of the flattened portion called the blade, the edge or the margin, the petiole, and the veins.

Animal cell Versus Plant cell

Comparing animal cell and plant cell

List the similarities and differences based on Diagram given.

FAQ-Chapter2-Cell Structure N OrganisationLets focus on some of the FAQ for this Chapter. especially for Paper 2- Structure and Essay Qs.

1. Comparing animal cell and plant cell structurally. [ Comparing means listing its similarities and differences ]2. Identifying and Labelling the organelles and non organelles in the cells and know their functions.3. Popular organelles are : mitochondria, chloroplast, nucleus, vacuole, rough endoplasmic reticulum, Golgi apparatus, ribosomes, lysosome

4.Living process in Amoeba- unicellular organism: Its feeding Phagocytosis !!

5.Living process in Paramecium : Its osmoregulatory mechanism which involves the contractile vacuoles. And relate it with the conditions of its habitat : Hypotonic/ hypertonic ?

6. Cell specialisation in animals and plants in order to carry out specific function: Red blood cell, sperm, muscle cell,nerve cell.

7. In plants : the ground tissue !!8. Cell organisation: Cell, tissue, organ, system, organism.

Ground Tissue in plants- SclerenchymaI have posted about Parenchyma and Aerenchyma in response to one of the students question .. But I dont think it is complete without the notes on an overall types of Ground tissue in plants....So lets have a look at the overall facts about Ground tissue in plants:

The types of ground tissue found in plants develop from ground tissue meristemand consists of three simple tissues:

1. Parenchyma (cells with thin primary walls that retain their protoplasm)2. Collenchyma (cells with thick primary walls that retain their protoplasm)3. Sclerenchyma (cells with lignified secondary walls that have lost their protoplasm at maturity, i.e. are 'dead')

...So I' m going to discuss here about Sclerenchyma :

Sclerenchyma is a supporting tissue in plants.

Two groups of sclerenchyma cells exist:Fibres and Sclereids.

Their walls consist of cellulose, hemicellulose and lignin.

Sclerenchyma cells are the principal supporting cells in plant tissues that have ceased elongation. Sclerenchyma fibres are of great economical importance, since they constitute the source material for many fabrics (flax, hemp, jute, ramie).Unlike the collenchyma, mature sclerenchyma is composed of dead cells with extremely thick cell walls (secondary walls) that make up to 90% of the whole cell volume.The term "sclerenchyma" is derived from the Greek σκληρός ("sklē-rós"), meaning "hard".

It is the hard, thick walls that make sclerenchyma cells important strengthening and supporting elements in plant parts that have ceased elongation.The difference between fibres and sclereids is not always clear.(As for your SPM scope, you need not know about it so details )

Fibres usually originate from meristematic tissues.

Cambium and procambium are their main centers of production.They are usually associated with the xylem and phloem of the vascular bundles.The fibres of the xylem are always lignified, while those of the phloem are cellulosic.

Sclereids are small bundles of sclerenchyma tissue in plants that form durable layers, such as the cores of apples and the gritty texture of pears.

Sclereids are variable in shape.But compared with most fibres, sclereids are relatively short

Parenchyma Versus AerenchymaParenchyma :

Parenchyma is made up of thin walled living cell. The cell wall is usually unthickened and formed of cellulose. The intercellular spaces may or may not be present.Parenchyma is present in all the organs of plants. It fills up the spaces between different tissues and thus acts as a ground tissue or matrix.

Some of the modified parenchymatous tissues are follows:

I. chlorenchymaII. aerenchyma

The parenchymatous tissue performs a variety of functions:

• It forms the epidermis on the outermost surface of the plant organs.• It acts as a protective layer.• Sometimes an impermeable layer of cutin called cuticle lines the outer surface of the epidermis. This cuticle checks he rate of transpiration.• Guard cells of the stomata are means for exchange of respiratory gases in leaves and other organs. These guard cells are epidermal in origin.• The epidermis and root hairs in roots are not covered by cutin. The root hairs are cylindrical outgrowths from the walls of epidermal cells of roots and increase the water absorbing capacity of roots.

