Module 2 Flashcards

Question

Structure Ribosomes •

Answer 1

• No outer membrane • Tiny organelles • Each consists of 2 sub-units • Some in cytoplasm, some bound to ER

Answer 2

• Spherical or sausage shaped • Double membrane • Membranes separated by a fluid filled space • Highly folded inner membrane forms cristae • Central part called matrix

Answer 3

• Spherical sacs • Surrounded by single membrane

Answer 4

• Only found in plant cells and some protoctists • Double membrane • Separated by fluid filled space • Continuous inner membrane with elaborate network of flattened membrane sacs called thylakoids • Stack of thylakoids called a granum • Chlorophyll molecules repent on thylakoid membranes and in intergranal membranes

Answer 5

• Continuous outer membrane • Cell receptors present on surface

Answer 6

• Microtubules • Small tubes of protein fibres • Pair next to nucleus of animal cells

Answer 7

• Extension sticking out from cell • Cylinder contains nine microtubules arranged in a circle • Long • Usually present as 1 or 2

Answer 8

• Hair-like extensions • Stick out from cell surface • Cylinder contains nine microtubules arranged in a circle • Short • Usually present in large numbers

Answer 9

• Houses all of cell’s genetic material • Chromatin consists of DNA and proteins • Has instructions for making proteins

Answer 10

• Makes RNA and ribosomes • These pass into cytoplasm and are the site of protein assembly

Answer 11

• Pores allow passage of relatively large molecules

Answer 12

• Transports proteins made on attached ribosomes • Some proteins secreted from cell • Some placed on cell surface membrane

Answer 13

Involved in essential lipid production

Answer 14

• Receives proteins from ER and modifies them • Modifies proteins (e.g. Adding sugar) • Packages modifies proteins into vesicles, fro transportation • Some modified proteins are secreted from surface of the cell

Answer 15

• Site of protein synthesis in the cell • Act as an assembly line where mRNA is used to assemble proteins from amino acids

Answer 16

site of atp production • Almost all cell activities that require energy are driven by ATP

Answer 17

• Contain powerful digestive enzymes • Enzymes break down materials

Answer 18

• Site of photosynthesis in plant cells • Reactions driven by light energy

Answer 19

• Selectively permeable • Controls exchange between cell and environment • Receptors on cell surface allow for endocytosis and exocytosis

Answer 20

• Take part in cell division • From spindle fibres, moving chromosomes in cell division

Answer 21

• • ‘Tail’ • Enables movement

Answer 22

x | • ‘Hairs’ • Allow fro movement of substances

Answer 23

Contains DNA, which is essentially instructions for the cell to build individual proteins • One gene correlates to one specific protein • Genes are copied into mRNA, which leaves the nucleus via nuclear pores and attaches to a ribosome, which can be found on the rough endoplasmic reticulum (RER). Ribosome

Answer 24

‘Reads’ the gene • Accordingly assembles amino acids into a unique sequence • Forms a polypeptide • The polypeptide is pinched off the RER in a vesicle and transported to the Golgi apparatus

Answer 25

• Polypeptide is modified (by joining two or more chains of polypeptides, or adding carbohydrate branches) and... • Packaged into the final protein within a vesicle. • The vesicle is ready to be transported to the cell surface membrane and exocytosed.

Answer 26

network of fibres made from protein

Answer 27

• Cylinders • About 25nm in diameter • Made from Tubulin • May be used to move microorganisms through a liquid, or waft a liquid past a cell • Microtubule motors (proteins) present on microtubules use ATP to move cell contents along the fibres

Answer 28

• Move against each other • Cause the movement seen in white blood cells • Move some organelles around within cells

Answer 29

• Provide mechanical strength fro cell • Aids transport within cells ○ Movement of chromosomes during cell division ○ Movement of vesicles from ER to Golgi • Enable cell movement

Answer 30

May have membranes within the cell which form part of encapsulated organelles, e.g. mitochondria and chloroplasts Plant cell wall made out of cellulose; fungal cell wall made out of chitinRibosomes are 25–30nm in diameter DNA stored as chromosomes within the nucleusATP production takes place in mitochondrial cristae (inner membrane folds).Cell diameter 10–100 µm Strictly aerobic only prokaryotes Only one membrane: cell surface membrane Cell wall made out of peptidoglycan Ribosomes are 20nm in diameter DNA is free in cytoplasm, in the form of a single loop called a ‘circular chromosome’ — as well as some smaller DNA loops called ‘plasmids’.ATP production takes place in the cell surface membraneCell diameter 1–10 µm Sometimes capable of anaerobic respiration

