Hyndland Secondary SchoolBiology Department

National 5 - Unit 1 Cell BiologySummary Notes1

Unit Structure.....................................................................................2Cell structure......................................................................................4

Animal Cells.....................................................................................................................................4Plant Cells.........................................................................................................................................5Fungi.................................................................................................................................................6Bacteria.............................................................................................................................................8Uses of Single Celled Organisms....................................................................................................10

Transport across cell membranes.......................................................12Cell Membrane................................................................................................................................12Diffusion.........................................................................................................................................13Osmosis...........................................................................................................................................14Active transport...............................................................................................................................18

Producing new cells...........................................................................19Cell division....................................................................................................................................19Chromosome structure....................................................................................................................19Mitosis.............................................................................................................................................20Cancer.............................................................................................................................................21Tissue Regeneration........................................................................................................................21

DNA, production of proteins and genetic engineering..........................22Protein Production...........................................................................................................................23Proteins............................................................................................................................................25Enzymes..........................................................................................................................................26Genetic Engineering........................................................................................................................33

Chemical energy in cells.....................................................................36Photosynthesis.................................................................................................................................36Carbon Fixation...............................................................................................................................42

1 This booklet is available for download from the Hyndland Secondary School website in the Biology/ National 5/ Downloads section of the subject support http://www.hyndland-sec.glasgow.sch.uk

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Unit Structure

Outline The general aim of this Unit is to develop skills of scientific inquiry, investigation and analytical thinking, along with knowledge and understanding of cell biology. You will apply these skills when considering the applications of cell biology on our lives, as well as the implications on society/the environment. The Unit covers the key areas of: cell structure; transport across cell membranes; producing new cells; DNA and the production of proteins; proteins and enzymes; genetic engineering; photosynthesis and respiration. You will research issues, apply scientific skills and communicate information related to your findings, which will develop skills of scientific literacy. As a result you will be able to: 1 Apply skills of scientific inquiry and draw on knowledge and understanding of the key areas of this Unit to carry out an experiment/practical investigation 2 Draw on knowledge and understanding of the key areas of this Unit and apply scientific skills.

HomeworkThe homework is spilt into two types, written and online. The written homework is designed to help you learn problem solving skills and deals with graph drawing, calculations, data handling and experimental design and conclusion. Online homework contains some problem solving questions, but is more focussed on consolidating your knowledge of the course. Both types of homework are designed to help your preparation for the exam that forms a part of the Unit and also the external national 5 exam.

TestsThe unit includes 3 interim tests and a National 5 assessment at the end of the Unit.

QR codesAt points throughout this booklet you will encounter funny looking squares (like the one opposite). These are called QR codes and are like the bar codes on tins of beans. A mobile phone with a camera can be used to scan them and they then take you to a web page. In your summary notes, they typically take you to a Youtube video to help you better understand a particular part of Biology, or remind you of an experiment you have carried out in class, or even a 10 mark multi-choice quiz to help test your learning (the questions are selected at random, so you can use them again and again. If you start a quiz, you need to finish it and review your score, otherwise it can be difficult to start a new quiz).

To make use of them you need a little app, a phone, tablet or the like with a camera and access to the internet. The system has been tested using an Android phone with the app Quick Barcode scanner – which is free to download; Blackberry offers the free, QR Code Scanner Pro-Free, which hasn’t been tested; the Appstore also offers free QR code scanners, QR reader or Bakodo – again not tested.

Please ask your parents’ permission to use this feature and as always ensure your security when downloading any app from the internet. In particular ensure you have disabled in app purchases before downloading any of the apps.

The links have been carefully selected by your teachers, however if you find any link that you think explains it better, please let us know and we will modify future editions for next

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Hyndland Secondary School National 5 Unit 1 - Cell Biologysession. Even better if you create your own version, give us the link and we can add it in. Enjoy your learning.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Cell structure cell ultrastructure and functions to include cell walls, mitochondria, chloroplasts, cell membrane, vacuole, nucleus,

ribosomes and plasmids in typical plant, animal, fungi and bacteria cells

Word Bank

aerobic respiration, cell sap, cellulose, controls, chemical reactions, function, information, photosynthesis, ribosomes, support, unicellular

Every living thing is made of at least one cell. The cell is the basic unit of life. Multicelluar organisms are made up of many cells that work together. ____________ organisms, such as Amoeba, are made of only one cell.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Animal Cells

All animal cells have:

A nucleus that contains ____________ and _________ the activities of the cell. The information is contained in chromosomes which are made of DNA. The DNA carries the genetic code for all the proteins a cell requires.

Cytoplasm, where most of the _______ __________ take place. The reactions are controlled by enzymes

A cell membrane that controls what enters and leaves the cell.

Mitochondria in the cytoplasm where ___________ _______________ takes place to release energy.

