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First year B > L8-14: cell biology > Flashcards

L8-14: cell biology Flashcards

1
Q

Name the 2 main categories

organisms are classified as

A

Prokaryotes and Eukaryotes

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2
Q

Prokaryotes

A
  • Example = Bacterium
  • No membrane bound organelles (nucleus, chloroplasts or mitochondria)
  • Nucleoid: region where DNA is located
  • Ribosome (small)
  • Plasma membrane: enclosing cytoplasm
  • Cell wall: rigid structure outside of plasma membrane
  • Glycocalyx: outer coating consisting of slime layer
  • Flagella: locomotion organell
  • Single circular chromosomes
  • circular plasmids in the cytoplasm
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3
Q

Eukaryotes

A
  • Example = plant cells, animal cells and (yeast cells)
  • Have membrane bound organelles such as nucleus and mitochondria (also chloroplasts *but only for plant cells)
  • Nucleus
  • Centrosome (animals)
  • Ribosome (large)
  • plasma membrane
  • Endoplasmic Reticulum
  • Golgi complex
  • Cytoskeleton
  • Mitochondria
  • linear chromosomes
  • No plasmids (apart from yeast)
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4
Q

Name features common to all cells

A
  • plasma membrane
  • chromosomes
  • ribosomes
  • cytosol
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5
Q

Eukaryote: nucleus

A
  1. Houses the genetic material

2. Coordinates cell growth, protein synthesis and cell division.

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6
Q

Eukaryote: Centrosome

A
  • Present in cytoplasm of animal cells
  • Region where cells microtubules are initiated
  • Functions as a microtubule organising centre
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7
Q

Eukaryote: Endoplasmic Reticulum

A
  • Rough and smooth ribosomes-studded regions

- Active in synthesis of membrane and other synthetic metabolic processes.

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8
Q

Eukaryote: Golgi complex

A

Active in synthesis, secretion, modification and sorting of other cell products

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9
Q

Eukaryote: Cytoskeleton

A

Functions in cell movement and reinforces cells shape.

  • Microfilaments
  • Intermediate filaments
  • Microtubules
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10
Q

Eukaryote, Cytoskeleton: Microfilaments

A

-Protein = actin

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11
Q

Eukaryote, Cytoskeleton: Intermediate filaments

A

cell movement:
can rapidly change length by pushing in/out pseudopodia

– cell division

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12
Q

Eukaryote, Cytoskeleton: Microtubules

A
  • Protein = tubulin
  • Microtubules mediate intracellular movement of organelles (including vesicles)
  • Motor molecules attach to microtubules as cargo:

kinesin moves to+end(periphery)
cytoplasmic dynein moves to–end(nucleus)

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13
Q

Eukaryote: Mitochondria

A

Act as power-generating centres for the cell (synthesise ATP)

-Cristae = folded inner membrane

-Inner membrane:
matrix
inner membrane space

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14
Q

Eukaryote: Chloroplasts

A

Third internal membrane structure, the thylakoid membrane – contains
chlorophyll and the electron transport chains

-Contains the Stroma and Granum

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15
Q

Eukaryotes: Cell junctions

A
  • Regulates the movement of water and solutes between cells
  • An anchoring junction that anchors one cell to another
  • Allows chemical communication between cells
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16
Q

Functions of the Plasma membrane

A
  • Defines the cell boundary
  • Controls traffic into and out of the cell
  • Provides a controlled internal environment
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17
Q

Definition of the Plasma membrane

A

The cell membrane is made from a bilayer of protein and phospholipid molecules forming a fluid mosaic structure. The molecules hydrophilic heads face outwards and their hydrophobic heads face eachother in the middile of the bilayer.

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18
Q

Describe how the plasma membrane controls traffic in and out of the cell

A

-Passive diffusion
Substance moves down a concentration gradient, thereby releasing energy

-Active transport

Substances move up a concentration gradient, requires energy from metabolic processes

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19
Q

Diffusion

A

Allows lipid-soluble materials can cross the membrane without transport mechanism

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20
Q

Osmosis

A

The diffusion of free water across a selectively permeable membrane.

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21
Q

Osmosis: Hypertonic solution

A

higher extracellular solute concentration than cytoplasm, causes water loss from cell

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22
Q

Osmosis: Hypotonic solution

A

lower extracellular solute concentration than cytoplasm, causes water gain to cell

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23
Q

Osmosis: Isotonic solution:

A

same extracellular solute concentration as cytoplasm, no water loss or gain

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24
Q

Facilitated diffusion

A

The passage of molecules or ions down a concentration gradient across a membrane with the assistance of specific transmembrane transport proteins, requires NO energy expenditure.

