cellstructure Flashcards
surface area: volume
surface area/volume
surface area=
length x height
volume=
length * height * depth
surface area= (2*2)6=24µm^2
volume=8µm^3
SA:V= 3:1
Surface area to volume ratio decreases as
cells get larger.
Single celled organisms have relatively
large SA:V ratio compared to large multicellular organisms.
The larger the surface area to volume ratio,
the quicker the rate of diffusion takes place.
number of multicellular cells in humans
100 trillion
sa:v ratio in humans(multicellular)
less
diffusion distance in humans
large
diffusion speed in humans
slow
Hence, humans need respiratory, circulatory and excretory systems to
speed up the diffusion process.
number of cells in amoeba
1
sa:v ratio in amoeba
more
diffusion distance in amoeba
less
diffusion speed in amoeba
fast
Amoeba does not need systems as
diffusion is facilitated.
typical plant cell size
10-100µm
Principles of Cell Theory
All living things are made of cells
Smallest living unit of structure and function of all organisms is the cell
All cells arise from pre-existing cells (this principle discarded the idea of spontaneous generation)
why are cells small
Easier to replace if damaged or old.
High surface area to volume ratio.
Diffusion distance is less. So, the speed of diffusion is faster
Magnification:
The number of times greater that an image is than the actual object
40
magnification =
image size ÷ actual (real) size of the object
Resolution
the ability to distinguish between two objects very close together; the higher the resolution of an image, the greater the detail that can be seen.
TYPES OF MICROSCOPES
- Light microscope
- Electron microscope
types of electron microscope
Transmission electron microscope & Scanning electron microscope
light microscope adv
Portable
Can observe living things
Provide coloured images
No need of technical training
Can observe life processes like mitosis
light microscope DisAd
Resolution is only x200 nm
ELECTRON MICROSCOPE adv
Very high resolution – 0.5 nm
Detailed image can be seen
Use electron beams with low wavelength
ELECTRON MICROSCOPE DisAd
Non portable
Only dead specimen are seen [or need to kill living cells as it works in vacuum]
Gives only black and white image
Need heavy metals for staining
TEM
Electron beam pass through the sample. Inner structure can be seen as electrons get transmitted through the specimen
Magnifying power x5,000,000
Maximum resolution is 0.5 nm
Produces 2-D and black & white image
SEM
Electrons scan over the surface of the sample. Only reflected beam form the image
Magnifying power x1,000,000
Maximum resolution is 3- 20 nm
Produces 3-D black & white image
eyepiece lens
magnifies and focuses the image from the objective onto the eye
objective lens
collects light passing through the specimen and produces a magnified image
condenser lens
focuses the light onto the specimen and held between the cover slip and slide
electron gun or anode
produces a beam of electrons
When object in the specimen are much smaller than the wavelength of the radiation,
then the waves are not stopped by them and they are not seen.
If the object is transparent,
it will allow light waves to pass through it and therefore will not be visible.
microscopy long
Microscopy is the technical field of using microscopes to view samples & objects that cannot be seen with the unaided eye (objects that are not within the resolution range of the normal eye)
radiation used in light microscope
visible light
radiation source in light microscope
Bulb [light]
radiation wavelength in light microscope
400 nm to 700nm
nature of lens in light microscope
Glass / convex lens
light microscope image seen on
eye
radiation medium for light microscope
air
type of specimen in light microscope
Living/ dead
stain used in light microscope
Coloured dye
nature of image in light microscope
Seen in real colour /colour of stain
cost/space in light microscope
Less expensive and need less space
magnification in light microscope
×1000
limit of resolution in light microscope
Lower than electron microscope
Maximum resolution is :
the shortest distance between 2 separate points
equal to half the wavelength used
Longer the wavelength,
lower the resolution
visible light is from 400 nm to 700 nm the maximum resolution of a light
microscope is 200 nm
Why can’t we see the ribosomes using light microscope?
The shortest wavelength of light is 400 nm, therefore the resolution of a light microscope is 200 nm. The diameter of a ribosome is much smaller than this, namely 25 nm. So can’t be seen
Electron microscopy
Electron microscopes use a beam of electrons rather than visible light to illuminate the sample. They focus the electron beam using electromagnetic coils instead of glass lenses (as a light microscope does) because electrons can’t pass through glass.
radiation used in electron microscope
Electron beams
radiation source in electron microscope
Electron gun / thermionic emission.
