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IMAT > The Cell > Flashcards

The Cell Flashcards

1
Q

Modern cell theory

A
  1. All living organisms are composed of one or more cells
  2. Cells are the smallest unit of life ( it it is hot made you cell it cannot be considered ling).
  3. All cell come from pre-existing cells and have the ability to reproduce
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2
Q

Prokaryotic cell

A
  • Small and simple
  • 0.1 - 5 micrometer / 1-10 micrometer
  • Unicellular
  • Nucleus is absent
  • Circular naked DNA
  • Single haploid
  • Lack membrane bound organelle
  • Sexually and asexually reproduction
  • Call division by binary fission
  • Chromosome located in the nucleoid
  • have cell wall ( peptidoglycan)
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3
Q

Eukaryotic cell

A

Large and complex
10 - 100 micrometer
Unicellular or multicellular
Has a nucleus
Linear DNA
Paired diploid
Has a membrane bound organelles
Mostly reproduce sexually
Cell division by mitosis

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4
Q

What are the similarities between prokaryotic and eukaryotic cells?

A

They both have:
Cell membrane
Cytoplasm
Ribosomes
DNA (but in different shapes)

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5
Q

Cytoplasm

A

Intercellular liquid with a gel like consistency
- refer to the total content of the liquid

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6
Q

Plasma membrane

A

• Delimits the cytoplasm
• ** Composed of:* *
Phospholipids, cholesterol and proteins with some oligosacharide chains
• Selectively permeable
• 5-10 nm thick
• lipid bilayer
• hydrophilic areas points outward while the hydrophobic areas points toward one another
• flexible (“fluid”)

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7
Q

Why is the plasma membrane considered flexible?

A

phospholipids can drift to positions elsewhere in the membrane ( rotational, lateral, transverse “flip flop “ )

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8
Q

What affects the membrane fluidity ?

A
    • Fatty heads length **
      The shorter the chain length the move hid the membrane is (the longer the tails, the more interactions they have with one another, the more rigid the membrane is )

** number of double bonds in the tail **
More “kinks”, less packed, more fluid
More unsaturated tails, more fluid

** cholesterol concentration **
Cholesterol function as a buffer - prevents from higher temp. From increasing fluidly and lower temp. From inhibiting fluidity.
Cholesterol stiffens membranes making them rigid - decreases lipid membrane permeability

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9
Q

What are sterols?

A

Family of lipids
Carbon skeleton consisting of 4 fused rings - also known as steroid nucleus
3 ring with 6 carbons and 1 with 5
Planar
Very rigid

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10
Q

What is cholesterol?

A

Type of steroid (most common)
Amphipathic molecule
Integral components of cell membranes

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11
Q

What types of cells can cholesterol be found in?

A

Only animals cells (humans included )
In plants there is ** phytosterol **
Prokaryotes don’t have cholesterol

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12
Q

The relationship between membrane fluidity and temp.

A

A more rigid membrane has a higher melting point

Temp. Increases → kinetic energy of lipids increases → intermolecular interactions between lipids get weaker → increasing membrane fluidity

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13
Q

Selective permeability

A

The plasma membrane creates an effective barrier between the cell and the extracellular environment
Prevents water soluble content inside the cell from escaping outside
Oxygen & carbon dioxide can easily travel though

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14
Q

What is the fluid mosaic model ?

A

Fluid = the ability of the phospholipids to freely diffuse within their own lipid mono -layer.
Mosaic = the whole structure of the plasma membrane as “‘mosaic” of components

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15
Q

What are the three major classes of membrane lipid molecules?

A

Phospholipids
Sterols
Glycolipids

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16
Q

What are lipid rafts?

A

Combination of membrane proteins with different types of lipids and carbohydrates that creat specialized membrane domain

Can drift freely laterally within the membrane bilayer.

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17
Q

integral membrane proteins

A
  • Embedded in the plasma
  • span the entire membrane’s internal hydrophobic area
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18
Q

What are Channels?

