Topic 2: Genes and Health Flashcards

Question

Proteins

Answer 1

Proteins are made up of one or more polypeptides

Answer 2

-Amino acids contain the elements carbon, hydrogen, nitrogen and oxygen. - They consist of: - Central carbon atom (a alpha carbon) - NH2 (an amine group) - COOH (carboxyl group) - H (a hydrogen atom) - 'R' (variable/side group).

Answer 3

Amino acid monomers are linked together by condensation reactions to form polypeptides. A molecules of water is released during the reaction. The bonds formed between amino acids are called peptide bonds and they form between the carboxyl group on one amino acid and the amine group on another.

Answer 4

1) Primary structure 2) Secondary structure 3) tertiary (three-dimensional) structure 4) Quaternary structure

Answer 5

- This is the specific order of amino acids in a polypeptide chain. - The primary structure is important because the R group variation in amino acids produce differnt bonds which determine the final 3 dimensional shape of the protein molecule and the shape of a protein is critical for its function.

Answer 6

- Hydrogen bonds form between the amino acids in the polypeptide chain and these hydrogen bonds cause the chain to coil in a alpha helix or fold into a beta pleated sheet. - The secondary structure is made more stable by hydrogen bonds, as even though they're weak, there are many of them.

Answer 7

- They give gas exchange organs (like the lungs) a large surface area to volume ratio. - They're thin (often just one layer of epithelial cells) - this provides a short diffusion pathway across the gas exchange surface. - The organism also maintains a steep concentration gradient of gases across the exchange surface. All of these features increase the rate of diffusion.

Answer 8

Rate of diffusion is proportional to (area of diffusion surface x difference in concentration) / thickness of diffusion surface

Answer 9

Rate = P x A x ((C1-C2)/T) P=permeability constant A=Surface Area (C1-C2) = difference in concentration T = thickness of the exchange surface Rate of diffusion: 0.012 x 2.2 x ((2.3x10^-16 - 9.0x 10^-17)/1.0) = 3.7 x 10^-18 mol um^-2s^-1

Answer 10

The mammalian lungs have the following features, which all help to increase the rate of gas exchange: - Lots of alveoli means there is a large surface area for diffusion to occur across. - The alveolar epithelium and capillary endothelium (a type of epithelium that form the capillary wall) are each only one cell thick, giving a short diffusion pathway. - All the alveoli have a good blood supply from capillaries - they constantly take away oxygen and bring more carbon dioxide, maintaining the concentration gradient. - Breathing in and out refreshes the air in the alveoli, keeping the concentration gradient high.

Answer 11

- Cell membranes have a a 'fluid mosaic' structure. - Phospholipids molecules form a bilayer. The bilayer is 'fluid' because the phospholipids are constantly moving. - The membrane is partially permeable - fat soluble/non-polar molecules can move through the gaps between the phospholipids, but large molecules, like ions, can only pass through via channel proteins. - Phospholipid molecules arrange themselves into a bilayer with the hydrophilic heads facing out towards the water on either side of the membrane (because hydrophilic attracts water). The hydrophobic tails are on the inside (because they repel water), making the centre of the bilayer hydrophobic. This means that the membranes don't allow water-soluble substances (like ions) through it. The phospholipid bilayer contains other components: - PROTEINS are scattered through the bilayer and can move around within it. They are involved in cell transport and communication and can be intrinsic (embedded) or extrinsic (on the surface). - CHOLESTEROL - fits in between the phospholipids and regulates membrane fluidity. They increase the fluidity at low temps by stopping the phospholipids from packing too closely together and decrease fluidity at high temperatures by forming bonds with the tails of phospholipids, stabilising them and causing them to pack more closely together. Cholesterol increases the mechanical strength and stability of membranes. - GLYCOLIPIDS AND GLYCOPROTIENS are present on the surface of the cell, where they aid cell-to-cell communication. Glycoproteins are proteins are proteins with carbohydrates attached,, while glycolipids are lipids with carbohydrates attached. These bind with substances at the cells surface, e.g. hormones.

