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Molecular Biology > General cell biology and cell organelles > Flashcards

General cell biology and cell organelles Flashcards

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1
Q

Characteristics of life on earth

A
  • growth - metabolism - excitability - spontaneous movement - reproduction/genetic material
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2
Q

Types of macromolecules:

A
  • proteins - lipids - carbohydrates - nucleic acids
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3
Q

Systematic characteristics of viruses

A
  • reproduce as obligatory intracellular parasites - contain DNA or RNA - are assembled from parts; no growth, no cell division - lack their own metabolism; do not produce energy - resilient to antibiotics; affected by interferons - can be crystallized
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4
Q

The natural scientists whose work is most important for cell theory:

A
  • Robert Hooke - coined the term “cell” - published “Micrographia”, describing observations made with microscopes. - Theodore Schwann - cell theory, Schwann cells, metabolism, pepsin - Matthias Jakob Schleiden - co-founder of cell theory - extended it to plants - Rudolf Virchow - omnis cellula e cellula
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5
Q

Typical sizes of cells:

A
  • 2um to mm/cm
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6
Q

Typical sizes of organelles:

A
  • 0.2um to 20um
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7
Q

Sizes of molecules:

A
  • 0.2nm to 20nm
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8
Q

A micrometer is …

A

1*10^-6m (a millionth of a meter); a thousandth of 1mm

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9
Q

A nanometer is…

A

1×10^-9m (a billionth of a meter); a thousandth of 1um

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10
Q

Define optical resolution:

A
  • the distance between two points that can be resolved
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11
Q

What is the index of refraction of air, pure water, and oil?

A
  • air 1.0, water 1.33, oil 1.56
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12
Q

The formula for the optical resolution of a microscope:

A
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13
Q

The characteristics of cells: typical size, plasmalemma, cell nucleus, cell walls

A
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14
Q

Basic tissue types:

A
  • Epithelia
  • Connective tissues (connective tissue, muscle, blood)
  • Nervous tissue
  • Gametes
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15
Q

Properties of epithelia:

A
  • polar
  • sometimes with cilia
  • secretory vesicles
  • specialized cell-cell junctions
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16
Q

Properties of connective tissue:

A
  • general - in and between organs (e.g. fibroblasts, ECM)
  • muscle - contraction (types: smooth, striate, heart muscle0
  • blood (erythrocytes, leukocytes)
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17
Q

About nervous tissue:

A
  • neurons and glia (CNS, PNS, various cell types; synapses)
  • sensory receptors (sensory epithelia)
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18
Q

About gametes:

A
  • sperm & egg
  • haploid
  • potentially immortal
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19
Q

Find the organelles:

A
20
Q

Organelles surrounded by membranes and membrane systems:

A
  • cell nucleus
  • mitochondria
  • plastids

Membrane systems:

  • Endoplasmic reticulum
  • Golgi
  • Lysosomes
  • Peroxisomes
21
Q

Organelles without membranes:

A
  • ribosomes
  • microtubules (and structures that consist of microtubules: centrioles, flagella, cilia, cytoskeleton)
  • protein filaments (cytoskeleton)
  • proteasomes
22
Q

Identify parts of the cell nucleus

A
23
Q

What is a crista?

A

A crista (pl. cristae) is a fold in the inner membrane of a mitochondion.

The cristae give the inner mitochondrial membrane its characteristic wrinkled shape providing a large amount of surface area for chemical reactions to occur on. This aids aerobic cellular respiration (since the mitochondrion requires oxygen). Cristae are studded with proteins, including ATP synthase and a variety of cytochromes.

24
Q

Why are mitochondria considered semi-autonomous?

A
  • they have their own DNA
  • they have their own ribosomes
  • they divide (not formed de novo)
25
Q

Important metabolic functions of mitochondria:

A

In the matrix:
- Citric acid cycle
(metabolic center, synthesis of amino acids, oxidative degradation of pyruvate, the product of glycolysis)

  • beta-Oxidation of fatty acids (degradation to acetyl-CoA)
  • At the inner mitochondrial membrane:*
  • *Oxidative chain reaction** (cell respiration, ATP-synthesis by oxidation of NADH+H+, FADH2)
26
Q

Differences between plastids/chloroplasts and mitochondria:

A

Plastits are:

  • larger
  • have an outer and inner, as well as a thylakoid membrane with grana
  • responsible for different metabolic processes
27
Q

Why are plastids semi-autonomous organelles?

