A2.2 Cell Structure Flashcards
cell theory
Cells are the basic structural unit of all living organisms
cells can only arise from pre existing cells
smallest units of life
unicellular
consisting of a single cell
protists
eukaryotes consisting of single celled organisms
NOT plant animal or fungi
features common in all cells
NOT STRUCTURES
- Are surrounded by a membrane
- Contain genetic material
- Have chemical reactions occurring within the cell that are catalysed by enzymes
How do optical microscopes work
Light is directed through the thin layer of biological material that is supported on a glass slide
This light is focused through several lenses so that an image is visible through the eyepiece
optical microscopes
light
optical microscopes advantages
easy to use
cheaper
can observe dead or living in colour
cell movement can be studied
quick preparation
optical microscopes disadvantages
max magnification of 1500x
low resolving power
components of an optical (light) microscope are
The eyepiece lens
The objective lenses
The stage
The light source
The coarse and fine focus
graticule
small disc that has an engraved scale. It can be placed into the eyepiece of a microscope to act as a ruler in the field of view
calibrated
This is done by using a scale engraved on a microscope slide
By using the two scales together, the number of micrometers each graticule unit is worth can be worked out
Magnification general formula
magnification = image / real
electron microscope
in which a beam of electrons replaces light so the powers of magnification and resolution are corresponding much greater
advantages of electron microscope
magnification of 100000 x to 300000 x
disadvantages of electron microscope
expensive
cells have to be killed
no movement
has to be stained or dyed
preparation takes days
1 m in mm
1000 mm
1mm in um
1000 um
1 um in nm
1000 nm
1 cm in um
10000 um
resolution
amount of detail that can be seen
scale bar
straight line on the drawing or micrograph that represents the actual size before the image was enlarged
Qualitative data
non-numerical data such as colour and presence of structures which can also be determined using microscopes
quantitative observations
collection of data which are focused on numbers and values such as measurements of length, height, volume, or values of quantity and frequency
staining
chemicals that bind to structures within the sample and are used to make them show more clearly when viewed under microscope
iodine staining
starch - blue black
methylene blue
cell nuclei and DNA - stain blue
gram stain
divides nucleus into gram positive and negative
Gram-positive organisms - purple or blue
gram-negative organisms - pink or red
DNA
- The presence of DNA means that a new cell can be formed from an old cell, as genetic material is able to be stored and transferred
- DNA also controls the production of enzymes and other vital proteins within the cell
Cytoplasm
composed of mainly water with dissolved substances, such as ions - cytosol
cells chemical reactions take place within the cytoplasm
Plasma membrane
surrounds the cell and encloses all the cell contents
The membrane is responsible for controlling the interactions of the cell’s interior with the exterior
- Materials required by the cell are transported into the cell interior
- Waste substances are exported out of the cell to the surrounding environment
structures common to most prokaryotes
lack nucleus
70S ribosomes
DNA in a loop
Cytoplasm
Plasma membrane
Cell wall
Ribosomes
protiensynthesis
binding and reading of mRNA during translation to produce proteins
found freely or in RER
genetic material in prokaryotic cells
in the form of a “naked” single circular DNA molecule (not associated with proteins) located in the nucleoid and in smaller loops called plasmids
Plasmids
small loops of DNA that are separate from the main circular DNA molecule
- Plasmids contain genes that can be passed between prokaryotes (e.g. genes for antibiotic resistance)
Cell wall
The cell wall acts as protection, maintains the shape of the cell and prevents the cell from bursting
Additional structures of prokaryotic cells
Plasmids
Capsules
Flagellum
Pili
capsule
helps to protect bacteria from drying out and from attack by cells of the immune system of the host organism
Flagellum
are long, tail-like structures that rotate, enabling the prokaryote to move
Pili
They assist with movement, avoidance of attack by white blood cells, conjugation and are commonly used to allow bacteria to adhere to cell surfaces
key differences between animal and plant cells
- Animal cells contain centrioles and microvilli
- Plant cells have a cellulose cell wall, large permanent vacuoles and chloroplast
nucleus
Present in all eukaryotic cells (except red blood cells), the nucleus is relatively large and separated from the cytoplasm by a double membrane which has many pores
nucleus contains chromatin
has nucleolus inside nucleus
nucleolus
sites of ribosome production
Rough endoplasmic reticulum
connected to nuclear envelope membrane
used as a site for protien sythesis
has ribosomes
help makes polypeptides
Mitochondria
