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E) Cell Biology - Term 1 > Cell Membrane and prokaryotes > Flashcards

Cell Membrane and prokaryotes Flashcards

Cell membrane Prokaryotes

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1
Q

Who was the first person who observed cells under a microscope? how did they describe what they saw?

A

It was Robert Hooke. He said he saw Little boxes, referring to cells.

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2
Q

First to observe living cells?

A

Anton van Leeuwenhoek. He also made lenses and microscopes

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3
Q

where were the moving animalcules from? who did this?

A

Anton van Leeuwenhoek Examined pond water and bacteria scraped from his teeth -described them as moving “animalcules”

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4
Q

who are the three scientists that developed the cell theory? what did each of them say and when?

A

Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.

  1. Mathias = Plants were made of cells and plant embryos arose from a single cell
  2. Theodor = All organisms are composed of one or more cells. The cell is the structural unit of life.
  3. Rudolf = 3rd principle of cell theory: “cells can arise only by division from pre-existing cell”
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5
Q

What are the three basic tenets of modern cell theory?

A
  1. All living things are made up of cells
  2. Cells are the basic unit of structure and function in living things
  3. Living cells come only from other living cells
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6
Q

The 9 fundamental properties of the cells

A
  • Cells are highly complex and organized
  • Cells possess a genetic program and the means to use it.
  • Cells are capable of producing more of themselves
  • Cells acquire and utilize energy
  • Cells carry out a variety of chemical reactions
  • Cells engage in mechanic activities
  • Cells are able to respond to stimuli
  • Cells are capable of self-regulation
  • Cells evolve
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7
Q

who performed the first culture of human cells? when? what type of cells did he culture?

A

1951
George Gey of Johns Hopkins University
• Malignant tumor from Henrietta Lacks –HeLa cells
Still cultured in labs today

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8
Q

what do we mean by cells are complex? what is the consequence of this complexity?

A

Complex –consisting of many different and connected parts

The more complex a structure, the greater the number of parts that must be in their proper place,
the less tolerant of errors in the nature and interactions of the parts,
and the more regulation or control that must be exerted to maintain the system.

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9
Q

what is the general morphology of bacteria ?

A

Nano 0.05-0.2 micro meters in diameter

To very large 600 x 80 micro meters

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10
Q

why are bacteria small?

A

Nutrients and wastes are transported in and out of the cell via the cytoplasmic membrane.

The rate of Transport determines the metabolic rate and therefore the growth rate of microbial cells.

The smaller the size of the bacteria the larger the surface area of the cytoplasmic membrane to volume therefore the faster the potential growth rate

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11
Q

what are the different types of shapes for bacteria?

A

Cocci
Bacilli
Filamentous - form long multinucleate filaments that made branch to produce a network called a mycelium

Spirilla - rigid spirals
Spirochetes - flexible spirals
Misc shapes and
Pleomorphic - variable in shape

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12
Q

how is the prokaryotic cell organization? name them inner to outer.

A
  • it has a cytoplasm which contains a variety of components
  • plasma membrane
  • periplasmic space with periplasm
  • cell wall
  • slime layer or capsule
  • flagella and pili
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13
Q

what is cytoplasm matrix? where is it and what are the 7 things found in it?

A

The cytoplasmic matrix is a substance lying between the plasma membrane and the nucleus which contains mostly water and a variety of components.

Found in it are:

  1. Ribosomes
  2. Proteins
  3. Inclusion bodies
  4. Organic materials
  5. Inorganic materials
  6. Carboxysomes
  7. Gas vacoules
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14
Q

what organic materials are found in cytoplasmic matrix?

A
  • glycogen a polymer of glucose it is a carbon source
  • poly beta hydroxybutyrate also a carbon source
  • cyanophycin nitrogen source
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15
Q

what inorganic materials are found in cytoplasmic matrix?

A

Polyphosphate or volutin it’s a phosphate source also there is iron and sulphur

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16
Q

discuss carboxysomes and gas vacuoles.

