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Human Physiology > cells > Flashcards

cells Flashcards

1
Q

where does the word cell come from?

A

Hooke looked through slice of cork and called tiny hollow structures cells’

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2
Q

what does cell theory state?

and who proposed it?

A

Schwann

  1. all organisms made up of one or more cells
  2. cell = basic unit of life & smallest unit which has all characteristics of life
  3. all cells come from pre-existing ones (cell division)
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3
Q

what are the key characteristics of a prokaryotic cell?

A

(bacteria)
- lack distinct nucleus bounded by membrane
- lack membrane bound organelles e.g mitochondria
- plasmids - single circular DNA which is self replicating(used in cloning)

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4
Q

what are the key characteristics of a eukaryotic cell?

A

(animals, plants and fungi)

  • true nucleus separated from cytoplasm
  • cytoplasm contains membrane-bound organelles
  • mitochondria for respiration
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5
Q

how many cells do humans contain?

A

37.2 trillion

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6
Q

name 2 different types of cells and their jobs?

A 
osteoblasts (collagen)
skeletal myocytes (contractile proteins)
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7
Q

what is an organelle?

A

a specialised subunit within a cell that has a specific function

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8
Q

describe the cytosol?

A

(cytoplasm)

  • jelly-like material in which organelles float
  • consists mainly of water with dissolved substances such as amino acids in it
  • facilitates chemical reactions in the cell (metabolism)
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9
Q

describe a nucleus?

A

contains DNA, condensed and organised with proteins as chromatin

surrounded by nuclea envelope

contains nuclear pores, regulated by protein structure called nuclear pore complex, in which small molecules can pass through

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10
Q

describe the nucleolus?

A
  • spherical body of the nucleus that becomes bigger during protein synthesis (facilitates it)
  • makes rRNA
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11
Q

is the DNA of all cells in the body identical?

A

YES

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12
Q

how many genes do humans have?

A

25 000

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13
Q

describe the central dogma of molecular biology?

A

DNA replicated (DNA polymerase)
DNA transribed to RNA (RNA polymerase)
translated to protein (ribosome)

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14
Q

describe the structure and function of proteins?

A

most diverse and complex macromolecules of the cell

used for structure, fuction and info

made of linearly arranged amino acid residues (folded up with active regions)

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15
Q

describe oxidative phosphorylation?

A

oxidative phosphorylation in mitrochondria:

  • occurs in membrane bound electron transport system by using oxygen
  • enzymatic oxidation of cell metabolites is converted into ATP (using H+ gradient)
  • makes more than 80% of cellular ATP
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16
Q

what is the endosymbiotic theory?

A

mitochondria were primitive bacteria cells

mitochondria and eukaryotes became mutually beneficial so now permanent dependent relationship

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17
Q

describe the mitochondria?

A

oxidative phosphorylation

contain own circular DNA
zygote derives mtDNA from ovum

encode 37 genes

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18
Q

describe the endoplasmic reticulum?

A

forms an interconnected network of tubules, vesicles and cisternae within cells

site of protein synthesis and packaging o cell chemicals into transport vesicles

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19
Q

describe the smooth endoplasmic reticulum?

A

synthesis of membrane lipids and steroids

more prominen in adrenal cortex (secrete steroid hormones)

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20
Q

describe the rough endoplasmic reticulum?

A

protein synthesis

smooth ER but with ribosomes (translate mRNA into protein)

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21
Q

what is the golgi apparatus?

A

stocks of membrane-boundedcisternae located between ER and cell surface

processes the proteins synthesised in the RER (packaging and shipping)

vesicular enzymes modify and transport molecules in cells

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22
Q

describe ribosomes?

what do the APE sites do?

A

mRNA translation:

made of protein and rRNA

clamps over the tRNAs and mRNAs to make new protein

A site receives new tRNA
P site receives peptide-bearing tRNA after peptide bond formation
E site is where tRNAs exit

23
Q

what are the 4 main proteolytic systems?

A

lysosomes
proteasome
calpains
caspases

24
Q

what do lysosomes do?

A

created by addition of hydrolytic enzymes to endosomes from Golgi apparatus

bulk protein degredation (breakdown) by creating space where cell can digest molecules safely

25
Q

what does ubiquitin proteasome do?

A 
bulk protein breakdown
breakdown tagged (by ubiquitin) cellular proteins

essential part of normal cell turnover

26
Q

what do calpains do?

A

not bulk protein breakdown enzymes

more targeted and only breakdown limited amount of proteins

27
Q

what do caspases do?

A

involved in programmed cell death

more targeted and after stimulus

28
Q

what do peroxisomes do?

A

oxidation reactions (can break down fatty acids etc) which catalase can convert to H20

29
Q

what is the cytoskeleton and what does it function in?

