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Biosci107 > Lecture 6 > Flashcards

Lecture 6 Flashcards

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1
Q

What is the cell theory

A

All living organisms are composed of one or more cells
The cell is the basic unit of structure and organisation
All cells arise only from pre existing cells

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2
Q

Universal similarities between cells

A

Dna as heritable material Rna as messenger and proteins as workers
Major cellular organelles - functions and arrangements within the cell
Atp is energy source

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3
Q

Central dogma

A

Theory genetic info flows in one direction from dna to rna to protein

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4
Q

What do both prokaryotes and eukaryotes have

A

Plasms membrane, cytosol, Dna, rna, protein and ribosomes

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5
Q

Prokaryotes

A

Lack membrane bound nucleus

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6
Q

Eukaryotic cells

A

Have membrane bound organelles and are much larger

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7
Q

What is cytoplasm

A

Everything inside plasma membrane including organelles but excluding nucleus
Fluid portion called cytosol

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8
Q

What is cytosol made of

A

Water plus dissolves and suspended substance like atp and ions and proteins and lipids

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9
Q

What is the endomembrane system

A

Along with plasma membrane the organelles work together to package label and ship molecules
Membrane molecules are shared and vesicles can go from one to another

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10
Q

Major organelles in the endomembrane system

A

Nucleus
Rough and smooth er
Golgi apparatus
Lysosomes

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11
Q

Major organelles not in endomembrane system

A

Ribosomes
Mitochondria - has membrane but is not shared

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12
Q

Plasma membrane

A

Semi permeable barrier controlling the passage of substances in and out of the cell

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13
Q

Key feature of cell membrane

A

Double layer phospholipid with embedded protein - it is a physical barrier which separates the inside and outside of cell

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14
Q

Phospholipid features

A

Hydrophilic polar phosphate heads
Hydrophobic lipid tails of fatty acids
Arranged as double layer around cytoplasm tail to tail

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15
Q

Plasma membrane proteins

A

Mediate movement of hydrophilic substances
Often amphipathic - made up of different amino acids that are folded in 3D outward facing protein part is hudrophilic and inside is hydrophobic

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16
Q

Two different types of plasma membrane proteins

A

Integral proteins
Peripheral membrane proteins

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17
Q

Integral proteins

A

Partially or fully embedded into membrane (sometimes might not go fully to other side)
Transmembrane proteins are integral membrane proteins that go from one end to the other and fully span entire membrane - contracting both extracellular and cytoplasmic areas
Intercellular communication
The region in lipid hydrophobic area of cell membrane must also be hydrophobic but can be prevented by mutations

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18
Q

Peripheral membrane proteins

A

Associated with the membrane but not actually embedded in it

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19
Q

What do plasma membrane proteins do

A

1 - transport via channels and transporters eg passive transport for atp - may be general or selective gated or not
2 - enzymatic activity - carry out chemical reaction by being part of team of enzymes and substrates bind to active site
3 - signal transduction - binding to external signal molecule causes protein shape to change and communicates message to other side of cell
4 - cell-cell recognition
5 - intercellular joining
6 - attachment to cytoskeleton and ecm

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20
Q

Membranes are not static

A

Molecules bobbing in fluid bilayer of phospholipids and cell specific and dynamic repertoire of membrane bound proteins present as required

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21
Q

Nucleus features

A

Enclosed by double lipid bilayer called nuclear envelope , continuous with rough er
Entry and exit through nuclear pores
Protein signals at the end of protein with import and export signals
Ribosomes
Nuclear envelope
Outer membrane
Inner membrane
Nuclear pore
Nucleolus
Chromatin
Rough er

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22
Q

Functions of nucleus

A

To house and protect dna
Make rna and assemble rna
Pores regulate movement of substances eg protein and mrna in and out
Molecules segregation to allow temporal and spatial control of cell function
Dynamic

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23
Q

How does dna form chromatin

A

Dna wrapped 2x around group 8 histones to form nucleosomes which are collectively known as chromosomes

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24
Q

How does chromatin form chromosomes

A

As cell prepares for division, chromatin condenses to form chromatin fibers then condenses further into loops and then stacks as chromosomes

