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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?

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?

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?

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?

A

• Several ribosomes translating the same mRNA template

24
Q

What is the endoplasmic reticulum?

A

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

25
Q

What is the path travelled by proteins for secretion by the cell?

A

Endoplasmic Reticulum (ER) = Golgi Apparatus = Secretory Vesicles

26
Q

What is the difference between Smooth vs Rough Endoplasmic Reticulum?

A

• Ribosomes!:

  • smooth - no ribosomes
  • rough - bound ribosomes
27
Q

What does the rough endoplasmic reticulum do?/What is its function?

A

-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
Q

What are the other differences/similarities between Smooth vs Rough Endoplasmic Reticulum?

A
  • Smooth ER – site of lipid synthesis
  • Rough ER – site of protein synthesis (translation)
  • Synthesis generally occurs in lumen of the cisternae (for both)
29
Q

What is the Golgi apparatus and what does it do?

A

• 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
Q

What is a vesicle?

A
  • “Small”, spherical, sealed, single membrane (lipid bilayer) contains ICF
  • Not a micelle! (SOS)
31
Q

What is vesicular trafficking?

A
  • 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
Q

What are the secretory pathways?

A

-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
Q

What are the digestive organelles?

A
  • Endosomes
  • Lysosomes
  • Peroxisomes
34
Q

What is an endosome?

A

• 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
Q

What is a lysosome?

A
  • Late endosome fuses with vesicle containing “lysozymes” (acid hydrolyases)
  • At low pH, hydrolyse chemical bonds to degrade contents of lysosome
36
Q

What is a peroxisome?

A 
• 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
Q

What are prokaryotes and eukaryotes?

A
  • 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
Q

Do Prokaryotic and eukaryotic cells simply

differ with respect to having a nucleus?

A

-FALSE
• Absence vs presence of ANY membrane bound organelles
(i.e. nucleus, mitochondria, Golgi apparatus, etc.)

39
Q

How else does a prokaryote differ from a eukaryote?

A

-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
Q

“Cells are either prokaryotic or

eukaryotic” - True or False?

A

-FALSE

• Classification refers to organisms not cells - Prokaryota vs Eukaryota

41
Q

“Prokaryotes are simple; eukaryotes are

complex” - True or False?

A

-FALSE
• 5 kingdoms of eukaryotes
• 2 kingdoms of prokaryotes but each with multiple phyla

42
Q

What are the Eukaryote kingdoms?

A 
- Eukarya:
\+ Multicellular:
• Animals
• Plants
• Fungi
\+ Unicellular:
• Yeast
• Amoeba
43
Q

What are the Prokaryote kingdoms?

A 
- Prokarya:
\+ Bacteria:
• Gram positive vs gram negative
• >12 phyla
\+ Archaea:
• Euryarchaeota vs Crenarchaeota
• >6 phyla
44
Q

What are the prokaryote morphologies?

A

4 morphologies:

1) Cocci (spherical
(2) Bacillus (rods/rod-like)
(3) Spirochetes (spiral)
(4) Vibrio (“commas”/curved rods)

45
Q

“Prokaryotes are unicellular; eukaryotes

are multicellular” - T/F?

A

-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
Q

Do all eukaryotic cells have nuclei?

A
  • 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
Q

Do all cells have the same number/type of mitochondria?

A

-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
Q

How would you expect the number of mitochondria in the midpiece of the sperm to relate to fertility?

A
  • 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
Q

Which cells should contain the most abundant golgi apparatus?

A
  • Specialised secretory cells!

- need for lots of packing for secretion

BIO111 Cell Biology (11 decks)

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