Author: science4all

University of Auckland B. Science degree in Biological Science University of Auckland GDip. Teaching (Secondary) course in 2009.
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What is kinetic energy and potentional energy?

Kinetic energy

Kinetic Energy is energy that is in motion. Moving water and wind are good examples of kinetic energy. Electricity is also kinetic energy because even though you can’t see it happen, electricity involves electrons moving in conductors.

Energy makes change possible. We use it to do things for us. It moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. Energy is needed for our bodies to grow and it allows our minds to think.

Scientists define energy as the ability to do work. Modern civilization is possible because we have learned how to change energy from one form to another and use it to do work for us and to live more comfortably.

Energy is found in different forms including light, heat, chemical, and motion.

Potential Energy

Energy is measured in the amount of “work” it does. Potential Energy is stored energy. Examples of potential energy are oil sitting in a barrel, or water in a lake in the mountains. This energy is referred to as potential energy, because if it were released, it would do a lot of work.

Energy can change from one form to another. A good example is a Roller Coaster. When it is on its way up, it is using kinetic energy since the energy is in motion. When it reaches the top it has potential (or stored) energy. When it goes down the hill it is using kinetic energy again.

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Science fair help: Burning peanut experiment

Measuring Energy

burn a peanut and boil water to meaure its calorie content

This is a particular method that measures energy in a peanut. A peanut burns producing an impressive amount of flame for a long time. The flame is used to boil away water and count the calories contained in the peanut.

Equation for calculating the calories in a peanut: To raise the temperature of 10 grams of water from 20 °C to 100 °C it takes:

Q = mcDT

Or, use the following equation to calculate the calories per gram of the peanut:

calories per gram = (heat gained by water)/(mass lost when peanut burned)

This is another way of doing the experiment.

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To learn more about this experiment visit

http://www.exo.net/~pauld/activities/food/burnapeanut.html

http://www.chymist.com/energy%20of%20a%20peanut.pdf

http://www.cerlabs.com/experiments/10875406238.pdf

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Bacteria

Functions of major parts

  • DNA: Contains genetic information for the bacteria. Controls all the chemical reactions within the cytoplasm.
  • Capsule: Protects bacteria from heat and chemicals
  • Flagellum: For movement.
  • Fimbriae/Pilli: For attachment (eg. on the surface of stomach)
  • Cell wall: Maintains the shape of the bacteria.
  • Ribosomes: For making protein.
  • Cytoplasm: This is where all the chemical reaction happens (including making proteins).
  • Plasma-membrane/ cell membrane: Controls what comes in and goes out.

Uses of Bacteria :

ref http://hubpages.com/hub/Uses-and-Classifications-of-Bacteria

  • A bacterium breaks down the organic fertilizer (decomposed vegetables and animal matter) into material that can be used by plants.
  • Some species of soil bacteria convert nitrogen into nitrites, compounds that are readily absorbed by plants.
  • Different commercial processes also need certain bacteria, like Anaerobic bacteria that ferment certain substances are used in the production of vinegar and some drugs, and in the aging process of cheeses.


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Hepatic portal vein

Usually the capillary beds of most tissues drain into veins are lead directly back to the heart. However hepatic portal vein is an exception. In this case, blood draining the intestine is leaded to a second set of capillary beds in the liver. Then the liver removes many of the materials that were absorbed by the intestine:

  • Glucose is removed and converted into glycogen.
  • Other monosaccharides are removed and converted into glucose.
  • Excess amino acids are removed and deaminated.
    • The amino group is converted into urea.
    • The residue can then enter the pathways of cellular respiration and be oxidized for energy.
  • Many nonnutritive molecules, such as ingested drugs, are removed by the liver and, often, detoxified.

The liver serves as a gatekeeper between the intestines and the general circulation. It screens blood reaching it in the hepatic portal system so that its composition when it leaves will be close to normal for the body.