A

Same as mitochondria:

  • have their own DNA, ribosomes, and they divide
28
Q

Important metabolic functions of plastids:

A

at the thylakoid membranes:

Photosynthesis (ligth reaction, electron transfer reactions, chlorophyll, ATP-synthesis, NADP reduction)

in the stroma:

Calvin-Cycle (CO2 fixation in dark reaction, products of photosynthesis enter the cell metabolism, RUBISCO)

Energy storage: starch

29
Q

Evidence for the endosymbiontic theory:

A
  1. Mitochondrial DNA, circular structure, no histones, similar to bacterial DNA
  2. Mitochondrial ribosomes similar to those of bacteria in size, compatibility of subunits
  3. Double membrane
  4. Composition of the inner membrane similar to bacterial membrane, details of protein biosynthesis, sensitivity to antibiotics, tRNAF-Met
  5. Living model organisms
30
Q

Where can ribosomes be found?

A
  • floating freely in the cytosol
  • at the rough endoplasmic reticulum, rER
  • in plastids and mithochondria
31
Q

Subunits of a ribosome:

A

large subunits: 60 S = 1/3 protein (49 molecules) + 2/3 rRNA (28S, 5,8S, 5S)

small subunits: 40 S = 1/3 protein (33 molecules) + 2/3 rRNA (18S)

32
Q

Find the rough and smooth ER:

A
33
Q

Membrane continuity within the cell:

A
34
Q

Functions of the rER

A

Protein biosynthesis: Membrane proteins, lysosomal proteins, exportable proteins; signal sequence in primary structure, SRP, docking of ribosomes, transcription, chaperones

Glykosylation of proteins: at asparagine residues, transfer of an oligosaccharide from dolichol

35
Q

Functions of the sER

A

Posttranscriptional modification: glycosylation Lipid synthesis: steroids, phospholipids, glycolipids, sphingomyelin of the membranes

Storage function: Ca2+, proteins, lipids, glycogen

36
Q

The Golgi complex: parts and functions

A

Golgi complex:
• Membrane system: ER – Golgi - Lysosomes
• Golgi cisterns, dictyosomes, transport vesicles

Functions of the Golgi complex:

  • Transport and distribution within the cell: soluble proteins, membrane segments, vesicles of exo- and endocytosis
  • Modification and sorting of proteins: glycosylation, modification of oligosaccharide side chains
  • Production of lysosomes: intracellular degradation
37
Q

More on the structure of the Golgi complex:

A

Found within the cytoplasm of both plant and animal cells, the Golgi is composed of stacks of membrane-bound structures known as cisternae (singular: cisterna). An individual stack is sometimes called a dictyosome (from Greek dictyon: net + soma: body),[4] especially in plant cells.[5] A mammalian cell typically contains 40 to 100 stacks.[6] Between four and eight cisternae are usually present in a stack; however, in some protists as many as sixty have been observed.[3] Each cisterna comprises a flat, membrane enclosed disc that includes special Golgi enzymes which modify or help to modify cargo proteins that travel through it.[7]
The cisternae stack has four functional regions: the cis-Golgi network, medial-Golgi, endo-Golgi, and trans-Golgi network. Vesicles from the endoplasmic reticulum (via the vesicular-tubular clusters) fuse with the network and subsequently progress through the stack to the trans Golgi network, where they are packaged and sent to their destination. Each region contains different enzymes which selectively modify the contents depending on where they reside.[8] The cisternae also carry structural proteins important for their maintenance as flattened membranes which stack upon each other.[9]

38
Q

More on the functions of the Golgi complex:

A

The Golgi apparatus is integral in modifying, sorting, and packaging these macromolecules for cell secretion[10] (exocytosis) or use within the cell.[11] It primarily modifies proteins delivered from the rough endoplasmic reticulum but is also involved in the transport of lipids around the cell, and the creation of lysosomes.[11] In this respect it can be thought of as similar to a post office; it packages and labels items which it then sends to different parts of the cell.

