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cells Flashcards

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Biology 101 flashcards
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
Q

What does the nucleolus contain?

A

Genes coding for ribosomal ribonucleic acid (rRNA)

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26
Q

What is the function of the nucleolus ?

A

Functions as the site of transcription of rRNA and assembly of ribosomal subunits

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27
Q

What are the functions of the nucleus ?

A

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

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28
Q

What is the structure of a mitochondrion ?

A

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
Q

What is present in mitochondrion makes its special ?

A

Circular DNA
70S ribosomes

Both only present in prok cells

30
Q

What is the function of the mitochondrion circular DNA ?

A

Codes for some proteins and enzymes in the organelle - allows for protein synthesis to occur

31
Q

What is the function of mitochondrion ?

A

Site of cellular respiration, a series of biochemical reactions to produce ATP

32
Q

Is mitochondrion or chloroplast larger ?

A

Chloroplast

33
Q

What is the structure of chloroplast?

A

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
Q

What are thylakoids ?

A

Flattened coin-like sacs enclosing a fluid-filled thylakoid space

35
Q

In which parts of a chloroplast are photosynthetic pigments found ?

A

Grana
Intergranal lamellae

36
Q

What are the three distinct compartments found in chloroplast ?

A

Intermembrane space - between the two membrane of the chloroplast envelope

Stroma - inside envelope but outside thylakoid membrane

Thylakoid lumen

37
Q

What structures that chloroplast has that makes it special ?

A

70S ribosomes
Circular DNA

38
Q

What is the function of chloroplast ?

A

Site of photosynthesis
- light dependent reactions of photosynthesis occur on the thylakoid membrane
- light independent reactions ( Calvin cycle ) occur in the stroma

39
Q

What is the endosymbiotic theory ?

A

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
Q

What is the structure of endoplasmic reticulum ?

A

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
Q

What is cisternae and cristae ?

A

Cisternae : interconnected membranous sacs and tubules in ER

Cristae : Infoldings of the inner membrane of mitochondrion

42
Q

What is the function of rER ?

A

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
Q

Can carboxylation of proteins occur in rER?

A

Addition of carbohydrates can take place in rER but limited to a few types

44
Q

What is the fate of proteins synthesised by rER ?

A

Secreted out of cell

45
Q

What is the function of sER ?

A

Site of lipid synthesis
Involved in detoxification of drugs and poison
Storage of calcium ions required for signal transduction

46
Q

What is the structure of Golgi apparatus ?

A

Stack of flattened membrane-bound sacs known as cisternae not physically connected

Has distinct structural polarity
- forming/cis face
- maturing/trans face

47
Q

What is the cis and trans face of the GA ?

A

Cis face : where transport vesicles from ER fuse to

Trans face : where secretory vesicles bud off

48
Q

What is the difference between cisternae in ER and that in GA?

A

In ER cisternae is physically connected
In GA they are not

49
Q

What is the function of GA ?

A

Chemically modify, sort and package the proteins or lipids made in the rER and sER

50
Q

What is the additional function of GA in plant cells ?

A

Involved in formation of new cell wall during nuclear division
- GA vesicles move between daughter nuclei forming new cell membrane with their membranes

51
Q

What are lysosomes ?

A

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
Q

What are the three functions of lysosomes ?

A
  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
Q

What are ribosomes made of ?

A

Proteins
rRNA

54
Q

What type of ribosomes are found in euk? Subunits ?

A

80s ribosomes
- large 60s subunit
- small 40s subunit

55
Q

What is the function of ribosome ?

A

Site of protein synthesis where AA are joined together to form polypeptide via formation of peptide bonds

56
Q

Where are proteins synthesised by free ribosomes designed ?

A

Within cytosol

57
Q

What is the structure of centrioles ?

A

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
Q

What are the differences between animal cells and plant cells ?

A

Centrioles present in animal cells, absent in plant cells

Chloroplast present in plant cells, absent in anima cells

59
Q

What are microtubules ?

A

Long hollow tubes made up of tubulins

60
Q

What is the function of centrioles ?

A

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
Q

What is the prok cell wall made up of ?

A

Peptidoglycan

62
Q

What is the structure of peptidoglycan cell wall ?

A

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
Q

What is the function of peptidoglycan cell wall ?

A

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
Q

What are the differences and similarities between cell surface membrane in proks and euks ?

A
  • 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
Q

What type of DNA does prok have ?

A

Single, double-stranded circular DNA

66
Q

What are plasmids ?

A

Smaller, double-stranded, circular, extra chromosomal DNA located in cytoplasm of proks

67
Q

What type of genes do plasmids contain ?

A

Genes not essential for survival or reproduction under normal conditions but are beneficial under stressful condition
- eg antibiotic resistance gene

68
Q

Where is bacterial chromosomes found in prok ?

A

In nucleoid region

69
Q

What type of ribosomes present in prok ? Subunits ?

A

70s ribosome
- large 50s subunit
- small 30s subunit

bio (23 decks)

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