A

Integral membrane protein
Allow ions & other molecules to ** passively ** diffuse through them

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19
Q

What are transporters?

A

Integral membrane proteins

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20
Q

What are pumps?

A

Integral membrane proteins
Actively transport molecules into and out of the cell

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21
Q

What are enzymes?

A

Integral membrane proteins
Catalysts that meet some metabolic needs

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22
Q

What are receptors?

A

Integral membrane proteins

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23
Q

What types are there for integral membrane proteins?

A

Channels
Transporters
Pumps
Enzymes
Receptors

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24
Q

Passive transport

A

Molecules that cross the membrane without use of energy (- water, ions, hormones … )
Include - diffusion, facilitated diffusion, osmosis

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25
Q

Diffusion

A

Passive movement of molecules across a membrane from higher region to lower region of concentration - until reaching equal concentration on both sides of the membrane.

No energy is needed

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26
Q

Simple diffusion

A

Substances simply dissolves through the lipid membrane
Example -
Oxygen enters
Carbon dioxide exits

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27
Q

Facilitated diffusion

A

Requires the use of either carrier proteins or protein channels
No energy is needed!!

28
Q

What types of proteins are required for facilitated diffusion?

A

** Carrier proteins**
aka transporters
They physically move relatively large water-soluble molecules, or small changed ions, by changing their own shape
Resemble a PAC -man
Each transporter is specific to one type of molecule!

** protein channels **
Create hydrophilic pores in the membrane
Usually necessary for molecules that are electricalIy charged ( ions )

29
Q

What are aqua porins?

A

Specific protein channels for water molecules.

30
Q

Osmosis

A

Passive passage of water molecules across a semi- permeable membrane from hypotonic area to hypertonic area

31
Q

Water potential

A

Chemical explanation of osmosis.
Symbolized of the Greek letter psi.
Measured in units of pressure (ie. kPa)
The tendency of water molecules to diffuse from one place to another in a solution.
Pure water has a value of 0
Water with solute will have negative value

32
Q

Active transport

A

Pumps or active carriers
Needs energy
Substance is moved against the concentration gradient - the cell invest energy (ATP)
The energy required for this process to occur is used to transfer ions across the membrane, by changing the ** transport protein shape **

33
Q

Endocytosis

A

A process in which the ** outer plasma membrane is pulled inward ** and surrounds the liquid/solid to be moved from the extracellular space into the cell.

There are 3 types:

  • phagocytosis (“cell eating”) -
    engulfment of large particles or small cells by forming pseudopods, extensions of the membrane, and enclosing them in a vesicle or vacuole.
  • pinocytosis (“cell drinking “ ) -
    Random process. Fluid and macromolecules are taken up by the cell
  • receptor mediated Endocytosis -
    Special type of pinocytosis.
    Occur when molecules are selectively needed in higher amounts or with relatively small amounts of extracellular fluid.
    Specific receptors of specific molecules
34
Q

What are the 3 types of endocytosis?

A
  1. Phagocytosis - cell eating
  2. Pinocytosis - cell drinking
  3. Receptor mediated endocytosis - type of pinocytosis
35
Q

Exocytosis

A

Materials are exported or removed from the cell.
Usually carried by vesicles from the Golgi apparatus and fuse with the plasma membrane.
Enables:
- secreting materials os hormones, enzymes…
- supplying the membrane with fresh made lipids and proteins
- In plants, transporting cell wall building materials to the outside surface of the cell membrane

36
Q

What are the functions of the plasma membrane?

A
  1. Protection for the cell
  2. Fixed environment inside the cell
  3. Transport nutrients into the cell
  4. Transport toxic substances out of the cell
37
Q

Cell size

A

Animal cells diameter range from 10 -100 micrometer (not always)
Most cells are invisible to us

38
Q

What is a Light microscope?

A

A microscope that uses light source and various sizes of magnifying lenses du visualize a certain object.
** magnify up to 1000 -1500 times **
Minimum diameter is can magnify is 0.2 micrometer

39
Q

What kinds of objects are seen by a light microscope?

