Chapter 1: Cell Structure Flashcards
How many millimetres in a metre
1000mm
How many micrometers in a metre
10^6 Mm
How many nanometers in a metre
10^9 nm
How many metres in a Mm and nm
Mm- 10^-6 m
nm- 10^-9 m
What is magnification
Number of times greater an image is than an object
What is formula for magnifications
M=I/A
image/actual
What are cell organelles?
Structurally and functionally distinct parts of cells that have their own functions
Nucleus is enclosed by a _ made up of _ also called _
Double membrane
Outer and inner membranes
Nuclear envelope
Nucleus continues to form ER. What do these 2 aid in? (#4)
Ribosome, nucleotide, hormone, ATP production
What are the raw materials for protein synthesis in a non dividing cell
RNA
Ribosomes
What makes up the chromatin network? How does it behave during cell division?
Loosely coiled threads of DNA and proteins called histones
Condenses (wraps tightly around histones and coils further) to form chromosomes containing genes in DNA
Function of nucleolus?
Ribosomal factory with it’s own DNA and RNA
Function of nuclear pore :
Controls material exchange between nucleus and cytoplasm
What is transcription?
When DNA is converted to mRNA in nucleus
(gene switched on, RNA polymerase at promoter, unzipped gene, complementary RNA bases, modifications to remove noncoding regions)
What is translation?
When mRNA is converted to proteins in the cytoplasm/ribosomes
(ribosome reads, tRNA brings amino acids(20) each of 3 bases- codons, and form a chain)
ER has _ membrane
1
Appearance of rough ER + function:
Ribosomes present
Protein synthesis
Appearance of smooth ER + function:
No ribosomes
Lipid, cholesterol, steroid synthesis
A ribosome is a _
Non membrane bound organelle
Where are 70S ribosomes found?
Prokaryotes (bacteria), mitochondria, chloroplasts
Where are 80S Ribosomes found?
Eukaryotes
What are Ribosomes made of
rRNA
Proteins
What is the Svedberg unit and what does it depend on?
Measure of ribosome size
Rate of sedimentation in centrifuge
What are the functions of Golgi complex?
Collection
Modification
Sorting of proteins and lipids
And of course distribution
How is a protein modified? Give 4 ways
- Glycosylation- addition of glucose residue to form glycoprotein
- Methionine amino acid group is removed to convert inactive protein to active one
- Phosphorylation- addition of phosphate group
- Protein folds into tertiary/quarternery protein
How are lipids modified? 2 ways
Glycosylation- giving glycolipid
Phosphorylation- giving phospholipid
Protein/lipid loaded vesicles from ER fuse with Golgi body at _ end and leave at _ end
Cis/forming end
Trans/budding
The secretory pathway has 2 targets. Either _ or _
Other organelles eg lysosome
Cell membrane; vesicles fuse with it and contents are thrown out - exocytosis
Lysosomes have _ and are a site of _
Hydrolytic enzymes
Intracellular digestion
How do lysosomes breakdown 1)old organelles 2)damaged cells
1) organelle is unfolded by membrane into phagocytic vacuole, +enzymes, egestion
2) it breaks and spreads contents across cytoplasm
Sperm heads have _ for _
Acrosome
Destroy path to egg
4 functions of lysosome
Old organelles breakdown
Old cells breakdown
Foreign disease organisms breakdown
Sperm head
pH of lysosome is
Acidic
Outer mitochondrial membrane is _ and consists of aqueous _ called _ which _
Permeable
Protein channels
Porins
Passes small water soluble molecules
pH of intermitochondrial space is
Acidic (H+)
Inner mitochondrial membrane is _ and has folds called _ to increase _ for _
Semi permeable
Cristae
Surface area
Efficiency of respiration/ATP production
The matrix is site of
Krebs cycle/aerobic respiration
Where is Atp synthase found and it’s function?
Cristae
Atp synthesis
Mitochondria have _ ribosomes
70S
Mitochondria are able to replicate because?
They have circular DNA
Function of mitochondria is
Acts as powerhouse for cells/ATP production
Chloroplasts are site of
Light reactions of photosynthesis
State chloroplasts membranes and eachs nature
Envelope made of
Outer- permeable
Inner- semipermeable
Why can chloroplasts self replicate
Have own circular DNA
What is the matrix of a chloroplast? It’s the site of?