The ________________ are where proteins are made. Growing cells and cells producing digestive enzymes would have many of these in the cytoplasm.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Plant Cells

In addition to a nucleus, cytoplasm, cell membrane, ribosomes and mitochondria, plant cells also always have:

A cell wall made of ______________, which strengthens the cell and provides ___________.

They often have:

Chloroplasts* which contain the green pigment chlorophyll. This absorbs light energy for _____________.A permanent vacuole filled with _____ _____ (a dilute solution of minerals, sugars and amino acids), which also provides support.

* Chloroplasts are only found in green parts of plants e.g. root cells don’t have chloroplasts, being underground, they can’t capture light and so can’t photosynthesise. They therefore don’t need chloroplasts.

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Cell Wall

Ribosome

Cell Membrane

Mitochondria

Nucleus

Cytoplasm

Hyndland Secondary School National 5 Unit 1 - Cell Biology

FungiWord Bank

anaerobic, carbohydrate, carbon dioxide, cell wall, contamination, cytoplasm, decomposition, energy, fermentation, malting, maltose, optimum, photosynthesise,

plant, respiration, starch, sterilising

The cells of fungi are similar to _________ cells. They have a nucleus, ______________, ribosomes and mitochondria. Whilst fungi do have a________ ________, it is made of chitin, a different type of ___________from cellulose. They are however not green – they don’t ________________and so don’t contain chloroplasts. Fungi need to get nutrients and

energy from other organisms. Fungi are involved in __________________- recycling nutrients from dead organisms back into the ecosystem. Humans have made great use of fungi, e.g. yeast are fungi and are used to make wine,

beer and bread.

Industrial Uses of Fungi

Yeast can use sugar as food to produce energy. It is used in BREWING and BAKING. In baking __________ ____________ produced by the yeast causes bread to rise. This is produced as a result of yeast respiring anaerobically. In brewing (the manufacture of beer) and wine making the alcohol (ethanol) is produced by yeast performing _____________ RESPIRATION:

GLUCOSE → ETHANOL + CARBON DIOXIDE + ENERGY*.

* As brewing occurs, the _________ released by yeast is detected as an increase in temperature – the brew heats up! The carbon dioxide is released as a gas. Anaerobic respiration by micro-organisms, such as yeast is called _______________.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

In commercial breweries, the yeast are given the best possible conditions for growth by maintaining the following at _____________ levels:

TemperatureOxygen supplypHglucose supply

They also ensure the brew is kept free from unwanted microbes, which would spoil the brew, by _____________ all the equipment using high temperatures and/or chemicals. ______________ would be expensive as the brew would need to be thrown away.

Beer is made from barley which is a seed. However, seeds, including barley only contain _________, which yeast cannot use as a food source. Consequently, the brewer has first to germinate the barley. This is called ___________ and as the seeds germinate, they produce an enzyme (amylase) which breaks the starch down into___________. The yeast then use anaerobic ___________ to change the maltose into alcohol.

Starch maltose alcohol

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malting of barley anaerobic respiration

(amylase enzyme in barley) enzymes

Hyndland Secondary School National 5 Unit 1 - Cell Biology

BacteriaWord Bank

chemical reactions, cytoplasm, DNA, mitochondria, plasmid, proteins

Bacteria have a much simpler structure than either plant or animal cells. They do not have ______________ , but do have _____________. The bacterial cell carries out all its____________ _____________, including aerobic respiration (which occurs in the mitochondria of the other cells types above) in the cytoplasm. In the cytoplasm, bacteria also have ribosomes, upon which bacterial ____________ are made.Bacteria are the simplest of all cells. They don’t have a nucleus, but keep their genetic information in a structure called a nucleoid, which is a large ring of________. In addition, they also have extra genetic information in a small ring of DNA called a ___________. These plasmids can be swapped between bacteria and usually help the bacteria survive e.g. by giving antibiotic resistance. Scientists have learnt to use plasmids to insert new genes, even human genes into bacteria (see .

Test your knowledge of Cell Structure & Function

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Handling Micro-organismsIndustrial processes which handle or produce food must prevent contamination with micro-organisms. Some micro-organisms produce spores which can survive very dry conditions and can even withstand boiling water.To avoid contamination, foods should be kept covered and containers and surfaces which food contacts should be regularly cleaned and sterilised.

Culturing Micro-organisms

Micro-organisms are grown or cultured in petri dishes designed to prevent escape or contamination from outside. A suitable culture medium is needed for them to grow. This is agar, a jelly to which certain nutrients have been added to suit the requirements of the organisms to be grown.

In addition, the micro-organisms need to be protected from contamination. Aseptic technique is used when handling micro-organisms in a lab to prevent contamination by unwnated micro-organisms.