Chlorenchyma :

Chlorenchyma is seen in green leaves and some other green aerial organs.Its cells contain chloroplasts.Chlorenchyma is differentiated into :(a) Palisade (b) Spongy chlorenchyma

(a) Palisade:In this tissue the cells are columnar.The columnar cells are arranged at right angles to the upper surface of the leaf.The intercellular spaces are relatively few.The cells are somewhat compactly arranged.The location of palisade in leaf and other flattened aerial, green organs is such as to receive strong, straight sun-rays.

(b) Spongy Chlorenchyma:Spongy chlorenchyma is located in leaf and other aerial green organs in such a way as to receive mild sun rays.Cells in spongy chlorenchyma are round or oval, parenchymatous and have large intercellular spaces.

In most leaves, the spongy chlorenchyma lies near the lower epidermis.

The cells of both palisade and spongy chlorenchyma tissues contain chloroplasts and hence perform the function of photosynthesis synthesizing glucose.

Aerenchyma :

Hydrophytes are plants growing in water or water logged habitats. E.g.Trapa, Lotus, Pistia etc. Hydrophytes have aerenchyma as one of the tissues.Aerenchyma consists of small cells so arranged as to form large air spaces.Due to air contained the respective plant organs become soft, light and spongy.As a result the organs can keep themselves floating and obtain sufficient light for photosynthesis in the hydrophytes.

Some of the air spaces show special type of partition walls, which provide them mechanical strength

Regulating the internal EnvironmentBrief Account1. The cells of the multicellular organisms body live within an internal environment.

2. The internal environment of multicellular organism consists of the interstitial fluid and the blood plasma.

3. The interstitial fluid / Tissue fluid fills the spaces between the cells and constantly bathes the cells

4. In order for the cells to function optimally, the physical factors and chemical factors of the internal environment must be maintained constant.

5. The physical factors include temperature, blood pressure and blood osmotic pressure. The chemical factors include concentration of oxygen and carbon dioxide in blood, salt and blood glucose content and blood pH value.

6. The body mechanism which maintain the internal environment of the cells constant so that it can function optimally is called homeostasis. Homeostasis is very important because when it fails you become ill and may die.

7. The internal environment has to be maintained constant so that all enzymes in the organism can function efficiently at all times.

8. In maintaining the internal environment constant, cells, tissues, organs and organ systems are working together. For example, both nervous system and endocrine system work together to maintain the blood pH.

Appreciating the uniqueness of the cell.

1. A cell is the basic unit of all living organisms which is capable of functioning on its own.

2. All the organelles in the cell work together so that cells are able to function at its optimum level.

3. Just as there are many cell types, there are varied cell functions. The generalized cell functions include movement of substances across the cell membrane, cell division to make new cells, and protein synthesis.

4. Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

5. Cells are unique but without organelles, hundreds of regular cellular functions could not be performed.

Possible Question :

Predict what happen if the following organelles are absent / damage.( You must explain your answer)Organelles and Effect if absent - Nucleus----All cell activity cannot be controlled.Golgi apparatus----Synthesis of carbohydrates, glycoprotein and hormone cannot be completedVesicle----Protein which has been modified cannot be transport out of the cell.Smooth endoplasmic reticulum----Synthesis and transported of fat and glycerol cannot be done.Rough endoplasmic reticulum----Transported of protein synthesized by ribosome could not be done.Mitochondrion----No energy produced.Cells unable to carry out its activities.Lysosome----Worn our organelles could not be digestedRibosomes----Protein could not be synthesizedChloroplast----Photosynthesis could not take place in plantsVacuoles----The plant cell would loss its shape and turgidity--There is no place to store sugars, amino acids and waste products.

Cell OrganisationBrief Account

1. There are two category of organisms:-unicellular organism-multicellular organisms

2. Unicellular organisms are organisms with just one cell, for example Amoeba and Paramecium

3. Unicellular organisms are small and simple animals which are able to carry out vital functions within a single cell.

4. Unicellular organisms can feed, respire, excrete, move and respond to stimuli, grow and reproduce.

5. Unicellular organisms does not have any organs or systems thus it depends largely on its cellular components.

6.Most spesies of Amoeba are free-living in fresh water environment.