Stroma
Dark reactions of photosynthesis
State the main structures in chloroplasts which capture light
Grana are stacks of thylakoids which house chlorophyll pigment and electron carriers
Light reactions produce - and - which provide raw material for - and the end product is -
ATP
NADPH
Dark reaction
Starch
What is the Endosymbiotic Theory?
Eukaryotic cell originated from a symbiotic relationship among prokaryotes
Free living Prokaryotes such as ancestral aerobic/photosynthetic bacteria began living inside eukaryotes and were modified as to be useful to the host cell and make it efficient
Why can mitochondria and chloroplasts now not grow outside host cells?
They lost cell walls and much of DNA
They aren’t likely to adapt too quickly
3 evidences for Endosymbiosis?
Like bacteria;
- chloroplasts and mitochondria divide by binary fission
- own circular DNA
- own 70S ribosomes
What is cell membrane made of
Phospholipids + transport proteins
Function of cell membrane?
Controls substance exchange between cell and it’s environment ie boundary
Nature of cell membrane is
Semipermeable
2 modifications of cell membrane with regard to microvilli
They increase surface area of small intestine for absorption of digested food
Line pct of nephron for maximum reabsorption
1 microtubule made of _ _
13 protofilaments
Protofilaments are made of
Tubulin proteins; α and β, which together form a dimer by polymerisation . This dimer is a helical ring with hollow centre
Where does assembly (polymerisation) and disassembly of microtubules occur?
MTOC
microtubule organizing centre
How are MTOC in animal cells
Centrosomes
How are MTOC in plant cells
Absent
How are MTOC in organisms having cilia and flagella ie beating movements
Centriole OR basal body
3 functions of microtubules?
- acts like a cytoskeleton holds cell in place
- intracellular transport ie movement of organelles, vesicles to organelles
- form spindle fibres for separation of chromosomes during cells division
State the composition of centrosome and Centriole
Centrosome : 2 centrioles perpendicular
Centriole : 9+0 arrangement of 9 microtubule triplets
Location of microtubules
Cytoplasm
What are Paramecium
Unicellular ciliate
Moves and sweeps prey using cilia
What are Euglena
Unicellular flagellate (2 flagellae) Motor to push through water
How do plants produce spindle fibres
MTOC in centrosome region
Nature of cell wall
Freely permeable
Plant cell wall made of
Cellulose
What are plasmodesmata
Cytoplasm strands linking adjacent plant cells
What is middle lamella
Sticky substance made of calcium pectate cementing adjacent plant cells together
2 functions of cell wall
Gives cell shape
Prevents cell from bursting when water enters by osmosis
Functions of vacuole
1) Regulates osmotic properties or cell by controlling water movement inside and outside the cells
2) Stores pigments, sugars, minerals, O2, CO2, waste substances and enzymes
State vacuole size and no in plants and animals
Plants: one big central v
Animals: many small vs
What is a tonoplast
The surrounding membrane of vacuole which is semipermeable and controls exchange in and out of it
What are isotonic, hypotonic, hypertonic
Iso : same concentration no net change
Hypo : solution is less concentrated water flows into cell and swells (no burst in plants)
Hyper : solution more concentrated water flows out and cell shrinks (in plants flaccid and plasmolysis)
What’s the size of the nucleus?
10-20 Mm diameter
What’s the size of the nucleus?
10-20 Mm diameter
What’s the size of the nuclear pore?
40-100 nm
What’s the size of the chloroplast?
3-10 Mm
What’s the size of the mitochondria?
1-10 Mm
What’s the size of the ribosome?
20-25 nm
What’s the size of the nucleolus?
1 Mm
What’s the size of the lysosome?
0.1-1.2 Mm
What’s the size of the Centriole?
0.5 Mm
What’s the size of the cell membrane?
7 nm thickness
State virus composition
Nature: Nucleic acid (DNA/RNA)
Protein coat called capsid made of smaller subunits ie capsomeres
DNA has - strands
RNA has - strands
2
1
Nature of virus:
Parasitic, only active inside living organisms bodies
How do viruses reproduce?
