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MCD Year 1 > Practicals > Flashcards

Practicals Flashcards

1
Q

What is the Beer-Lambert law?

A 
A = λ x b x c
Absorbance = wavelength x path length x concentration
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2
Q

What is spectrophotometry?

A

The measure of light absorbed by a solution compared to black; expressed as a logarithmic number known as absorbance or optical density

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3
Q

What is absorbance? What is the formula to calculate it?

A

Absorbance is the fraction of incidence light absorbed by a measured solution
A= log10(light transmitted through blank solution/ light transmitted through test solution)

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4
Q

Where will maximum absorption of orange, green and purple solutions occur in the spectrum?

A

Orange- Max absorption in the blue region
Green- Max absorption in the red region
Purple- Max absorption in the yellow region

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5
Q

What are the differences between oxyhaemoglobin, deoxyhaemoglobin and methaemoglobin?

A

Oxyhaemoglobin- Oxygen loaded form of haemoglobin
Deoxyhaemoglobin- Form of haemoglobin without oxygen
Methaemoglobin- Haemoglobin with oxidised iron (Fe2+>Fe3+). This state gives blood it’s brown colour when it dries

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6
Q

What is electrophoresis?

A

Separates macromolecules based on their size. A negative charge is applied so proteins move towards the anode

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7
Q

Why can HbA and HbS be separated using electrophoresis?

A

HbA (normal) HbS (sickle cell)
HbS- point mutation of 1 amino acid on the β chain (glutamate (-) replaced by valine (hydrophobic uncharged)
HbA will migrate further towards the anode due to increased negative charge

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8
Q

What is the purpose of SDS in electrophoresis buffer?

A

SDS neutralises the charge on proteins making them negatively charged (allows comparison of size)

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9
Q

What is gel electrophoresis?

A

Uses a porous gel to compare the size of proteins. SDS neutralises the charge, and the pores allow smaller proteins to migrate more quickly towards the anode

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10
Q

What is the H&E stain? How does it work?

A

Haematoxylin and eosin stain.
Haematoxylin is a purple/blue component that binds to acidic components of cells (in particular it binds to DNA and shows up the nucleus)
Eosin is a pinkish stain that binds protein components, particularly in the cytoplasm

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11
Q

How do you conduct a red cell count?

A

Using a microscope and Neubauer haemocytometer slide
Blood diluted 200 times and placed on the slide. (5μL added to 995μL HAYEM’s solution)
Normally 500 RBC for each WBC so error for counting WBC is negligable

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12
Q

How do you measure haematocrit?

A

Using a centrifuge and measuring packed red cells. Work out percentage of packed red cells from total volume

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13
Q

How do you measure haemoglobin concentration of a blood sample using an optical density method?

A

Based on releasing the haemoglobin from the red cells and converting it to the stable derivative cyanmethaemoglobin using modified Drabkin’s Cyanide-ferricanide solution.
Spectrophotometry of the diluted pigment is conducted. If a standard measurement is also taken the unknown haemoglobin concentration can be caluculated

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14
Q

What is the normal range and mean red blood cell count for males and females?

A

Male: 4.3-5.9 (mean-5.1)x10^12/L
Female: 3.7-5.3 (mean-4.5)x10^12/L

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15
Q

What is the normal range and mean haematocrit for males and females?

A

Male: 40-52% (mean-46%)
Female: 35-47% (mean-41%)

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16
Q

What is the normal range and mean haemoglobin level for males and females?

A

Male: 13.3-17.7g/dl (mean-15.5)
Female: 11.7-15.7g/dl (mean-13.7)

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17
Q

What is the formula for mean cell volume? What is the normal range and mean?

A

MCV (fl)=haematocrit/RBC count x 100

Range= 80-100 (90)fl

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18
Q

What is the formula for mean cell haemoglobin? What is the normal range and mean?

A

MCH (pg)= (Hbx10)/RBC count

Range= 26-34 (30)pg

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19
Q

What is the formula for mean cell haemoglobin concentration? What is the normal range and mean?

A

MCHC (g/dl)= (Hbx100)/Hct

Range= 32-36 (34)g/dl

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20
Q

What is anaemia? What measurements give an indicator to the type of anaemia a patient has?

A

Anaemia: Low blood haemoglobin concentration. Blood can’t carry enough oxygen to meet the body’s needs. Either not enough erythrocytes or not enough haemoglobin in erythrocytes.
Indicators of anaemia- MCV, MCH, MCHC
MCV= small (microcytic), normal (normocytic), large (macrocytic)

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21
Q

What is Vinblastine? What does it do?