Answer 12

1) Before the 1970s, most scientists believed cell membranes composed of a PHOSPHOLIPID LAYER between TWO CONTINOUS LAYERS OF PROTEIN. This was because ELECTRON MICROSCOPE (EM) IMAGES appeared to show THREE LAYERS in a cell membrane. 2) In time, IMPROVED EM techniques showed a BILAYER of phospholipids, and NEW METHODS for ANALYZING PROTEIN showed that they were RANDOMLY DISTRIBUTED in cell membranes, not in a continuous layer. 3) Scientists also carried out experiments that proved the cell membrane was FLUID - e.g. they fused a MOUSE CELL with a HUMAN CELL, and found that the mouse and human MEMBRANE PROTIENS completely INTERMIXED throughout the cell membrane - the proteins could only MIX like this if the membrane was fluid. 4) All of this new evidence led to the FLUID MOSAIC MODEL.

Answer 13

- Osmosis is the diffusion of free water molecules across a PARTIALLY PERMEABLE MEMBRANE from an area of HIGHER CONCENTRATION of water molecules to an area of LOWER CONCENTRATION of water molecules. - (Water molecules will diffuse both ways through the membrane, but the net movement will be to the side with the lower concentration of water molecules.)

Answer 14

Facilitated diffusion usually occurs when a molecule cannot pass through the plasma membrane because of their polarity, charge or size. Proteins that aid in facilitated diffusion shield these molecules from the hydrophobic core of the membrane, allowing molecules to cross the membrane through a pore or channel. - Facilitated diffusion moves particles DOWN A CONCENTRATION GRADIENT and is a PASSIVE PROCESS (It doesn't require energy). - Uses carrier and channel protiens

Answer 15

Carrier proteins and channel proteins

Answer 16

Channel proteins are TRANSMEMBRANE PROTEINS involved in facilitated diffusion. They form HYDROPHILIC tunnels across the membrane. These channels are HIGHLY SELECTIVE of the molecules they allow across, and will usually only aid in the transport of one molecule or a group of similar molecules. Channel proteins act like PORES in the membrane that let water molecules or small ions through quickly. They transfer CHARGED PARTICLES across the semipermeable biological membrane, down their concentration gradient.

Answer 17

Carrier proteins are proteins that are able to CHANGE THEIR SHAPE to allow LARGE MOLECULES to diffuse across the cell membrane, down their concentration gradient, but they do not actively push them through. Carrier proteins are VERY SELECTIVE and unique to each type of molecule that needs to be transported across a membrane.

Answer 18

Active transport uses ENERGY to move MOLECULES and IONS across plasma membranes, AGAINST a CONCENTRATION GRADIENT. This process involve CARRIER PROTIENS.

Answer 19

The energy used in active transport comes from ATP: ATP is produced by RESPIRATION and acts as IMMEDIATE ENERGY SOURCE in the cell. When ATP is HYDROLYSED (broken down) in the cell, energy is RELEASED. This energy is used to move the molecule against it's concentration gradient.

Answer 20

Endocytosis is the process of ACTIVELY TRANSPORTING molecules, which are too large to be taken into the cell by carrier proteins, into the cell by ENGULFING it with its membrane. (The cell surrounds a substance with a section of its cell membrane. The membrane then pinches off to form a VESICLE inside the cell containing the ingested substance). (uses ATP)

Answer 21

- Exocytosis is the process by which a cell SECRETES LARGE SUBSTANCES (such as digestive enzymes or hormones) that have been produced inside the cell. New lipids and proteins produced inside the cell are processed in an organelle called the GOLGI APPARATUS. The Golgi Apparatus exists as a series of flattened sacs of membrane. - VESICLES containing these substances PINCH OFF from the sacs of the GOLGI APPARATUS and MOVE TOWARDS the cell membrane. The vesicles FUSE with the CELL MEMBRANE and RELEASE their contents OUTSIDE the cell. - Uses ATP as an energy source.

Answer 22

An example of a white blood cell that uses endocytosis to take in things like microorganisms and dead cells so that they can destroy them.

Answer 23

Globular proteins are round structures. Like their name, globular proteins have a round, spherical formation. This is because the hydrophobic parts of the protein fold inwards while the hydrophilic parts become arranged around the external surface. Globular proteins are water soluble. Have tertiary or quaternary structures.

Answer 24

- Haemoglobin is a GLOBULAR PROTEIN made of FOUR polypeptide chains. It CARRIES OXYGEN around the body in the blood. - IT's SOLUBLE, so can be EASILY TRANSPORTED in the blood (this is due to their hydrophobic R-groups facing inwards (helping preserve their 3 dimensional spherical shape) and their hydrophilic R-groups facing outwards (helping maintain it's solubility)). - Each subunit has an IRON-containing PROSTHETIC HAEM GROUP that is able to BIND TO OXYGEN.