Answer 31

* Any polar molecule ill dissolve in water • Metabolic processes rely on chemicals being able to react together in solutions • Allows cells to maintain concentration gradients * 70-95% of cytoplasm is water • Important chemical reactions take place here

Answer 32

* Transport medium • Freezes at 0°C • Boils at 100°C • Vast majority of water on earth is liquid • Transport of essential materials around organisms and cells * Blood is an important transport tissue of oxygen, cholesterol and hormones • Around 80% water

Answer 33

* Water molecules stick to each other, creating surface tension * Transport of water in xylem relies in cohesion of water • Some small organisms make use of this and ‘walk’ on water surface

Answer 34

* Water freezes forming ice • Ice is less dense than water and floats * Frozen ice floats to the top, allowing for organism to survive the water beneath

Answer 35

* Large bodies of water have fairly constant temperatures • Evaporation removes heat energy * Oceans provide thermally stable environment • Evaporation used as a cooling mechanism

Answer 36

Water is a reactant in important chemical processes • Chemically inert • Used in hydrolysis and photosynthesis • Very predictable and will not form any unexpected products

Answer 37

Water is a common habitat • Nutrients can be dissolved in water • Water contains oxygen that is essential to life • Water is an important habitat to many different species of animals • Fish and marine creatures

Answer 38

• Highly abundant in cell walls, making it most common molecule on the planet. • Polymer of about 10,000 β-glucose molecules in a long unbranched chain called a microfibril. • High stability due to structure - several polysaccharide chains running parallel to each other with cross links between them. • The chain cross links are hydrogen bonds and contribute to the strength of the molecule. • Stability renders plants strength and resistance to wind and rain.

Answer 39

energy store, thermal insulator, for buoyancy, and protection of vital organ

Answer 40

• interaction of individual amino acids which are in the same polypeptide • causes the polypeptide to coil or fold on itself • direct result of hydrogen bonds • results in the polypeptide chain taking one of two forms: ○ B-pleated sheet – Weak – Strength achieved through layering and bonds between layers ○ a-helix – Strong – Helical shape

Answer 41

• the way in which an a-helix or B-pleated sheet further coils or folds on itself • forms a more complex 3D shape which often improves its solubility • Due to interactions between R groups and involves: ○ ionic bonds ○ disulphide bonds ○ hydrogen bonds ○ hydrophilic/hydrophobic interactions. • Not all proteins have a tertiary structure • Some polypeptides remain simple long chains, such as keratin or collagen. ○ Such proteins are generally insoluble

Answer 42

• interaction between two or more polypeptides • Quaternary structure only exists in proteins consisting therefore of two or more polypeptides • A good example of such a protein is Haemoglobin (Hb) (shown in diagram) ○ bHb ecomes a biologically active molecule upon the establishment of its quaternary structure ○ Hbhas 4 sub-chains and its role is to carry iron and oxygen around the body ○ Has a globular quaternary structure • Another example is collagen ○ has a fibrous quaternary structure

Answer 43

* Roll up to form balls * Any hydrophobic R groups turn inwards • Any hydrophilic R groups turn outward • This makes these proteins water soluble * Usually have metabolic roles * Enzymes (e.g. lactase) • Plasma proteins • Antibodies • Some hormones (e.g. insulin) • Haemoglobin

Answer 44

* Form fibers • Regular, repetitive sequence of amino acids * Usually insoluble • Usually have structural roles * Collagen • Keratin

Answer 45

Globular Soluble Range of amino acids present in primary structure Prosthetic haem group Majority is wound into alpha helix structures • 2 a-chains • 2 B-chains

Answer 46

Fibrous Insoluble No prosthetic group | Majority is left-handed helix structures

Answer 47

The biuret test enables us to test a sample for the presence of protein. 1. Biuret reagent (composed of copper sulphate and potassium hydroxide) is normally blue 2. The reagent turns purple in the presence of peptide bonds, indicating presence of protein

Answer 48

All monosaccharides are reducing sugars, while disaccharides can be either reducing or nonreducing. 1. Benedict’s reagent is composed of copper-II sulphate in alkaline solution 2. Add the reagent to the sample and heat in a water bath (80°C) for 3 minutes 3. In the presence of a reducing sugar, Cu2+ ions are reduced to Cu+ and the sugar is oxidised 4. Colour changes to red 5. If no colour change present, this could indicate either: a. Absence of any sugar b. Presence of non-reducing sugar

