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BIO111 Cell Biology > Lecture 3 & 4 Cell Organelles: Structure-Function Relationships > Flashcards

Lecture 3 & 4 Cell Organelles: Structure-Function Relationships Flashcards

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1
Q

What are cells? What are cells made of?

A
  • Small units bound by a plasma membrane (or cell wall)
  • Contain aqueous fluid (cytosol) plus:
  • chemicals (cytoplasm)
  • structural support (cytoskeleton)
  • membrane bound organelless
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2
Q

What kind of membrane surrounds cells?

A

• All cells are surrounded by a plasma membrane
• Single membrane (lipid bilayer)
• Membrane is selectively permeable;
IntraCellular Fluid (ICF) (cytosolic face) ≠ ExtraCellular Fluid (ECF) (non-cytosolic face)

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3
Q

What is the plasma membrane made of?

A
  • Plasma membrane = complex of:
  • Lipids (amphipathic)
  • Proteins
  • Carbohydrates (CnH2nOn)
  • Glycolipids
  • Glycoproteins
  • Peptidoglycans
  • Glycosaminoglycans
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4
Q

Why is the Plasma Membrane Selectively Permeable?

A

• Because lipids are amphipathic (Ampithatic both hydrophilic and hydrophobic)

  • hydrophobic core (hydrophobic lipid tails)
  • hydrophilic exterior (hydrophilic phosphate heads)
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5
Q

What is the selectively permeable model called and what does it entail?

A
  • Fluid mosaic model:
  • Integral & peripheral membrane proteins
  • Transport hydrophilic solutes
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6
Q

What is the cell wall?

A
  • Plant cells and bacteria have a cell wall surrounding the plasma membrane
  • Further limits passage of molecules in to / out of the cell
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7
Q

What is the cell wall in plant?

A
  • Plant cell walls composed of cellulose
  • Complex carbohydrate
  • Has to be digested by cellulase (which animals don’t have!)
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8
Q

What is the cell wall in bacteria?

A
  • Bacterial cell walls composed of peptidoglycans
  • Can be surrounded by gelatinous polysaccharide layer:
  • capsule
  • glycocalyx
  • “slime layer”
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9
Q

What is an experiment with which we can test the cell wall in bacteria?

A
  • Can stain bacteria with Gram’s Stain
  • Gram positive bacteria: thick peptidoglycan layer to cell wall prevents stain being washed out (means cell wall exists)
  • Gram negative bacteria: peptidoglycan layer to cell wall allows gram stain to be washed out (no cell wall)
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10
Q

What are the Cell Surface Appendages?

A
  • Plasma membrane and/or cell wall can have:
  • villi / microvilli
  • cilia
  • flagella
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11
Q

Why do Cell Surface Appendages exist?

A
  • To move the cell (flagella / cilia)
  • To move ECF (cilia)
  • To increase the cell’s surface area (villi / microvilli)
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12
Q

What is the function of the nucleus?

A
  • Nucleolus-site of ribosomal synthesis
    -Contains chromosomes the cells blue-print for proteins – DNA
    + In dividing cells the DNA is replicated
    • Mitosis
    -Chromosomes composed of condensed chromatin
    -Chromatin = DNA + histone proteins
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13
Q

What is DNA used for in non-dividing cells?

A

• In non-dividing cell, use DNA blueprint for protein synthesis:
+Two step process:
-Transcription of DNA to RNA (in nucleus)
-Translation of RNA to protein (in rough endoplasmic reticulum)

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14
Q

How are the Nucleus and Nucleolus separated from the cytoplasm?

A
  • Double membrane (nuclear envelope) around nucleus with nuclear pores
  • No membrane around nucleolus
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15
Q

What are centrioles?

A
  • Only found adjacent to nucleus in animal cells
  • Perpendicular pair of specialist microtubules
  • Organise mitotic (or meiotic) spindle
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16
Q

What is the mitochondrial structure?

A
  • Bounded by double membrane
  • Inner and outer mitochondrial membranes separated by aqueous intermembrane space
  • Inner mitochondrial membrane (IMM) convoluted into cristae (larger surface area for citric acid cycle=makes ATP)
  • Inside IMM is the mitochondrial matrix
  • Mitochondrion has its own mit.DNA
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17
Q

What is the mitochondrial function?

