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1
Q

What are the principles of cell theory ?

A
  1. All living organisms are composed of one or more cells
  2. The cell is the smallest and most basic unit of life
  3. Cells arise from pre-existing cells
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2
Q

How is SA:V ratio affected when cell size increases ?

A

SA:V decreases

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3
Q

What are the two types of cells ?

A

Prokaryotic cells
Eukaryotic cells

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4
Q

Why is a large SA:V ratio of cells bad ?

A

The cell surface membrane does not have sufficient surface area to support the rate of diffusion required for larger cell volume

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5
Q

Which type of cells are smaller ?

A

Prokaryotes

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6
Q

What does the small size of prokaryotes allow for ?

A

Allows ions and molecules that enter to quickly diffuse to other parts of the cell while any waste products can quickly diffuse out

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7
Q

What are the two types of microscopes ?

A

Light microscope
Electron microscope

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8
Q

Which type of microscope is used to see the organelles within eukaryotic cells?

A

Electron microscope

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9
Q

What is cell fractionation ?

A

A technique used to separate and isolate specific organelles so as to study their respective features and functions

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10
Q

What are the two steps in cell fractionation ?

A

Homogenisation
Centrifugation

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11
Q

What is homogenisation ?

A

The process of breaking open cells to release their cellular contents

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12
Q

How are cells broken apart through homogenisation ?

A

Cutting or grinding process using chemicals, enzymes, sound waves or forcing cells through small spaces at high pressure

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13
Q

What is centrifugation ?

A

The separation and isolation of the difference size cell organelles using centrifugal force

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14
Q

What are the two types of centrifugal techniques ?

A

Differential centrifugation
Density gradient centrifugation

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15
Q

What does differential centrifugation involve ?

A

A series of centrifugation at successively higher speeds, spinning down organelles of increasingly smaller sizes

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16
Q

What does density gradient centrifugation involve ?

A

Setting up a sucrose gradient and organelles of specific sized will migrate during centrifugation to form a band at the position in the gradient where its own density equals that of the sucrose solution

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17
Q

What are the three major differences between prokaryotes and eukaryotes ?

A
  1. Location of DNA
  2. Presence of membrane-bound organelles
  3. Internal membranes
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18
Q

Where is DNA located in eukaryotes and prokaryotes ?

A

Euk :
- linear DNA found in nucleus, enclosed by nuclear envelope
- mitochondria and chloroplast also contain DNA

Prok :
- circular DNA found in nucleoid region not enclosed by membrane
- smaller circular DNA molecules, plasmids, are found throughout the cytoplasm

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19
Q

What are the membrane bound organelles found in euk and prok ?

A

Euk :
- double membrane bound (nucleus, mitochondria, chloroplast)
- single membrane bound (ER, GA, lysosome)

Prok :
- no membrane bound organelles
- have few organelles than euk

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20
Q

What is the membrane system in euk called ? Function ?

A

Endomembrane system
- involved in the synthesis, transport and modification of proteins and lipids

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21
Q

What makes up the endomembrane system in euks ?

A

Nucleus
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Golgi apparatus
Lysosomes and vesicles

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22
Q

What are the three non-membrane bound organelles in an euk ?

A

Ribosomes
Centrioles
Nucleolus

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23
Q

Describe nucleus structure

A

Spherical shape

Enclosed by a double membrane called the nuclear envelope
- nuclear pores present
- outer membrane is continuous with rER

Nucleoplasm, semi-fluid matrix, fills nucleus

Presence of nucleolus

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24
Q

What is the function of nuclear pores present on nuclear envelope ?

A

Function as channels for regulated movement of molecules between nucleus and cytoplasm