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25
Q

Transport proteins

A
  • Pores
  • Pumps
  • Enzymes
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26
Q

Transport proteins: Pores

A

Pores are channels which can be found at the centre of some proteins. Pores allow molecules with the appropriate size and charge to pass through the membrane by diffusion. No energy is required since molecules move from higher to lower concentration gradients.

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27
Q

Transport proteins: Pumps

A

Protein pumps move molecules across the membrane against the concentration gradient; this process requires energy from ATP produced during active transport.

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28
Q

Transport proteins: Enzymes

A

Enzymes which catalyse some metabolic processes can be found within the plasmid membrane of some proteins.

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29
Q

Symport

A

-Two molecules move in SAME direction

One substance moves down its concentration gradient through a transporter protein
This releases enough energy to …
Drive another substance up its concentration gradient through the same transporter,

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30
Q

Antiport

A

-Two molecules move but in OPPOSITE direction

One substance moves down its concentration gradient through a transporter protein
This releases enough energy to …
Drive another substance up its concentration gradient through the same transporter,

31
Q

Active transport

A

The movement of a substance across a cell membrane against its concentration gradient, mediated by specific transport proteins and requires an expenditure of energy (provided by ATP).

32
Q

Exocytosis

A

The cellular secretion of biological molecules by the fusion of vesicles containing them within the plasma membrane.

33
Q

Endocytosis

A

The cellular uptake of biological molecules via the formation of vesicles from the plasma membrane.

34
Q

Signal transduction pathways

A

A series of steps linking a mechanical, chemical and electrical stimulus to specific cellular response.

35
Q

Requirement for cell communication

A

Plasma membrane is impermeable to most molecules therefore require signal transduction pathways.

36
Q

Hormones

A

chemical recreated by specialised cells, travel around the body and act on specific target cells in other parts of the organism, changing the target cells functioning

37
Q

3 stages of cell signalling

A

1-Reception
2-Transduction
3-Response

38
Q

Cells signalling: Reception

A

target cell detects that a signal cell bound to a receptor protein

39
Q

Cell signalling: Transduction

A

Signal cell changes the receptor in someway so that it brings about a specific cellular response

40
Q

Cell signalling: Response

A

Cellular responcse occurs

41
Q

Describe the Hydrolysis of GTP

A

Hydrolysis of GTP is mediated by the GTPase enzyme, producing GDP, Inorganic phosphate (Pi) and energy.
Active GTPases can control signalling cascades.
GEF proteins mediated the exchange of GDP for GTP, switching on the GTPase
GAP enzymes catalyse the hydrolysis of GTP, switching off the GTPase

42
Q

Outcomes of cell signalling

A

-Short-term changes are usually mediated by changing an enzymes activity
•-Long-term changes are usually mediated by altering gene expression

Both can be made by altering cytoskeletal proteins

43
Q

Plasma membrane receptors

A
  • G protein-coupled receptors
  • Receptor tyrosine kinases
  • Ion channel receptors
44
Q

Intracellular receptor:

A

-Steroid receptor

45
Q

G-Protein Coupled Receptors (GPCR)

A

A signal receptor protein in the plasma membrane that responds to the binding of a signalling molecule by activating a G-protein

Function:

  • Neuronal communication
  • Endocrine signalling
  • Embryonic development
  • Sensory reception
46
Q

Tyrosine Kinase Receptors (RTK)

A

A signal receptor protein in the plasma membrane that responds to the binding of a signalling molecule by activating kinase-protein

Functions

  • Cell growth
  • Cell differentiation
  • Cell survival
47
Q

Ion channel receptors

A

A signal receptor protein in the plasma membrane that responds to the binding of a signalling molecule by opening or closing channels

Important function in the nervous system

48
Q

Intracellular Receptors

A
  • Steroid hormones and Thyroid hormones bind to intracellular receptors, rather than receptors on the plasma membrane.
  • The hormone must be hydrophobic so that it can cross the plasma membrane
  • The hormone-receptor complex often acts as a transcription factor, regulating gene expression
49
Q

Positive feedback loop

A

A component of the signal transduction pathway stimulates an earlier component, promoting further signalling.