A

• Mitochondrion contains series of oxidative enzymes
• Catalyse aerobic catabolism of fuels (carbohydrates, fatty acids and amino acids / proteins)
• Harness energy as ATP
=
• Mitochondria harness energy from C-based fuels by oxidative phosphorylation
• Generate and metabolise reactive oxygen species (ROS) and free radicals
• Mediate apoptosis

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18
Q

What happens in the ICF (intracellular fluid)(cytosolic face)?

A

-Anaerobic carbohydrate metabolism (glycolysis) (first step but outside mitochondria)
-Aerobic oxidation of carbohydrates, lipids and amino-acids (β-oxidation and Kreb’s/TCA cycle)
-Phosphorylation of ADP to ATP
• Oxidative metabolism of glucose
• Harness energy as ATP:
C6H12O6 + 6O2 = 6CO2 + 6H2O+ ATP

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19
Q

What are the synthetic organelles?

A
  • Chloroplasts – photosynthesis
  • Ribosomes – translation of proteins
  • Endoplasmic reticulum – protein and lipid synthesis
  • Golgi apparatus – protein processing, sorting & secretion
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20
Q

What is a chloroplast and what does it do?

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A

• Only found in photosynthetic cells
• Catalyse anabolic (rather than catabolic) metabolism
• Harness light energy in photosynthesis:
Energy + 6CO2 + 6H2O = C6H12O6 + 6O2
• Bounded by double membrane
• Has its own DNA

21
Q

What are ribosomes?

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A
  • In nucleus (nucleolus), DNA is transcribed into RNA:
  • Messenger (m)RNA
  • Ribosomal (r)RNA
  • Transfer (t)RNAs
  • mRNA code is translated into amino-acid sequence (peptide / protein) by ribosomes
22
Q

What is the structure of ribosomes?

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A 
• Ribosomes have 2 subunits: small and large
• Each subunit is a complex of:
• rRNA
• proteins
• Which component is enzymatic? = rRNA!
-Prokaryotes = 70S ribosomes
-Prokaryotes = 80S ribosomes
\+can be exploited with antibiotics (only target 70S)
23
Q

What are polysomes?

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A

• Several ribosomes translating the same mRNA template

24
Q

What is the endoplasmic reticulum?

