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OCR Additional ScienceOCR Additional Science

B4 The Processes of LifeB4 The Processes of Life

W RichardsThe Weald School

12/27/14B4.1 How do Chemical Reactions B4.1 How do Chemical Reactions take place in living things?take place in living things?

12/27/14Photosynthesis IntroductionPhotosynthesis IntroductionBasically, photosynthesis is the process through which a plant makes large food molecules using carbon dioxide and water and it happens in plants as well as some micro organisms:

That’s a nice plant. I’m going to put it in the sun and give it lots of water

and air…

CO2

H2O

12/27/14Respiration IntroductionRespiration IntroductionI enjoy taking samples using quadrats. In order to do this, I need energy. Where

does this energy come from?

All living things, including plants, get their energy from respiration. Respiration is basically the process of breaking down the large food molecules that were probably originally made in plants.

12/27/14Enzyme use in natureEnzyme use in nature

Cells use glucose to generate energy – this process is called “respiration”. Respiration happens in mitochodria and is catalysed by enzymes.

Photosynthesis is catalysed by enzymes in the cells.

Enzymes are proteins that speed up chemical uses. Here are two important natural uses for them:

12/27/14EnzymesEnzymesEnzymes are biological catalysts. They help the reactions

that occur in our bodies by controlling the rate of reaction.

An enzyme is basically a protein molecule made up of long chains of amino acids. Cells make enzymes according to the instructions carried in their genes.

The enzyme’s shape helps another molecule “fit” into it:

This shape can be destroyed by high temperatures or the wrong pH:

Enzyme Substrate

12/27/14The “Active Site”The “Active Site”

Enzyme Substrate

Active site

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Enzymes are denatured

beyond 40OC

EnzymesEnzymesEnzymes work best in certain conditions:

Enzyme activity

Temp pH pH400C

Could be protease (found in the stomach)

Could be amylase (found in the intestine)

Enzymes are used in industry to bring about reactions at normal temperatures and pressures that would otherwise be expensive. However, most enzymes are denatured at high temperatures and can be costly to produce.

12/27/14B4.2 How do Plants make food?B4.2 How do Plants make food?

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Travels up from the roots

WATER

CARBON DIOXIDEEnters the leaf through small holes on the underneath

SUNLIGHTGives the plant energy

CHLOROPHYLLThe green stuff where the chemical reactions happen

Photosynthesis – the 4 things you needPhotosynthesis – the 4 things you need

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Carbon dioxide + _____ glucose + _____

6CO2 + 6H20 C6H12O6 + 6O2

Sunlight

Chlorophyll

Sunlight

Chlorophyll

The GLUCOSE produced by photosynthesis is used by the plant for _______ (through ____________). It is stored in the plant as ___________.

Words – respiration, starch, water, oxygen, energy

Photosynthesis equationsPhotosynthesis equations

12/27/14What is the glucose used for?What is the glucose used for?1) Glucose (sugar) can be used to make long chains of insoluble starch…

Glucose molecules

Starch molecule

2) Glucose can be used to make cellulose for cell walls…

3) Glucose can be combined with nitrates to make proteins (for growth)…

Glucose molecules

Glucose molecules

Cellulose

Proteins

Glucose can also be used for respiration, either by the plant or by what eats it!

12/27/14A Typical Plant Cell:A Typical Plant Cell:Cell wall – made of cellulose which strengthens the cell

Cell membrane – controls what comes in and out

Nucleus – controls what the cell does and stores genetic info for making proteins

Large vacuole – contains sap and helps support the cell Cytoplasm –

Chemical reactions happen here

Chloroplasts – contains chlorophyll and enzymes for photosynthesis reactions

12/27/142 common nutrients…2 common nutrients…

Nitrates: Used to make proteins Lack of it leads to stunted growth

Magnesium: Used to make chlorophyll Lack of it leads to yellow leaves

12/27/14DiffusionDiffusionDiffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger…

The “scent particles” from this hamburger are in high

concentration here:

Eventually they will “diffuse” out into this area

of low concentration:

Carbon dioxide and oxygen pass in and out of leaves by diffusion.

12/27/14Diffusion SummaryDiffusion SummaryDiffusion is when particles spread from an area of high concentration to an area of ___ concentration. The particles move along a “concentration _____” and this process takes no _____ (it’s a “passive” process”). Diffusion can be accelerated by increasing the _______ of the particles, which makes them move _______.

Words – faster, low, gradient, temperature, energy

12/27/14OsmosisOsmosisOsmosis is a “special kind of ___________”. It’s when water diffuses from a __________ area to a less concentrated area through a partially permeable _________ (i.e. one that allows water to move through but not anything else):

Water Sugar solutionIn this example the water molecules will move from left to right (along the concentration ______) and gradually _____ the sugar solution. Plants use osmosis to take in water through their roots.

Words – membrane, concentrated, dilute, diffusion, gradient

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Strong sugar

solution

Medium sugar

solution

Weak sugar

solution

Pota

to c

ells

12/27/14Active TransportActive TransportIn diffusion substances moved along a concentration gradient. In active transport, substances move against this gradient:

Outside cell Inside cellThis process takes ______ and this comes from ___________. It enables cells to take in substances even though there are in very small __________. Root hair cells take in ______ using active transport.