Furthermore, this homeostatic mechanism works both ways. When, for example, the concentration of glucose in the blood drops between meals, the liver releases more to the blood by

  • converting its glycogen stores to glucose (glycogenolysis)
  • converting certain amino acids into glucose (gluconeogenesis)

ref: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/G/GITract.html

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Bile and Pancreatic juice

As the contents of the stomach become thoroughly liquefied, they pass into the duodenum(Small intestine). Duodenum is the first segment (about 10 inches long) of the small intestine.

Two ducts enter the duodenum:

  • one draining the gall bladder and hence the liver
  • the other draining the exocrine portion of the pancreas.

Bile

  • pH 7.6
  • bile acid: large globules of fat (liquid at body temperature) are emulsified into tiny droplets (about 1 µm in diameter) that can be more easily digested and absorbed.
  • Bile contains the products of the breakdown of hemoglobin removed by the liver from old red blood cells. The brownish/greenish color of the bile pigments imparts the characteristic brown color of the faeces.

Pancreatic juice

  • The pancreas consists of clusters if endocrine cells and exocrine cells whose secretions drain into the duodenum.
  • Contains:
  1. sodium bicarbonate (NaHCO3): This neutralizes the acidity of the fluid arriving from the stomach raising its pH to about 8.
  2. pancreatic amylase: This enzyme hydrolyzes starch into a mixture of maltose and glucose.
  3. pancreatic lipase: The enzyme hydrolyzes ingested fats into a mixture of fatty acids and monoglycerols. Its action is enhanced by the detergent effect of bile.
  4. trypsin
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RNA and DNA

Our body is made up of very complex proteins. In fact, it is not just us that is made up of very complex proteins. It is more accurate to say that all the living things are made up of very complex proteins. There are two kinds to proteins – functional protein and structural protein. What is the difference? Well, the functional protein helps with the chemical reactions in our cells – but the structural protein is like what you can see with your eyes and touch. You can touch your skin, finger nail, hair, skin… and organs inside your body!

Why am I talking about these things?

Because I am about to let you know that your cells contain all the information about these proteins. The information is used to make and control every single things which are inside and outside your cell. It is like an encyclopedia, written in the language that our body understands. Where can we find the information then? The famous DNA – inside the nucleus of a cell.

The DNA is a long double helix molecule. Helix is the shape of a twisted ladder.

May be you have seen this picture before. The DNA is made up of thousands and millions of a single unit called NUCLEOTIDE.

Nucleotides have another name – Nucleic acid. This is because we often have to see things from chemistry perspective to understand their property as a molecule.

DNA and RNA is all made up of nucleic acids. But only difference is that DNA is like a ‘REFERENCE COPY’ book in the library. As you know these REFERENCE COPY books cannot be taken out side the library. So, what do you do when you need an information from the book? You would photocopy the pages you need wouldn’t you? The RNA is like the photocopied pages which can take information from DNA in the nucleus to the cytoplasm to make proteins. This is because making protein needs big chemical reaction and this reaction can only take place in the cytoplasm.

This is how RNA and DNA looks like. As you can see RNA is single stranded and DNA is doubles stranded. The part you cannot see is the difference in length. DNA is way way longer than RNA because it contains whole information, unlikely, RNA is way way shorter than DNA because RNA only contains copy of a section in a DNA strand.

You will actually more things about RNAs and DNAs when you take senior Biology subject. Hope this helps for you to kick start! :)

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[Yr13 NCEA Internal] – Biotechnology

Question: DNA profiling is being used as part of an international research project to identify twenty thousand marine fish species by the year 2010. Scientists will identify the sequence of bases in a specific region of mitochondrial DNA which does not show much variation within species, but between species is very different. The DNA is sourced from muscle tissue using standard DNA extraction techniques.

Discuss the human need or demand for DNA profiling technology in relation to identifying marine fish species.

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[‘MERIT’ ANSWER]

This use of DNA profiling enables fish species to be accurately identified. This allows biodiversity / conservation issues to be addressed, Evolutionary links to be identified.