Answer 49

we first need to break down the sugar into its reducing sub-parts. For instance, sucrose needs to be broken down into glucose and fructose before it will react with Benedict’s reagent. We can achieve this by: 1. Heat solution with acid to hydrolyse any glycosidic bonds present 2. Neutralise solution with sodium hydroxide 3. Add benedict’s reagent and heat in water bath for 3 minutes 4. If colour changes to orange/red then a non-reducing sugar was originally present

Answer 50

1. Use potassium iodide solution as source of iodine 2. In the presence of starch, the solution will turn a dark blue-black colour 3. This is due to iodine becoming trapped inside the coils of starch

Answer 51

1. Shake sample with ethanol 2. Pour solution into water 3. If the mixture turns cloudy, lipids are present 4. This is due to lipids’ solubility in ethanol and insolubility in water

Answer 52

• Can be cellulose chromatography paper or • Thin-layer chromatography (TLC) plate

Answer 53

• Solvent for molecules to be identified • Use water for polar molecules • Use ethanol for non-polar molecules

Answer 54

1. Prepare a beaker with a small amount of solvent (mobile phase) 2. Draw a line along the bottom of the chromatography paper piece a. Draw in pencil b. The line should high enough on the strip to not be submerged in solvent when placed in the beaker 3. Draw a tiny dot on the line to mark where you will apply your sample 4. Place the paper in the beaker 5. Cover the beaker with a glass plate 6. Leave the apparatus until the solvent has been absorbed by the paper and travelled to the other end of it 7. Use where a. x = distance travelled by each solute and b. y = distance travelled by the solvent 8. Each biological molecule has its own Rf and is thereby identifiable

Answer 55

Acts as an information store • Bases projecting from backbone act as a coded sequence • Organisms differ in their DNA only because they contain different sequences of bases in DNA • Contains ‘information’ to inform the primary structure of a protein Needs to be replicable • Produce copies that preserve the base sequences • Preserve information • Base-pairing rules allow for this Long molecule • Lots of information can be stored • Double helix provides stability

Answer 56

• Deoxyribonucleic Acid • Stable Polynucleotide ○ long-chain polymer of nucleotide monomers • Usually double stranded

Answer 57

• DNA strands run parallel to each other • Bases project inwards, running in opposite directions (‘anti-parallel’) • Chains always the same distance apart as bases pair in a specific way ○ A-T ○ G-C • When a purine appears on one side, a pyridimine appears on the other • As the strands come together, hydrogen bonds form between the base pairs • Differing structure of the bases, means that base pairing rules always apply • This form of pairing is described as complementary ○ A is complementary to T ○ G is complementary to C • The 2 strands twist to form double helix of final structure • Held together by hydrogen bonds which are strong enough to maintain DNA structure but weak enough to be overcome during DNA replication

Answer 58

• ensures the preservation of genetic information stored in DNA • Important as the structure and functions of proteins coded according to DNA relies entirely upon the correct sequences being copied • Some mutations occur very infrequently and randomly • These might not result in a phenotypic change, but sometimes can have life-altering consequences

Answer 59

1. DNA double helix unwinds and “unzips”; the hydrogen bonds between base pairs are broken. This process is brought about by an enzyme called DNA helicase. 2. The exposed nucleotide bases act as a template for assembly of the new DNA strand. 3. Free nucleotides move towards these exposed bases according to the base pair rule. 4. An enzyme called DNA polymerase binds the nucleotides together with covalent bonds, forming the new sugar-phosphate backbone. 5

Answer 60

Transcription = the process of copying RNA from DNA 1. DNA strand unwinds and unzips by DNA helicase 2. Instead of a new DNA strand being formed, RNA nucleotide bases pair up with the exposed DNA bases 3. An enzyme called RNA synthase forms covalent bonds between the nucleotide bases 4. Unlike DNA, RNA is single-stranded 5. A messenger RNA (mRNA) strand is formed and breaks away from the DNA which then rezips itself up thanks to the natural formation of hydrogen bonds 6. mRNA is now free to migrate out of the nucleus through nuclear pores

Answer 61

= the process of creating polypeptides based off mRNA 1. Once mRNA has left the nucleus, it attaches to a ribosome on the rough endoplasmic reticulum 2. Transfer RNA (tRNA) carries the corresponding amino acid to each on the mRNA 3. The anti-codon is a triplet of bases that form part of a tRNA molecule and ensure that the correct amino acid is joined onto the polypeptide chain 4. This process is active and requires ATP 5. The amino acid transported by the tRNA attaches to the ribosome 6. Adjacent amino acids join together by peptide bonds, creating a polypeptide chain 7. This process continues until the ribosome reaches a ‘stop’ codon (triplet) on the mRNA. At this point, the polypeptide breaks loose from the ribosome and is free.