A

Carboxysomes contain the enzyme ribulose 1.5 bisphosphate carboxylase which is important for incorporation of carbon dioxide.

Gas vacoules?

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17
Q

what is the plasma membrane? what is it also called?

A

A plasma membrane also called inner membrane or cytoplasmic membrane is a phospholipid bilayer with proteins inserted into it.

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18
Q

describe the structure and functions of plasma membrane.

A

Lipid bilayer.
Functions of plasma membrane:
1. Retains cytoplasm
2. The plasma membrane is a selectively permeable barrier it allows small neutral or charged molecules to come in (h2o, o2, co2). These can Transverse through the membrane.

But large molecules like glucose and ions or small charged atoms and protons H+ require specific transport systems.

  1. Transport of nutrients and waste
  2. Generation of energy, biosynthesis
  3. Contains receptor proteins for environmental signals
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19
Q

protoplast?

A

Cytoplasm + plasma membrane = protoplast

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20
Q

what is the fluid mosaic model?

A

-the fluid mosaic model describes the structure of the plasma membrane as a mosaic of components including phospholipids cholesterol proteins and carbohydrates that gives the membrane a fluid like character.

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21
Q

what are the three basic components of the structure of eubacterial membrane?

A
  1. Phospholipid bilayer
  2. Proteins
  3. Hopanoids
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22
Q

what is phospholipid bilayer and where is found?

A

The phospholipid bilayer

the bilayer is composed of two sheets each composed of phospholipids

nonpolar hydrophobic fatty acid ends of each of the two sheets of the bilayer they interact with each other

the polar hydrophilic water loving, face either the aqueous cytoplasm or the periplasm

Lipids are frequently bound to glycerol molecules in ether linkages

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23
Q

why are there proteins on the plasma membrane?

A

Integral proteins
are inserted in the membrane amphipathic

Peripheral proteins
are loosely associated with the membrane they can be dissociated with salt

distribution and properties of proteins on each side of the bilayer are different therefore the functions of the two bilayers are different.

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24
Q

hopanoids?

A

They are rigid planar Penta cyclic molecules similar to cholesterol that stabilize the membranes in some but not all eubacteria

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25
Q

what is the basic structure of archaebacterial membranes?

A

Lipids are isoprenoids instead of fatty acids

Ether linkage to glycerol instead of Ester

some have a monolayer instead of by layer due to tetra ethers

the diversity of membranes is related to the diverse habitats in which archaebacteria live

for example thermophiles live at extremely high temperatures and have almost all tetra ethers which stabilizes the membrane at high temperatures

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26
Q

in internal membranes, what are mesosomes?

A

Mesosomes are invaginations in the plasma membrane function unclear may be an artefact of sample preparation

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27
Q

describe the cell wall and its functions.

A

The cell wall is a strong structural layer that lies outside the plasma membrane but does not include capsule or slime layer cell wall plus capsule equals cell envelope

functions include shape protection from osmotic lysis defence against host immune response

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28
Q

what are gram positive bacteria?

A

Gram-positive bacteria are bacteria with peptidoglycan, t e i c h o i c acid and l i p o t e i c h o i c acid

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29
Q

what are gram negative bacteria?

A

Gram negative bacteria have peptidoglycan periplasmic space outer membrane proteins and lipo polysaccharide

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30
Q

discuss the chemical composition of eubacterial cell walls.

A

Cell walls are made up of peptidoglycan also known as murein layer

peptidoglycan is a polymer of two sugar derivatives called glycans its n a g and letter n a m.

The nag is n acetyl glucosamine and the nam is n acetyl muramic acid.

Connection of polymer strands in the different bacteria:
1. Gram-negative bacteria link between their amino acids is attached to one nam on one polymer and amino acid on nam on another polymer.

  1. Gram-positive bacteria peptide interbridge typically five glycines that connects the peptides on different polymers
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31
Q

nucleoid in bacteria. describe it.

A

The nucleoid of bacterial cell usually contains a single long continuous and frequently circularly arranged thread of double-stranded DNA called the bacterial chromosome.