A

extensive network of protein fibres

  1. mechanical strength
  2. locomotion
  3. chromosome separation in mitosis and meosis
  4. intracellular transport of organelles
  5. cellular signalling
30
Q

what does the cyctoskeleton contain?

A

microfilaments: resist bucling and filament fracture
microtubules: conveyer belts in cells
intermediate filaments : withstand mechanical stress

31
Q

what do focal adhesion complexes do?

A

anchor contractile filaments to cell membrane

enables contraction and movement

32
Q

what is the extracellular matric?

A

connective tissue

33
Q

what is endocytosis?

A

cell membrane invaginates and creates vesicle enclosing contents

34
Q

what is exocytosis?

A

membrane vesicle fuses with cell membrane, releases enclosed material to extracellular space
e.g collagen synthesis

35
Q

what are hydropilic and hydrophobi molecules referred o as?

A

hydrophilic - polar

hydrophobic - non-pola

36
Q

what is the fluid mosaic model of the cell membrane structure?

A

arrangement of amphiathic lipid molecules form a lipid bilayer

hydrophilic (inside) head groups separate hydrophobic (outside) tails from acqueous cytosolic and extracellular enviro

37
Q

what is the cell membrane of a cell?

A

selectively permeable

38
Q

what are the 2 processes referred to as passive transport?

A

simple diffusion

facilitated diffusion

39
Q

describe osmosis?

A

diffusion of water across a semi-permeable membrane from a region of its high concentration (low solute concentration) to a region of its low concentration (high solute concentration)

40
Q

what is the difference between a solvent and a solute?

A

solute - substance thta is put into the solvent

solvent - liquid which contains the solute

41
Q

what do hyper/hypo and isotonic fluids mean?

A

isotonic - fluid has same conc of solutes as fluid in cell so no net movemet of water

hypertonic - fluid has greater conc of solutes than fluid inside cell so water moves out of cell (cell atrophy)

hypotonic - fluid outside cell has lower conc of solutes than inside cell so water moves into cell (expansion)

42
Q

describe simple diffusion?

A

small, non-polar molecules move along conc gradient (high-low) across cell membrane

(to create a state of equilibrium either with 2 or 1 solute both inside and outside embrane)

43
Q

describe facilitated diffusion?

A

polar molecules and charged ions diffused in water but can’t simple diffuse due to hydrophobic nature of fatty acid tails of lipid bilayer (e.g glucose)

SO, integral membrane proteins form channels/carrier proteins
solute molecules bind with channel protein to pass across membrane without energy
direction determined by conc gradient (high-low)

44
Q

what is secondary active transport?

A

transport of molecules across cell membrane against conc gradient (low to high)

energy supplied by electrochemical gradient (no ATP) from pumping ions in/out of cell (co-transporters move down their concentration gradient whilst the other molecules are moving up their concentration gradient)

45
Q

what are symports and antiports in secondary active transport?

A

both referred to as ‘coupled transport’

symport - transported molecule and co-transported ion both move in same direction

antiport - transported molecules and co-transported ion move in opposite directions

46
Q

what is RMP?

and what is it regulated bby?

A

membrane potential charge (more negative than posiitve charges inside the cell and more posiitve than negative charges outside the cell)

regulated by selective permeability to organic molecules and ions e.g more permeable to + than Na+ ions

47
Q

what is heart failure associated with?

A

reduced myocardial Na+-K+-ATPase content

48
Q

describe the Na+/K+ pump?

A
  1. 3 Na+ molecules bind to the carrier protein
  2. phosphate group attaches (as released by split ATP molecule) causing carrier protein to change conformation
  3. expels Na+ to outside and binds to 2 K+
  4. triggers release of phosphate group which restores orginal conformation
  5. K+ is released into cell and Na+ sites are receptive again
49
Q

what are signalling molecules?

and some examples of responses to these signals?

A

molecules that enable cells to receive info and communicate with other cells

hormone production
activation of enzymes within the cell

50
Q

when is the balance posiitve between protein synthesis and breakdown?

A

when there is more protein synthesis than breakdown

51
Q

what are the slow and fast routes of signals change behviour of cell?

A

fast: extracellular signal molecule - cell surface receptor protein - intracellular signaling pathway - altered protein function - altered cytoplasmic machinery - altered cell behaviour
slow: signal - receptor protein - dna to rna in nucleus - altered protein synthesis - altered cytoplasmic machinery - altered cell behaviour

52
Q

what will signal processing in a cell involve?

A

series of molecular steps called a signal transduction pathway

53
Q

what is meant by polar and non-polar molecules?

A

polar - covalet bond pair of electrons not shared equally between atoms

non-polar - covalent bond where do share pair of electrons equally

Human Physiology (9 decks)

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