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semi-solid sewage

methane

Hyndland Secondary School National 5 Unit 1 - Cell BiologyUses of Single Celled Organisms

Sewage Treatment

Sewage presents us with two main dangers:

1. Sewage is a source of energy and nutrients for bacteria. They use oxygen to break it down and may lower the oxygen concentration so much that other organisms die.

2. Sewage contains many species of micro-organism. Some of these cause diseases including typhoid, dysentery and cholera.

TreatmentThe aim of sewage treatment is to break it down into products which are harmless to the environment. As there is a large range of chemicals in sewage, a large variety of micro-organisms is required to break them down.

The first stage in treatment is to separate the liquid waste from solid waste. This is done in large settling tanks.

Solid sewage is poured into digesters where anaerobic action by micro-organisms produces methane gas which can be used as fuel. The solids which remain are dried and used as fertiliser

Liquid sewage is treated by mixing it with air. This maintains aerobic conditions in which a variety of micro-organisms break it down. Without aerobic conditions, complete breakdown is not possible.

There are two main ways of adding air.

1. The liquid is sprinkled over a pile of stones which contains many air spaces. As it trickles down, micro-organisms on the stones break down the sewage.

2. Liquid is poured into large tanks where propellers turn to mix it with the air.

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stones

sprinkler

treated sewage

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Upgrading Waste

Recently, techniques have been developed in which micro-organisms are used to make useful products from waste.

1. Anaerobic breakdown of solid sewage produces:

a) methane which is a useful fuel.b) fertiliser.

2. Molasses left over from sugar refining are fed to yeast which produce alcohol and organic acids such as vinegar.

In the yeast factory in Menstrie (near Stirling), molasses are used to grow yeast which is then sold around the world for baking, brewing and flavouring.

3. Whey left over from cheese making can be converted by yeast to protein which can then be used for animal feed.

Vitamins can also be extracted from the yeast.

4. Methanol produced in the gas and oil industry can be converted by bacteria to protein which is suitable for animal feed.

5. Spoil heaps from metal mines often contain insoluble metal salts. Bacteria can be used to convert them to soluble salts which can be extracted in water and the metal recovered.

Advantages of Upgrading Waste

1. The waste has greater value and so can lower the cost of disposing of it.

2. The waste can be used instead of dumping it.

3. The waste can produce materials more cheaply than from other sources, and it reduces the need to access natural resources.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Transport across cell membranes cell membrane structure concentrations gradients, passive transport, including diffusion and osmosis

the energy requirement for active transport

Cell Membrane

Word Bank

channels, entry, phospholipids, proteins, selectively

All cells are surrounded by a cell membrane. It is the cell membrane which controls the _______ and exit of materials into or out of the cell. The cell membrane has tiny holes in it that only small molecules can pass through; because of this, the cell membrane is described as ______________ permeable. A cell membrane is made of proteins and ________________. The phospholipids form a double layer (bilipid layer) and the _____________ are found stretching through, or on the surface of this bilipid layer. Some of the proteins can form ____________ which can allow the movement of molecules into or out of the cell.

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Phospholipidbilayer

Channel protein

protein

Hyndland Secondary School National 5 Unit 1 - Cell Biology

DiffusionWord Bank

concentration gradient, energy, equal, high, passive

Diffusion is the movement of a substance from a ________ concentration to a LOWER concentration.Diffusion continues until the concentrations are__________.

A _____________ ____________ is a difference in the concentration of a substance between two areas. Diffusion is said to occur down a concentration gradient. For diffusion to occur, a cell does not need to add any extra __________, for this reason diffusion is described as ___________ transport.

Importance of DiffusionSubstance needed by the cell pass INTO the cell by diffusion e.g. oxygen & dissolved food (glucose).Waste substances pass OUT of the cell e.g. carbon dioxide (from respiration) or urea (from the breakdown of amino acids)In the body, diffusion occurs in the lungs (to absorb oxygen into the blood and remove carbon dioxide from the blood – the opposite occurs in the body’s tissues where respiration uses up the oxygen and produces carbon dioxide) and small intestine, to allow the absorption of digested food molecules.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

OsmosisOsmosis is a special case of diffusion and the term only applies when describing, the diffusion of water across selectively permeable membranes.Osmosis = the movement of water from a higher water concentration (HWC) to a lower water concentration (LWC) across a selectively permeable membrane*.*The cell membrane is a selectively permeable membrane (only small molecules can pass through them)

In the diagram opposite:Water moves by osmosis from a HWC outside the bag to a LWC inside the bag.Glucose is at a high concentration inside the bag, so diffuses out. Starch is too large to move through the pores in the membrane so stays in the bag.

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Visking tubing(a man made material containing tiny pores).

