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MCD > Cells > Flashcards

Cells Flashcards

1
Q

What units are used to measure cell size?

A

Eyes: m-mm
Light: mm-μm
Electron: 10μm-10nm

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2
Q

Describe how cells assemble to form tissue?

A
  1. stem cells divide to form colonies
  2. specialisation–> particular genes switched on/off
  3. polarity established
  4. enzymes produced and induce formation of cytoskeleton, organelles, secretion and absorption
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3
Q

Recall the organelles in a cell

A

nucleus, nucleolus, nuclear envelope, mitochondrion, rough endoplasmic reticulum, smooth endoplasmic reticulum, ribosomes, golgi apparatus, secretory granule, plasma membrane

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4
Q

What is chromatin? and what’s its function?

A

Combination of DNA and proteins that make up the contents of nucleus
functions: package DNA into a smaller volume, strengthen DNA to allow mitosis, protection and control gene expression

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5
Q

What are nuclei? and describe them

A

genetic info bound to chromatin
Describe: nuclear envelope= double membrane is perforated with nuclear pores
outer membrane associated with ER and inner membrane with the nuclear lamina

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6
Q

What’s the nucleolus?Function?

A

non-membrane bound structure composed of proteins and nucleic acids.
Function: to transcribe ribosomal RNA and assemble it

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7
Q

Which cell types don’t contain a nucleus?

A

erythrocytes and thrombocytes

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8
Q

What are ribosomes?

A

Protein synthesis occurs here using mRNA template.
Eukaryotes 80s–> 60s +40s
prokaryotes 70s–> 50s +30s

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9
Q

Describe the RER and SER

A

RER: granular due to proteins attached to surface and has a flattened like appearance
-involved in packaging proteins to be sent to the golgi
SER: tubular structure where lipid synthesis occurs and stores and releases ca2+ ions

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10
Q

Describe the golgi apparatus and its function

A

Flattened membranous sacs, contains membrane enclosed vesicles.
Function: sorting, modification of proteins, transportation

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11
Q

What are endosomes?

A

membrane bound that lie between the golgi and membrane
certain vesicles pinch off from membrane and fuse with endosome
involved in sorting, modifying and directing cellular traffic

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12
Q

Describe the mitochondria

A

Oxidative phosphorylation occurs here-ATP synthesis
Formed by double membrane–> outer membrane is continuous whereas the inner membrane is folded into cristae, extending into the matrix
Note: beta- oxidation and synths of lipids i.e oestrogen and progesterone

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13
Q

What are peroxisomes?

A

Break down H202 formed from o2 being used to remove H2 from organic substances
-also needed for lipolysis of f.a into 2-c fragments(to generate ATP)

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14
Q

List the predominant molecules in the cytosol?

A

soluble proteins, ions( ca2+, na+, k+), sugars, nucleotides(ATP, cAMP, GTP), a.a, mRNA, tRNA

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15
Q

What processes within cells require energy and specialised motor proteins?

A

hydrolysis of ATP, transport of molecules against conc, gradient, movement of organelles, ruffling(movement of cell membranes), growth and migration, cell division, muscle contraction

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16
Q

What are the diff. between eukaryotes and prokaryotes?

A

p- no organelles; e- organelles
p- single haploid; e- haploid/diploid
p-poorly defined cytoskeleton; e-better cytoskeleton
p- have cell walls made of peptidoglycan

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17
Q

Describe the mutation rates of humans and bacteria

A

bacteria and humans have the same mutation rate 10^-8

-but generation time is h-26years and b-min/hrs

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18
Q

Describe the distinguishing features of the diff types of pathogens

A

virus: obligate parasites which takes over host synthetic machinery in order to replicate
bacteria: divide by binary fission-bacillus, coccus and spirillus
fungi: single celled eukaryotes that can either exist as yeasts or moulds
protozoa: single celled eukaryotes
Helminths: parasitic multicellular organisms e.g. flatworms, roundworms and tapeworms

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19
Q

Give e.g. of virus, bacteria, fungi, protozoa, helminths

A 
virus- HIV/influenza, SARS
bacteria-neiserra, shigella
fungi- candida albicans
protozoa- plasmodium spp.
helminths- schistosoma spp
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20
Q

key features of erythrocytes?

A
  • transport o2 and co2
  • biconcave shape
  • no organelles
  • life span of 120 days (removed by macrophages)
  • molecules on surface confer blood group
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21
Q

how is the shape of RBC adapted for function?