A

Used as part of chemotherapy treatment of certain cancers; dose carefully regulated so it affects the most rapidly dividing cells
It disrupts the microtubule assembly and proper formation of the mitotic spindle and kinetochore- particularly important for the separation of chromosomes during anaphase of mitosis

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22
Q

What are dehydrogenases used for?

A

The oxidise their substrate with a parallel reduction of the cofactor NAD+→NADH. They can alternatively catalyse the reverse reaction
L-malate+NAD+→oxaloacetate+NADH (catalysed by malate dehydrogenase)

23
Q

Why are NAD+ and NADH used in enzyme assays?

A

Enzymes which catalyse reactions involving NAD+ and NADH can be assessed using spectrophotometry to measure the rate of reaction. This is because NADH absorbs light at 340nm, whereas NAD+ does not.

24
Q

What is Km? What effect does competitive inhibition have on Km? What about non-competitive inhibition?

A

Km is a measurement affinity. It is the substrate concentration at which the rate of reaction is half of Vmax.
Competitive inhibition lowers the enzymes affinity for it’s substrate so Km increases.
Non-competitive inhibition will reduce Km. The initial rate of reaction will remain the same because at very low substrate concentration there is little enzyme-substrate complex for the inhibitor to bind, so negligible effects.

25
Q

What is Vmax? What effect does competitive inhibition have on Vmax>

A

Vmax is the maximum rate at which the enzyme can work in the presence of infinite substrate
Competitive inhibition does not affect Vmax. This means competitive inhibition can be overcome by increasing substrate concentration
Non-competitive inhibition reduced Vmax because the total ‘pool’ of enzymes available to react has reduced

26
Q

What is non-disjunation?

A

A failure of homologous chromosomes or sister chromatids from separating properly during cell division

27
Q

What is the karyotype of Down syndrome?

A

47, XX+21

28
Q

What is the karyotype of Klinefelter’s syndrome?

A

47, XXY (phenotypically male)

29
Q

What is the karyotype of trisome 13?

A

47, XY+13 (die after birth)

30
Q

What colour do Gram-positive and negative bacteria stain?

A

Gram positive: purple/blue

Gram negative: pink/red

31
Q

What does the use of MacConkey agar show?

A

Pink plate shows if bacteria are lactose fermenters

Colourless/yellow plate shows bacteria are lactose non-fermenters

32
Q

What does the use of blood agar show?

A

Some pathogens show haemolysins which haemolyse the blood in the agar.
α= very small zone of haemolysis and colonies can appear green
β= large clear zone of haemolysis around the bacterial colonies
γ= no haemolysis

33
Q

What is the use of the oxidase test in microbiology?

A

To determine is an organism produces the enzyme cytochrome c oxidase.
Oxidase positive bacteria are aerobic and can use oxygen as an electron acceptor during respiration
The test strip contains tetramethyl-p-phenylenediamine (TMPD) which is a redox indicator and acts as an artificial electron acceptor in this test.
Oxidase positive- dark blue/purple (oxidised)
Oxidase negative- colourless (reduced)

34
Q

What is the use of the catalase test in microbiology?

A

Hydrogen peroxidase is a toxic end-product of aerobic breakdown of sugars.
Catalase is a common enzyme found in many living organisms and can break down hydrogen peroxide into gaseous oxygen and water
Bubbles show catalase positive

35
Q

What are the two methods for measuring antibiotic sensitivity?

A

1) Measuring the zone of inhibition surroudning antibiotic discs on a bacterial plate
2) Using the E-test to measure the minimum inhibitory concentration (MIC) for a specific antibiotic

36
Q

What is the histological structure of the intestinal epithelium?

A

Simple columnar absorptive epithelium with goblet cells
Crypts- glands
Paneth cells- secretory cells

37
Q

What is the histological structure of the mesentery epithelium?

A

Simple squamous epithelium
(Thin layer of tissue that attaches to parts of the intestine to the rest of the body, allows folding and connection as well as movement in peristalsis)

38
Q

What is the histological structure of the oesophagus?

A

Stratified squamous epithelium

Makes it resistant to damage

39
Q

What is the histological structure of the skin?

A

Stratified squamous epithelium

Protection strategy. Has to be waterproof so becomes keratinized, and absorbs oily secretions to become waterproof

40
Q

What is the histological structure of the trachea?