50
Q

Negative feedback loop

A

A component of the signal transduction pathway inhibits an earlier component, inhibiting further signalling.

51
Q

Termination of signalling

A
  1. Decrease the affinity of the ligand for the receptor, causing the ligand to leave the receptor
  2. Inactivate the receptor
  3. Remove the receptor from the membrane (endocytosis)
  4. Inactivate the signalling proteins
52
Q

Metabolic pathway

A

They are intergrated and controlled pathways of enzyme-catalysed reactions within a cell.

53
Q

Anabolic reactions

A

Reactions which build up large molecules from small molecules and require energy

54
Q

Example of anabolic reactions

A
  • Protein synthesis

- Photosynthesis

55
Q

Catabolic reactions

A

Reactions which break down large molecules into smaller molecules and release energy.

56
Q

Example of catabolic reactions

A
  • Aerobic respiration

- Digestion

57
Q

Metabolism

A

The totality of an organism’s chemical reactions

*Sum of catholic and anabolic reactions

58
Q

First Law of Thermodynamics

A

Within an isolated system, energy cannot be created or destroyed, but it can be transferred and transformed.

59
Q

Second Law of Thermodynamics

A

Every energy transfer or transformation increases disorder (entropy) of the universe.

60
Q

Cells create order, do they therefore defy the 2nd law of thermodynamics

A

NO

Cells undergo millions of chemical reactions every second, these reactions can produce oder within cells however each of these reactions produce byproducts such as heat, this heat goes on to create disorder within the universe.

61
Q

Free Energy

A

The energy available to do work

ΔG = ΔH − TΔS

(ΔH) = change in enthalpy (total energy)

(ΔS) = change in entropy

(T) = temperature in Kelvin units

62
Q

Types of cell work

A

Chemical e.g. pushing endergonic reactions
Transport e.g. moving substances against a concentration gradient
Mechanical e.g. Muscle contraction

63
Q

Exergonic reactions

A

Spontaneous and release free energy (-ΔG). These are catabolic processes

64
Q

Endergonic reactions

A

Not spontaneous and consume free energy (+ΔG). These are anabolic processes

65
Q

Enzymes

A

Enzymes are biological catalysts which speed up the rate of reaction and remain unchanged in the process. This is acheived since enzymes lower the activation energy required for a reaction to take place by providing an alternative pathway; thus biological reactions are able to occur rapidly at relativly low temperatures.

66
Q

Enzyme induced fit

A

Enzymes action is specific since enzymes can only act on the one substrate which has a high affinity and complementary shape to it’s active site. The active site is flexible and will change shape slightly to allow a specific substrate to move in and bind very closely to it’s active site. The close contact between the active site and substrate increases the chance of a reaction taking place. Once a product is formed the active site will open and return to its orginal shape allowing the product, which has a low affinity for the active site, to move out.

67
Q

Factors affecting enzyme action

A
  • Temperature
  • pH
  • Substrate concentratiom
  • End-product concentration
  • Presence/absence of Inhibitors
68
Q

Effects of substrate concentration

A
  • Low concentration: too few substrate molecules present to make use of all active sites = low rate of reaction.
  • Increase of substrate concentration: increase in rate of reaction.
  • Further increase: Excess of substrate causes NO further increse in rate of reaction since all active sites are already occupied.
69
Q

feedback inhibition

A

Feedback inhibition occurs when the end-product in the metabolic pathway reaches a critical concentration. The end-product binds an earlier enzyme slowing down the reaction and eventually blocking the pathway to prevent the synthesis of end product.

70
Q

Competative inhibitors

A

Competative inhibitors bind to the active site preventing the substrate from binding; this can be reversed by increasing substrate concentration.

71
Q

Non-competative inhibitors

A

Non-competative inhibitors bind to the enzyme away from the active site but change the shape of the active-site preventing the substrate from binding; this cannot be reversed by increasing substrate concentration.

72
Q

Enzyme regulation

A

Involves use of cofactors which work alongside enzymes to mediate substrate binding.

Common regulators are: 
• Phosphorylation
• Allosteric activation and inhibition
• pH and temperature
• Competitive and Non-competitive inhibitors
73
Q

Allosteric activators and inhibitors

A

Enzymes have active and inactive forms:
• Binding of the activator promotes the active form, thus promoting the reaction.
• Binding of the inhibitor promotes the inactive form, thus inhibiting the reaction.

First year B (11 decks)

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