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F211 Cell Structure Flashcards

0
Q

Magnification

Formula

A

Magnification = Image Size / Actual Size

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1
Q

Magnification

Definition

A

Degree to which size of image is larger than the object itself

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2
Q

Resolution

Definition

A

Degree to which it’s possible to distinguish between two objects that are close together

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3
Q

Light Microscope

Magnification

A

1500x

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4
Q

Scanning Electron Microscope

Magnification

A

100 000x

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5
Q

Transmission Electron Microscope

Magnification

A

500 000x

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6
Q

Light Microscope

Advantages

A

Relatively cheap
Easy to use
Portable

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6
Q

Light Microscope

Disadvantages

A

Low resolution

Can’t give a detailed picture of internal cell structure

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7
Q

Light Microscope

Resolution

A

200nm

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8
Q

Light Microscope

Specimens

A

Wide range of organisms including:
Live organisms
Thin sections of larger plants and animals
Smear preparations of blood or cheek cells

Not for internal cell structure as the resolution isn’t high enough

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9
Q

Light Microscope

Specimen Preperation

A
  1. Staining - coloured stains allow the specimen to be seen easier e.g. acetic orcein stains DNA red, gentian violet stains bacterial cell walls
  2. Sectioning - specimens are embedded in wax allowing thin sections to be cut without distorting the structure, useful for soft tissue e.g. brain
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10
Q

Light Microscope

Function

A
  1. Light passes from a bulb under the stage, through a condenser lens, then through the specimen
  2. The beam of light is focused through the objective lens, then through the eye piece lens
  3. Different objective lenses can be rotated into position to change the magnification
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12
Q

Scanning Electron Microscope

Function

A
  1. The electron beam is directed at the sample
  2. Electrons aren’t absorbed, they are bounced off the sample
  3. The final image is produces a 3D. IWW of the surface of the sample
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14
Q

Electron Microscopes

Advantages

A

Resolution is 0.2nm
Can be used to produce detailed images of the structures (organelles) inside the cell
The SEM produces 3D images

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15
Q

Electron Microscope

Limitations

A

Samples have to be placed in a vacuum or electron beams are deflected by molecules in the air
Extremely expensive
Preparation of samples and microscope operation requires a high degree of skill and training

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16
Q

Vesicles

Definition

A

Membrane bound sacs found in cells

Used to carry various substances around cells

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17
Q

Nucleus

Structure

A

Surrounded by a nuclear envelope
The nuclear envelope is a structure made of two membranes separated by fluid
Holes called nuclear pores go right through the envelope and allow relatively large molecules to pass through
The nucleolus is a dense spherical structure inside the nucleus
When stained the nucleus shows darker patches known as chromatin

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18
Q

Nucleus

Function

A

Contains nearly all the cells genetic material
The chromatin consists of DNA and proteins, it has the instructions for protein synthesis
Some of these proteins regulate the cells activity
When cells divide chromatin divides in to two visible chromosomes
The nucleolus makes RNA and ribosomes which pass out into the cytoplasm

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19
Q

Transmission Electron Microscope

Function

A
  1. The electron beam passes through a very thin prepared sample
  2. Electrons pass through denser parts of the sample less easily giving some contrast
  3. Produces a final 2D image
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21
Q

Rough Endoplasmic Reticulum

Structure

A

Series of flattened membrane bound sacs

Studded with ribosomes

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22
Q

Rough Endoplasmic Reticulum

Function

A

Transports proteins that were made on the attached ribosomes
Some proteins may be secreted from the cell
Some proteins will be placed on the cell surface membrane

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23
Q

Smooth Endoplasmic Reticulum

Structure

A

Series of flattened membrane bound sacs called cisternae
No ribosomes
Fairly evenly distributed throughout the cell

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24
Q

Smooth Endoplasmic Reticulum

Function

A

Involved in making the lipids that a cell needs

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25
Q

Mitochondria

Structure

A

Two membranes separated by a liquid filled space
The inner membrane is folded to form cristae
The central part of the mitochondrion is called the matrix

