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Organelles Flashcards

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1
Q

What is the Fundamental Difference Between Prokaryotes & Eukaryotes?

A

The nucleus. Karyon = ‘kernel’ or nucleus.

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2
Q

Describe the subcategory of prokaryotes called eubacteria.

A

eubacteria

  • “true
    bacteria”

Eubacteria

  • found in
    environments familiar to us
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3
Q

Describe the subcategory of prokaryotes called Archea bacteria.

A
  • found in hostile environments as well as in more familiar ones
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3
Q

What are the main features of prokaryotes?

A

most diverse group of cells successfully inhabit many different environments exhibit many different growth forms

o spherical, rod-shaped, spiral, chains, clusters, organised
multicellular structures

  • may be
  • organotrophic (use any organic molecule as an energy source)
  • phototrophic (use light as an energy source)
  • lithotrophic (use inorganic molecules as an energy source)
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4
Q

Stuff to know regarding the differences between eubacteria and archaea.

A
  • Division between these two groups is based on molecular biological characterisations.

They are as different to each other as either is from eukaryotes.

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5
Q

A photo showing the main features of prokaryotes (no.1) (on the other side)

A
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5
Q

A photo showing the main features of prokaryotes (no.2) (on the other side)

A
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6
Q

Prokaryotes - Features

A

“simple” cells

  • a few micrometres (um) long

> tough, protective cell wall

  • plasma membrane
  • essentially no membrane-bound organelles
  • have no nucleus
  • circular DNA free in cytosol
  • ribosomes
  • may have a flagellum
  • can reproduce quickly, e.g. some divide every 20 min
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7
Q

Eukaryotes two types

A

> Unicellular

  • most protists
  • yeast
    Multicellular
  • animals, plants (including multicellular algae) & fungi
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8
Q

Ribosomes

A
  • prokaryotes and eukaryotes

> sites of protein synthesis

  • large complexes of
  • proteins &
  • ribosomal RNAs = rRNAs

> eukaryotic larger (80S) than prokaryotic
(70S)

  • two populations in eukaryotes
  • cytosolic
  • free or attached to Endoplasmic
    Reticulum (80S)
  • in mitochondria & chloroplasts (70S) = bacterial size
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9
Q

Membranes - Composition

A
  • Prokaryotes and eukaryotes
  • Bilayer of phospholipids → see L3
  • asymmetrical arrangement in the two halves

> Proteins

  • integral - embedded in the bilayer
  • peripheral - attached loosely to the bilayer
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10
Q

Membranes - Composition photo

A
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11
Q

Plasma Membrane photo

A
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11
Q

Membranes
- Selectivity

A

Selectively permeable

  • Small hydrophobic & small uncharged molecules can cross freely.
  • Larger uncharged polar molecules & charged solutes must interact with transmembrane proteins (transporters) to cross phospholipid bilayer.
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11
Q

Plasma Membrane

A

Plasma membrane involved in

  • cell signalling transport of solutes
  • cell growth & motility
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12
Q

Membranes
- Selectivity photo

A
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12
Q

Plasma Membrane - Carbohydrate groups

A

carbohydrate groups attached to lipids - glycolipids , carbohydrate groups attached to proteins - glycoproteins

› on external (non-cytosolic) side of plasma membrane play roles in:

  • cell-to-cell communication
  • protection from chemical & mechanical damage
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13
Q

Plasma Membrane - Carbohydrate groups photo

A
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13
Q

Membranes
- Create Compartments

A
  • Compartmentalise cells
  • separate cells from their environments
  • separate organelles from each other & from the cytosol
  • Double membranes surround
  • nucleus
  • mitochondria
  • chloroplasts
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14
Q

Endomembrane system includes….

A
  • Includes: nuclear envelope, ER, Golgi apparatus, transport vesicles, plasma membrane, and endosomes and lysosomes (animal cells) or vacuoles (plant cells)
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15
Q

Endomembrane system photo

A
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16
Q

structure of eukaryotes and prokaryotes - outcomes

A

You will be able to

  • memorize that cells are the basic unit of life sharing a basic chemistry,
  • memorize, identify and contrast characteristics of prokaryotic and eukaryotic cells,
  • describe the composition and roles of cellular membranes,
  • explain the roles of cellular organelles and compartments,
  • explain the origin of mitochondria and chloroplasts - endosymbiosis theory
  • describe in detail mitochondrial and chloroplastic structures,
  • describe the generation of cellular energy,
  • explain the role of proton gradients in ATP production,
  • describe the production of carbohydrates in chloroplasts
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16
Q