No histones

Plasmids - small usually circular double-stranded DNA molecules called plasmids

plasmids may carry genes for such activities as antibiotic resistance tolerance to Toxic metals the production of toxins and the synthesis of enzymes

Plasmids can be transferred from one bacterium to another in fact plasmid DNA is used for Gene manipulation in biotechnology

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32
Q

what are plasmids and where are they found?

A

A plasmid is a DNA molecule that is separate from and can replicate independently of the chromosomal DNA in bacteria

they are double-stranded and in many cases circular

plasmids usually occur naturally in bacteria but are sometimes found in eukaryotic organism

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33
Q

describe mesosomes.

A

Mesosomes are invaginations of inner cytoplasmic membrane they are there to increase the surface area for metabolism

they are in foldings of the cell membrane possible role in cell division photosynthetic pigments or respiratory chains

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34
Q

what are fimbriae/ pili and why do bacteria have these?

A

Fimbriae/pili are projections from the cell membrane through the cell wall to permit specific attachment to surfaces

found in gram negative bacteria they are shorter and finer than flagella they are composed of protein subunits called pilins

adhesins are minor proteins at the tips of the pili responsible for the attachment

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35
Q

ordinary pili vs sex pili

A

Ordinary Pili is for adherence of bacteria to host cells

Sex pill is for attachment of donor and recipient cells in bacterial conjugation

36
Q

what are flagella? what is the protein it is composed of?

A

Flagella are threadlike appendages and they are composed of protein subunits called flagellin

the flagella is a means to propel the bacteria it is a different what are two eukaryotic version

flagella is very highly antigenic

removed like if mechanically cut off or if it’s removed by mechanical agitating, a new flagella is rapidly formed and the motility is rapidly restored

37
Q

if flagella is chopped off, what happens next?

A

The flagella grows back

38
Q

list the functions of cell membranes.

A

It separates interior cell contents from the surroundings

forms a protective barrier and controls what moves in and out of the cell

Maintains electric potential of the cell

39
Q

what are phospholipids? describe the components of their structure.

A

Phospholipids are the structural units of membranes

they consist of one phosphate one variable one glycerol molecule 2 fatty acids saturated fatty acid and unsaturated fatty acid

40
Q

what happens when phospholipids come into contact with water? how do they arrange themselves?

A

When phospholipids come in contact with water and they will spontaneously arrange themselves in
micelles may also form bilayers

liposomes closed body or in a
membrane

The charged hydrophilic heads facing outward to interact with water the hydrophobic tails are facing inward to create nonpolar oily core un

41
Q

what is meant by hydrophobic and hydrophilic? how do these relate to phospholipids?

A

Hydrophobic means water fearing

hydrophilic means water loving

so what this means for phospholipids is that when they form the bilayer for cell membranes their heads Will line up and face the cytoplasm of water thingy and the tails will come in the middle and be away from the water

42
Q

— represents fundamental organization of all biological membranes.

A

Lipid bilayer

43
Q

what is the framework of membranes called?

A

Phospholipids

44
Q

what are the 3 general categories of membrane proteins?

A
  1. Integral proteins
  2. Peripheral proteins
  3. Lipid anchored proteins
45
Q

what are some of the properties of integral proteins?[2]

A

They are transmembranal and amphipathic

46
Q

what is meant by amphipathic? discuss

A

It means having a hydrophilic and hydrophobic region

hydrophilic regions react with hydrophilic phospholipid heads
hydrophobic regions form strong interactions with hydrophobic core of the phospholipid bilayer

47
Q

why are integral proteins well embedded in the membrane and difficult to remove experimentally?

A

Because of amphipathic property that they have.

48
Q

List the function of integral proteins.

A
  1. They are specialised ports that freely admit selected ions like sodium and potassium
  2. Transport proteins and facilitate movement of selected substances into and out of the cell
  3. They are enzymes larger globular proteins that carry out enzyme functions while embedded in the membrane
  4. Form a support that may form Bridges with cytoskeleton
49
Q

what are peripheral proteins? where are they found?