Data on fish species will also enable fish quotas/stocks to be ascertained. DNA profiling is faster and more accurate than any other method of identification so that data on fish species can enable fish quotas/stocks to be ascertained to ensure they are sustainable.


[‘EXCELLENCE’ ANSWER -add these statements to MERIT answer]

This use of DNA profiling is justified as it enables fish species to be identified faster and more accurately than any other method. This allows biodiversity and conservation issues to be addressed more accurately, as data on each fish species is more accurate. Without the use of DNA profiling different species of fish that look similar may have been misidentified and this would have made it appear that there were more of a species present than was actually the case.

When the stocks of a fish species are able to be quickly and accurately determined it helps to ensure that appropriate management strategies are implemented to maintain a sustainable catch.

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Physical change VS. Chemical change

1. Physical change is a reversible change.

Physical changes involve change in position. A physical separation involves moving one substance away from another. Iron can be moved away from sulfur and iron mixture by passing a magnet over a mixture containing the two substances. Water can be moved away from passing mixture of sand and water through a funnel and catching the sand in the funnel. We begin with two separate substances, which happen to be close to each other. We en up with the same two separate substances, but they are no longer close to each other. No new substances are formed and we can easily put the parts of the mixture together again.

Dissolving, melting, boiling, condensing, freezing and evaporating are all reversible changes.

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2. Chemical change is an irreversible change.

Chemical changes involve changes in the connections between substances. A chemical reaction can form a new substance. However, a chemical change involves the formation of a new substance, requires energy and cannot be reversed.

  • Cooking can cause an irreversible change. For example: an egg can be heated and cannot be returned to its previous state.
  • Burning materials, such as wood, paper, natural gas, causes an irreversible change.
  • Irreversible changes can form new materials that can be useful e.g. plaster of Paris and water.
  • Dead plants and animals decay and some metals rust. These chemical changes are permanent.
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Friction

Our life is pull of forces. We cannot see them but we can see how they affect things. Forces can change the shape of something, its speed, or the direction that it is moving in.

This is an example of friction.

Forces are either pushes or pulls. These pictures show some changes caused by forces. Many forces need to touch an object before they can affect it. These are called contact forces.

Friction is the force between two touching objects. It can slow things down or make things stand still. The friction between our clothes and a chair stops us from sliding off it. Walking would be very difficult without the frictions between our feet and the floor – we would slip and slide everywhere.

Friction can also wear things away. The brake pads on a bicycle eventually wear away, and so do car tyres. Parts of your clothes get thinner as friction wears them away.

Friction produces heat and noise. If a car engine runs without any oil in it, the large friction between the moving parts inside the engine causes it to overheat and stop working. Rusty door hinges squeak and make a door difficult to open.

We can increase friction by using certain materials. Rubber produces a lot of riction which is useful to use. The tyres of a Formula One racing car stop the car from sliding off the road as it speeds round a sharp bend. The rubber mat in a bath stops us from slipping.

We can reduce friction by making surfaces smooth. Skiers wax the bottom of their skis to make them very smooth. This reduces friction and allows them to ski faster.

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공부의 비법 1,2,3

케이블 방송같은데 한국에서 유명한 강사들이 매주 나와서 쇼프로 형식으로 강의를 한다.  과목별로 공부를 하는 방법을 알려주기때문에 꼭 한국에서 공부하는 학생이 아니더라도 한번쯤은 꼭 들어야 할 필요성이 있다.

한국의 수능은 미국이나 영국시험제도와 비슷하기때문에 우리가 하고있는 공부와 비슷하다. 꼭 한번 들어보길…

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공부의 비법 3회[사탐&과학]: http://joonmedia.net/videos/play/18631/4

공부의 비법 2회[수학]: http://joonmedia.net/videos/play/18486/4

공부의 비법 1회[국어]: http://joonmedia.net/videos/play/18013/4