Starch and glucose solution

water

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Osmosis in Plant Cells

cytoplasm

LIQUID OUTSIDE CELL WATER GAIN or LOSS CHANGE to CELLWater Cell gains water Cell swellsSolution equal to cell solution

No net gain or loss of water

Cell does not change

Solution stronger than cell sap

Cell loses water Cell shrinks

When plant cells take in water by osmosis they swell and become TURGID.When plant cells lose water by osmosis they become FLACCID.PLASMOLYSIS occurs when a cell becomes very flaccid. So much water has been lost that the cell membrane shrinks away from the cell wall. This usually starts at the corners.The membrane surrounding the vacuole is also selectively permeable and so the vacuole shrinks and expands with osmosis.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Osmosis in Animal CellsAnimal cells contain weak solutions of salt and sugar and only have a cell membrane. Consequently they BURST if too much pressure is placed on it. (Animal cells cannot become turgid, because they don’t have a cell wall.) Similarly, the term plasmolysed does not apply to animal cells because they don’t have a cell wall. Animal cells simply shrink if they lose water.Animal cells can gain or lose water by osmosis:Changes in red blood cells due to osmosis

Solution outside cell Water gain or loss Change to cellWater Cell gains water Cell swells & burstsSolution weaker than cell solution

Cell gains water Cell swells & burstsSolution equal to cell solution

No loss/ gain Cell does not changeSolution stronger than cell sap

Cells loses water Cell shrinks

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Industrial Applications of Osmosis

Using Osmosis for Power GenerationIf a tank of seawater and fresh water are separated by a selectively permeable membrane osmosis will cause water to move from the freshwater (higher water concentration) to the seawater (lower water concentration. This increases the height of the water in the seawater tank, storing potential energy. The water can then be allowed to flow down through a turbine and generate electricity as it does. Examples of working prototypes can be founds in continental Europe.

Reverse Osmosis in desalination plants.This process is called reverse osmosis because the water moves up its concentration gradient. This requires energy, and the water has to be pressurised to allow this to happen. A selectively permeable membrane only allows smaller molecules, such as water to pass through. If pressure is applied to seawater, the pressure will force the water across the selectively permeable membrane, but the salt, which cannot pass through the membrane will be left behind. In this way freshwater can be produced using reverse osmosis.

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Hyndland Secondary School National 5 Unit 1 - Cell Biology

Active transportActive transport is the movement of molecules and ions against their concentration

gradient• It requires energy supplied by respiration• It is controlled by carrier proteins (pumps) in the membrane• Ions may be actively pumped into the cell from the environment or out of the cell,

to the environment e.g. sodium ions are pumped out of cells and potassium ions are pumped into cells. Around 1/3rd of the cell’s energy is used doing just this!

• Ion uptake is selective i.e. each ion is concentrated to a specific level• Because active transport needs energy it is affected by the availability of glucose

(source of energy) and oxygen (required for aerobic respiration.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Producing new cells maintenance of chromosome complement (diploid) by mitosis sequence of events of mitosis, including equator

and spindle fibres cell production by cell culture using aseptic techniques

New cells are formed when existing cells divide (split in two) producing two new (daughter) cells. In some complex organisms (e.g. plants), cell division may occur only in special places (e.g. root/ shoot tip) called meristems. After a cell divides, the two new cells increase in size and once large enough may themselves divide to produce a further two new cells.

Cell division

When a cell divides the resulting two new cells are identical to the parent cell – cell division is a form of asexual reproduction. In order that the cells are identical, it follows that each new cell must receive exactly the same information as each other. The structure of the genetic material, which is DNA in the form of chromosomes, held in the nucleus ensures this occurs.

Chromosome structure

Chromosomes are thread like structures found in the nucleus of all plant and animal cells. Every cell in the body (except gametes) contains the same number of chromosomes.

A chromosome consists of lots of genes joined together. Each gene is responsible for producing a particular characteristic (e.g. hair colour, eye colour, height etc.).

Before cell division occurs, each chromosome is duplicated (replicated) and the chromosome then appears as an X-shape, consisting of two chromatids, joined at the centromere (see diagram). The chromatids are identical, carrying a full set of instructions for making a new cell. Consequently, each new cell needs only to receive one

chromatid from each X-shaped chromosome in order to receive a full set of instructions. The process by which this occurs is called mitosis.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Mitosis

sequence of events of mitosis, including equator and spindle fibres.

The process of mitosis is shown in the diagram below.

Terms to know:Equator: - this is the centre of the cell where the chromosomes assemble before being spilt apart.Spindle fibres: - these are protein “ropes” which attach to the centromere on the chromosomes. Spindle fibres originate in the centrioles of the cell which move to opposite ends of the cell as mitosis starts. The spindle fibres shorten and pull the chromatids apart to opposite ends of the cell. The cell subsequently splits down the equator, therefore each new cell receives a chromatid from each of the original chromosomes, i.e. a complete copy of the genetic information present in the original, parent cell.If any genes become changed or lost during cell division, the information required to produce a correctly functioning new cell will not be available. Consequently, cell processes will be changed or stop working altogether. New cells must contain exact

Hyndland Secondary School National 5 Unit 1 - Cell Biology

copies of the genetic information. The daughter nuclei need to contain the same number and kind of chromosomes as the parent nucleus.