When a metal [tungsten] becomes very hot, some of its electrons gain so much energy that they escape from their orbits
radiation wavelength in electron microscope
1nm
nature of lens in electron microscope
Electromagnetic lenses. Electrons are negatively charged particles and has negligible mass.
electron microscope image seen on
Fluorescent screen / photographic film. High energy can damage eye. Impossible to see electron beam
radiation medium in electron microscope
Vacuum to avoid scattering on Collison with particles
type of specimen in electron microscope
Dead and dehydrated- water boils at room temperature
the stain used in electron microscope
Heavy metal atoms
nature of image in electron microscope
Black and white / false color by computer [ARTEFACT]
magnification in electron microscope
×5,000,000
cost/space in electron microscope
Very expensive needs large space
limit of resolution in electron microscope
High [0.5nm] because of high frequency and low wave length
Disadvantage of SEM
Only surface structure is seen not internal structure
In SEM, resolution is between 3 nm and 20 nm which is lesser than TEM
S.I. unit of length
meter
While using light microscope
show units in μm
While using electron microscope
show units in nm
always measure an image in
mm
eyepiece graticule is placed on the
eyepiece lens
stage micrometer is placed on
the scale
eyepiece lens
eyepiece graticule
Cells and organelles can be measured with a microscope by means of an
eyepiece graticule.
The eyepiece graticule is placed in the microscope eyepiece so that it can be seen at
the same time as the object to be measured.
eyepiece graticule
transparent scale.
It usually has 100 divisions.
i epg=
stage micrometer scale/eyepiece graticule scale*1000= ans (microm)
diameter of cell
=1epg* measurement of cell on the eyepiece graticule
After adjusting the stage and eye piece graticule, if we change the magnification,
the eyepiece remains the same whereas the stage micrometer enlarges
Organelles
Functionally and structurally distinct part of a cell, Surrounded by membranes for compartmentalization
2 types of cells
prokaryotic and eukaryotic cells
Characteristics of all cells
A surrounding membrane
Protoplasm – cell contents in thick fluid
Organelles – structures for cell function
organelles without membrane
microtubule, centriole, ribosome
Organelles with single membrane
lysosome, Golgi body ,SER ,RER ,vacuole, cilia , microvilli ,vesicles
omeOrganelles with double membrane
Nucleus
Chloroplast
Mitochondria
CELL SURFACE MEMBRANE AKA
plasma membrane
function of cell surface membrane
Controls movement of substances in and out of the cell
cell surface membrane
phospholipid bilayer is made up of
cholestroal,phospholipid and protein
leaving nuclear pores
mRNA, tRNA and ribosomes
entering the nucleus
proteins to help make ribosomes, nucleotides, ATP and some hormones such as thyroid hormone T3.
nucleus function
Controls the cell activity
phospholipid bilayer
electron micrograph
Heterochromatin is the part of
the chromosome in which the DNA does not have coding genes.
euchromatin is part of
chromose in which coding sequences are present
two types of ribosomes
80S and 70S ribosomes
80S RIBOSOME
25 nm
Larger
70S RIBOSOME
Smaller
Each ribosome contains at least
one large rRNA and at least one small rRNA.
In the nucleolus, the large and small rRNAs combine with
ribosomal proteins to form the large and small subunits of the ribosome.
ROUGH ENDOPLASMIC RETICULUM [RER]
Network of membrane in cytoplasm
RER
Smooth endoplasmic reticulum in liver cells of vertebrates helps in
detoxifying poisons and drugs. It contains enzymes that catalyze a number of reactions that can make lipid-soluble drugs and metabolic wastes into water-soluble so that these can easily be expelled out from the body.
Sarcoplasmic reticulum is a network of specialized smooth endoplasmic reticulum that is necessary for
transmitting electrical impulses and also stores calcium ions. The muscle cells are rich in smooth endoplasmic reticulum so they are known as sarcoplasmic reticulum (membrane-bound structure rich in muscle cells)
Describe the differences in structure and function between RER and SER.