A

Pseudostratified columnar ciliated epithelium

Includes rings of cartilage to hold the airway open. Has cilia and goblet cells

41
Q

What is the histological structure of the urinary system?

A

Both stratified and pseudostratified (transitional)

Specialised to be highly impermeable to urine and to be able to stretch as the bladder fills

42
Q

What are the three types of extracellular matrix components?

A

1) Fibrillar structures that provide strength against tensile forces applied to tissue (collagen, elastin and fibrillin)
2) Viscous liquid component which provides resistance to compressive forces applied to the tissue (negatively charged polysaccharides which bind water and Na+ ions and are mainly glycosaminoglycans or proteoglycans. Liquid component also provides solvent in which oxygen, nutrients, waste products and small signalling molecules diffuse)
3) Other molecules whose main function is in binding to cells via specific cell surface receptors and mediating their attachment to the ECM (fibronectin)

43
Q

How does tendon receive nutrients and oxygen?

A

Blood vessels passing through the connective tissue to supply it and the adjacent structures with O2 and nutrients

44
Q

How does bone receive nutrients and oxygen?

A

Mineral prevents free diffusion, and small channels (canaliculi) provide a pathway for diffusion of O2 and nutrients from the blood vessels to the osteocytes

45
Q

What is the structure and composition of adipose tissue? Where is it found in the body?

A

Structure: A loose fibrous connective tissue packed with adipocytes that are specialized for storage of triglycerides
Function: Insulation, protection and storage
Forms a thick layer under the skin, around the kidneys and in the buttocks

46
Q

What is the structure and composition of loose connective tissue? Where is it found in the body?

A

Fibrous and cellular components. Thick and thin fibres with fibroblasts and migratory leucocytes (macrophages and mast cells)
e.g. areolar tissue, reticular tissue and adipose tissue

47
Q

What is the structure and composition of dense irregular connective tissue? Where is it found in the body?

A

Fibroblasts are the support cell responsible for synthesizing the ECM. Irregular because strength required in all directions. Can also contain adipocytes
e.g. in the skin

48
Q

What is the structure and composition of dense regular connective tissue? Where is it found in the body?

A

Fibroblasts are the support cell responsible for synthesizing the ECM. Regular because strength required in one direction. Collagen and other fibres are aligned in parallel
e.g. tendons and ligaments

49
Q

What is the structure and composition of cartilage? Where is it found in the body?

A

Secreted by chondrocytes which lie in regions called lacunae. Nutrients reach chondrocytes by diffusion through the cartilage. Dense network of collagen fibres and glycosaminoglycans rich in sulphated sugars
e.g. Trachea
Fibrocartilage- thicker collagen fibres e.g. intevertebral discs
Elastic cartilage- contains additional elastic fibres to provide pliability and resilience e.g. in external ear

50
Q

What is the structure and composition of bone?

A

ECM becomes mineralised with calcium phosphate crystals to provide great compressive strength. Relatively solid region around the edge of the bone shaft is compact bone or dense bone with osteocytes in lacunae. Also has cavities containing blood vessels.
Central part of a bone has spaces between the bone tissue (spongey /cancellous bone)

51
Q

What is the structure and composition of striated muscle? Where is it found in the body?

A

Skeletal and cardiac
Striped appearance due to repeating sarcomeres that make up the contractile apparatus. Muscle is made up of bundles of myofibrils, each containing multiple nuclei arranged around their perimeter.
Attached around the edge of each myofibril is an ECM containing collagen fibres that are ultimately continuous with those of the tendons or bones on which the muscle acts.
Cardiac muscle cells remain separated and are connected end to end by intercalated discs. Forms conducting heart system- skeletal muscle controlled by innervation from motor neurons

52
Q

What is the structure and composition of smooth muscle? Where is it found in the body?

A

Associated with organs and vessels; controlled by the autonomic nervous system.
e.g. wall of the bladder

53
Q

How is the strength of the skeleton maintained?

A

New bone laid down by osteoblasts (build) and bone is resorbed by osteoclasts (clear). Two processes are in balance but can be adjusted to strengthen bone in mechanical stress or to heal wounds.
Mineral component of bone can act as a store for Ca2+ and phosphate. Activities are under hormonal control from calcitonin and parathyroid hormone to maintain normal blood concentration of these ions.
Bone is lined in a dense layer of connective tissue- periosteum

54
Q

What is endochondrial ossification?

A

Cartilage precursors in the foetus are converted to bone

MCD Year 1 (10 decks)

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