Answer 62

Every enzyme has an active site which binds to a substrate • The enzyme’s active site is formed by its tertiary structure and is specific to the substrate • It will have no effect on a molecule that comes into contact with its active site but doesn’t relate to the enzyme’s function • The idea of active site specificity is called Lock and Key theory, because the active site acts like a lock and the substrate acts like a key.

Answer 63

• The enzyme’s active site is not perfectly matched to the substrate before the two bind to form the enzyme-substrate complex 47snaprevise.co.uk • When the complex is formed, the tertiary structure of the enzyme changes slightly • It is this change in shape that enables the reaction to happen at a lower activation energy.

Answer 64

The tertiary structure of an enzyme relies on hydrogen bonding. • Each enzyme has a tertiary structure that is optimal for most efficient action • changes in pH from the enzyme’s optimal pH change hydrogen bonding in tertiary structure • Enzymes are built to work optimally at the pH of their natural environment ○ e.g. trypsin, which works in the stomach, works best at low pH ○ arginase is often in the presence of ammonia which is alkaline, and this enzyme has a higher ‘optimal pH’. Effect

Answer 65

Small increase in temperature can increase enzyme activity as the kinetic energy of the enzyme and the substrate increase. • They are therefore more likely to come into contact with each other. • They also collide with greater force • Therefore are more likely to form an enzyme-substrate complex when they do meet. • As temperature increases, it will approach the enzyme’s optimal temperature: where the enzyme is working at maximum efficiency. • Beyond this temperature, the enzyme becomes denatured. • Bonds responsible for maintaining the enzyme’s tertiary structure become broken and the active site changes shape • Enzyme becomes totally inefficient

Answer 66

• Rate of reaction and enzyme concentration are directly proportional, ○ provided substrate molecules are in excess and enzyme availability is the only limiting factor. • Where substrate is in limited supply, as it all becomes reacted, less and less becomes available, so the rate of reaction curves off.

Answer 67

The rate of reaction and substrate concentration are directly proportional, up to a given point. • This point is called Vmax, • At Vmax, all the enzyme active sites are said to be ‘saturated’ or occupied. • There are no available active sites free to bind with substrates. • At Vmax, the amount of enzyme becomes the limiting factor.

Answer 68

= non-protein component of an enzyme that is required in order for the enzyme to function. • E.g. Cl – is a co-factor for amylase

Answer 69

= organic, non-protein molecule whose role is to transport chemical groups between enzymes, linking together controlled enzyme reactions. • E.g. Vitamins are a diverse group of coenzymes • NADP is a coenzyme to photosynthesis • NAD and FAD are coenzymes in respiration

Answer 70

coenzyme that is a permanent part of the enzyme • E.g. Zn2+ is a prosthetic group in carbonic anhydrase

Answer 71

• Can fit into the active site, but does not react • Competes with substrate for access to the active site • Effect is concentration dependent • Can be minimized by raising the concentration of substrate • Effects are reversible

Answer 72

• Binds to allosteric site • Changes the shape of the molecule, preventing it from working • This is permanent and cannot be rectified • Effect is independent of substrate concentration

Answer 73

• Bind reversibly to the enzyme • Have no long-lasting effect since they detach themselves after a while

Answer 74

• Binds irreversibly • Even if in high competition with substrate, can eventually inhibit a large proportion of available enzyme 52snaprevise.co.uk • Can have long-lasting effects • Until organism generates more enzyme and the inhibitor is outnumbered by enzyme • E.g. aspirin

Answer 75

Some poisons act as metabolic inhibitors. For example, potassium cyanide is a non-competitive inhibitor to the enzyme cytochrome oxidase. The effect of this poison is to decrease the body’s ability to respire using oxygen, so it begins to respire anaerobically, causing lactic acid accumulation in the blood

Answer 76

1. To act as partially (and sometimes selectively) permeable membranes between: ○ A cell and its environment ○ An organelle and the cytoplasm which surrounds it ○ Within organelles (e.g. mitochondria/chloroplasts) 2. Sites of chemical reactions 3. Sites of cell communication and signalling

Answer 77

that the membrane is constructed from several different components including phospholipids, proteins, and modified proteins, and that these membrane constituents (phospholipids and are continually moving relative to each other, i.e. not fixed.