- RER has ribosomes and SER does not have ribosomes
-RER is made up of flattened sacs where as SER is tubular
-RER produces proteins, SER produces lipids and cholestroal
golgi bodies AKA
Golgi apparatus / complex
function of golgi body
Modification of proteins and lipids[e.g. glycosylation, phosphorylation, cutting and folding of proteins]
Packaging molecules into vesicles for release of proteins out of the cell
Formation of lysosomes
How proteins move out of a cell?
ribosome -> RER -> transport vesicle -> golgi body -> secretory vesicle ->cell surface membrane -> out
LYSOSOMES
a spherical organelle found in eukaryotic cells; it contains digestive (hydrolytic) enzymes and has a variety of destructive functions, such as removal of old cell organelles.
hydrolases
The enzymes in lysosomes
60 + enzymes: including proteases, lipases and nucleases
Hydrolysis works fastest in an
acidic environment, therefore a pH of 4 – 5 is maintained inside the lysosomes
hydrolysis happens in
lysosomes
golgi bodies are made up of
cisternae
RER made up of
interconnected sacs known as cisternae
Space inside the cisternae are called
lumen
Hydrolysis
process by which chemical compounds are broken apart by the addition of water.
lysosome features
small spehrical sacs
lysosome size
0.1 – 0.5 μm in diameter
lysosome mebrane
single outer membrane
golgi body synthesizes
lysosomes
lysosomes helps to destroy worn out organelles or dead cells
as in mammary glands after lactation;
the heads of sperm contain a special lysosome, the acrosome, for digesting a path to the ovum;
in WBC, lysosomes help to digest bacteria during phagocytosis
activites of lysosome
1) getting rid of unwanted cell components - autophagy
2)endocytosis
3)exocytosis
4)self digestion - autolysis
SELF-DIGESTION
Contents released into the cytoplasm
Whole cell gets digested [autolysis]
In mammary glands, cells are destroyed after lactation period is over
E.g. tadpole tail during metamorphosis; restoring uterus after pregnancy
mitochondria can be seen in
various shapes
mitochondria size
1 μm in diameter
functions of mitochondria
Help in aerobic respiration
Energy is stored as special molecule called ATP [Adenosine Triphosphate]
Synthesize ATP / produce energy in the form of ATP
ATP
The molecule that is the universal energy currency in all living cells; the purpose of respiration is to make ATP
small, soluble,highly mobile,
ATP made in the mitochondria spreads wherever
they are needed and releases energy by getting converted to ADP [can be recycled later in the mitochondria] – by the process of hydrolysis
mitoxhondria
1 particles/oxysomes are present in the
inner mitochondrial space of the mitochondrion. It is attached on the infoldings called the cristae. It has enzyme called ATP synthase. It is responsible for ATP synthesis and oxidation.
cristae in mitochondria
folds of the inner membrane of the mitochondrial envelope on which are found stalked particles of ATP synthase and electron transport chains associated with aerobic respiration
ADP: adenosine diphosphate
the molecule that is converted to ATP by addition of phosphate [a reaction called phosphorylation] during cellular respiration; the enzyme responsible is ATP synthase; the reaction requires energy
respiration in cells
Glycolysis
Happens in cytoplasm
No O2 needed
Kreb’s cycle
Happens in the matrix of mitochondria
Electron transport chain
Happens in inner mitochondrial membrane [oxysomes]
1 molecule of glucose
can release 38 ATP
CHLOROPLAST shape
Chloroplasts tend to have an elongated
or oval shape
size of chlorophlast
3 μm to 10 μm
Inside the chloroplast:
Thylakoid = flattened, fluid-filled, membrane bound sacs
Grana = thylakoid stacks
Stroma = interior solution
Stroma in chlorophlast contains
70S ribosomes[seen as small black dots in the stroma], small circular DNA and starch grains
Have prokaryotic origin – endosymbiont theory
Main function of chlorophlast
Site of photosynthesis
to carry out photosynthesis
photosynthesis occurs in 2 steps
light and dark reaction
STAGE 1: Light reaction / light dependent reaction
Site of light dependent reaction - GRANA
Light energy is absorbed by photosynthetic pigments, particularly the green pigment chlorophyll [seen on the membranes of chloroplast] using sunlight
STAGE 2 : Dark reaction / light independent reaction
ATP/ the energy from stage 1 is used to convert CO2 to sugar
Occurs in stroma
Sugars made is stored as starch grains in the stroma
Lipid droplets are also seen in the stroma – helps to make membranes
This requires a cycle of enzyme-controlled reactions called the Calvin cycle and takes place in solution in the stroma.