CancerIf control of cell division is lost, then tumours can develop, which can lead to cancer. Cancer develops when some damage occurs to the DNA of a single cell in the body. Sometimes the damage is inherited from a parent, but more usually the damage occurs during the lifetime of the patient. The damage can often be caused by exposure to chemicals called carcinogens (e.g. in cigarette smoke, mustard gas, asbestos) or radiation (e.g UV radiation, X-rays or gamma rays). If untreated the cell repeatedly divides forming a lump of cells, known as a tumour. Not all tumours become cancerous, but if they do they can be fatal because they grow big enough to damage surrounding parts of the body.Nowadays, depending on the type of cancer and how early it is detected, many people are able to be successfully treated for cancer. In the past, treatments have involved using poisons which stop cell division (often breaking the spindle fibres). As a result, sometimes a patient’s hair can fall out. In the future, cancer treatments will be less toxic and increase survival rates even further.

Tissue RegenerationMitosis is important in the growth of an organism, producing the new cells to allow the growth to happen. In addition, when tissue damage occurs, mitosis allows the production of new cells to repair that damage. In humans, the ability to repair damage is limited, a cut in the skin can be repaired although often the repair is not perfect, a full liver can be regenerated from a smaller piece (this technique can be used to repair liver damage). However, lose a limb and no re-growth is possible, despite the fact that all cells in the body (except gametes and red blood cells) contain all the instructions needed to build a whole body (as demonstrated by Dolly the sheep). Other animals are capable of much more extensive repair, amphibians like newts are able to re-grow whole limbs, and lizards can re-grow tails. As scientists have begun to better understand stem cells, in the future it is likely that humans will be able to be treated to allow them to re-grow new body parts that have become damaged.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

DNA, production of proteins and genetic engineering structure of DNA — double-stranded helix held by complementary base pairs

function of DNA — base sequence determines amino acid sequence in protein

messenger RNA in protein production; protein structure — amino acid sequence determines protein shape and

function; proteins to include structural, enzymes, hormones, antibodies, and their functions; the effects of

temperature and pH on proteins transfer of genetic information and genetic engineering

The chromosomes contained in every nucleus of every cell in the body (with a few exceptions) is made from a complex substance called DNA (deoxyribonucleic acid). DNA is an extremely long and thin molecule and is made of two strands which coil around each other forming a double helix shape.

A double strand of DNA

Hydrogen bonds between bases

DNA double helix

Each DNA molecule is made of only 4 different types of bases (A, G, C, T). The two strands of DNA are held together because the bases pair up with each other; A pairs with T only and G pairs with C only. The two strands are held together by weak forces (hydrogen bonds) which means they can be easily separated. This ability to separate the strands easily is very important when the cell wants to copy its DNA before mitosis starts.

DNA is the most important molecule in all living things. This is because it contains the code for all the proteins needed to ‘run’ the cell’s reactions and all the proteins needed to make the cell structure itself. Proteins are made by joining amino acids together into long chains, which then fold up to make things like enzymes, hair, nails and every other protein in your body. There are around twenty different types of amino acids which the cell can use to make the protein.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

nitrogen

amino

proteins.

acid

20

If a cell places the wrong amino acid in the wrong place in the chain, the protein will not work properly and the cell will likely die. The DNA tells the cell in which order to place the amino acids to build the protein molecules correctly. It is the order in which the bases, in the DNA, are arranged in each strand that tells the cell the correct order to place the amino acids. Any change in the order of the bases on the DNA molecule (called a mutation) will lead to a change in the protein, and the protein will not work correctly.

Protein Production

Protein synthesis takes place on the ribosomes found in the cytoplasm of a cell. However, the instruction code for the protein is contained in the nucleus, on the DNA. Clearly the cell needs to get that information from the nucleus into the cytoplasm. To do this it creates a special copy (or transcript) of the code using RNA (ribonucleic acid). RNA is a very similar molecule to DNA, but contains only one strand. There are different types of RNA, but the one used to carry the code (or message) from the nucleus is called messenger RNA (or mRNA). mRNA is made by enzymes in the nucleus and moves to the cytoplasm where the information it contains is “translated” by the cell, using ribosomes, into the protein sequence. The ribosomes join together amino acids in the order that the mRNA instructs them to. This process requires energy.Once made the protein is transported to the part of the cell in which it is needed.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

http://learn.genetics.utah.edu/content/begin/dna/

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Proteins.protein structure — amino acid sequence determines protein shape and function

proteins to include structural, enzymes, hormones, antibodies, and their functions