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26
Golgi Body | Structure
A stack of membrane bound flattened sacs
27
Ribosomes | Structure
Tiny organelles Some are free in the cytoplasm Some are bound to endoplasmic reticulum Each is made up of two subunits
28
Ribosomes | Function
Site of protein synthesis in the cell
29
Golgi Body | Function
Receives and modifies proteins from the ER May add sugar molecules to them Packages the modified proteins into vesicles that can be transported Some modified proteins may go to the surface of the cell to be secreted
30
Mitochondria | Function
Produce most of the adenosine triphosphate (ATP) during respiration Almost all activities that take place in the cell are driven by energy released from ATP Contain their own mitochondrial DNA, genes which are essential for respiration
31
Plasma Membrane | Structure
Phospholipid bilayer Channel and carrier proteins Glycoproteins and glycolipids Cholesterol between phospholipids
31
Plasma Membrane | Function
Protects the cell from its surroundings Selectively permeable Controls the movement of substances in and out of the cell
31
Cellulose Cell Wall | Structure
Primary cell wall made up of cellulose microfibrils, pectin and soluble proteins Primary cell wall in between plasma membrane and middle lamella
31
Cellulose Cell Wall | Function
For support and structure Protection against mechanical strength and infection Enables the transport of substances in and out of the cell
32
Vacuole | Structure
Membrane bound mass of fluid containing nutrients and waste products Surrounded by tonoplast membrane
33
Vacuole | Function
Isolates and stores materials within a cell
34
Lysosomes | Structure
Spherical sacs surrounded by a single membrane
35
Lysosomes | Function
Contain powerful digestive enzymes to break down materials in the cell
36
Chloroplasts | Structure
Two membranes separated by a fluid filled space Inner membrane is continuous Inside the membranes is an elaborate network of flattened membrane sacs called thylakoids Stacks of thylakoids are called grana (granum singular) Chlorophyll molecules are present on the thylakoid membranes and the inter granal membranes
37
Flagella | Function
Propels a cell Used for movement Allows a cell to move
38
Cilia | Structure
Short extensions if eukaryotic cells | Hair like appearance
38
Cilia | Function
May be used for locomotion | Used to move fluids or mucus over a surface
39
Chloroplasts | Function
Site of photosynthesis in plant cells
40
Flagella | Structure
Whip like structure
42
Centrioles | Structure
Small tubes of protein fibres | There is a pair of the next to the nucleus in animal cells and in the cells of some protoctists
43
Centrioles | Function
Take part in cell division | Form fibres known as the spindle which move chromosomes during nuclear division
44
Micro Filament | Size
7nm
44
Protein Synthesis | Transcription
The base sequence of the DNA is copied on to the mRNA
44
Protein Synthesis | mRNA travels to ribosome
Single stranded mRNA leaves the nucleus through a nuclear pore Enters the cytoplasm to find a ribosome either attached to the rough Endoplasmic reticulum or free in the cytoplasm
45
Protein Synthesis | Stages
``` Transcription mRNA travels to ribosome Translation Primary structure of polypeptide enters RER where it assumes secondary and tertiary structures Modified and packaged in the Golgi body Exocytosis ```
46
Cytoskeleton
``` A network of fine filaments or fibres that run through the cytoplasm of a cell There are three types of filament 1. Micro filaments 2. Intermediate Filaments 3. Microtubles ```
47
Micro Filament | Composition
Long thin stringy proteins | Mostly actin
48
Protein Synthesis | Translation
Occurs at the ribosome The base sequence on the mRNA is 'read' and used to join the correct amino acids together in the correct sequence to form the primary structure of a polypeptide
48
Protein Synthesis | Rough Endoplasmic Reticulum
Primary structure if the polypeptide enters the rough Endoplasmic reticulum As it moves through the RER it assumes its secondary and tertiary (3D) structure The polypeptide is packaged into a vesicle and pinched off of the RER The cytoskeleton is involved in transporting the vesicle to the Golgi body
49
Micro Filament | Function
Help cells move
50
Protein Synthesis | Golgi Body
The vesicle fuses to become one of the flattened sacs of the Golgi body The Golgi body modifies the protein and packages it into a vesicle The vesicle is pinched off the Golgi body and carried by the cytoplasm to the cell membrane
51
Protein Synthesis | Exocytosis
The vesicle fuses to the cell surface membrane and ten protein is released out of the cell
52
Intermediate Filament | Size
8-10nm
53
Function of the Cytoskeleton
Moving organelles around the cell Supports the structure of the cell Hold organelles in place inside the cell Transports vesicles around the cell
54
Intermediate Filament | Composition
Rope like and fibrous | Variety of proteins
56
Intermediate Filament | Function
Increase cellular stability Provide mechanical strength to cells and tissues Resist stress
58
Microtubles | Size
25nm
60
Microtuble | Composition
Thick strong spirals of thousands of subunits made of protein - tubulin
61
Microtuble | Function
Helps with various transport functions Can move a microorganism through a liquid Used to waft liquid past a cell

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