photosynthesis reaction
CELL WALL seen in
plants and prokaryotes
cell primary wall size
0.1 μm thick
cell wall has 2 walls
primary wall and secondary walls
primary walls
rigid [parallel fibres of cellulose running
through a matrix of pectin and hemicellulose]
Cellulose adv
– inelastic and provides high tensile strength
– gives strength when being turgid due to osmosis
Extra layers of cellulose added to the primary layer – making a
secondary wall – cellulose is parallel but run in different directions
– thus increasing the rigidity
cell wall is fully __
permeable
why is cell wall fully permeable?
because there are spaces / gaps in between
fibres
addition of lignin in cell makes it more
e rigid [e.g. sclerenchyma, xylem vessel elements]
functions of cell wall
-Mechanical strength and support
-Prevents cells from bursting
-help determine the shapes of cells
- Apoplastic movement
- Symplastic movement
wdym by Mechanical strength and support
e.g. lignification
cell wall prevents cell from bursting from
osmosis
Different orientations of the layers of cellulose fibres
help
determine the shapes of cells as they grow
Apoplastic movement
a system of interconnected
cell walls in a plant; transport route for water, inorganic
ions and other materials
Symplastic movement
living connections through
neighboring cell walls, the plasmodesmata, forms
another transport route
Cell walls of root endodermis
suberin [waterproof
substance that limits the intake of water and minerals]
Epidermis – waxy cuticle –
– helps reduce water loss by
transpiration
eukaryotes
protists, plants, fungi and animals
prokaryote differences compared to eukaryotes
Cell wall made up of peptidoglycan – a polysaccharide combined with amino acids
eukaryotes ( fungi) differences compared to prokaryotes
Cell wall – made up of chitin [a nitrogen containing polysaccharide similarto cellulose]
eukaryotes (plants) differences compared to prokaryotes
Cell wall - made up of cellulose and lignin
eukaryotes (animals) differences compared to prokaryotes
NO CELL WALL
cellulose fibres
cellulose structure
PLASMODESMATA
strands of cytoplasm passing through channels, where there is no cell wall,
plasmodesmata function
- Allows substances to pass from cell to cell without passing
through the cell wall - e.g. water, sucrose, amino acids, minerals ions, ATP
- Allows more rapid transport of substances
vacuoles are commonly found in
plants [large permanent central vacuole]
vacuole in animals
small and temporary[phagosomes, food vacuoles, autophagic vacuoles]
vacuole is surrounded by
single membrane called tonoplast
vacuole function
- support -by being turgid in nonwoody plants
- plant central vacuole – has lysosomal activities
- presence of secondary metabolites
- food reserves
- waste products
- Growth in size
- osmotic uptake
– helps in growh
secondary metabolites
anthocyanin – red, purple, pink and blue colours to flowers and fruits
Alkaloids and tannins – deter herbivores from eating plants
Latex – e.g.in rubber tree [latex in opium poppy – alkaloids such as morphine
from which opium and heroine are made]
food reserves –
sucrose in sugar beet, protein storage in seeds
Waste products –
– e.g. crystals of calcium oxalate
microtubules size
- Very small [25 nm]
- Long, rigid, hollow tubes
microtubules are made from
a protein called tubulin – dimers – protofilaments –13 protofilaments make 1 microtubule
microtubules are formed and broken down at
MTOCs[Microtubule Organising centres]
microtubules functions
-Make up the cytoskeleton
-Provides mechanical support
-Acts as an intracellular transport system for the movement of
vesicles or other components
- Beating of the flagella and cilia
-Makes up spindle fibres and centrioles used in cell division