A

-biconcave shape maximises surface area and thus increasing the rate of diffusion

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22
Q

where does erythropoiesis occur?

A

bone marrow

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23
Q

describe the regulation of erythropoiesis

A
  • erythropoiesis is controlled by the kidney
  • when delivery of o2 to renal cells falls below normal
  • kidney releases erythropoietin
  • bone marrow responds by increasing RBC production
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24
Q

why may the delivery of o2 to renal cells fall below normal?

A
  • high altitudes (compensated polycythaemia), where partial pressures of o2 in lungs and blood are reduced
  • anaemia–> low levels of haemoglobin in the blood
  • lung/heart disease
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25
Q

describe the use and abuse of erythropoietin?

A
  • chronic renal failure may cause anaemia, treated with en

- synthetic en used in athletes to improve performance

26
Q

describe the stages of erythropoiesis

A
  • pluripotent stem cells divide into erythroid stem cells
  • erythroids divide and mature, synthesising Hb and turning into normoblasts
  • nuclear material removal = reticulocyte
  • once all organelles have been removed, erythrocyte is formed
27
Q

Describe how an erythrocyte is destroyed/recycled in the body

A
  • RBC destroyed after 120 days
  • phagocytic cells of the reticule-endothelial system degrade the Hb
  • iron and global molecules are recycled
  • porphyrin ring converted into bilirubin, metabolised by the liver and excreted as bile
28
Q

Describe the key features of Hb

A

4 subunits- each polypeptide with haem group(porphyrin ring and ferrous iron)

  • each fe2+ binds to one o2
  • oxidised for-fe3+- can’t carry 02
  • carries co2 in conjunction with carbonic anhydrase
  • 14-16 gdl males and 12-14gdl females
29
Q

describe cooperative bonding

A
  • Hb has a low affinity for 02 due to conformational shape of globin
  • o2 binding breaks conformation and opens up structure
  • 2nd o2 binds more easily and so on
30
Q

whats the normal haematocrit levels?

A
  • 0.4-0.54 males

- 0.35-0.47 females

31
Q

what is the normal red cell count?

A
  1. 4x10^12 males

4. 8x10^12 females

32
Q

define anaemia

A

low blood Hb concentration

33
Q

describe the diff. types of Hb

A
  • Microcytic (small MCV)- failure of Hb synthesis. Fe deficiency
  • normacytic-acute blood loss
  • macrocytic (large MCV)- deficiency of B12 and folic acid
  • sickle cell anaemia–> Hb mutation , distorted erythrocytes destroyed. heterozygou- malaria resistant
  • polycythaemia
34
Q

why may iron deficiency occur in microcytic anaemia?

A

-menstruation, GI tract lesions/cancers, parasitic infection

35
Q

How may B12/folate deficiency arise?

A 
folic acid deficiency may arise due to pregnancy, cancer or diet
vit B12(needed for folic acid actions) deficiency caused by autoimmune disease which destroy B12 uptake in gut; vegans
36
Q

what are the diff. types of leukocytes?

A

polymorphonuclear granulocytes:

  • neutrophils (phagocytic, abundant)
  • eosinophils(allergy, parasitic worms)
  • basophils (inflammatory)
  • lymphocytes(antibody producing)
  • monocytes (phagocytic, reticuloendothelial)
37
Q

Describe the key features of granulocytes

A

-first on scene, segmented nucleus, full of cytoplasmic granules, adhere to blood vessels in infected area and migrate to tissue; engulf, kill and digest microorganisms; release inflammatory mediators: toxic o2 products, digestive enzymes, vasodilators, chemotaxis

38
Q

Describe the key features of B-lymphocytes

A
  • mature in bone marrow
  • humoral(anti-body mediated) immunity
  • foreign antigen causes immunoglobulin production
  • antibody-antigen reactions: assist phagocytosis by precipitation; agglutination; opsonisation; neutralisation
39
Q

What’s the diff. between primary and secondary response?

A

1-first exposure, antibodies appear after latent period, peak then fall
2-greater, quicker, longer response due to memory cells

40
Q

What is passive immunity?