The site of aerobic respiration within all eukaryotic cells
small circular pieces of DNA and ribosomes also found in matrix
Golgi apparatus
Flattened sacs of membrane called cisternae
Modifies proteins and lipids before packaging them into Golgi vesicles
prominent in metabolically active sites
site of specific biochemicals
Vesicles
A membrane-bound sac for transport and storage
Lysosome
membrane bound vesicles containing digestive enzymes
breakdown of food vacuoles
digest pathogens engulfed by phagocytes
non permanent vacuole
small vacuoles in animal cells used to temporarily store materials or to transport substances
Chloroplasts
only plant cells
site of photosynthesis
- Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
- Grana are joined together by lamellae (thin and flat thylakoid membranes)
- stroma - light independent stage
Centrioles
- Hollow fibres made of microtubules
- Not found in flowering plants and fungi
Microtubules
Found in all eukaryotic cells
Makes up the cytoskeleton of the cell and are about 25 nm in diameter
Thirteen protofilaments in a cylinder make a microtubule
cytoskeleton
The cytoskeleton is used to provide support and movement to the cell
three main types of fibre in cytoskeleton
- microtubules
- micro filaments
- intermediate filaments
Functions of Life
m - movement
r- reproduction
s- sensitivity
g- growth
r- response
e- excretion
n- nutrition
Metabolism
all the enzyme-catalysed reactions occurring in a cell, including cell respiration
Reproduction
the production of offspring. It may be sexual or asexual
Homeostasis
the ability to maintain and regulate internal conditions within tolerable limits, including temperature
Growth
the permanent increase in size and dry mass
Response
the ability to respond to external or internal changes (stimuli) in their environment. Thus improving their chance of survival
Excretion
the disposal of metabolic waste products, including carbon dioxide from respiration
Nutrition
the acquisition of energy and nutrients for growth and development, either by, absorbing organic matter or by synthesising organic molecules
Atypical Cell examples
Skeletal muscle, aseptate fungal hyphae, red blood cells and phloem sieve tubes are examples of cells/tissue with structures that question the integrity of the cell theory
Striated muscle fibres
Longer than typical cells
formed from multiple cells which have fused together (which is how they have many nuclei rather than one) that work together as a single unit
Aseptate fungal hyphae
Fungi have many long, narrow branches called hyphae
Hyphae have cell membranes, cell walls and some have septa
Aseptate fungal hyphae do not have septa, thus these cells are multinucleated with continuous cytoplasm
The cells have no end walls making them appear as one cell
Red blood cells
Red blood cells, a type of animal cell, are unique in that they do not contain a nucleus and are concave
transport of oxygen
haemoglobin
calculating of mag of an image using scale bar steps
- measure scale bar in mm
- convert measurement to um
- divide measurement with number on top of scale bar
calculation of size of specimen using scale bar steps
- measure size of specimen in mm
- measure scale bar in mm
- divide specimen by scale bar
- multiply answer with number written on the scale bar (um)
calculation of size of specimen using magnification steps
- measure specimen in mm
- convert measurement to um
- divide specimen length by magnification
SER
RER without ribosomes
makes lipids and cholesterol
site of storage of calcium ions
apoptosis
program cell death which occurs in cells damaged by infection or mutation
lysosomes involved in this - the all burst
tubulin simple defination
helically arranged globular protien
tubulin functions
movement of chromosomes during cell division achieved by lengthening and shortening of microtubules
maintains shape of cell
guide and direct other components
microfilaments
thinnest class of cytoskeletal fibres made of solid robs of globular protein called actin
functions of microfilaments
involved in cleavage furrow formation to divide cell during cell division
cell motility
maintain and change cell shape
spindle
structure formed by microtubules
movement of chromosomes in mitosis and meiosis
centrosomes
- Two centrioles at right angles to each other form a centrosome, which organises the spindle fibres during cell division
near nucleus
transport vesicles
move molecules between locations inside cells by budding off one organelle component and fusing with another
secretory vesicles
secret molecules from the cell via exocytosis
also how new phospholipids are added to cell membrane
paramecium
fresh water eukaryotic organisms can carry out all life processes
chlorella
algae found in freshwater ponds
colours the water green
chlamydomonas
eukaryotic organisms that live in soil, fresh water, oceans and snow
autotrophs
can make their own food by using sources like the sun
heterotrophs
can’t make their own food and obtain it from other organisms
features of fungus
cell wall of chitin
uni or multi cellular
saprotrophs
parasitic can be
decomposers
saprotrophs
feed on non living decaying matter
external digestion