alpha tubulin and beta tubulin make
dimers and many dimers together make protofilaments and 13 protofilaments together make up a microtubule
centriole shape and size
Centrioles – hollow - cylindrical – 500 nm long
CENTRIOLES appearance
Non-membrane bound structures
centrioles are found in
pairs– lie right angles to each other near to the nucleus in a region called centrosome
centrioles made up of
9 triplets of microtubules
centrioles are not found in
plant cells
Function of centriole
- Involved in cell division
- Replicates before cell division and moves to opposite poles of a cell
- Found at the base of cilia and flagella – where they are known as basal bodies
- Microtubules extend from basal bodies – for the beating movement of cilia and flagella
cilia and flagella have
identical structures
Cilia:
whip like structures projecting from the surface of many animal cells and the cells of
many unicellular organisms; they beat, causing locomotion or movement of fluid across the cell surface
cillia is surrounded by
extension of cell surface membrane
cilla size and number
short and numerous
At the base of cilium and flagellum are
basal bodies – identical to centriole structure
* Cilia and flagella grows from basal bodies
cillia functions
- Free living cells – to swim through the fluid
- For cells attached – to move the fluid on the cell surface e.g. ciliated epithelium pushing mucus in the respiratory tract
- Smaller in diameter compared to microvilli
microvilli is found only in
animal cells
microvilli is found on
epithelial cells in the intestines and kidneys
MICROVILLI size and shape
- Finger-like extensions of the cell surface membrane
- Diameter – 50 to 550 nm
- Length – 100 nm to several microns
Functions of microvilli
- Increase surface area of the cell
membrane for:
Reabsorption – in PCT
Secretion of enzymes
Absorption in small intestines
Excretion of waste substances
Structures seen using HQ light microscope without stain
- Nucleus
- Chloroplast
- Cell wall
- Cytoplasm
- Vacuole
Structures seen using HQ light microscope With proper stain
- Mitochondria [not clear but as tiny dots]
- Nucleolus
- Centriole
- Golgi bodies
- Chromosome only during cell division
- Starch grain
not visible in daylight microscope
Golgi body, mitochondria and endoplasmic reticulum
plant cell size
[10 – 100 microns]
plant cell size
[10 – 30 microns]
plant cell organelles ONLY
chlorophlast, cell wall, large permanent vacuole, plasmodesmata
animal cell organelles ONLY
centriole and centrosome, lysosome
bacteria size
[1 μm – 5 μm]
BACTERIA
A group of single celled microorganisms that comes under the prokaryotes[pro primitive; karyon - nucleus];. They have a number of characteristics, such as the ability to form spores, which distinguish them from the other group of prokaryotes known as
Archaea.
structure of cell wall in bacteria
containing murein
murein,
a peptidoglycan [a polysaccharide combined with amino acids]
MEURIN IMPORTANCE
very essential for the survival of bacteria
structure of cytoplasm in bacteria
without membrane bound organelles
structure of ribosome in bacteria
70S ribosomes
structure of circular DNA in bacteria
found in a region called nucleoid
nucleoid in bacteria contains
proteins and smaller
amounts of RNA. Not surrounded by double layer of nuclear membrane like in eukaryotes
flagellum in bacteria
swim
flagellum in bacteria structure
simple hollow cylinder made up of identical protein molecules
how does flagellum in bacteria work
by rotating its base like a propeller, resulting in the corkscrew-shaped motion in bacteria
Infolding of cell surface membrane in bacteria
space for biochemical reactions; In blue-green bacteria,