Genetic material takes over protein synthesis machinery of host to reproduce virus particles (fuses with host dna, produces altered virus mrna and hence translates it’s own proteins)
5 differences between plant and animal cells:
1) cell wall in plants only
2) chloroplasts in plants only for photosynthesis
3) large permanent central vacuole in plants, many small in animals
4) centrioles centrosomes present in animals only
5) plasmodesmata and middle lamella in plants only
Similarities between plant and animal cells
cell membrane, nuclei, mitochondria, golgi, ER present
What is in folding of cell membrane in prokaryotes called and what’s it’s function (#3)
Mesosome
Increase surface area for: respiration/photosynthesis/nitrogen fixation
Prokaryotes DNA is
Circular ring and free lying
Prokaryotes only have plasmids. What are they and what are 2 functions
Extrachromosomal circular DNA
Responsible for antibiotic resistance in bacteria and used in genetic engineering as a gene vector
What does bacteria cell wall contain?
Murein A peptidoglycan (protein+carbohydrate)
Nature of prokaryotes cell membrane is
Semipermeable
What are pili on prokaryotes used for?
Attachment to surfaces, or other cells for sexual reproduction
What and where is capsule of prokaryotes
Additional protection
Surrounding cell wall
Which structures are always present in prokaryotes
Circular DNA Cell wall Cell membrane Cytoplasm 70S ribosome
Compare the diameter of prokaryotes and eukaryotes
P- 0.5-5Mm
E- 40Mm, and 1000-10,000× the volume
Compare the DNA shape, structure and location in P and E
P- circular, naked, free in cytoplasm
E- linear, proteins(histones)+DNA giving chromosomes, double membrane nucleus
Compare ribosome size in P and E
P- smaller 70s, 20nm diameter
E- larger 80s, 25nm diameter
Compare ER in P and E
P- not present
E- present, may have ribosomes
Compare types of organelles present in P and E in terms of compartmentalization and division of labour
P- no membrane bound organelles unless formed by infoldings of cell membrane
E- single, double or no membrane bound organelles
Compare examples of organelles in P and E
P- ribosome, microtubules, centriole (no membrane)
E- lysosome, golgi, vacuole, ER (single)
- nucleus, mitochondrion, chloroplast (double)
- ribosome, microtubule, centriole (no membrane)
Compare cell walls in P and E
P- made of murein, a peptidoglycan (Polysaccharide+amino acids)
E- plants- cellulose/lignin
- fungi- chitin (nitrogen containing polysaccharide like cellulose)
What is a microscope
It helps visualise very small objects that cannot be seen with the naked eye
State the source of illumination for a light microscope
Light
What is the resolution of light microscope and why is it significant
200nm
Any object with less less than 200nm cannot be seen using a light microscope because it cannot block light waves
State and explain each of the 3 lens in a light microscope
Condenser lens: focuses light onto specimen on slide
Objective lens: collects light passing through specimen and produces magnified image
Eye piece lens: magnifies and focuses image from objective lens onto eyev
What is light microscope lens made of
Glass
What stain is used for light microscope
Colored dye
Why are objects stained?
If transparent light passes through and won’t be visible. And the dye each part of a cell retains will make it easy to identify separate parts eg nucleus holds more so less light passes hence darker compared to cytoplasm
Source of illumination for Electron microscope ?
Electron beam
State and explain each of the 3 lens in a electron microscope
Condenser lens: focuses light onto specimen on slide
Objective lens: collects light passing through specimen and produces magnified image
Projector lens: focuses magnified image onto screen
What are EM lens made of
Electromagnet
What stain is used in EM
Heavy metal
Stops electron passage
Why can only dead specimen be seen using EM, unlike LM
Specimen need to be dehydrated ie dead because water boils at room temp in a vacuum and can hinder view under EM
Why is specimen kept in vacuum in EM?
Prevent collision of electrons and air molecules
Which would scatter prevent a sharp picture
Compare resolution of SEM with TEM
TEM is higher
SEM - 0.5nm
TEM- 0.05nm
State the difference between how SEM and TEM work
SEM - reflected electron beam forms image
TEM - transmitted electron beam firms image
What can SEM and TEM help in viewing
SEM - cell surface structure
TEM - internal structure
What is resolution?