Endomembrane System:
Golgi Apparatus

A

➢ stacks of flattened sacs (cisternae)

➢ one or more per cell

➢ synthesis and packaging of molecules to be secreted from cell

➢ routing of newly synthesised proteins to their correct cellular
locations

➢ associated with many transport vesicles

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17
Q

Endomembrane System:
Golgi Apparatus photo

A
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18
Q

Endomembrane System: Microbodies photo

A
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19
Q

Golgi Apparatus has
a distinct orientation

A

cis face - adjacent to ER,

vesicles arrive from the ER

trans face - points toward plasma membrane

➢ transport vesicles pinch off &
fuse with cisternae

➢ carry proteins being modified
by the addition of sugar groups

➢ correlation of enzyme location (e.g. which cisterna) & what step it catalyses in sugar-modification pathway

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19
Q

golgi apparatus cis and trans orientation photo

A
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19
Q

Endomembrane System: Microbodies

A

Peroxisomes

▪ single-membrane bound

▪ contain oxidative enzymes

In animals

➢ sites of detoxification (e.g. lots in
liver)

In plants

➢ sites of detoxification

➢ photorespiration (carbon recycling)

➢ conversion of stored fats into
sucrose during germination of
some seeds (= glyoxysomes)

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19
Q

Endomembrane system
– Exocytic Pathway photo

A
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19
Q

Endomembrane system
– Exocytic Pathway

A

Membrane growth,
secretion

➢ Outward = exocytic pathway

➢ Proteins synthesised on rough
ER & glycosylated

➢ Vesicles containing glycoproteins
bud off ER & fuse with cis Golgi
cisternae

➢ Glycoproteins are further glycosylated as they travel through Golgi cisternae by vesicle budding & fusion

➢ At the trans face of the Golgi, vesicles are directed to plasma membrane or lysosome/vacuole

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19
Q

Endomembrane system
– Endocytic Pathway photo

A
19
Q

Endomembrane system
– Endocytic Pathway

A

➢ Inward = endocytic pathway

➢ Ingestion & degradation
or recycling) of extracellular molecules

▪ Regions of the plasma membrane containing molecules to be degraded bud inward to form vesicles

▪ Vesicles fuse with early endosomes

▪ Ultimately molecules are degraded in the lysosome /vacuole

▪ Some degradation products can be reused by the cell

19
Q

Endomembrane System:
Vacuoles

A

➢ Vacuoles of plant cells are sites of
degradation

➢ They also act as:

▪ storage organs (e.g. seed proteins)

▪ detoxification sites (e.g. tannins)

▪ pigment deposition (e.g. anthocyanins)

19
Q

Eukaryotes Cells
- Double Membrane bound Organelles

A

o nucleus – double
membrane
o Mitochondria – double
membrane
o chloroplasts – double
membrane

20
Q

Endomembrane System:
Vacuoles photo

A
21
Q

Nucleus photo

A
22
Q

Nucleus

A

➢ Surrounded by a double
membrane

  • continuous with ER
  • interrupted by pores

▪ allow passage of selected molecules between cytosol & nucleus

➢ Contains most cellular DNA

  • heterochromatin

▪ DNA + proteins - highly condensed, even at interphase

  • euchromatin

▪ DNA + proteins - not condensed until mitosis

➢ Typically contains a nucleolus

  • site of ribosomal RNA
    (rRNA) synthesis & ribosomal subunit assembly
22
Q

Mitochondria

A

➢ sites of cellular respiration & major energy (ATP) production
in a process called oxidative phosphorylation

➢ surrounded by a double membrane

▪ smooth outer membrane

❖ permeable to ions & small
molecules

▪ inner membrane

❖ highly folded (into cristae)

❖ impermeable

❖ transport proteins control substrate movement across the inner membrane

❖ contains an electron transport chain & ATP synthase

23
Q

Chloroplasts
– Thylakoids and Lumen

A

Thylakoids

▪ formed by a folded internal membrane system

▪ folded into stacks – grana

➢ light-harvesting pigments

➢ electron transport chain

➢ ATP synthase Lumen

➢ space between thylakoids

23
Q

Mitochondria photo

A
24
Q

Mitochondrial Matrix

A

➢ Region not taken up by membranes

➢ Contains:

▪ DNA ➔ mitochondrial genome

❖ codes for

o mitochondrial tRNA

o mitochondrial rRNA

o mitochondrial mRNA

  • proteins for DNA synthesis & oxidative reactions

▪ Mitochondrial ribosomes (70S)

▪ Enzymes for the tricarboxylic acid (citric acid, Krebs) cycle

25
Q

Chloroplasts – Organelle with a double membrane

A

➢ sites of photosynthesis

❖ two sets of reactions:

▪ light harvesting

▪ carbohydrate production

➢ surrounded by a double membrane:

❖ outer membrane

▪ permeable to ions & small molecules

❖ inner membrane

▪ impermeable

▪ transport proteins control movement of substrates across internal membrane system

26
Q

Chloroplasts photo

A
27
Q

Chloroplasts
– Thylakoids and Lumen photo 1

A
28
Q

Chloroplasts
– Thylakoids and Lumen photo 2

A
29
Q

Chloroplasts - Stroma

A

➢ region not taken up by thylakoid membranes

➢ contains

❖ DNA codes for

▪ tRNA

▪ rRNA

▪ mRNA ➔ proteins for DNA synthesis & photosynthesis

❖ ribosomes (70S)

❖ enzymes for carbohydrate production

30
Q

Chloroplasts - Stroma photo

A
31
Q

Mitochondria & Chloroplasts
are Products of Endosymbiosis

A
  • An ancestral eukaryotic cell ingested, but did not digest an aerobic bacterium, which over time evolved into a mitochondrion. ➔ eukaryotic cells
  • Eukaryotic cells later ingested a photosynthetic bacterium without
    digesting it.

Over time, this ingested bacterial cell evolved into a chloroplast ➔ plant cells

32
Q

Mitochondria & Chloroplasts
are Products of Endosymbiosis photo

A
33
Q

Energy Production Overview

A

➢ Digestive enzymes breakdown:

  • proteins to amino acids
  • polysaccharides to simple sugars
  • fats to fatty acids & glycerol

➢ Breakdown products enter cell
cytosol for gradual oxidation & production of some energy (ATP) and reducing molecules (NADH)

➢ The final stages and the majority of energy production takes place in the mitochondria.

34
Q

Energy Production Overview photo

A
35
Q

Cytosol Energy Production: Early Stages

A

CYTOSOL:

➢ Glucose & other sugars are converted to pyruvate through
glycolysis.

➢ This generates some energy molecules (ATP, NADH)

➢ Some amino acids are converted to pyruvate.

36
Q

Mitochondria
Energy Production: Early Stages

A

➢ Pyruvate, some amino acids and fatty acids enter the
mitochondrion.

➢ Pyruvate, fatty acids and some amino acids are oxidised
to acetyl CoA in the mitochondrion.

36
Q

Mitochondria
Production of Reducing Molecules photo

A
37
Q

Mitochondria
Energy Production: Early Stages photo

A
37
Q

Cytosol Energy Production: Early Stages photo

A
38
Q

Mitochondria
Production of Reducing Molecules

A

➢ Acetyl CoA is further oxidised by
the citric acid cycle

Produces:

  • CO2

diffuses out of
mitochondria via membranes
o NADH & FADH2

(FADH2 not shown)

o NADH and FADH2 are

molecules with strong
reducing power

Note: some amino acids can enter
the citric acid cycle at intermediate
steps & be oxidised directly

39
Q

Electron Transport Chain (ETC)
Using reducing power to generate ATP - overview

A

➢ NADH & FADH2 have strong
reducing power = ‘high energy
electrons’

➢ NADH & FADH2 donate
electrons to electron transport
chain (ETC) in the inner
mitochondrial membrane.

➢ The electrons move through the
electron transport chain ➔
consist of multiprotein
complexes

➢ This results in:

▪ oxidation of NADH & FADH2

▪ reduction of O2
to H2O

▪ ATP production.

40
Q

Electron Transport Chain (ETC)
Using reducing power to generate ATP - overview photo

A
41
Q

Mitochondria – Finally, ATP production

A

➢ Pumping of electrons leads to a H+
(proton) gradient

▪ higher concentration of protons in the inter membrane space than in the
matrix

➢ ATP is synthesised as protons move through the ATP synthase from the inter membrane space into the matrix.

➢ ATP is transported out of the mitochondrion for use by the cell.