Answer 25

- Made of LONG, INSOLUBLE POLYPEPTIDE CHAINS that are TIGHTLY COILED round each other to form a ROPE SHAPE. - They are INSOLUBLE in water due to their large number of hydrophobic R groups. - The chains are held together by LOTS OF BONDS (e.g. disulfide and hydrogen bonds), which make the proteins STRONG. Because of their strength they are often found in SUPPORTIVE TISSUE. - Usually **secondary structure**. Have little to no tertiary structure.

Answer 26

The amino acid sequence of a protein determines what bonds will form and how the protein will fold up into it's 3D structure. The 3D structure of a protein determines its properties. Its properties relate to its function in the body.

Answer 27

Collagen is a STRONG, FIBROUS PROTEIN that form connective tissue in ANIMALS. - The presence of the MANY HYDROGEN BONDS within the TRIPLE HELIX STRUCTURE of collagen results in GREAT TENSILE STRENGTH. This enables collagen to be able to withstand large pulling forces without stretching or breaking - **Secondary structure**

Answer 28

- Interactions between R groups (the side chains on amino acids) creates the complex 3D tertiary structure of the protein. - The 3D structure is usually coiled or folded. -There are many weak and strong interactions that determine the final 3D shape of the protein: - hydrogen bonds - ionic bonds - disulphide bonds - hydrophobic and hydrophilic interactions. - For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.

Answer 29

An ionic bond is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions.

Answer 30

Whenever two molecules of the amino acid cysteine come close together, the sulfur atom in one cysteine bonds to the sulfur in the other cysteine, forming a disulfide bond. (S-S bonds)

Answer 31

When hydrophobic (water-repelling) groups are close together in the protein, they tend to clump together. This means that hydrophilic (water-attracting) groups are more likely to be on the outside, which affects how it folds up in into it's final structure.

Answer 32

A weak bond of attraction between a hydrogen atom and another atom. Hydrogen bonds are relatively weak, but when there are many the overall stability of the tertiary structure increases.

Answer 33

Some proteins are made of several different tertiary polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains are assembled together. (A protein consisting of more than one amino acid chain) The quaternary structure can be influenced by all the bonds involved in the tertiary structure.

Answer 34

A conjugated protein is a specific type of globular protein that contains a prosthetic group

Answer 35

A prosthetic group is a non-protein part of a protein. in haemoglobin this is the heme group.

Answer 36

- The lock and key model - The substrate fits into the enzyme's active site in the same way that a key fits into a lock, forming an enzyme-substrate concentration and then producing products. The enzyme is unchanged after the reaction. - The induced fit model - As the substrate binds, the active site changes shape slightly. This helps to explain why enzymes are so specific and only bond to one particular substrate. it suggests that the enzyme and substrate don't just fit together perfectly from the start. Instead, the initial interaction causes a slight change in the enzyme's shape, making it more complementary to the substrate. Conformational Change: This change in shape is called a conformational change. The enzyme's active site (the region where the substrate binds) adjusts its structure to better accommodate the substrate. Improved Fit: This dynamic interaction allows for a more precise fit between the enzyme and the substrate, which can lead to enhanced catalytic activity.

Answer 37

Enzymes are biological catalysts that speed up the rate of chemical reactions without being used up or undergoing permanent change. They are made up of proteins and are essential for many cellular processes, such as metabolism and energy production. Enzymes lower the activation energy required for a reaction to occur, allowing reactions to happen at a lower temperature so they can take place at body temperature. Enzymes are usually specific to only one reaction and have an active site that acts as a catalyst.

Answer 38

When a substrate fits into the enzyme's active site it forms an enzyme-substrate complex - it's this that lowers the activation energy. Here's two reasons why: 1) If two substrate molecules need to be JOINED, being attached to the enzyme holds them CLOSE TOGETHER, REDUCING any REPULSION between the molecules so they can bond more easily. 2) If the enzyme is catalysing a BREAKDOWN REACTION, fitting into the active site puts a STRAIN on bonds in the substrate, so the substrate molecule BREAKS UP more easily.