A

Most animal cell
Most plant cell ( 40 micrometer)
Cellular structure - nuclei, mitochondria (1 micrometer)
Most bacteria ( 500 - 1000 nanometer = 0.5 - 1 micrometer)

40
Q

What is an electron microscope?

A

A microscope hat uses a beam of electrons that passes through a specimen (sample), it can magnify up to 500,000 Times & see objects with diameter as small as 0.5 nm.
Cannot distinguish individual molecules.

41
Q

What kind of objects can be seen by an electron microscope?

A

Viruses
Ribosomes ( ~ 20 nm )
Thickness of the cell membrane
Diameter of a DNA molecule

42
Q

How can you calculate magnification?

A

Magnification = observed size of the image / actual size of the object
M = I / A

43
Q

What is the actual size of a Red blood cell?

A

8 micrometer

44
Q

Surface area to volume ratio

A

The ratio between surface of membrane and volume of cytoplasm need to be as high as possible.

45
Q

What will happen if the ratio between the surface area to the volume is too small?

A

Decreased rate of chemical exchange → cellular needs aren’t met→ the cell will die

46
Q

Some prokaryotic cells also have…?

A
  • Pili: for attachment to other cells or surfaces & sexual reproduction
  • plasmids: small circles of DNA that may be present in several copies. Different types may be present within the same cell
  • capsule: my provide additional protection
  • flagellum: locomotion
47
Q

What is the nucleus?

A

A prominent organelle inside an eukaryotic cell.
Contains DNA
Has a bilayer membrane - “nuclear envelope”- has “holes” called nuclear pores that enable the passage of materials.
Prominent structure called nucleolus - specialized in synthesis of molecules called ribosomal- RNA

48
Q

Endoplasmic reticulum (ER)

A

Network of membranes continuous with the nuclear envelope
Built from 2 subunits - rough surfaced ER (rER) & smooth surfaced ER (sER)

49
Q

Rough ER

A

In rER, the ER membrane is coated with attached ribosomes.
It consists of parallel sheets of flattered cistrnae.
** main site of synthesis and folding of proteins ** - mainly proteins destined for secretion, integral membrane protein and cytosolic proteins (lysosomes)

50
Q

Smooth ER

A

No ribosomes bound to it.
Contains enzymes
Generally tubular
Functions :
1. Synthesis of lipids - steroid hormones & phospholipids (formed by enzymes that are bound to the cytosolic surface )
2. Storage of Ca ions in muscle cells
3. Detoxification of drugs & alcohol - in liver cells

51
Q

Golgi apparatus

A

Made up of steels of flattened, membrane enclosed sacs, called cisternae (near the nucleus)
Surrounded by ** single ** lipid bilayer

Function as “post translational modification “ -
Golgi “process” the protects hat have been synthesized in the rER.
The synthesized protein are collected and then modified by different enzymes.

Two Sistine faces: cis & trans
Substances move from the rER cisternae to the Golgi apparatus in small transport vesicles, which merge with the receiving region (cis face ) and exit through the shipping region (trans face).

52
Q

Lysosomes

A

” The garbage can of the cell “
- In animal cell - 0.1 - 0.5 micrometer
- In plant cells- the large central vacuole may act as lysosome
- pH -5.5 ( optimal for enzymes function)
- contain proof pumps in their membrane
- * * functions: **
1. Degradation of exogenous macromolecules
2. Removal of excess or nonfunctional organelle

53
Q

what is autophagocytosis?

A

Also called autophagy
A membrane from the sER wraps around the nonfunctional organelle or cytoplasmic portion to destined be removed, thus producing an autophagosome
Which later will fuse with lysosomes to allow digestion.
Than the digested products from the Autophagesames are recycled and used again in the cytoplasm.