Answer 78

which form the bilayer and the bulk of the membrane surface area

Answer 79

which regulate membrane mobility and flexibility

Answer 80

which are involved in more complex functions such as carrying out chemical reactions or regulating cross-plasma transport ○ Can be intrinsic/integral (span the entire membrane) ○ Can be extrinsic (embedded in one half of the membrane) ○ Can form cross-membrane channels

Answer 81

which can be antigens or receptor molecules

Answer 82

can denature some of the components of the membrane, such as the proteins and glycoproteins, changing their effect and reducing their ability to control transport of molecules across the membrane. Therefore, at high temperatures, the membrane becomes denatured and more permeable.

Answer 83

pH has a similar effect, by denaturing the proteins in the membranes that are in pH other than the optimal pH for that cell or organelle.

Answer 84

• Movement of molecules or ions from an area of high concentration to an area of lower concentration • Until the concentrations of the two regions are equal • Dynamic equilibrium established • Passive process • The rate of diffusion is proportional to the concentration gradient the distance over which the diffusion must occur • Substances capable of diffusion across the cell surface membrane include ○ Oxygen ○ carbon dioxide ○ Steroids ○ the fat-soluble vitamins (A,D,E,K) ○ Glycerol ○ alcohols and ○ ammonia.

Answer 85

• Specialised form of diffusion • Diffusion of water molecules from an area of high water potential (high concentration) to an area of low water potential (low concentration) • Through a partially permeable membrane • Passive process

Answer 86

Faster than normal diffusion • Used to transport molecules such as ○ Glucose ○ Fructose ○ non fat-soluble vitamins ○ urea and ○ many ions across the membrane. • Occurs down the concentration gradient • Passive process

Answer 87

○ Glucose binds with transport protein molecules on the cell surface. Different cells have different types of glucose transporter. ○ The transport protein changes shape. ○ The glucose is transported through the membrane to the inside of the cell. ○ The glucose detaches from the transporter protein and the protein reverts to its original shape. The glucose is then immediately phosphorylated, so the concentration of glucose inside the cell remains low and the concentration gradient across the membrane is maintained

Answer 88

Ions such as ○ sodium (Na+) ○ potassium (K+) ○ chloride (Cl-) ○ hydrogen (H+) and ○ molecules such as amino acids and glucose require active transport across the cell surface membrane • ATP is required • Active process • This is because the movement of these ions/molecules is against the concentration gradient • All of these substances can cross the membrane by facilitated diffusion if the concentration gradient is the right way round and if transporter channels are available. • Commonly involves a protein which acts as a Na+/K+ pump. The

Answer 89

• Water potential outside cell higher than inside • Water moves in by osmosis • Cell swells may burst • (Haemolysis)

Answer 90

• Water potential both inside and outside are equal Water flows in and out at an equal rate

Answer 91

• Water potential outside cell lower than inside • Water moves out of the cell by osmosis • Cell shrinks • (Crentation

Answer 92

• Solution has higher water potential than vacuole • Water flows in by osmosis • Cell swells, becomes turgid • Cannot burst because of cell wall

Answer 93

• Neither turgid nor plasmolysed • Water moving in and out at same rate

Answer 94

• Solution has lower water potential that vacuole • Water flows out by osmosis • Cell shrinks, becomes plasmolysed • Cell wall rigid and does not collapse

Answer 95

• Biosynthesis • Growth phase • Biosynthetic activities resume at a high rate • Amino acids used to form millions of proteins • Proteins required in DNA replication • Chromosomes still exist as chromatin • DNA replication has not yet occurred

Answer 96

• Synthesis of new DNA • DNA replication begins • When completed, all chromosomes are replicated • Occurs very quickly

Answer 97

• Cell continues to grow • Proof-reading enzymes check the DNA • Check to see if the chromosomes have been replicated properly

Answer 98

• Nuclear division • The process of mitosis is carried out

Answer 99

• Molecules of DNA wrapped around proteins called histones ○ Allows DNA to be highly condenses ○ Compact and condensed DNA is able to fit inside the nucleus • DNA and histone protein together are called chromatin ○ Chromatin thread about 30nm thick • Before cell division, DNA of each chromosome must be replicated ○ 2 replicas produced, both exact copies of the original ○ Held together at the centromere

Answer 100

To avoid abnormal cell activity that can lead to, for example, tumour growth, the cell cycle has three checkpoints to regulate itself.