Enzymes within the cisternae are able to modify the proteins by addition of carbohydrates (glycosylation)[12] and phosphates (phosphorylation). In order to do so, the Golgi imports substances such as nucleotide sugars from the cytosol. These modifications may also form a signal sequence which determines the final destination of the protein. For example, the Golgi apparatus adds a mannose-6-phosphate label to proteins destined for lysosomes.

The Golgi plays an important role in the synthesis of proteoglycans, which are molecules present in the extracellular matrix of animals. It is also a major site of carbohydrate synthesis.[13] This includes the production of glycosaminoglycans (GAGs), long unbranched polysaccharides which the Golgi then attaches to a protein synthesised in the endoplasmic reticulum to form proteoglycans.[14] Enzymes in the Golgi polymerize several of these GAGs via a xylose link onto the core protein. Another task of the Golgi involves the sulfation of certain molecules passing through its lumen via sulfotranferases that gain their sulfur molecule from a donor called PAPS. This process occurs on the GAGs of proteoglycans as well as on the core protein. Sulfation is generally performed in the trans-Golgi network. The level of sulfation is very important to the proteoglycans’ signalling abilities as well as giving the proteoglycan its overall negative charge.[13]

The phosphorylation of molecules requires that ATP is imported into the lumen of the Golgi[15] and utilised by resident kinases such as casein kinase 1 and casein kinase 2. One molecule that is phosphorylated in the Golgi is Apolipoprotein, which forms a molecule known as VLDL that is a constituent of blood serum. It is thought that the phosphorylation of these molecules is important to help aid in their sorting for secretion into the blood serum.[16]
The Golgi has a putative role in apoptosis, with several Bcl-2 family members localised there, as well as to the mitochondria. A newly characterized protein, GAAP (Golgi anti-apoptotic protein), almost exclusively resides in the Golgi and protects cells from apoptosis by an as-yet undefined mechanism.[17]

39
Q

Functions of lysosomes

A
  • Degradation and intracellular recycling of lipids, sugars and proteins; pH 5 (cytosol: pH 7.2; proton pumps in the membrane)
  • Enzymes: acidic hydrolases (lipases, proteases, glycosidases, phosphatases, sulfatases, phospholipases; A-B + H2O A-H + B-OH; A-B: ester bond, peptide bond, glycosidic bond)
40
Q

Lysosome types and the difference between them:

A

Heterolysosomes

Phagocytosis by single cell organisms, macrophages, leukocytes in the immune system

Autolysosomes

normal turn over of organelles: e.g. mitochondrial halflife in the liver is only 10 d; processes of regeneration, metamorphosis

Aging pigment, non-degradable residues in lysosomes: lipofuscin

41
Q

Lysosome-related medical problems:

A

Autolysis (rare): toxins of bacteria, ureic acid cristals in gout, asbestos particles in the lungs: disruption of membranens, destructive enzymes are released into the cytosol

Lysosomal storage diseases: accumulation of filled lysosomes, whose content can not be degraded due to the lack of certain enzymes, results in cell death

Examples:

  • Tay-Sachs-Disease (autosomal recessive, ganglioside GM2, mental retardation, high incidence in Ashkenazi jews)
  • I-Cell-Disease (lack of many enzymes in the lysosomes of fibroblasts, no phosphorylation of mannose, thus defective targeting, enyzmes go into the blood instead, inclusion bodies in fibroblasts)
42
Q

Properties and functions of peroxisomes:

A

Properties:

  • Vesicles with membranes, d = ca. 0.5 μm (microbodies)
  • contain oxidases, characteristic enzyme: catalase

Functions:

Catalase reaction: 2 H2O2 2 H2O + O2

Participate in:
• oxidation of fatty acids to acetyl-CoA (-oxidation in mitochondria)
• amino acid metabolism
• degradation of N-containing bases of nucleic acids:

  • adenine to xanthine

guanine to hypoxanthine to ureic acid to allantoin (most mammals; in humans secretion of ureic acid)

43
Q

About proteasomes:

A
  • Multi enzyme complexes (not surrounded by membranes)
  • characteristic structure: barrel with lid
  • second pathway of protein degradation: ubiquinilation as signal
44
Q

Number and relative proportion of organelles in a cell:

A
45
Q
A

Molecular Biology (9 decks)

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