Answer 39

- Enzymes are PROTEINS. Their properties relate to their TERTAIRY STRUCTURE. - Enzymes are VERY SPECIFIC - they usually only catalyse ONE reaction. - This is because ONLY ONE COMPLEMENTARY SUBSTRATE WILL FIT into the active site. - The active site's SHAPE is determined by the enzyme's TERTAIRY STRUCTURE (which is determined by the enzyme's primary structure) - Each different enzyme has a different tertiary structure and so a different shaped active site, if the substrate shape doesn't match the active site, an enzyme-substrate complex won't be formed and the reaction won't be catalysed. - If the tertiary structure is ALTERED in any way, the SHAPE of the active site will CHANGE. This means the SUBSTRATE WON'T FIT into the active site, an enzyme-substrate complex WON'T be formed and the enzyme will no longer be able to carry out it's function. - The tertiary structure of an enzyme may be ALTERED by changes in pH or TEMPERATURE. - The PRIMARY STRUCTURE of a protein is determined by a GENE. if a MUTATION occurs in that gene, it could change the structure of the enzyme PRODUCED.

Answer 40

Catalyse reactions inside cells

Answer 41

Produced and secreted by cells to catalyse reactions outside cells.

Answer 42

DNA copies itself before cell division so that each new cell has the full amount of DNA. The method is called semi-conservative replication because half of the strands in each new DNA molecule are from the original DNA molecule. This means that there's genetic continuity between generations of cells.

Answer 43

DNA replicates by semi-conservative replication: Stage 1: The enzyme DNA HELICASE BREAKS the HYDORGEN BONDS between bases on the two POLYNUCLEOTIDE DNA strands. This makes the helix UNWIND to form two single strands. Stage 2: Each ORIGINAL single strand acts as a TEMPLATE for a new strand. COMPLEMENTARY BASE PAIRING means that FREE-FLOATING DNA NUCLEOTIDES are attracted to their complementary EXPOSED BASES on each original template strand - A with T and C with G. Stage 3: CONDENSATION REACTIONS join the nucleotides of the new strands together - catalysed by the enzyme DNA POLYMERASE. Hydrogen bonds FORM between the bases on the original and new strands. Stage 4: Each new DNA molecule contains ONE STRAND from the ORIGINAL DNA molecule and one NEW STRAND - semi-conservative replication.

Answer 44

- In the nucleus there are **free nucleotides** (also known as **nucleoside triphosphates** or 'activated nucleotides') which contain **three phosphate groups**. - The bases of the free nucleoside triphosphates align with their complementary bases on each of the template DNA strands. - The enzyme **DNA polymerase synthesises new DNA strands** from the two template strands. - It does this by **catalysing condensation reactions** between the **deoxyribose sugar** and the **phosphate groups** of the adjacent nucleotides within the new strands, creating the **sugar-phosphate backbone of the new DNA strands** - DNA polymerase **cleaves (breaks off) the two extra phosphates** and uses the **energy released** to created the **phosphodiester bonds** (between adjacent nucleotides). - **Hydrogen bonds** then form between the **complementary base pairs** of the template and new DNA strands.

Answer 45

If the method was Conservative, the original DNA strands would stay together and the new DNA molecules would contain two new strands.

Answer 46

1) Two samples of bacteria were grown - one in a nutrient broth containing light **nitrogen (14N)**, and one in a broth with heavy **nitrogen (15N)**. As the bacteria reproduced, they took up nitrogen from the broth to help make nucleotides for new DNA. So the **nitrogen gradually became part of the bacteria's DNA.** 2) A sample of DNA was taken from each batch of bacteria, and spun in a **centrifuge**. The **DNA from the heavy nitrogen bacteria settled lower down the centrifuge tube than the DNA from the light nitrogen bacteria** - because it's heavier. 3) Then bacteria grown in the** heavy** nitrogen broth were** taken out **and put in a broth containing** only light nitrogen**. The bacteria were left for **one round of DNA replication**, and then **another DNA sample was taken out and spun in the centrifuge.** 4) If the replication was** conservative**, the original **heavy** DNA, which would still be together, would **settle at the bottom **and the **new light DNA** would **settle at the top**. 5) If replication was **semi-conservative**, the new bacterial DNA molecules would contain **one strand of the old DNA containing heavy nitrogen** and **one strand of new DNA containing light nitroge**n. So the DNA would **settle out in the middle**. 6) The DNA did settle out in the** middle**, showing that the DNA molecules contained a **mixture of heavy and light nitrogen.** The bacterial DNA had **replicated semi-conservatively **in the light nitrogen.