Answer 101

• ○ Checks for cell size and DNA replication

Answer 102

○ Checks that chromosomes appropriately attached to spindle

Answer 103

○ Checks cell size, nutrient availability, growth factor availability and confirms intact DNA

Answer 104

• DNA replication • Organelle doubling • Proteins made • Cell ‘double checks’ for mutations

Answer 105

• Replicated chromosomes super coil (shorten and thicken) • Chromosomes already replicated in Interphase • Chromosomes shorten and thicken • Pair of sister chromatids can be seen using a light microscope • Nuclear envelope breaks down and disappears • Centrioles divides in 2, forming 2 daughter centrioles ○ Each daughter centrioles moves to opposite ends of cell • This forms the spindle • This is ‘threads’ of protein (look like latitude lines on a globe) • Nuclear membrane breaks down

Answer 106

• Replicated chromosomes line up down middle of ell • Move to central region of spindle • Each becomes to spindle thread by its centromere

Answer 107

• Replicas of each chromosome pulled apart • Towards opposite ends of the cell • Sister chromatids separated as centromere splits • Each sister chromosomes effectively become individual chromosomes • Each one genetically identical to the parent cell from which it was copied • Spindle fibers shorten • This pulls sister chromatids further and further away from each other • Form a v-shape as spindle fibers, joined to the centromere, lead

Answer 108

• Two nuclei formed • As each sister chromatids reaches the pole of the cells, new nuclear envelope forms around each set • Spindle breaks down and disappears • Chromosomes uncoil • Can no longer be seen under a light microscope

Answer 109

• Cytoplasm and surface membrane divide

Answer 110

Capable of mitosis and cytokinesis • Cytokinesis starts from outside (‘nipping’ in the cell)

Answer 111

• Only meristem cells can divide this way • Do not have centrioles • Tubulin protein threads made in cytoplasm • Cytokinesis starts with the formation of a new cell plate where spindle ‘equator’ was • New cell membrane and wall laid down along this plate

Answer 112

Capable of mitosis and cytokinesis • Cytokinesis starts from outside (‘nipping’ in the cell)

Answer 113

• Only meristem cells can divide this way • Do not have centrioles • Tubulin protein threads made in cytoplasm • Cytokinesis starts with the formation of a new cell plate where spindle ‘equator’ was • New cell membrane and wall laid down along this plate

Answer 114

• All organisms need to produce genetically identical daughter cells • Mitosis is incredibly significant in many different settings Asexual Reproduction • Single-celled organisms divide to produce 2 daughter cells, that are separate organisms • E.g. Paramecium • Some multicellular organisms can produce offspring from parts of the parent plant • E.g. Hydra Growth • Multi-cellular organisms grow by producing new cells • Each new cell is genetically identical to parent cell Repair • Damaged cells need to be replaced • New cells need to perform the same function – so need to be identical Replacement • Red blood cells and skin cells are regularly replaced by new cells

Answer 115

Importance • Takes place in sex organs • Gametes produced here • Important to have genetically different gametes • This promotes genetic variation and allows for Natural Selection to take place. Importance • Takes place in sex organs • Gametes produced here • Important to have genetically different gametes • This promotes genetic variation and allows for Natural Selection to take place

Answer 116

is the process of cell division which produced four daughter cells which are not identical - they are different from each other. They have half the number of chromosomes as the parent cell, making them haploid. The process involves 2 nuclear divisions.

Answer 117

during prophase I, recombination occurs. This is what creates genetic diversity and involves chromatids swapping genes between themselves. Recombination ensures that the four daughter cells are not genetically identical.

