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Biosci107 > Lecture 6 > Flashcards

Lecture 6 Flashcards

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
Q

How is dna present most of the time

A

Chromosome and chromatin fibers

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26
Q

What is a chromosome

A

Comprises of many genes

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27
Q

What is a gene

A

Segment of dna that codes for a trait - phenotypr

28
Q

What are ribosomes

A

Two subunits small and large made of ribosomal rna (rRNA) in complex with many proteins. These are translating proteins

29
Q

What is the function of ribosomes

A

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
Q

Where protein is made is dictated by what its function will be

A

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
Q

Where is rrna made

A

Nucleolus - subunits assemble in the nucleolus and leave via nuclear pores
They then hang in cytosol until needed by rna for ribosome activities

32
Q

Two types of er

A

Rough and smooth

33
Q

What is the er

A

An extensive network of tubes and tubules stretching out from the nuclear membrane

34
Q

What is the rer

A

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
Q

Why does rer membrane surround protein to form transport vesicles

A

Protein needs to be membrane bound to travel

36
Q

Major function of rer is production of

A

Secreted proteins
Membrane proteins
Organelle proteins

37
Q

Process of rer

A

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
Q

Smooth er functions

A

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
Q

Examples of smooth er

A

Liver houses enzymes for detoxification and for glucose release
Muscle - calcium ions

40
Q

What is the golgi apparatus

A

Squiggly shape outside er
The warehouse for recieving and modifying

41
Q

How is the golgi made

A

3-20 flattened membranous sacs called cisternae stacked on top of one another - pita bread

42
Q

Functions of golgi

A

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
Q

Golgi in goblet cells

A

Goblet cells need to release mucus into the duodenum
Means more golgi present as they need to be modifying and secreting more mucus

44
Q

Cis face of golgi

A

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
Q

Trans face of golgi

A

Shipping side of golgi

46
Q

Golgi to destination

A

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
Q

Endocytosis vs exo

A

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
Q

What are lysosomes

A

Vesicles formed from golgi membrane and they contain powerful digestive enzymes which destroy things

49
Q

Main function of lysosomes is digestion of

A

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
Q

Lysosomes are important for the

A

Destruction of pathogens

51
Q

Main function of the mitochondria

A

Generation of atp through cellular respiration

52
Q

Mitochondria are made up of

A

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
Q

More mitochondria where

A

More energy is required by cell - more atp must be made and therefore more
Mitochondria

54
Q

Unique mitochondria feature

A

Has its own ancestry - carries a seperate small (37 genes) genome encoding mitochondrial specific products

55
Q

Enzymes in mitochondria found where

A

Cristae and ribosomes floating in matrix

56
Q

What is the cytoskeleton

A

Structural support system of the cell
Fibres or filaments that help to maintain the size shape and integrity if the cell

57
Q

Three types of fibres from smallest to largest in cytoskeleton

A

Microfilaments
Intermediate filaments
Microtubules

58
Q

Function and purpose of cytoskeleton

A

Acts as scaffolding across the cell
Involved in intracellular transportation and cell movement

59
Q

Cytoskeleton microfilaments

A

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
Q

Diameter of cytoskeleton microfilaments

A

7nm

61
Q

Function of cytoskeleton microfilaments

A

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
Q

Cytoskeleton intermediate filaments diameter

A

8-12nm

63
Q

Features of intermediate filaments in cytoskeleton

A

Found in cytoplasm
Comprised of diverse range if different materials eg keratin

64
Q

Function if intermediate filaments in cytoskeleton

A

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
Q

Diameter of microtubules

A

25nm with central lumen 15nm

66
Q

Features of microtubules

A

Comprised of tubulin dimers alpha and beta which are coiled to form a tube
Microtubules extend from centriole into cytoplasm/nucleus

67
Q

Functions of microtubules

A

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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