Ability of a microscope to distinguish between 2 objects very close together. The higher the resolution, the greater the detail that can be seen
What is formula for resolution
Lambda/2 where lambda is wavelength of light source
What is the electromagnetic spectrum?
Whole range of wavelengths
Relate wavelength to frequency
Lambda = 1/V(frequency)
Relate frequency and wavelength to energy
V α E greater the frequency, greater the energy
Shorter the wavelength, greater the energy
Electrons and light are both forms of -
Radiation
Cell surface membrane is also called -
Plasma membrane
What is DNA
Molecule containing instructions that control cell activities
What is nucleolus
Made of loops of DNA from several chromosomes
What is the cytoplasm
Aqueous material between nucleus and cell surface membrane
What is compartmentalization and why is it important
Organelles are surrounded by membranes so their activities are separated from the cytoplasm
Efficiency
What does it mean when a cell shows division of labor?
Sharing of work between different specialised/function organelles
What is function of chlorophyll/in chloroplast
Absorbs light during photosynthesis
2 differences between cell wall and cell membrane?
Wall is thick, membrane is thin
Wall is freely permeable, membrane is partially
What is an eye piece graticule
Transparent scale with 100 divisions. Used in microscope eyepiece so it can be seen along with object
How is eyepiece graticule calibrated
A small transparent ruler with subdivisions (0.1-0.01mm) called stage micrometer is placed on the microscope stage and superimposed with graticule
How is eyepiece graticule calibrated
A small transparent ruler with subdivisions (0.1-0.01mm) called stage micrometer is placed on the microscope stage and superimposed with graticule
Formula or what ever for calibrating value of 1 eyepiece unit
x mm of stage micrometer in y eyepiece units/100
this value× no of eye piece units gives actual size of object
To convert from mm to Mm you should?
×1000
How to calculate magnification using scale bar?
Measure scale bar (observed)
Convert to Mm
Divide by given scale bar length (A)
What’s photomicrograph/electron micrograph
Image from light microscope/electron micrograph
If 2 objects are closer than 200nm they can’t be seen as separate points on a -?
Light microscope
How does the brain distinguish between visible light wavelengths
Converts them to colors
All waves travel at the same
Speed
What is the maximum magnification of light microscope
1500
Why is 200nm the best resolution of LM
The smallest wavelength is 400nm of violet, and half of radiation is the limit of resolution. Hence <200nm cannot be seperately from nearby objects
State types of radiation in increasing wavelength
Gamma Xray Ultraviolet Visible light Infrared Microwaves Radio waves
Why are electrons suitable for microscopy
Wavelength is very short so resolution can be very small
They are negatively charged and can be focused easily using electromagnets (alters beam path) in comparison with similar wavelength xray hard to focus
How are electrons produced for microscopy
Metal heated. Energy gained by electrons and escape orbits
1 advantage and disadvantage of SEM
Specimen is in focus and a 3d picture achieved at the same time
Resolution not as good as TEM
What is ultrastructure
Fine structure of a cell as revealed by an EM
ER and golgi have an extended system of flattened sacs called _
Cisternae
What is a golgi body
Constantly forming and broken stack of cisternae and it’s vesicles
Golgi enzymes convert sugars in plants to
Cell wall components
Golgi vesicles are used to make digestive organelles called
Lysosomes
Lysosome structure :
Spherical sac
Single membrane
Hydrolytic enzymes inside
The inner mitochondrial membrane is a selective barrier meaning
Controls what ions and molecules enter matrix
Function of mitochondria
Aerobic respiration
3 organelles with envelopes/double membrane
Nucleus
Mitochondria
Chloroplast
Lipids in chloroplasts are used for
Making membranes of from breakdown of membranes
Group containing most unicellular eukaryotes :
Protoctists
3 principles of modern cell theory :
Basic unit of life is cell
All living organisms are made of cells
Cells arise from preexisting cells
Formula to convert millimetres to micrometers
mm/0.0001
Organelles with no membranes
Ribosome
Centriole
Microtubule
Organelles with single membrane
Lysosome
ER
Golgi