Answer 47

- Mutations are changes to the base sequence of DNA. They can be caused by errors during DNA replication. - The order of DNA bases in a gene determines the order of amino acids in a particular protein. If a mutation in a gene, the primary structure of the protein it odes for could be altered: This could change the final 3D shape of the protein so it doesn't work properly. - If a mutation occurs in a gene it can cause a gentic disroder, which is then passed on e.g. Cystic fibrosis.

Answer 48

- Substitution - One base is substituted/swapped with another. - Deletion - One base is randomly deleted (frameshift mutation) - Insertion - One extra base is added (frameshift mutation) - Duplication - One or more bases are repeated (can be a frameshift mutation). - Inversion - A sequence of bases is reversed.

Answer 49

Genetic disorder are often caused by a mutation in a gene that results in a differently functioning or non-functioning protein that alters the phenotype of the individual. Some genetic disorders can be caused by lots of different mutations. Mutations can be inherited from parents and present at birth, or they can be acquired during an individual's lifetime.

Answer 50

- A **genetic disorder** caused by a **recessive allele** mutation on chromosome 7. So a person will only have the disorder if they're **homozygous** for the allele - they must inherit a recessive allele from each parent.

Answer 51

1) Cystic Fibrosis is caused my a **mutation** in the gene that codes for the **CFTR** protein. 2) CFTR is a **channel protein**. It transports **chloride ions** out of cells into **mucus** - this causes water to move **into** the mucus by **osmosis**, which makes mucus **watery**. 3) **Mutant CFTR** protein is much ** less efficient** at transporting chloride ions **out ** of the cell, so **less water moves out by osmosis**. This makes the mucus of people with CF abnormally **thick** and **sticky**. 5) This thick and sticky mucus causes problems in the **respiratory**, **digestive** and **reproductive systems**. There are many different mutations in the CFTR gene that can lead to cystic fibrosis.

Answer 52

1) The Celia are **unable** to **move** the mucus towards the throat because it's so thick and sticky. 2) This means that **mucus builds up** in the airways. 3) Some airways can become completely **blocked** by the mucus - **gas exchange** can't take place in the area bellow the blockage. 4) This means that the **surface area** available for gas exchange is reduced, causing breathing difficulties. 5) People with CF are also more prone to **lung infections** as mucus containing microorganisms can't be removed.

Answer 53

1) The **tube** that connects the **pancreas** to the **small intestine** can become **blocked** with mucus - preventing **digestive enzymes** produced from the pancreas from **reaching** the small intestines. This reduces the ability of someone with CF to **digest food** and so **fewer nutrients** can be absorbed. 2) The mucus can cause **cysts (growths)** to form in the **pancreas**. These **inhibit** the **production** of **enzymes**, which also reduces the ability to digest food and absorb nutrients. 3) The mucus **lining** the **small intestines** is abnormally thick - this inhibits the **absorption** of nutrients.

Answer 54

1) In some men with CF, the **tubes** connecting the **testicles** (where sperm are produced) to the **penis** are **absent** and can become **blocked** by the thick mucus in others. So, any **sperm** produced **can't reach the penis**. 2) In women, thickened **cervical mucus** can **prevent** the sperm from **reaching the egg**. The sperm has to travel through this mucus to reach the egg - thick mucus reduces the **motility** of the sperm, reducing it's chances of **making it** to the egg.

Answer 55

A sequence of bases on a DNA molecule that codes for a protein, which results in a characteristic e.g. the gene for eye colour.

Answer 56

Alleles are different forms/version of genes that code for different versions of the same characteristics. They are found in the same place on the chromosome and determine the phenotype (expressed characteristics) of an organism.

Answer 57

The alleles a person has, e.g. BB, Bb, or bb for eye colour.

Answer 58

The characteristics displayed by an organism, e.g. brown eyes.