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A

• Continuous, highly convoluted membrane system – nucleus to plasma membrane

25
What is the path travelled by proteins for secretion by the cell?
Endoplasmic Reticulum (ER) = Golgi Apparatus = Secretory Vesicles
26
What is the difference between Smooth vs Rough Endoplasmic Reticulum?
• Ribosomes!: - smooth - no ribosomes - rough - bound ribosomes
27
What does the rough endoplasmic reticulum do?/What is its function?
-Rough ER makes membrane and organelle proteins and virtually all proteins secreted by the cell: • protein synthesis, transport and sorting • ribosomes protein synthesis translate RNA into protein • proteins made by the bound ribosomes cross the rough ER membrane • proteins folded and modified in ER • Have sugars added glycosylation to protect proteins
28
What are the other differences/similarities between Smooth vs Rough Endoplasmic Reticulum?
* Smooth ER – site of lipid synthesis * Rough ER – site of protein synthesis (translation) * Synthesis generally occurs in lumen of the cisternae (for both)
29
What is the Golgi apparatus and what does it do?
• Series of specialised, stacked cisternae through which proteins (and lipids) are processed prior to: • insertion into plasma membrane • secretion • Molecules enter on cis face and exit from trans face of GA – move via vesicular trafficking + Enzymes in Golgi can add carbohydrate: • carbohydrate + lipid = glycolipid • carbohydrate + protein = glycoprotein • Golgi Apparatus “sorts” molecules for final destination
30
What is a vesicle?
* “Small”, spherical, sealed, single membrane (lipid bilayer) contains ICF * Not a micelle! (SOS)
31
What is vesicular trafficking?
* Vesicle buds off from one membrane (cisterna) * Vesicle passes through the cytoplasm and fuses with another membrane * Traffics luminal and membrane content of vesicle
32
What are the secretory pathways?
-Two types: • Exocytosis- constitutive i.e. not regulated e.g. Extra cellular matrix proteins by fibroblasts • Secretory vesicles-regulated by signals e.g. Insulin-b cells in islets of Langerhans
33
What are the digestive organelles?
* Endosomes * Lysosomes * Peroxisomes
34
What is an endosome?
• Incoming vesicle formed by endocytosis • Buds off from plasma membrane • Pinocytosis • Phagocytosis • 3 types: early, recycling and late endosome (EE, RE & LE) -EE first one to form/ forms from endocytosis then becomes: -RE for exocytosis or -LE for lysosomal pathway or golgi apparatus
35
What is a lysosome?
* Late endosome fuses with vesicle containing “lysozymes” (acid hydrolyases) * At low pH, hydrolyse chemical bonds to degrade contents of lysosome
36
What is a peroxisome?
``` • Contain peroxidase enzymes: RH2 + O2 → R + H2O2 (HOOH) • Also contain catalase enzyme: RH2 + H2O2 → 2 x H2O • Initial catabolism of long chain FA, branched chain FA, amino acids and polyamines ```
37
What are prokaryotes and eukaryotes?
* Historical (antiquated) terms * “Karyon” = “nut / kernel” (nucleus surrounded by double membrane / nuclear envelope) * Prokaryotes – don’t have a nucleus; “before the nucleus” * Eukaryotes – cells with nucleus
38
Do Prokaryotic and eukaryotic cells simply | differ with respect to having a nucleus?
-FALSE • Absence vs presence of ANY membrane bound organelles (i.e. nucleus, mitochondria, Golgi apparatus, etc.)
39
How else does a prokaryote differ from a eukaryote?
-A prokaryote has: • Relatively simple internal structure; only common organelle = ribosome • Nucleoid = bacterial chromosome: single circular molecule of “naked” DNA (no histones) • Metabolism occurs in cytosol (no ER or mitochondria)
40
“Cells are either prokaryotic or | eukaryotic" - True or False?
-FALSE | • Classification refers to organisms not cells - Prokaryota vs Eukaryota
41
“Prokaryotes are simple; eukaryotes are | complex” - True or False?
-FALSE • 5 kingdoms of eukaryotes • 2 kingdoms of prokaryotes but each with multiple phyla
42
What are the Eukaryote kingdoms?
``` - Eukarya: + Multicellular: • Animals • Plants • Fungi + Unicellular: • Yeast • Amoeba ```
43
What are the Prokaryote kingdoms?
``` - Prokarya: + Bacteria: • Gram positive vs gram negative • >12 phyla + Archaea: • Euryarchaeota vs Crenarchaeota • >6 phyla ```
44
What are the prokaryote morphologies?
4 morphologies: | 1) Cocci (spherical (2) Bacillus (rods/rod-like) (3) Spirochetes (spiral) (4) Vibrio (“commas”/curved rods)
45
“Prokaryotes are unicellular; eukaryotes | are multicellular” - T/F?
-FALSE • Some prokaryotes can be multicellular at specific stages of their life cycle • Some eukaryotes are unicellular -Prokaryotes: • Archaea always unicellular • Bacteria usually unicellular (e.g. E.coli, Pseudomonas & Streptococcus) • Some bacteria have multicellular stages (e.g. myxobacteria) or form colonies (e.g. cyanobacteria)
46
Do all eukaryotic cells have nuclei?
* All mammals – mature erythrocytes lack nuclei * Most non-mammalian vertebrates have nucleated red blood cells * “Lens fibre” cells in the eye have no nuclei
47
Do all cells have the same number/type of mitochondria?
-NO +eg.: Hepatocytes have c.2,000 mitochondria per cell (accounting for 20% of cell volume) - Why? = perform most of the livers function = need lots of ATP • Unicellular organisms usually have a single mitochondrion • Erythrocytes and some unicellular eukaryotes* have zero mitochondria *(microsporidians, metamonads & archamoebae) +implies they have no need/less need for ATP • Mature “lens fibre” cells (long, thin cells which comprise the lens) of the eye have: • No nuclei • No mitochondria • No endoplasmic reticulum
48
How would you expect the number of mitochondria in the midpiece of the sperm to relate to fertility?
- Sperm contain spiral mitochondria wrapped around flaggelum (midpiece) - mitochondria provides energy for flagellum to move, acrosome (head) no need for energy as soon as it enters the ovary
49
Which cells should contain the most abundant golgi apparatus?
- Specialised secretory cells! | - need for lots of packing for secretion

BIO111 Cell Biology (11 decks)

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