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AS Biology > F211 Cell Structure > Flashcards

F211 Cell Structure Flashcards

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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
Q

Golgi Body

Structure

A

A stack of membrane bound flattened sacs

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27
Q

Ribosomes

Structure

A

Tiny organelles
Some are free in the cytoplasm
Some are bound to endoplasmic reticulum
Each is made up of two subunits

28
Q

Ribosomes

Function

A

Site of protein synthesis in the cell

29
Q

Golgi Body

Function

A

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
Q

Mitochondria

Function

A

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
Q

Plasma Membrane

Structure

A

Phospholipid bilayer
Channel and carrier proteins
Glycoproteins and glycolipids
Cholesterol between phospholipids

31
Q

Plasma Membrane

Function

A

Protects the cell from its surroundings
Selectively permeable
Controls the movement of substances in and out of the cell

31
Q

Cellulose Cell Wall

Structure

A

Primary cell wall made up of cellulose microfibrils, pectin and soluble proteins
Primary cell wall in between plasma membrane and middle lamella

31
Q

Cellulose Cell Wall

Function

A

For support and structure
Protection against mechanical strength and infection
Enables the transport of substances in and out of the cell

32
Q

Vacuole

Structure

A

Membrane bound mass of fluid containing nutrients and waste products
Surrounded by tonoplast membrane

33
Q

Vacuole

Function

A

Isolates and stores materials within a cell

34
Q

Lysosomes

Structure

A

Spherical sacs surrounded by a single membrane

35
Q

Lysosomes

Function

A

Contain powerful digestive enzymes to break down materials in the cell

36
Q

Chloroplasts

Structure

A

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
Q

Flagella

Function

A

Propels a cell
Used for movement
Allows a cell to move

38
Q

Cilia

Structure

A

Short extensions if eukaryotic cells

Hair like appearance

38
Q

Cilia

Function

A

May be used for locomotion

Used to move fluids or mucus over a surface

39
Q

Chloroplasts

Function

A

Site of photosynthesis in plant cells

40
Q

Flagella

Structure

A

Whip like structure

42
Q

Centrioles

Structure

A

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
Q

Centrioles

Function

A

Take part in cell division

Form fibres known as the spindle which move chromosomes during nuclear division

44
Q

Micro Filament

Size

A

7nm

44
Q

Protein Synthesis

Transcription

A

The base sequence of the DNA is copied on to the mRNA

44
Q

Protein Synthesis

mRNA travels to ribosome

A

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
Q

Protein Synthesis

Stages

A 
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
Q

Cytoskeleton

A 
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
Q

Micro Filament

Composition

A

Long thin stringy proteins

Mostly actin

48
Q

Protein Synthesis

Translation

A

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
Q

Protein Synthesis

Rough Endoplasmic Reticulum

A

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
Q

Micro Filament

Function

A

Help cells move

50
Q

Protein Synthesis

Golgi Body

A

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
Q

Protein Synthesis

Exocytosis

A

The vesicle fuses to the cell surface membrane and ten protein is released out of the cell

52
Q

Intermediate Filament

Size

A

8-10nm

53
Q

Function of the Cytoskeleton

A

Moving organelles around the cell
Supports the structure of the cell
Hold organelles in place inside the cell
Transports vesicles around the cell

54
Q

Intermediate Filament

Composition

A

Rope like and fibrous

Variety of proteins

56
Q

Intermediate Filament

Function

A

Increase cellular stability
Provide mechanical strength to cells and tissues
Resist stress

58
Q

Microtubles

Size

A

25nm

60
Q

Microtuble

Composition

A

Thick strong spirals of thousands of subunits made of protein - tubulin

61
Q

Microtuble

Function

A

Helps with various transport functions
Can move a microorganism through a liquid
Used to waft liquid past a cell

AS Biology (15 decks)

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