A

Peripheral proteins that also membrane proteins they are found on the surface of the membrane.

They are held in place by either ionic interactions with charged phospholipid heads

Or interaction with integral proteins

they are easily extracted from the membrane with salt Solutions unlike integral proteins

50
Q

what holds peripheral proteins in place?

A

Ionic interactions with charged phospholipid heads or interaction with integral proteins

51
Q

how are peripheral proteins extracted from the membrane?

A

Salt solution

52
Q

lipid anchored proteins, what are they and where are they anchored?

A

Extend part of the way through the membrane but well into the core where they are anchored they are anchored in the core

Anchorage is provided by lipid side chains which intermingle with those of the membrane.

53
Q

what provides anchorage for these proteins?

A

Lipids side chains which intermingle with those of the membrane.

54
Q

what is meant by glycocalyx? and its functions.

A

Glyco calyx means sugar coating appears as a fuzzy in distinct outermost layer on TEM.

55
Q

define glycoproteins.

define glycolipids. why they are outside?

A

Short chains of carbohydrate attached to the surface proteins and lipids
they can either be glycoproteins or glycolipids

Glycoproteins: Integral proteins with only their carbohydrate chains protruding from the surface

Glycolipids: lipid tail anchored in phospholipid bilayer with the carbohydrate chain protruding from the surface

56
Q

what are their functions? [glycolipids and glycoproteins]

A

Glycolipid function is binding of bacterial cells to each other and to cell surfaces of organisms they invade.

Glycoproteins act as receptors for chemical messengers and cell recognition

glycolipids and glycoproteins on red blood cells are antigens used for determining Abo blood groups.

57
Q

briefly discuss the fluid mosaic model.

A

It refers to the fluid like properties of phospholipid bilayer and patchwork arrangement of its components

model means it’s still tentative

the bilayer is a stable configuration for phospholipids but other molecules can move quite freely in the membrane because it is held together by hydrophobic forces or bonds which are weak forces

molecules generally slide around but don’t flip planes

58
Q

why can other molecules move easily in the membrane even though there’s a bilayer?

A

Because the membrane has got hydrophobic bonds holding it which are weak forces

59
Q

—generally slide around but don’t flip planes.

A

Molecules

60
Q

name 3 factors that the degree of fluidity (of the membrane) depends on.

A

The degree of fluidity of the cell membrane depends on

number 1 which type of fatty acids predominate in the membrane
number 2 depends on temperature
number 3 depends on the amount of cholesterol

61
Q

what is the function of tight junctions? what is another name for tight junctions?

A

Tight junctions aka Occluding junctions (zonula occludens)
Found: on the lateral surface of cells immediately below the luminal surface

Functions of tight junctions:
1. Binds cells tightly together so luminal contents don’t pass between the cells also known as zonula occludens.

  1. Prevent movement of membrane components between different compartments for example integral proteins etc on apical surface from moving to lateral surface
  2. Form interconnected ridges with no intercellular space
62
Q

describe the composition of tight junctions?

A

Composed of a complex of proteins which connect two membranes tightly together by forming a series of studs which appear as interconnected ridges with no intercellular space

63
Q

define adhering junctions. what is their function?

A

Adhering junctions are called anchoring junctions

their function is to maintain cellular position

there are different types of desmosomes(adhering junctions)

  1. Belt desmosomes also known as zonula adherens
  2. Spot desmosomes also known as macula adherens

they form plaques just below cell membrane bound to cytoskeletal elements and to a similar structure in an adjacent cell or the extracellular Matrix.

64
Q

what are the different types of desmosomes? [2]

A
  1. Zonula adherens

2. Macula adherens

65
Q

what are gap junctions?

A

Gap junctions are communicating junctions

66
Q

what is a cluster of pores called?

A

Connexon.

Each each connexon is aligned with a similar pore in an adjacent cell

each connexon is made of six integral membrane proteins called connexins

67
Q

discuss what is meant by this cluster.