this space contains photosynthetic pigments; in some bacteria nitrogen fixation occurs in this infolding
capsule in bacteria
an extra layer outside the cell wall, forming a capsule or a slime layer
capsule –
rigid, made of polysaccharides
capsule function
provides protection from antibiotics and also prevents phagocytes from engulfing them;
slime layer function
more diffuse and is easily washed off
plasmid in bacteria
small circle of DNA; contains only a few genes; these genes can help by providing
antibiotic resistance;
plasmid can copy and spread from
from one bacterium to another
plasmid ,DNA is not associated with
proteins and is referred to as ‘naked’ DNA
Pili [singular - pilus] in bacteria structure
fine protein rods; vary in length and stiffness; one to several hundred
present in one cell;
Pili [singular - pilus] in bacteria funcyion
used for attachment and interactions with other cells or surfaces [e.g. transfer of genes including plasmids]
prokaryotes nucleus
primitive nucleus
eukaryotes nucleus
true nucleus
prokaryotes are thought to have evolved
about 3.5 billion years ago
eukaryotes are thought to have evolved
about 1.5 billion years ago
prokaryotes diameter
1 – 5μm
eukaryotes diameter and size
40 μm diameter and up to 1000 times the volume of prokaryotic cells
DNA in prokaryotes
circular and lies free in the cytoplasm
DNA in eukaryotes
not circular and is contained in a nucleus – the nucleus is surrounded by an envelope of two membranes
ribosomes in prokaryotes
slightly smaller (70S) ribosomes (about 20nm diameter) than those of eukaryotes
ribosomes in eukaryotes
slightly larger (80S) ribosomes (about 25nm diameter) than
those of prokaryotes
prokaryotes organelles
very few cell organelles – no separate
membrane-bound organelles are present
eukaryotes organelles
many types of cell organelle are present:
■ single membrane, e.g. lysosomes, Golgi body, vacuole, ER
■ double membrane e.g. nucleus, mitochondrion,
chloroplast
■ no membrane, e.g. ribosomes, centrioles, microtubules
cell wall in prokaryotes
cell wall present – wall contains murein, a peptidoglycan
cell wall in eukaryotes
cell wall sometimes present, e.g. in plants and fungi –contains cellulose or lignin in plants, and chitin in fungi
cell division in prokaryotes
Cell division – binary fission; does not involve spindle
cell division in eukaryotes
Cell division – takes place by mitosis or meiosis; involves a spindle
nitrogen fixation in prokaryotes
Some carry out nitrogen fixation
nitrogen fixation in eukaryotes
None carries out nitrogen fixation
VIRUSES shape and size
A very small [20-300 nm]infectious particle which can replicate only inside living cells; it consists of a molecule of DNA or RNA (the genome) surrounded by a protein coat; an outer lipid envelope may also be present
viruses cell structure
Do not possess a cell structure – no cytoplasm or cell organelles
viruses mostly consist of
DNA or RNA,a protective coat of protein molecules called capsid - its protein
coat (or capsid) is made up of separate protein molecules, each
of which is called a capsomere,* In some viruses – a membrane like outer layer called envelope made of phospholipids, proteins may project from the envelope
* All viruses are parasitic - because they can only reproduce by
infecting and taking over living cells.
size of organelles in order
nucleus, chloroplast, Mitochondria ,nucleolus , lysosome , centriole, Ribosome
CENTRIFUGATION
- The idea of rupturing cells, and spinning them at very high
speed - Largest structures will sediment first
ORDER OF SEDIMENTATION
- Nucleus
- Chloroplast
- Mitochondria
- Other organelles
- Ribosomes
mitochondria membrane
has double membrane, have intermembrane space
mitochondria is what type of organelle?