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25
How is dna present most of the time
Chromosome and chromatin fibers
26
What is a chromosome
Comprises of many genes
27
What is a gene
Segment of dna that codes for a trait - phenotypr
28
What are ribosomes
Two subunits small and large made of ribosomal rna (rRNA) in complex with many proteins. These are translating proteins
29
What is the function of ribosomes
Protein production (translation) found in two places within the cell. After transcription and modification then dna goes through ribosomes for translation Found free in cytoplasm or attached in rer
30
Where protein is made is dictated by what its function will be
Free in cytoplasm - making proteins to be used in the cytosol (non-endomembrane destinations) - all proteins that are made in cells start life by getting translated in ribosomes which are free in the cytoplasm and some go thru rer Or attached to rer - making non cytosolic proteins/endomembrane - these proteins leave and go outside of cell
31
Where is rrna made
Nucleolus - subunits assemble in the nucleolus and leave via nuclear pores They then hang in cytosol until needed by rna for ribosome activities
32
Two types of er
Rough and smooth
33
What is the er
An extensive network of tubes and tubules stretching out from the nuclear membrane
34
What is the rer
Rough er - continuous with nuclear envelope Dotted with attached ribosomes Proteins enter lumen within the rer for folding Rough er membrane surrounds the protein to form transport vesicles destined for the golgi.
35
Why does rer membrane surround protein to form transport vesicles
Protein needs to be membrane bound to travel
36
Major function of rer is production of
Secreted proteins Membrane proteins Organelle proteins
37
Process of rer
Starts off on free cytosol ribosome but if there is a certain signal with that amino acid then it will dock onto the outside of the ribosome and protein will be synthesised into the inside of the rer Vesicles form around protein and take it where it needs to go
38
Smooth er functions
Vary greatly from cell to cell and are very tissue/cell specific - housing unit for proteins and enzymes - synthesizes lipids, including steroids and phospholipids - storage of cell specific proteins, not all cells make all proteins
39
Examples of smooth er
Liver houses enzymes for detoxification and for glucose release Muscle - calcium ions
40
What is the golgi apparatus
Squiggly shape outside er The warehouse for recieving and modifying
41
How is the golgi made
3-20 flattened membranous sacs called cisternae stacked on top of one another - pita bread
42
Functions of golgi
Modify, sort, package and transport proteins received from the rough er using enzymes in each cisternae Formation of - secretory vesicles (proteins for exocytosis) -membrane vesicles (pm molecules) -transport vesicles (molecules to lysosomes)
43
Golgi in goblet cells
Goblet cells need to release mucus into the duodenum Means more golgi present as they need to be modifying and secreting more mucus
44
Cis face of golgi
Receiving side of golgi and closest to rer to receive vesicles that come out of rer and modifies them further to make molecular signatures
45
Trans face of golgi
Shipping side of golgi
46
Golgi to destination
Each sac or cisternae contains enzymes of different functions Proteins move cis to trans from sac to sac Mature at exit cisternae Travel to destination Modifications occur within each sac (formation of glycoprotein, glycolipid and lipoproteins)
47
Endocytosis vs exo
Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane, and bringing it into the cell. Exocytosis describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell.
48
What are lysosomes
Vesicles formed from golgi membrane and they contain powerful digestive enzymes which destroy things
49
Main function of lysosomes is digestion of
Substances that enter a cell Autophagy of cell components and old organelles that need destroying - the lysosome engulfs breaks down and recycles the parts - entire cells is autolysis Once digested all building blocke like amino acids lipids etc are recycled
50
Lysosomes are important for the
Destruction of pathogens
51
Main function of the mitochondria
Generation of atp through cellular respiration
52
Mitochondria are made up of
Outer mitochondrial membrane Inner mitochondrial membrane with folds called cristae Fluid filled interior cavity called matrix Although there are 2 membranes mitochondria are not part of the endomembrane system as there is no vesicle sharing
53
More mitochondria where
More energy is required by cell - more atp must be made and therefore more Mitochondria
54
Unique mitochondria feature
Has its own ancestry - carries a seperate small (37 genes) genome encoding mitochondrial specific products
55
Enzymes in mitochondria found where
Cristae and ribosomes floating in matrix
56
What is the cytoskeleton
Structural support system of the cell Fibres or filaments that help to maintain the size shape and integrity if the cell
57
Three types of fibres from smallest to largest in cytoskeleton
Microfilaments Intermediate filaments Microtubules
58
Function and purpose of cytoskeleton
Acts as scaffolding across the cell Involved in intracellular transportation and cell movement
59
Cytoskeleton microfilaments
Found under microvilli - around periphery and lining the interior of cell Comprised of actin molecules assembled in two long chains twisted around each other
60
Diameter of cytoskeleton microfilaments
7nm
61
Function of cytoskeleton microfilaments
Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins and promote amoeboid mobility if required eg macrophage - structure and support and microvilli creation They are dynamic and assembled/disassembled as required for cell
62
Cytoskeleton intermediate filaments diameter
8-12nm
63
Features of intermediate filaments in cytoskeleton
Found in cytoplasm Comprised of diverse range if different materials eg keratin
64
Function if intermediate filaments in cytoskeleton
Bear tension and weight throughout the cell eg during cell anchoring Acts as scaffolding for cellular organelles like nucleus Usually the most permanent of cytoskeleton structures as they are less dynamic
65
Diameter of microtubules
25nm with central lumen 15nm
66
Features of microtubules
Comprised of tubulin dimers alpha and beta which are coiled to form a tube Microtubules extend from centriole into cytoplasm/nucleus
67
Functions of microtubules
Support cell shape and size Guide for movement of organelles like vesicles from golgi to membrane Chromosome organisation - cell division Support and movement of cilia/flagella Are dynamic so assembled and disassembled as required

Biosci107 (3 decks)

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