A

This is a cluster of pores called connexon, each is aligned with a similar pore in an adjacent cell, the cell next to it has a similar connexon so that they they can have an opening like a pipe to allow stuff to go through and each of these connexons is made of 6 integral proteins called connexins.

68
Q

what is the function of gap junctions?

A

So, gap junctions function as a channel between adjacent cells

they function as a free passage of water small molecules some signalling molecules and positive ions

they allow movement of excitation across sheets of muscle. the pore is closed by high concentrations of calcium

Seals off apoptotic cells from neighboring cells

69
Q

what causes the closure of the gap junction pore?

A

The pore is closed by high concentrations of calcium

70
Q

define cilia and flagella.

A

They are mobile projections of the plasma membrane they are composed of microtubules

core axoneme 9 microtubule doublets around a central

  • doublet (9 +2) Containing a basal body anchored in cell membrane.
  • 9 microtubule triplets same as centrioles

Dyeins attached to doublet and enable movement

71
Q

what is core of actin filaments?

A

Core of actin filaments is attached to Terminal web of actin filament running under the apical surface of the cell

72
Q

discuss hemidesmosomes.

A

On Basal surface of the cell membrane in some epithelia

They connect cell to basement membrane
They consist of a plaque of integral proteins with intermediate filaments attached

73
Q

what are microvilli, discuss properties?

A

Microvilli are small finger-like projections of the cell membrane on the apical or luminal surface

they are there to increase the surface area up to 30 fold
they are found on epithelia with absorptive function like the intestinal lining

they are up to 3000 microvilli per cell
they are visible as a brush border on the light microscope.

74
Q

which side of the cell are microvilli found on?

A

Apical or luminal surface

75
Q

describe stereocilia. where are they found?

A

Stereocilia are longer than microvilli and they are branched

they have a similar actin core to microvilli

they are found in epididymis in male reproductive tract and they may have absorptive function

76
Q

differentiate between saturated and unsaturated fatty acids.

A

Saturated fatty acids have no double Bonds in their structure and unsaturated fatty acids have at least one double bond between its carbons in its structure

77
Q

what is the effect of the amount of cholesterol on membrane fluidity?

A

The more cholesterol the more fluid the membrane

fluidity can increase or decrease in response to temperature as well but this is different for different cell types

78
Q

effect of temperature on fluidity of the membrane.

A

Cold temperature mean less fluidity some cells adjust phospholipid content of membrane when exposed to cold temperature

79
Q

what are the apical and basal surfaces in contact with?

A

Apical surface is in contact with the lumen and the basal surface is in contact with the basement membrane

80
Q

list the 3 types of junctions between cells.

A
  1. Tight junctions - prevent movement of substances between cells
  2. Adhering Junction - maintain cellular positions
  3. Gap junctions - allow movement of substances

the hemidesmosome is a junction between cells and basement membrane

81
Q

what are the functions of these types?

A

Tight junctions prevent movement of substances between cells

adherens junctions maintain cellular position

gap junctions allow movement of substances

the junction between cells and basement membrane is called hemidesmosomes yo!

82
Q

what is the junction between cells and basement membrane called?

A

Hemidesmosome

83
Q

list the specialization (special structures) of the apical membrane.

A

Microvilli stereocilia cilia flagella

84
Q

what are tight junctions? where are they found?

A

Tight junctions are occluding junctions also called zonula occludens

they are found on the lateral side or lateral surface of cells immediately below the luminal surface

85
Q

Ribosomes

A

Found in all eukaryotic and prokaryotic cells function is protein synthesis

cells that have high rates of protein synthesis such as those that are actively growing have a larger numbers of ribosomes

Ribosomes are composed of two subunits the 50s and 30s larger subunit and smaller subunit respectively and they have a type of RNA called ribosomal RNA

prokaryotic ribosomes are called 70s ribosomes and those of eukaryotic cells are known as 80s ribosomes.

E) Cell Biology - Term 1 (2 decks)

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