54
Q

Mitochondria

A
  • The largest factory for the production of energy (mainly ATP ).
  • enveloped by a double membrane
  • 0.5-1 micrometer diameter
  • length up to 10 micrometer
  • contain their own cyclic DNA & enzymes necessary for aerobic respiration
  • have inter-membrane space between the layers
  • the inner membrane : delimits the matrix, has numerous long folds called cristae (increase membrane surface)
  • no. Of mitochondria ill end cell is associated with the cell energetic demands
55
Q

Peroxisomes

A
  • Single lipid-bilayer membrane
  • the membrane contains different enzymes
    1.oxidases - make H2O2
    2. Peroxifases - breaks H2O2
    3. b oxidation enzymes - ( metabolism of fatty acids ) produce & degrade H2O2
  • 0.1 -1 micrometer
  • can be formed by 2 possible ways:
    1. growth & subsequent division of pre-existing peroxisomes
    2. Budding of precursor vesicles from the ER
56
Q

Cytosol

A

Refers to the “Net” liquid inside the cell, exclude the organelles the liquid found inside of them.( unlike cytoplasm ).

57
Q

Vacuoles

A
  • Large membrane bound vesicles
  • found in plant cells
  • provide storage.
  • 2 types:
    1. Central vacuole - can occupy were than A half of the cell’s volume & storage organic nutrition and water inside → helping the cell expand und keep its shape
    2. Food vacuoles - formed by phagocytosis of exogenous material.
58
Q

Chloroplasts

A
  • Enveloped by a double-layerd membrane
  • large
  • only in plant cells & algae
  • inner system called thylakoids (made made of stacks of membrane) - contain green pigment called chlorophyll
  • contain DNA
59
Q

Endomembrane system

A

System of membranes and organelle that interact to allow the transport of proteins and lipids within the cell
Members of the system: plasma membrane nuclear envelope, ER ( smooth & rough ), Golgi apparatus & lysosomes

60
Q

The cytoskeleton

A
  • A network of fibers extending throughout the cytoplasm of the cell
  • maintain the cell’s shape
  • Organizes structures & activities
  • assist with transport
  • provide anchoring points for the other cellular structurs/organelles

** 2 main roles**
Support - mechanical support, maintain shape, anchoring
Mobility - changes in cell location & movement of cell parts (requires interactions with motor proteins ).

** components **
1. Microtubules
2. Intermediate filaments
3. Microfilaments

61
Q

Microtubules

A
  • 25 nm
  • hollow tubes
  • made from globular proteins (tubulins)
  • tubulin protein is a dimer
  • grow in length by adding tubulin dimers
  • ** enable the cell to resist external compressive forces **
  • create pathways that guide vesicles from the ER to the Golgi and from there to the plasma membrane
  • involved in the separation of chromosomes (formation of centrioles & centromeres)
  • responsible for cell motility ( cilia / flagella)
62
Q

Centrosomes & centrioles

A

centrosome -
a region usually located near the nucleus.
Within there is a pair of centrioles.

Centriole -
Composed of 9 sets of triplet microtubules arranged in a ring.

  • help organize micro tubule assembly in animal cells
  • not every cell have centrosome with centrioles
63
Q

Cilia & flagella

A
  • Microtubule - containing extensions
  • provide motility
  • Flagella: * longer, usually limited to just one or several per cell, whip like motion
  • Cilia: * shorter, more abundant, similar motion to the oars of a racing crew boat
  • non-mobile primary cilia have a 9 +0 organization and May act as a single receiving “Athena”
64
Q

Axoneme

A
  • Microtuble-based cytoskeleton structure
  • forms the core of a cilium or flagellum
  • internal machinery structure formed through a 9+2 organization of microtubules
  • responsible for the beating of flagella & cilia
65
Q

Intermediate filaments

A
  • Fibrous proteins
  • 8-12 nm
  • their structural vole is to **bear tension **
  • heterogeneous class of cytoskeleton elements → each filament type is constructed from a particular molecular subunit.

Example: a -keratin

66
Q

Microfilaments

A
  • 7 nm
  • they are made of globular protein called actin
  • also called “ actin filaments “
  • are used for: motility, shaping and signaling

IMAT (32 decks)

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