Answer 59

An allele whose characteristics only appear in the phenotype if two copies are present. e.g. bb

Answer 60

An allele whose characteristic appears in the phenotype even when there's only one copy. e.g. Bb

Answer 61

When the trait from a dominant allele isn't completely shown over the trait produced by the recessive allele, so both alleles influence the phenotype. Some flowers show incomplete dominance e.g. snapdragons can have alleles for red flowers (RR), white flower (rr) or pink flowers (Rr).

Answer 62

An organism that carries two different alleles for a certain characteristic, e.g. Bb.

Answer 63

An organism that carries two coppies of the same allele for a certain characteristic, e.g. BB or bb.

Answer 64

Genetic screening involves **analysing DNA** to see if it contains **alleles** for genetic disorders. The three main uses are: 1) **Identification of carriers** 2) **Preimplantation Genetic Diagnosis (PGD)** 3) **Prenatal Testing**

Answer 65

**carrier testing** is offered to people with a **family history** of genetic disorders to see if they carry an **allele** that causes a disorder. Couples can be tested **before having children** to determine the **chances** of any **future** children having the disorder. Benefits: - Carrier testing allows people to make **informed decisions** about things like **whether to have children** and whether to carry out **prenatal testing** if the women is pregnant. Social and ethical issues: - Finding out you're a carrier may cause **emotional distress** or affect your ability to find a partner - Test **aren't** always 100% **accurate** - they could give a **false result**, which means poor decisions could be made based on **incorrect information**. - Other genetic **abnormalities** may be found, which could cause **further stress**. - concerns that results of genetic tests could be used by **employers** or **life insurance companies** - resulting in **genetic discrimination**.

Answer 66

Involves **screening embryos** produced in **IVF** for genetic disorders **before** they're implanted into the woman. Only embryos without the genetic disorder will be implanted. Advantages: - **Reduces** the chance of having a baby with a genetic disorder. - Performed **before implantation** so avoids the issue of **abortion**. Social and ethical issues: - It can be used to find out **other characteristic** (e.g. gender, eye-colour) - leading to concerns that in the future, embryos may be selected for other characteristics (**designer babies**). - **False results** could provide incorrect information and lead to poor decisions being made about the fate of embryo.

Answer 67

Involves **screening fetuses** for genetic disorders and are offered to pregnant women with a family history of genetic disease. Two types: - **Amniocentesis** - **Chorionic villus sampling (CVS)**

Answer 68

- Usually carried out at **15-20** weeks of pregnancy. - A sample of **amniotic fluid** is obtained via the **abdomen** using a very **fine needle**. This fluid contains **fetal cells**. The cells **contain DNA**, which can be **analysed**. - **1% risk of micarraige**. - Results aren't available for **2-3 weeks** after sample is taken. **Rapid test** results, which only look at few common disorders, are available in **3-4 days**.

Answer 69

- Usually performed at **11-14 weeks** of pregnancy - an **early decision** can be made, meaning that the procedure is **less physically traumatic** than amniocentesis. - A sample of cells is taken from the **chorionic villi/placenta** (part of the fetus that connects it to it's mother). The **cells contains fetal DNA** which can be **analysed**. This procedure is done via either the **abdomen** using a **fine needle**, or the **vagina**, using a **catheter**. - CVS has a **1-2% risk of miscarriage**, which is greater than Amniocentesis. - **Initial results** available in a **few days** but **more detailed** results can take **two weeks or more**.

Answer 70

Benefits: - Allows parents to make **informed decisions**. - **Helps parents prepare** for the future care of the child - any **medical treatment** can be started immediately after birth. Social and ethical Issues: - Slightly **increases the risk of miscarriage**. - **False results** could provide incorrect information. - Some people considered it **unethical to abort** a fetus because it has a genetic disorder.

Answer 71

A machine that passes light of specific wavelength through a liquid and measure how much of that light is absorbed.