7. Table shows the components of Amoeba sp. and their roles in carrying out life processes in Amoeba sp.

8.Amoeba sp is a holozoic organisms which feeds on microscopic organisms such as bacteria.

9.Figure shows the process of phagocytosis in Amoeba sp.

10. Amoeba sp reproduces asexually by binary fission. If the environment is favourable. However,when the environment is not conducive , it forms spore.

Why is that a Paramecium sp. which lives in the ocean does not possess a contractile vacuole where as a similar Paramecium sp. which lives in fresh water must have such a cytoplasm organelle?

Because salt water go's through them instead of inside them so they dont need to expel salt water

In 2006- SPM Paper 2, there was a question like this:

9(b)Multicellular organisms like humans, need specific transport sysems as compared to unicellular organisms like Amoeba sp., which do not need a transport system.

Give an evaluation of the above statement based on the physical features of the organisms with the following physiological processes:

* Respiration* Nutrition* Excretion [10 marks]

1. The question need you TO EVALUATE. ..

(The highest level of skills in Bloom Taxonomy)2. Look at some of the keywords of the question.3. You have to be able to compare THE PHYSICAL FEATURES of BOTH ORGANISMS: Unicellular and Multicellular!!!4. But of course with respect to 3 processes asked:RESPIRATIONNUTRITIONEXCRETION5. Dont forget MARKS ALLOCATED is 10 marks...So how lengthy you should write?..Write your answer using paragraph by paragraph NOT BULLETED like I do....I do it in bullet forms so that it is easier for you to locate the points/Facts required.SUGGESTED ANSWER:· The physical features of multicellular organism are big size and the TSA/V ratio is small· So the rate of diffusion of substances into and out of the body cells is low· Cells in the inner part of the body are not in direct contact with the surroundings· Whereas the physical features of unicellular organism are small size and the TSA/V ratio is big· So the exchange of substances between organism and surrounding occurs easily· Body cell is directly in contact with

surrounding[ 4 marks maximum given ]

· As for multicellular organism, they need a specific gas exchange surface/organs such as lungs to exchange oxygen and carbon dioxide· whereas unicellular do not need specific organ since gas exchange can takes place by simple diffusion through the plasma membrane. [ 1+1]...RESPIRATION

· Multicellular organism needs digestive system to bring in food from surroundings into alimentary canal, digest then absorbed.· Digested food then transported to the body cells by blood and lymphatic system( Any ONE)

· Whereas in unicellular organism, it does not need transport system because food is directly taken in through membrane cells by phagocytosis· Then digested by intracellular enzymes (in the vacuole)(ANY ONE) [ 1+1 ]..NUTRITION

· Multicellular organism needs transport system to take excretory waste /urea from liver to the kidney· Excretory waste is then taken out from

kidney /excretory organs.(Any one)· Whereas in unicellular organism excretory waste are directly eliminated from body cells to the surroundings through the cell membrane· Excretory waste is excreted out in contractile vacuole.( Any one) [ 1+1 ]..EXCRETORY

.......................So Total Marks = 10 marks...

..So you see how beautifully written the essay is!!!It includes all the FACTS required by the Marking Scheme..And definitely you will score full marks if you write such..TIPS:To produce good essay answer, you have to understand the task of the question..Dont forget to take note of all the important keywords in the question which might give you an idea to write about what..And of course, you must know the subject content well as to discuss it correctly...and for the last minute students...understanding and memorising the marking schemes could do a bit of help to you..(If such question ever being asked again...)Cell specialization and organization in multicellular organisms

1.A multicellular organism is an organism which consists of more than one cell.

2.These cells grow, change shape and differentiate to carry out specific function.

3. Cells of a multicellular organism differentiate and undergo specialization in order to perform their task efficiently.

4. Cells may become specialized in transport: example, red blood cell, which is biconcave disc-shaped and very flexible in order to move easily along the narrow blood capillaries.

5.Table shows some of the specialized human cells and their function.

6. Diagram shows some of the specialized plant and animal cells and their function

http://www.livingscience.co.uk/year7/cells/specialised%20cells.gif

7. Cells of the same type which carry out a common function are organized into tissues.

8. A tissue is a group of similar cells which are specialized to perform a particular function. There are four primary tissue types in the human body: epithelial tissue, connective tissue, muscle tissue, and nerve tissue.