Answer 118

• Chromosomes pair up • Pair of sister chromatids can be seen using a light microscope • Centrioles divides in 2, forming 2 daughter centrioles • Nuclear membrane breaks down

Answer 119

• Replicated chromosomes line up down middle of cell • Centrioles move to opposite poles of the cell, forming spindle • Chromosomes move to central region of spindle • Each becomes to spindle thread by its centromere

Answer 120

• Sister chromosomes pulled apart towards opposite ends of the cell • Sister chromatids separated as centromere splits • Each sister chromosomes effectively become individual chromosomes • Each one genetically unique • Spindle fibers shorten • This pulls sister chromatids further and further away from each other

Answer 121

• New nuclear envelope forms around each chromatid • Spindle breaks down and disappears • Chromatids uncoil and can no longer be seen under a light microscope

Answer 122

• Cytoplasm and surface membrane divide, creating four independent haploid daughter cells.

Answer 123

• Come from undifferentiated stem cells in bone marrow • Cells lose all organelles • Bi-concave shape • Maximizes oxygen carrying capacity • Maximizes space for haemoglobin

Answer 124

• Lobed nucleus • Granular cytoplasm contain lots of lysosomes • Potent enzymes in lysosomes specialized to kill microorganisms

Answer 125

• Cover external and internal surfaces • 2 types ○ Squamous cells ○ Ciliated cells

Answer 126

• Many mitochondria generate energy for movement • Sperm head contain specialized lysosomes to break down wall of egg • Small, long and thin to ease movement • Tail helps to propel the sperm • Diploid, in order to fulfill role as gamete

Answer 127

• Long shape maximizes light absorption • Contain large amounts of chlorophyll • Specialized for photosynthesis

Answer 128

• Hair like projections • Greatly increase surface area • Root able to absorb more water and minerals from soil

Answer 129

• Spiral thickenings of cellulose • When turgid, cell opens • When flaccid, stoma closes • Controlling passage of gases

Answer 130

a group of similar, specialised cells in a multicellular organism, which collectively are able to carry out a specific or several specific functions

Answer 131

group of tissues combined to form a distinct structure and which collectively might carry out a specific function which has an effect on the entire organism, e.g lungs, liver, heart

Answer 132

collection of organs with related and interdependent functions, e.g. cardiovascular and digestive systems.

Answer 133

• Found in lining of oral cavities, blood vessels, alveoli of lung, skin epithelium, and other places • Some variants of squamous epithelium are thin and lubricated to enable efficient gas exchange, e.g. in lung • Others are reinforced with keratin to improve resistance to friction and infection, e.g. the skin

Answer 134

Found in upper airway tract (trachea) and fallopian tubes • Cells constituting this type of epithelium are specialised with large number of cilia • They are able to waft material in a single direction, e.g. pathogens and mucus away from the lungs and towards the oral cavity, or ova away from the ovary and towards the uterus

Answer 135

• Cells in cartilage are specialised to resist pressure and provide lubrication for joint movement • Muscle • Cells in muscle (myocytes) can store and convert large amounts of energy • Phloem • Transports glucose and some other compounds up and down the plant stem - is highly specialised to ensure efficient movement of sugar to areas of the plant that need it most

Answer 136

• transports water up the stem of a plant • Highly specialised to transport water against the direction of the force of gravity

Answer 137

Forms cells of tissue in which they were formed

Answer 138

only forms one type of tissue

Answer 139

can develop into every cell in the bodty

Answer 140

• Red blood cells • Cell loose nucleus, mitochondria, Golgi apparatus and rough E.R • Packed full of hemoglobin • Shape changes, forming biconcave discs • This allows them to transport oxygen

Answer 141

• A type of white blood cell • Keep nucleus • Cytoplasm appears granular • Large number of lysosomes produced • This aids their role of ingesting invading microorganisms

Answer 142

the growing tip and the cambium. They are produced from meristem cells in the meristem, and also found in roots.

Answer 143

Bone marrow transplants • Already widely used • Bone marrow is major source of stem cells - especially stem cells capable of becoming blood cells ○ E.g. red blood cells and white blood cells • Used therapeutically to treat blood and immune disorders Drug research • In theory, stem cells can be used to grow artificial tissues • Drugs can then be tested on these tissues before being tested on human subjects Developmental biology • Stem cells provide insight into embryological development • Important information about how our organs are formed • Can explain why they fail, or have abnormalities • This information can be used to improve medicine Replacement of lost or damaged tissues • The dream’ of stem cell research • Mice have been treated for Type 1 diabetes mellitus with artificial pancreatic cells which secrete insulin normally • Stem cells could also be used to grow into specific organs or even limbs • They have the potential to treat many conditions

Module 2 Flashcards

(167 cards)