autonomous organelle
respiration in mitochondria happens in
occurs in the matrix and in the cristae
Intermembrane space
the space between the 2 membranes
mitochondria divides by
binnary fission
why is mitochondria seen in different shapes
they can be of different ages, the cross-section can be different, shows variety in size but in different planes
RER
Plant cell
CSA size
about 7 nm thick
CSA is _ permeable
partially
CSA made up of
made of phospholipid bilayer
CSA under very high magnification
it is seen as three layers [trilaminar appearance] under very high magnification
Nucleus size
largest and the most visible cell organelle
nucleus is approximately 6 micrometres (µm)
nucleus membrane
surrounded by two membrane forming nuclear envelope
outer membrane is continuous with the ER
nucleus has _
nuclear pores and loosely coiled structures called chromatin which have DNA
nucleolus is _ an organelle
not
nucleolus size
Covers nearly 25% volume of the nucleus
nucleolus has genes that code for synthesis of
rRNA and tRNA
nucleolus function
Its function is to make ribosomes using the information in its own DNA
are the different parts of the nucleolus always together
The different parts of the nucleolus only come together during the manufacture of ribosomes
The heterochromatin region of the chromosome is highly
condensed
ribosome is considered the
smallest organelle
ribosome size
25 nm
does ribosome have membrane
no membrane
ribosome is made up of
Made of rRNA that is synthesized in the nucleolus and proteins
ribsome has _ subunits
2
ribsome function
produces protein [site of Protein Synthesis]
where are 80s ribosome found
cytoplasm and RER of all eukaryotes
where are 70s ribosomes found
Found in the mitochondria and chloroplast of eukaryotes
Prokaryotes also have 70S ribosomes
RER function
Provides a large surface area for the synthesis of proteins
Provides a pathway for the transport materials, especially proteins throughout the cell
Site of protein synthesis [due to the presence of 80S ribosomes]
Protein modification [e.g. protein folding; glycosylation – addition of carbohydrate chains to protein]
transport proteins made to
golgi apparatus
WHY IS SER CALLED SER
because it lacks ribosomes
SER function
Secretion of lipid hormone and steroids [testosterone, estrogen and cortisol]
very high number of SER in liver cells to
detoxify toxins
SER IN OVARY
to make oestrogen and progesterone;
SER IN TESTES
TO MAKE TESTOSTERONE
SER IN MUSCLE CELLS
STORING CALCIUM IONS
Golgi body structure
Have layered appearance
No connection between members
Not continuous with nuclear envelope
Swellings at the end of sacs for vesicle formation
Vesicles are constantly being formed and broken down in golgi
Being formed by: transport vesicles from RER on cis face
Broken down to form: secretory vesicles and lysosomes on trans face
mitochondria structure
inner membrane – CRISTAE - folded to increase the surface area
Matrix – interior of the mitochondria, enzymes, 70 S ribosomes and small circular DNA are seen in the matrix
mitochondria divides by
binary fission
Have prokaryotic origin
Mitochondria number increases as the
energy demand of cell increases [liver cell – 2000 mitochondria]
chlorophlast is a _ organelle
relatively large
chlorophlast membrane
2 outer membranes
chlorphlast contains
chlorophyll
Chloroplasts can change their orientation within the cell in order to
receive the maximum amount of light.
vacuole size
1/3 rd of cell volume is vacuole
refering to protein synthesis
not enough ATP for transcription
which data must the student collect in order to callibrate eyepeice graticule
number of divsions of the eyepiece graticule scale equivalent
convert micro metre to cm and divide the 1/ans
Ribsome mcq
non membrane bound cylindrical structures
SER mcq
membranes which surround an enclosed cavity
centriole mcq
non membrane bound cylindrical structures
nucleus mcqmi
mRNA passes through to the ribosome
actual length is 5
convert length of image into micro metre
do M=I/A
DNA from Q were of two types, with different base sequences. We know that there are two types of mesophyll cells in the leaves namely palisade mesophyll and spongy mesophyll
What features show that the given electron micrograph is from the TEM?
Higher magnification, higher resolution than light microscope
Images is in 2D/ no surface contours
Organelle ultrastructure structure can be seen (give named examples such as internal structure of chloroplast)
Very thin sectionmm measurements
Advantages of using light microscope instead of electron microscope
Can observe living tissue and living processes
Different types of stains can be used to observe specific tissue
Portable and easy to move
Colour can be seen
Lower costs and maintenance.
what is the function of smooth endoplasmic reticulum?
steroid synthesis
why is sucrose solution used when mitochondria are extracted?
to prevent them from changing in structure
large sa of cristae?
enzyme reaction
actively growing cell supplied with radioactive amino acids, which cell
component first shows an increase in radioactive activity?
rer
if tis supplied with glucose, answer would be golgi
in which animal cell is golgi appartus most abundant?
goblet cells [contains highest proportion of single membrane-bound
structure]
what increase efficiency of active transport
large sa of csm
membranous sacs containing products of metabolism are formed by the
endoplasmic reticuluim in cells. where are these products used?
inside and outside the cell
cell under 400x magnification; what can be seen? - qs could be reworded as
simple light microscope with daylight as the only source
cytoplasm, csm, nucleus and nucleolus
chloroplast also (i guess up till 3 microm)
light miscrocope and em resolution/magnification
light - low, low //// em - high, high
range of most eukaryotic cells?