Proteins are large organic molecules made up of the elements C, H, O, NThe sub-units of proteins are known as amino acids which are linked together into long chains by peptide bondsThere are twenty different amino acids give rise to a huge variety of proteins all different in :-

The number of amino acids in the chain The order of amino acids in the chain The variety of amino acids in the chain

Two main types of proteins are found:- Fibrous Proteins - Long parallel chains often wound around each form very strong structures. e.g.:- Collagen in bone and tendons Elastin in ligaments Keratin in hair

Globular Proteins - Long chains are folded into spherical structures similar to a tangled ball of string. These proteins have a variety of functions. e.g. :- Structural proteins of the cell membrane Enzymes which speed up reactions e.g. amylase Hormones – these are chemical messengers in the body e.g. insulin Antibodies – defend the body against bacteria and viruses. Transport –e.g. haemoglobin in the blood. Proteins in the membrane involved in

active transport of materials across the cell membrane.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Enzymesthe effects of temperature and pH on proteins

CatalystsWord Bank

catalase, catalyst, changed, enzymes, manganese dioxide, oxygen, temperature, used, water,

There are two ways in which chemical reactions can be speeded up. You can either raise the ________________ or add a ______________. A catalyst speeds up the rate of a chemical reaction without itself being _________ up in it, therefore the catalyst can be used again.

Hydrogen peroxide breaks down very slowly without a catalyst to speed up the reaction. A chemical, such as ________________ _______________ can be used to speed up this reaction.The equation below shows the products of the breakdown of hydrogen peroxide:

_____________ are biological catalysts and are found in all living cells. The enzyme that speeds up the breakdown of hydrogen peroxide into water and oxygen is ______________.

Enzymes are needed in cells to: Synthesise useful products Release energy during cell respiration Change poisonous wastes into safer materials Change substances into a form that can be stored or used Perform the chemical reactions of photosynthesis and respiration on which all life

depends.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Examples of Enzymes:Name of Enzyme Where found What it Does Test for ActivityDegradation reaction (Breaking down reactions)CATALASE In plant and animal

tissuesBreaks down hydrogen peroxide into OXYGEN and WATER

Glowing splint relights in the gas given off

AMYLASE In digestive juices (saliva, pancreatic juice)

STARCH is broken down into MALTOSE

Benedict’s reagent turns orange

Synthesis reactions (Building up Reactions)PHOSPHORYLASE In potato tubers Builds special

reactive glucose (GLUCOSE – 1 – PHOSPHATE) into STARCH

Iodine turns blue black as starch is built up

The Nature of Enzymes

Word Bankactive site, Biuret’s, complementary, lock, one, protein, specific, substrate, violet,

unique

Enzymes are made of ____________. This is shown by using _________________ reagent, which turns from blue to _____________ when gently heated in the presence of a protein.

The substrate is the substance on which an enzyme works.Enzymes only work on a particular substance. This is because enzymes have a ____________ shape which is matched with the _____________ it works on. The shape of the substrate is said to be _______________ to the substrate.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

The ________ ______ of an enzyme is where the substrate binds. When the substrate binds to the active site, a chemical reaction occurs. From the diagram it is clear that the relationship between the shape of the active site and the substrate is the reason enzymes can act on only one enzyme. The two are said to match like a _____ and key because only one specific key (substrate) will fit into a specific lock (enzyme). This means that a _________________ enzyme is needed for every reaction in the body’s cells.Breakdown ReactionsWord bank

amylase, Benedict’s solution, degradation, control, enzyme, iodine solution, maltose, product, saliva, smaller, substrate,

Breakdown or _______________ reactions convert large molecules into ______________ molecules. ______________ is an example of an enzyme which will do this, breaking large starch molecules into smaller ______________ molecules. Amylase is found in __________,

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Synthesis ReactionsWord bank

Calcium phosphate, chemical, diffuse, glucose-1-phosphate, glycogen, larger, light, phosphate, phosphorylase, photosynthesis, structural, synthesis, respiration, water

Plants with green leaves, such as potatoes, can convert _____________ energy into ____________ energy in the process of _____________________. The plant’s leaf cells will use some of the glucose produced as a source of energy and the rest will transported to the growing potatoes, where it is stored.

In plants, energy is stored as starch for later use because the molecules are _____________ than glucose molecules and so will not _______________ out of the cells. Just like plants, humans can also use synthesis reactions to build up storage molecules such as _________________ which can be broken down when energy is required by the body. Effect of Temperature on Enzymes

At low temperatures enzymes work slowly –(Their reaction rate is at a MINIMUM)As the temperature increases, they work faster, up to a MAXIMUM RATE. The temperature at which an enzyme works at its maximum rate (not at which it works best!) is called the OPTIMUM TEMPERATURE.Any further increase in temperature causes the enzyme protein to be damaged. The enzyme’s shape changes above the optimum temperature, it is said to be denatured and the activity rapidly decreases to zero because the enzyme no longer works. It can no longer work because the shape of the active site has changed and the substrate can no longer fit in.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Denaturation of enzymes

.