Cell membrane Words – concentration, energy, respiration, nutrients

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Carbon dioxide diffuses into the leaf through holes in the bottom surface.

Diffusion and Active Transport in plantsDiffusion and Active Transport in plants

More concentrated

Less concentrated

Mineral

…while plant nutrients are taken in by root hair cells using active transport.

12/27/14Encouraging PhotosynthesisEncouraging PhotosynthesisUsing knowledge of limiting factors, explain how plant growth is encouraged in a greenhouse:

12/27/14Limiting PhotosynthesisLimiting Photosynthesis

1. Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down

2. CO2 – if there is more carbon dioxide photosynthesis will happen quicker

3. Light – if there is more light photosynthesis happens faster

What factors could limit the rate of photosynthesis?

12/27/14Drawing graphs of these factorsDrawing graphs of these factors1. Temperature

Photosynthesis is controlled by enzymes – these are destroyed at temperatures above 400C

2. Carbon dioxide

3. LightPhotosynthesis increases at first but is then limited by a lack of increase in temp or CO2

Photosynthesis increases at first but is then limited by a lack of increase in temp or light

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Fieldwork techniquesFieldwork techniques

Recording light levels

Using quadrats

Fieldwork techniques also involve using a key to identify plants.

12/27/14B4.3 How do living organisms obtain B4.3 How do living organisms obtain energy?energy?

12/27/14Uses for energy from respirationUses for energy from respirationAnimals and plants have many uses for the energy they generate from respiration:

1) To perform the life processes, such as moving, _____ etc

2) To build up body _______

3) To maintain a constant body ___________ (warm-blooded mammals only)

4) To build up sugars, ________ and other nutrients in plants

5) Active __________

Words – nitrates, tissue, proteins, transport, growing

12/27/14SynthesisSynthesis

1) Glucose (sugar) can be used to make long chains of insoluble starch…

Glucose molecules

Starch molecule

“Synthesis” means “making large molecules out of small ones”. Two examples:

2) Glucose can be combined with nitrates to make proteins (for growth)…Glucose molecules Proteins

12/27/14Respiration IntroductionRespiration IntroductionI enjoy taking samples using quadrats. In order to do this, I need energy. Where

does this energy come from?

Our energy comes from a process called respiration, which basically involves turning food and oxygen into energy and this reaction is controlled by enzymes.

12/27/14(Aerobic) Respiration(Aerobic) Respiration

Words – breathing, energy, grow, respiration, food, mitochondria

All living organisms have to move, _____, reproduce etc. Each of these life processes needs ENERGY. ___________ is the process our bodies use to produce this energy:

Glucose + oxygen water + carbon dioxide + ENERGY

The glucose we need comes from ______ and the oxygen from _________. Water and carbon dioxide are breathed out. The MAIN product of this equation is _________. Respiration happens in _________ in cells.

12/27/14Muscles and exerciseMuscles and exerciseWhen we exercise our muscles are supplied with more oxygen and glucose, increasing the rate of respiration.

Muscles store glucose as glycogen which can then be converted back into glucose during exercise.

12/27/14Anaerobic respirationAnaerobic respirationUnlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________:

This happens when the body can’t provide oxygen quick enough for __________ respiration to take place.

Anaerobic respiration produces energy much _______ than aerobic respiration but only produces 1/20th as much.

Anaerobic respiration can also take place in other low-oxygen conditions, such as plant roots in _________ soil or bacteria in ________ wounds.

Words – oxygen, aerobic, quicker, puncture, waterlogged

Glucose lactic acid + a bit of energy

12/27/14Making EthanolMaking EthanolEthanol is an important chemical. Many countries are increasing the amount of ethanol put into their petrol supplies:

Ethanol is another product of anaerobic respiration in plant cells and some micro organisms:

Ford Escape E85 – runs on 85% ethanol

Sugar ethanol + carbon dioxide + energy

12/27/14BacteriaBacteriaConsider a bacteria cell in more detail:

Bacteria – containing cytoplasm and a membrane surrounded by a cell wall. The genes are NOT in a distinct nucleus.

The cell contains a number of features, including:

1) Chromosomal DNA, containing the genetic info of the cell

2) Plasmid DNA, containing extra information such as defence mechanisms

3) Flagella, which helps the cell move

12/27/14The Structure of BacteriaThe Structure of Bacteria

Bacteria also have plasmids (circular strands of DNA) that can be copied and move between different bacteria. This means that resistance to antibiotics can be passed on without the need for reproduction.

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4)

2)

Respiration in CellsRespiration in CellsNotice that plant and animal cells (and bacteria) have many features that help respiration:

Mitochondria – contain enzymes for respiration reactions

Cell Membrane – controls what comes in and out

Cytoplasm - where enzymes are made

Nucleus – carries genetic info for making enzymes

1)

3)

In bacteria cells, this job is done by circular DNA

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Using Anaerobic RespirationUsing Anaerobic RespirationAnaerobic respiration in micro organisms is used to make fuels through:

1) Manure or other waste that can be used to release methane (biogas)

2) Corn or sugar cane that can be broken down in a fermenter to produce alcohols like bio-ethanol.

Anaerobic respiration is also used in fermentation to make bread and alcohol.