9. Muscle tissue is the most abundant tissue in the body. It is a specialized tissue that can contract. Muscle tissue contains the specialized proteins actin and myosin that slide past one another and allow movement. Examples of muscle tissue are contained in the muscles throughout the body.

Types of muscles tissuehttp://www.purchon.com/biology/muscles.htm

http://www.nvo.com/jin/homepage10/

10. There are three types of muscle tissues: smooth muscle, skeletal muscle, and cardiac muscle.

11. Table shows the type of muscle tissue and where can be found in the body.

http://www.human-body-facts.com/muscular-system.html

12. The cells of epithelial tissue pack tightly together and forms a continous sheets that serve as lining of all internal and external body surfaces.

13. Epithelial tissue serve as membranes lining organs and helping to keep the body's organs separate, in place and protected.

14. Some examples of epithelial tissue are the outer layer of the skin, the inside of the mouth and stomach, and the tissue surrounding the body's organs.

15. Table shows different function of epithelial tissue in relation with its location.

Epithelial tissuehttp://www.nvo.com/jin/homepage6/

16. When different type of tissue group and work together, they form an organ of the body. The stomach, for example is an organ which is composed of smooth muscle tissue, loose connective tissue, nervous tissue, blood and columnar epithelium

17. Several organs working in conjunction form organ systems. An example of a system is the circulatory system, which is composed of heart, blood vessels, and blood.

Happy Revising..

Posted by mahadiah at 6:09 PM 1 comments Email ThisBlogThis!Share to TwitterShare to Facebook Links to this postLabels: Cell Structure N Organisation

Wednesday, October 7, 2009

Animal Cell Versus Plant CellQuestions usually asked are:

Compare and contrast between animal cell and plant cell....Well, to answer to this question, you just have to produce a Table to show the similarities and the differences between the two.

TIPS:*Dont forget to look at the marks allocated befor you start answering because marks allocation will determine how many facts you should be writing for your answer...*Draw a Table with correct, proper headings*Put up similarities first (at least two)*Then proceed with the differences....as many as you can remember...*The sentences should be short and precise

Look at the suggested answer below:

Interesting facts (Extracted):

Cell walls in animal cells vs. plant cellsA notable difference between animal cells and plant cells is that animal cells do not have a cell wall where as plant cells do. Both plant and animal cells have plasma membranes.

ChloroplastsPlant cells have chloroplast for photosynthesis whereas animal cells do not have chloroplasts.

Shape of plant cells vs animal cellsAnother difference between plant cells and animal cells is that animal cells are round whereas plant cells are rectangular.Further, all animal cells have centrioles whereas only some lower plant forms have centrioles in their cells.

Vacuoles in plant cells vs. animal cells

Difference in shape and size of vacuolesAnimal cells have one or more small vacuoles whereas plant cells have one large central vacuole that can take up to 90% of cell volume.

Difference in function of vacuolesIn plant cells, the function of vacuoles is to store water and maintain turgidity of the cell. Vacuoles in animal cells store water, ions and waste.

Interesting Link to follow:http://www.diffen.com/difference/Animal_Cell_vs_Plant_Cell#Posted by mahadiah at 10:47 PM 0 comments Email ThisBlogThis!Share to TwitterShare to Facebook Links to this postLabels: Cell Structure N Organisation

Cell StructureBrief Account

1. Living organisms are made of basic units called CELLS.2. The living components of a cell is called protoplasm which actually consists of thecytoplasm and the nucleus.3. Cell membrane refers to all membranes found outside the cell which form the outer boundary of the cell, whereas, plasma membrane is the membrane at the surface which encloses the content of a cell.

Most popular Facts about cells frequently asked are about the Structure and The Function of the cell parts:

Cell membrane-Act as a selective barrier wall

-Provides and maintains the shape of the cell.-Gives support to the cell.-Controls movement of materials in/out of cell .-Protective barrier between the cell and its environment.-Maintain homeostasis.

Cytoplasm- Provides substances obtained from the external environment to the organelles.Supports and protects cell organelles .