A

inject immunoglobulins(vaccine) or cross placenta

41
Q

Describe the key features of T lymphocytes

A
  • thymus dependant(derive in the bone marrow and migrate to the thymus)
  • cellular immunity
  • circulate-> foreign antigen-> blast transformation-> progeny with receptors for antigen
  • activated t lymphocytes-> chemotaxins, interferons
42
Q

What are the sub groups of T cells?

A
  • cytotoxic T cells-CD8+ (killer cells)

- helper T cells- CD4+ (secrete cytokines to help CD8+ & CD4+)

43
Q

What are the key features of monocytes?

A
  • appear after granulocytes
  • large, single horse-shoe nucleus
  • in tissue becomes macrophages
  • engulf micro-organisms, tissue debris and dead polymorphs
  • secrete inflammatory mediators and stimulate angiogenesis
  • ingest and store antigens, present modified antigen to lymphocytes
44
Q

What is the normal leukocyte count in order of abundance?

A
  1. neutrophils, 2. lymphocytes, 3. monocytes, 4. eosinophils, 5. basophils
45
Q

describe the features of thrombocytes

A
  • derived from megakaryocytes

- life span 8-10 days

46
Q

what is the role of platelets and describe the mechanism?

A
  • role: to prevent bleeding–> haemostasis
  • which involves:
  • vascular spasms–> reduce arrest blood flow
  • platelet plugging- adhesion to exposed collagen in wound, release ADP and thromboxane A2 from cycloxygenase; increases platelet stickiness(platelet aggregation). occluding opening temporarily. Prostacyclin and nitric oxide inhibits adherence.
  • clotting/coagulation- clotting factors initiate coagulation cascade. Thrombin turns fibrinogen to fibrin.
47
Q

Describe how aspirin interferes with haemostasis

A

Aspirin inhibits cyclooxygenase in the pathways that generate prostaglandins and thromboxanes.
As thromboxane A2 is important for platelet aggregation, aspirin limits this and thus limits coagulation.

48
Q

What is blood plasma?

A

fluid component of the blood, carrier, organic/inorganic substances dissolved in water

49
Q

Name the plasma proteins and their functions

A

Albumin-colloid osmotic pressure of blood plasma, non-specific transport protein
Globulins-transport proteins, clotting factors
fibrinogen- converted into fibrin during clotting

50
Q

What is serum

A

Plasma with fibrinogens and other proteins removed due to clotting

51
Q

What are the structures phospholipids form when suspended in water?

A

to avoid the water the hydrophobic tails pack together. thus they may form: micelles/droplets; bilayer/liposomes

52
Q

Describe the structure of phosphatidylcholine

A
  • A glycerol molecule attached to 2 f.a. and a phosphate group attached to choline
  • a cis double bond in f.a chain can make it less densely packed in a bilayer
53
Q

what are the key properties of the plasma membrane?

A
  • selective permeability–> impermeable to macromolecules, permeable to nutrients
  • transfer of information
54
Q

can lipids switch sides in the bilayer?

A

this process is called ‘flip flop’ occurs less than once a month for any individual molecule

55
Q

what are lipid bilayers not permeable to?

A
  • cations–> k+, na+, ca2+
  • anions–> cl-, HCO3-
  • macromolecules= proteins, RNA
  • glucose
56
Q

List the key functions of membrane proteins?

A
  • transport(fac. diff)
  • receptor (hormones)
  • cell recognition and adhesion
  • electron carrier
57
Q

name the 2 types of coupled transporters?

A
  • symporters

- antiporters

58
Q

what is the picket and fence model of membrane proteins?

A
  • membrane proteins are not stationary, they are free to move within small compartments
  • compartments made from actin cytoskeleton
  • some proteins however are anchored to the membrane=picket model.
59
Q

Explain how glucose enters the cell?

A
  1. glucose=hydrophilic molecule and is impermeable
  2. glucose binds to a symporter which ‘flip flops’ the glucose into the cell
  3. facilitated by the na+ gradient (high na+ outside the cell)
60
Q

what’s the main function of the k+/na+ pump?

A

-the sodium-potassium pump maintains the osmotic balance by exporting sodium out of the cell
-import 2k+/ export 3na+
–> driven by phosphorylation of aspartyl residue
hydrolysis of aspartyl phosphate
results in the conformational change of the protein pump

61
Q

describe the movement of k+ through the cell membrane

A
  • k+ moves into the cell via the sodium-potassium pump

- however due to resulting high conc of k+ inside the cell, it leaks through the k+ channels

MCD (2 decks)

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