10-100 micrometer
plant cell = 40 micrometer
does protein synthesis require atp?
yes
formation of hydrolytic enzymes - which organells r involved
rer, mito, golgi
only requirement for a prokaryote is
circular dna THATS IT
why is an eyepiece graticule calibrated?
it can be used to make measurements
where would cisternae be found in a cell?
er, and golgi (not mito thats cristae)
at which magnification is light m not suitable cuz resolution is too low?
1500x (resolution and magnification are inversely proportional ig)
also more wavelength = less resolution
which organelle doesnt contain a partially permeable membrane?
ribosome (mit, golgi, lysosome have)
function of nucleolus?
synthesis of rRna, not of ribosomal proteins
comparison of phloem companion cell and b lymphocyte
both have proteins embedded in their cell surface membrane
what do ribosome subunits consist of?
rRNA and protein
diameter of a typical prokaryote?
750 nm - anything close to 1 micrometer
which organelle does not contain nucleic acids?
golgi apparatus [no ribosomes! so no dna/rna cuz no protein synthesis]
which structure can be seen only w em
csm
greatest number of cells in a field of view?
go for the least magnification
why do eukaryotes undergo division much slower than prokaryotes?
eukaroytes break down nuclear membrane during mitosis (time consuming
process i guess)
which cell components contain mrna?
chloroplast, mitochondria, nucleus and rer [all have ribosomes]
what leaves the nucleus through the pores in the nuclear envelope?
mRNA and ribosomes, not DNA
is plasmodium a prokaryote or a eukaroyte?is plasmodium a prokaryote or a eukaroyte?
eukaroyte!!
why do plant cells living in fresh wate rnot require vacuoles to expel excess
water?
plant cell walls limit cell size so laik it wont be bulged in the first place
which statement ab the graticulae are correct vs which statements about the
stage mm are correct
both WONT measure actual length
graticule allows correct proportion // stage allows you to calibrate graticule
graticule wont change in size when going from 10x to 40x BUT STAGE WILL
CHZNGE IN SIZE
which process occurs in a mature rbc?
active transport!
mature rbc’s do not have a nucleus so no cell division, transcription or
translation
features of microvilli and root hairs?
root hair has vacuole
microvilli is the more than one present on cell
root hairs increase surface area
which cell structures can form vesicles?
csm, golgi and er
which organelles are required for the formation of lysosomes containing
hydrolytic enzymes?
mito, golgi and rer
which types of rna are found in both prokaryotic and eukaryotic cells?
mrna, rrna, trna (cuz both cells have ribosomes ig)
how does the dna of eukaryotes differ from prokaryotes?
it has proteins attached to it and its linear!
function of microtubules?
movement of cilia in bronchus, attachemnt of centromeres, moving secretory
vesicles around a cell
glucose is not synthesised in
animal cells
no need to calibrate graticule on x10 objective lens cuz
ur vieweing it in x40
ifyk
vacuole contains
mineral ions
photosynthesis prokaryotes do not have
a cellulose cell wall or chloroplasts
nucleolus not really involved in
enzyme formation
circulae dna of prokaryotes and chloroplast does not code for
cell walls
a range of hydrolytic enzymes can be found in
mature plant vacuoels (can
carry out same function as lysosomes)
anything with ribosomes can be a site of
protein synthesis
there are no ribosomes attached to the inside of er
ONLY OUTSIDE
root cells can have
plasmodesmata
nucleus does not produce
ATP! [atp does not form part of the dna
mitosis/cell division only occurs when
nucleus is present (so wont happen in
prokaryotes, hydrolysis will happen in both pro/euk)
a glycoprotein is secreted AFTER
fusion of vesicle with csm (dont repeat the
mistake)
a virus will either have
rna or dna (not both)
a virus has no
carbohydrate, no phospholipid and no lipid (only protein)
centrioles are made up of
protein molecules! [only biomol present in
centriole, nothing else]
non-cellular =
not made up of cells for eg virus
semi conservative replication of dna occurs wherever
dna is present