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25
What does the nucleolus contain?
Genes coding for ribosomal ribonucleic acid (rRNA)
26
What is the function of the nucleolus ?
Functions as the site of transcription of rRNA and assembly of ribosomal subunits
27
What are the functions of the nucleus ?
Stores hereditary material (DNA) of an organism essential to provide continuity of genetic information to next generation of cells DNA within the nucleus contains genes which are templates for protein synthesis Nucleus controls and directs cell activities by regulating gene expression and protein synthesis
28
What is the structure of a mitochondrion ?
Rod-shaped Double membrane separated by intermembrane space - outer membrane forms smooth continuous boundary - inner membrane is extensively coded into cristae projecting into matrix
29
What is present in mitochondrion makes its special ?
Circular DNA 70S ribosomes Both only present in prok cells
30
What is the function of the mitochondrion circular DNA ?
Codes for some proteins and enzymes in the organelle - allows for protein synthesis to occur
31
What is the function of mitochondrion ?
Site of cellular respiration, a series of biochemical reactions to produce ATP
32
Is mitochondrion or chloroplast larger ?
Chloroplast
33
What is the structure of chloroplast?
Double membrane - chloroplast envelope Thylakoid membrane (3rd membrane) forms network of thylakoids enclosing thylakoid space Thylakoids are stacked to form grana, stacks are joined together by intergranal lamellae
34
What are thylakoids ?
Flattened coin-like sacs enclosing a fluid-filled thylakoid space
35
In which parts of a chloroplast are photosynthetic pigments found ?
Grana Intergranal lamellae
36
What are the three distinct compartments found in chloroplast ?
Intermembrane space - between the two membrane of the chloroplast envelope Stroma - inside envelope but outside thylakoid membrane Thylakoid lumen
37
What structures that chloroplast has that makes it special ?
70S ribosomes Circular DNA
38
What is the function of chloroplast ?
Site of photosynthesis - light dependent reactions of photosynthesis occur on the thylakoid membrane - light independent reactions ( Calvin cycle ) occur in the stroma
39
What is the endosymbiotic theory ?
Theory states that early ancestor of euk cells engulfed an oxygen-using non-photosynthetic prok cell, forming relationship thus becoming endosymbiont (cell living within another cell)
40
What is the structure of endoplasmic reticulum ?
Contains a series of interconnected membranous sacs and tubules called cisternae Rough ER - continuous with outer membrane of nuclear envelope - consists of network of flattened membrane-bound sacs called cisternae with attached ribosomes Smooth ER - series of interconnected tubules with no ribosomes attached
41
What is cisternae and cristae ?
Cisternae : interconnected membranous sacs and tubules in ER Cristae : Infoldings of the inner membrane of mitochondrion
42
What is the function of rER ?
Site of protein synthesis and transport - proteins are synthesised by attached ribosomes - proteins are folded into specific shape in ER lumen - then packed into transport vesicles which bud off rER
43
Can carboxylation of proteins occur in rER?
Addition of carbohydrates can take place in rER but limited to a few types
44
What is the fate of proteins synthesised by rER ?
Secreted out of cell
45
What is the function of sER ?
Site of lipid synthesis Involved in detoxification of drugs and poison Storage of calcium ions required for signal transduction
46
What is the structure of Golgi apparatus ?
Stack of flattened membrane-bound sacs known as cisternae not physically connected Has distinct structural polarity - forming/cis face - maturing/trans face
47
What is the cis and trans face of the GA ?
Cis face : where transport vesicles from ER fuse to Trans face : where secretory vesicles bud off
48
What is the difference between cisternae in ER and that in GA?
In ER cisternae is physically connected In GA they are not
49
What is the function of GA ?
Chemically modify, sort and package the proteins or lipids made in the rER and sER
50
What is the additional function of GA in plant cells ?
Involved in formation of new cell wall during nuclear division - GA vesicles move between daughter nuclei forming new cell membrane with their membranes
51
What are lysosomes ?
Small spherical vesicles formed by vesicles from GA Contains hydrolytic enzymes surrounded by a single membrane Contents are acidic and the enzymes have low optimum pH
52
What are the three functions of lysosomes ?
1. Fuses with vesicles formed by endocytosis and release hydrolytic enzymes into vesicles to digest the materials 2. Autophagy : lysosome fuse with vesicles containing worn-out organelles within a cell to degrade and recycle the contents 3. Autolysis : lysosomes trigger self-digestion of cell by releasing lysosomal contents within a cell
53
What are ribosomes made of ?
Proteins rRNA
54
What type of ribosomes are found in euk? Subunits ?
80s ribosomes - large 60s subunit - small 40s subunit
55
What is the function of ribosome ?
Site of protein synthesis where AA are joined together to form polypeptide via formation of peptide bonds
56
Where are proteins synthesised by free ribosomes designed ?
Within cytosol
57
What is the structure of centrioles ?
Pair of rod-like structures positioned at right angles to each other and situated next to nucleus at region called centrosome Made up of 9 triplets of microtubules arranged in a ring
58
What are the differences between animal cells and plant cells ?
Centrioles present in animal cells, absent in plant cells Chloroplast present in plant cells, absent in anima cells
59
What are microtubules ?
Long hollow tubes made up of tubulins
60
What is the function of centrioles ?
Play a role in nuclear division in animal cells, replicates before cell divides Function as microtubule organising centres (MTOC) for assembly of spindle fibres important for separation of homologous chromosomes and sister chromatids during nuclear division
61
What is the prok cell wall made up of ?
Peptidoglycan
62
What is the structure of peptidoglycan cell wall ?
Parallel polysaccharide chains made of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) The parallel polysaccharide chains are cross-linked at regular intervals by short chains of AA
63
What is the function of peptidoglycan cell wall ?
Prevents bacteria from bursting when it absorbs water - tiny pores in the cell wall allows passage of water Allows for classification into gram positive and negative
64
What are the differences and similarities between cell surface membrane in proks and euks ?
- Both consist of phospholipid bilayer and proteins - prok have higher proportion of proteins than euk - prok does not have cholesterol unlike euk - forms infoldings in prok to carry out specialised functions
65
What type of DNA does prok have ?
Single, double-stranded circular DNA
66
What are plasmids ?
Smaller, double-stranded, circular, extra chromosomal DNA located in cytoplasm of proks
67
What type of genes do plasmids contain ?
Genes not essential for survival or reproduction under normal conditions but are beneficial under stressful condition - eg antibiotic resistance gene
68
Where is bacterial chromosomes found in prok ?
In nucleoid region
69
What type of ribosomes present in prok ? Subunits ?
70s ribosome - large 50s subunit - small 30s subunit

bio (23 decks)

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