The effect of pH on enzymes

The pH of a solution measures how acid or alkali it is. Use the words acid, alkalis or neutral to label the pH scale below.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

An enzyme will work only in a narrow range of pH. The OPTIMUM pH is the pH at which the enzyme has most activity. The optimum pH is different for different enzymes. Pepsin is found in the stomach (acidic) and so has an optimum pH which is acidic. Trypsin works in the small intestine which is slightly alkali, and so it has an optimum pH of around 9.

If the pH becomes more acidic or more alkali than the optimum pH, the enzyme becomes denatured.

Rennet

Rennet is an enzyme which is used in the manufacture of cheese. There are several steps in the manufacture of cheese: special bacteria are added to convert the milk sugar into lactic acid enzymes are added to clot the proteins in milk.

Rennet is a enzyme that clots milk, and originally, it came from animals such as calves. Nowadays the enzymes used in cheese making can come from a variety of different sources including bacteria or a genetically engineered fungus.

Washing Powders

Washing powders contain detergents (chemicals), which dissolve dirt and stains. The ability of a washing powder to clean clothes improves as the temperature of the water increases. Boil washes (90°C) gives the best clean.Biological washing powders also contain detergents, but in addition have enzymes added. The enzymes are typically proteases and lipases which digest the proteins and fats which make clothes dirty. These enzymes have been produced by bacteria and are selected so that they work well at low temperatures (40˚C). Biological washing powders wash better than non-biological washing powders at these low temperatures. At higher temperatures, the enzymes are denatured.

The advantages of biological washing powders are:

Conserve heat energy, saving money

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Allow cleaning of delicate fibres (e.g. silk), that would be damaged by high temperatures.

plasmidgenechromosome

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Genetic Engineering

Genetic Engineering

Like other cells, bacteria are controlled by genes. Each bacterium has one chromosome which is circular. It also has one or more smaller plasmids which consist of genes.

In genetic engineering, new genes are transferred from one organism (such as a human), into another organism, (such as a bacteria). In this way the bacteria can engineered to produce human proteins e.g. the production of human insulin by bacteria. Insulin is used to treat diabetes.The bacteria produced in this way are “factories” producing useful products. The process of genetic engineering involves locating and removing the human gene, then joining it into the plasmid. Each step in the process below requires enzymes.

The plasmid is inserted into a fresh bacterium which is then cultured.

an enzyme is used to remove

the desired genefrom the chromosome

an enzyme is used

to open a plasmidof a bacterium

The desired geneis inserted into the

plasmidusing another enzyme

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Products of Genetic Engineering

1. Insulin is a hormone normally produced by humans. It is needed to maintain the correct sugar concentration in the blood. People who cannot make insulin suffer from diabetes and need regular injections of insulin.

Until recently, the insulin came from pigs. As pig insulin is not identical to human insulin, allergic responses sometimes occurred.

As a result of genetic engineering, diabetics now use human insulin made by bacteria.

2. Human growth hormone is given to babies who cannot produce enough of their own.

3. Enzymes. Biological soap powders depend on enzymes produced by bacteria.

4. Pyrethrum. This is a biodegradable insecticide extracted from the pyrethrum daisy. Recently, the Kenyans found that it grew well in their country and farms were set up

to produce it. However, scientists in the US transferred the gene to yeast so that the insecticide can now be produced anywhere. The Kenyans saw this as genetic piracy.

5. Antibiotics such as penicillin are often produced by bacteria.

6. Vaccines such as that used against the rabies virus are produced by bacteria.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Chemical energy in cells

chemistry of photosynthesis, as a series of enzyme-controlled reactions, in a two-stage process —

light reaction and carbon fixation

the end product of photosynthesis (sugar) and its use in cells

the impact of limiting factors on the rate of photosynthesis

chemistry of respiration as a series of enzyme-controlled reactions

ATP production and its use

in the absence of oxygen, energy is produced by alternative pathways, which produce different end-

products

Photosynthesis

Word bankCarbohydrates, carbon, environment, increase, photosynthesis, producers, starch, stored

Plants are said to be ___________________ because they do not consume other living things to obtain energy. Plants make their own food using simple chemicals from the _____________.Foods made by plants contain the elements ____________, hydrogen and oxygen. Consequently, they are known as ____________________. The process in which plants make food from raw materials and energy from the sun’s light is called ____________________ .