41
Q

Mitochondria – Finally, ATP production photo

A
41
Q

Chloroplasts
– Light Harvesting Reaction

A

➢ Light energy is collected by pigments in the thylakoid membranes

➢ Converted to reducing power (NADPH) and chemical energy (ATP) via a series of oxidation-reduction reactions

➢ H2O being the original electron donor and NADPH the final electron acceptor.

42
Q

Chloroplasts
– Light Harvesting Reaction photo

A
43
Q

The Chloroplast
- Electron Transport Chain

A

➢ During electron transport, protons move across the thylakoid membranes from the stroma into the thylakoid lumen, generating a proton gradient.

➢ ATP is synthesised as protons move back across the membrane, from the thylakoid lumen into the stroma, through the chloroplastic ATP synthase.

43
Q

The Chloroplast
- Electron Transport Chain photo

A
44
Q

Carbohydrate Production
in the Chloroplast

A

➢ Calvin cycle uses NADPH & ATP produced during the light reactions
for the synthesis of carbohydrates from atmospheric CO2 in the stroma.

➢ The enzyme Rubisco = ribulose 1,5-bisphosphate carboxylase/oxygenase catalyses the first reaction in the Calvin cycle

➢ Rubisco is the most abundant enzyme in the world.

44
Q

Carbohydrate Production
in the Chloroplast photo

A
44
Q

Cytoskeleton
- Overview

A

➢ complex, dynamic network of
interlinking protein filaments present
in the cytoplasm of all cells, including those of eukaryotes, bacteria and archaea.

➢ Functions: support, shape, motility,
intracellular transport, chromosome movement, cell division

➢ dynamic - continuously reorganised

➢ three types of components - each
formed from protein subunits

▪ actin filaments –
microfilaments

▪ intermediate filaments

▪ microtubules

45
Q

Cytoskeleton
- Overview photo

A
46
Q

Cytoskeleton
- Actin Filaments

A

➢ Also known as microfilaments

➢ found in all eukaryotic cells
Structure:

▪ composed of linear polymers made up of globular (G-) actin subunits

▪ G-actin monomers combine form a polymer which continues to form the actin filament (7 nm diameter). Two chains intertwine to from an F-actin(Filamentous actin) chain.

▪ cross-linked into bundles & networks

➢ maintenance of eukaryotic cell shape, cell movement, cell division, muscle contraction, intracellular transport and vesicular movement

➢ actin rearrangements within cells is the molecular basis for changes in cell shape & movement

47
Q

Cytoskeleton
- Actin Filaments photo

A
48
Q

Cytoskeleton
- Intermediate Filaments photo

A
48
Q

Cytoskeleton
- Intermediate Filaments

A

Actin 7nm < intermediate 10nm < microtubules 25nm

Found in:

➢ Cytoplasm and nuclear lamin of vertebrates, and many invertebrates Structure:

➢ subunits = heterogeneous family of proteins collectively called intermediate proteins

➢ Two proteins twisted together into an alpha helical dimer. Two dimers form a tetramer. Many tetramers
form a rope-like intermediate filament.

➢ Example: keratin filaments
Functions:

➢ strengthens the cytoskeleton and nuclear envelope

➢ attachment sites for chromatin

➢ anchoring organelles

➢ protein movement

48
Q

Can you …

A
  • … state characteristics of cells and their basic chemistry and life?
  • … differentiate between archae- and eubacteria, describe features
    and give examples?
  • … describe similarities and differences between prokaryotic and
    eukaryotic cells?
  • … explain features/structures and roles of ribosomes, membranes
    and organelles?
  • … explain a model for the origin of mitochondria and plastids?
  • … explain key metabolic processes in mitochondria and chloroplasts
    related to energy production and carbon metabolism?
  • … describe components of the cytoskeleton and give examples for
    their roles?
48
Q

Cytoskeleton
– Microtubules

A

Found in all eukaryotic cells
Structure

➢subunits = tubulin - dimers of - &

*- tubulin

➢dimers stack into filaments, which
form walls of stiff hollow tubes (25
nm in diameter)

Function

➢ Maintenance of cell structure

➢ intracellular organisation & transport, mitosis, internal structure of cilia & flagella

➢ Main constituents of mitotic spindles

Location

➢ extend from an organising structure, e.g. centrosome, spindle
pole, basal body

49
Q

Cytoskeleton
– Microtubules photo

A

Molecular Biology Flashcards (20 decks)

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