Answer 72

Beetroot cells contain a coloured pigment that leaks out - the higher the permeability of the membrane the the more pigment leaks out the cell. Soak some beetroot cubes in water at different temperatures: 1) Use a cork borer to cut beetroot into 5 identical cylinders. Then using a **scalpel**, carefully cut 5 **equally sized** discs of beetroot on a **cutting board**. 2) **Rinse** the beetroot to removes any pigment released during cutting 3) Use a **measuring cylinder or pipette** to measure **5cm^3 of water** into five different test tubes. 4) Place the test tubes into **water baths at different temps**, e.g. 10, 20, 30, 40 , 50 DC, for around 5 minutes. 5) Then place the 5 pieces of beetroot into the 5 different test tubes, for the **same length of time** (use stopwatch). 6) **Remove** the pieces of beetroot, leaving just the coloured liquid in the test tubes. Use a **colorimeter** to measure the absorbance of the coloured liquid: 1) allow colorimeter **5 mins to stabilise**, then set it up using a **blue filter**. Use pure **distilled water to calibrate machine to zero**. 2) Use **pipette** to transfer a **sample** of the liquid from the first beetroot test tubes to a clean **cuvette** - it should be about 3/4 full. 3) Put cuvette in colorimeter and **record absorbance** of the coloured solution. 4) **Repeated steps 2-3** for the liquids in the remaining test tubes (using a clean pipette and cuvette each time). 5) Analyse results - the **higher** the absorbance reading, the **less light** is passing through the solution. This means **more pigment** has been **released**, so the **higher** the **permeability** of the membrane.

Answer 73

As the temperature increases, the permeability of the cell-surface membrane also increases. This is because the proteins in the membrane **denature** as the heat **damages the bonds in their tertiary structure**. This creates gaps in the membrane so it is easier for molecules to pass through it. At low temperatures, phospholipids have little energy and are packed closely together to make the membrane rigid. This causes a decrease in permeability and restricts molecules from crossing the membrane. NB: At very low temperatures, ice crystals can form which pierce the cell membrane and increase the permeability

Answer 74

Increasing the alcohol concentration (i.e. ethanol) increases membrane permeability. This is because **alcohol dissolves the lipids** in the cell membrane, so the membrane loses it's structure. Lipids in the cell membrane are soluble in detergents.

Answer 75

Proteins/enzymes that are made in organisms/cells and speed up the rate of chemical reactions in the body by lowering the activation energy needed for reactions to take place.

Answer 76

- Trypsin Enzyme (A protease) - Casein - milk powder solution - substrate (protein) - Milk powder will clear as trypsin breaks down the protein in milk (casein) Variables: IV: Trypsin conc. (0.1%-0.5%) DV: measure of absorbance (using calorimeter) CV's: Same stock of enzyme and milk powder, vol. of milk solution, agitation (stirred up), temp, pH. Method: 1) Make up a range of concentrations of trypsin (0.1%-0.5%) 2) Have a beaker of milk powder solution (set conc. and vol.) 3) . Make a control by adding 2cm^3 of trypsin solution and 2cm^3 of distilled water. Use this to set the colorimeter absorbance to zero Calibrate to red absorbency. 4) Add 2cm^3 of milk powder solution to cuvette, add 2cm^3 of chosen trypsin conc. to this. **mix** for 10 seconds 5) Place in colorimeter and take a reading. 6) Take reading every 20 seconds for 5 minutes. 7) Repeat 3x for each conc. of trypsin, calc. mean, exclude anomalous results. 8) Plot data on graph measure of absorbance against time and draw tangent to work out initial rate. Conclusion: Increasing the conc. of trypsin enzyme, increases initial rate of reaction as there are more enzyme molecules (trypsin) for the substrate molecules (milk) to bind with. This is until the substrate becomes a limiting factor. To work out the effect of substrate concentration on initial rate of reaction: Keep trypsin concentration the same and vary the concentration of the milk solution.

Answer 77

- Exocytosis involves (molecules/substances) leaving the cell whereas endocytosis involves (molecules/substances) entering the cell. (1) - Exocytosis involves vesicles fusing with cell surface membranes whereas endocytosis involves the formation of vesicles (from the cell surface membrane). (1)

Answer 78

- Active transport only involves carrier proteins. - However, facilitated diffusion involves both carrier and channel proteins. - Facilitated diffusion is a passive process, whereas active transport requires energy in the form of ATP. - Facilitated diffusion occurs down a concentration gradient, whereas active transport is against the concentration gradient.

Answer 79

- Phospholipids have one glycerol connected to two fatty acids via ester bonds. - a phosphate group is covalently bonded to the glycerol. - one of the fatty acid chains is saturated, whereas the second fatty acid chain is unsaturated.

Answer 80

- (a recessive disorder is one) caused by a faulty allele (1) - that is only expressed in the { homozygous condition / absence of a normal allele } (1)

Topic 2: Genes and Health Flashcards

(104 cards)