Without plants and the process of photosynthesis, the planet’s animals would have virtually no source of energy to sustain life.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

The need for lightWhen plants are not using glucose, it is converted into __________ and stored in their cells. Testing leaves for starch indicates whether glucose was first made by photosynthesis or not. If green plants leaves are kept in constant darkness they will not produce glucose because photosynthesis requires light energy.

Starch Production during 24hours.The dry mass of something is the mass of all the material in a plant apart from the water. If there is an _________________ in the dry mass of a green plant, this shows that glucose is being made and ______________ as starch by photosynthesis.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Evidence for the importance of chlorophyll

Word bankby-product, carbon dioxide, composition, glucose, light, oxygen, water

Need for Carbon dioxidePlants are able to make their own food using light energy from the sun and raw materials from the environment, including ____________ ___________ and _____________. Carbon dioxide is a gas that is absorbed from the air, and water is absorbed from the soil.

If a green plant does not have both raw materials (carbon dioxide and water) as well as sunlight, photosynthesis would not occur.To carry out photosynthesis, plants combine the raw materials, carbon dioxide and water to produce the useful material, glucose and the waste product oxygen, which the plant releases into the atmosphere.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

As with all chemical reactions in living cells, photosynthesis occurs in a series of enzyme controlled steps. These can be separated into two major sets of reactions: The light reaction and carbon fixation.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

The Light ReactionAs the name suggests, the light reaction is the part of photosynthesis involving the capture of light energy and its conversion into chemical energy.

Capture of Light Energy by ChlorophyllSome of the _________ energy captured by chlorophyll is transformed into chemical energy. The ___________ energy is then used to produce glucose from the raw materials carbon dioxide and water.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Light energy from the sun is captured by _______________ and converted into chemical energy. Water is split by some of the ___________ energy into oxygen and hydrogen.Hydrogen captured here by a hydrogen acceptor is passed to the carbon fixation stage of photosynthesis Oxygen is released as a by-product: the majority of it is released from plant leaves into the atmosphere.Some light energy captured by chlorophyll is used to make ________, built up from ADP and Pi. The process by which ATP is generated using the sun’s light energy is known as photophosphorylation.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Carbon Fixation

Carbon fixation is the set of enzyme controlled reactions in which the energy captured by the light reaction is used to stick carbon dioxide molecules together, to form glucose. The hydrogen, produced by the splitting of water in the light reaction is also used at this stage.Energy is used up in this reaction. The energy is provided by the ATP, produced in the light reaction above.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Structure, Properties & Functions200, glucose, linear, functions, coiled, grain, insoluble, building, energy, parallel, sheets. permeable

Starch and cellulose molecules are both large molecules made up of smaller ____________ molecules. The ways in which the glucose molecules link up to each other results in the different types of molecule being formed. The structural arrangements of starch and cellulose are different, consequently they have different ___________________ .

Starch MoleculesA single starch molecule is made up of many glucose molecules. Glucose units are joined together to form a ________________ shape so that the molecule becomes entangled up with itself. With the addition of more starch molecules a dense starch ________________ is formed. Starch molecules are ________________ in water. They act as a concentrated source of energy as they contain up to 800

glucose molecules.Cellulose Molecules

A single cellulose molecule is made up of 1000 -1500 glucose molecules. The cellulose molecules line up in _____________ chains to form tough fibres. Cellulose is also insoluble in water and not easily broken down. The fibres

are arranged in _________________ at right angles to each other. This arrangement adds strength to the structure, while the gaps make cellulose freely _____________________ to small molecules like carbon dioxide, water and sugars.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Limiting factors in PhotosynthesisLight intensity as a Limiting FactorDarkness, limiting factor, slowly, increase, enzymes, denatured

A _______________ _____________ in photosynthesis is something, which, when in short supply, stops the reaction of photosynthesis working at its maximum possible rate. Light intensity can limt the rate of photosynthesis. In dim light, the rate of photosynthesis is slow, but increases if the light intensity is increased – all other factors being kept the same. In _____________ no photosynthesis will occur at all. The light intensity is therefore a limiting factor.An Elodea bubbler is used to investigate the effect of light intensity on photosynthesis. The rate of photosynthesis is measured by counting the number of bubbles released for the cut stem of the Elodea (pondweed).

The graph above shows the effect of light intensity on the rate of photosynthesis in pondweed. The rate of photosynthesis increases as the light intensity increases up to a light intensity of 10 units. Above 10 units, the rate is not increased, this must be because another factor, temperature or carbon dioxide concentration is limiting the rate of photosynthesis.

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

Hyndland Secondary School National 5 Unit 1 - Cell Biology

A _____________ is a copy of an experiment in which all factors are kept exactly the same except for the one being investigated in the original experiment. The control experiment shows that the factor we think is causing any change does. If in the control experiment we get a different result and as the only difference between the two experiments is a single factor, that factor must be responsible for the difference we see in the results.