Nucleus- Controls all the activities in the cell.-Contains all the genetic material of a cell in the form of chromosomes.-Produces ribosomes and RNA (Ribonucleic acids)-Plays an essential role in cell division.

Mitochondria- Involved in cellular respiration which releases energy stored in a form of ATP that can readily be used by cells.

Interesting Facts (Extracted):Mitochondria are known as the powerhouses of the cell.They are organelles that act like a digestive system that takes in nutrients, breaks them down, and creates energy for the cell.The process of creating cell energy is known as cellular respiration.Most of the chemical reactions involved in cellular respiration happen in the mitochondria.A mitochondrion is shaped perfectly to maximize its efforts. Mitochondria are very small organelles. You might find cells with several thousand mitochondria.The number depends on what the cell needs to do. If the purpose of the cell is to transmit nerve impulses, there will be fewer mitochondria than in a muscle cell that needs loads of energy.If the cell feels it is not getting enough energy to survive, more mitochondria can be created. Sometimes they can even grow, move, and combine with other mitochondria, depending on the cell's needs.

Vacuole- plays roles in intracellular digestion and the release of cellular waste products.-Stores sugars and amino acids in its sap.-Support herbaceous plants by tugor pressure

Endoplasmic reticulum-The rough RE transport proteins made by ribosomes.

-The smooth RE site of important metabolic reactions such as synthesis of lipid and membrane proteins.

Ribosome-Synthesis of proteins such as enzymes.Interesting Facts (Extracted):Ribosomes - Protein Construction TeamsCells need to make proteins. Those proteins might be used as enzymes or as support for other cell functions.When you need to make proteins, you look for ribosomes.Ribosomes are the protein builders or the protein synthesizers of the cell. They are like construction guys who connect one amino acid at a time and build long chains.Ribosomes are found in many places around the cell. You might find them floating in the cytoplasm (cytosol). Those floating ribosomes make proteins that will be used inside of the cell. Other ribosomes are found on the endoplasmic reticulum.Endoplasmic reticulum with attached ribosomes is called rough. It looks bumpy under a microscope. Those attached ribosomes make proteins that will be used inside the cell and proteins made for export out of the cell.Lysosome-Contain hydrolytic enzymes .-Eliminate worn out or damaged organelles to enable a cell to renew itself.Interesting Facts (Extracted):-Lysosomes - Little Enzyme PackagesYou will find organelles called lysosomes in nearly every animal-like eukaryotic cell.Lysosomes hold enzymes that were created by the cell.The purpose of the lysosome is to digest things. They might be used to digest food or break down the cell when it dies. What creates a lysosome? You'll have to visit theGolgi complex for that answer. A lysosome is basically a specialized vesicle that holds a variety of enzymes. The enzyme proteins are first created in the rough endoplasmic reticulum.Those proteins are packaged in a vesicle and sent to the Golgi apparatus. The Golgi then does its final work to create the digestive enzymes and pinches off a small, very specific vesicle. That vesicle is a lysosome.From there the lysosomes float in the cytoplasm until they are needed. Lysosomes are single-membrane organelles.

Centrioles-Strengthen cell & maintains the shape-Moves organelles within the plant cell

Golgi apparatus-Processing, packaging and transporting centre of carbohydrates, proteins, phospholipids and glycoproteins

Chloroplasts-Site of photosynthesis

Interesting Facts (Extracted):

One of the most widely recognized and important characteristics of plants is their ability to conduct photosynthesis, in effect, to make their own food by converting light energy into chemical energy.This process occurs in almost all plant species and is carried out in specialized organelles known as chloroplasts.All of the green structures in plants, including stems and unripened fruit, contain chloroplasts, but the majority of photosynthesis activity in most plants occurs in the leaves. On the average, the chloroplast density on the surface of a leaf is about one-half million per square millimeter.Interesting Links related to this chapter which you might like to follow are listed below:http://www.biology4kids.com/files/cell_mito.htmlhttp://www.enchantedlearning.com/subjects/animals/cell/

http://www.cellsalive.com/cells/cell_model.htm

....and of course the Diagrams.....Students must be able to identify and also able to draw and label all the structures above...