3a. CELL STRUCTURE Flashcards
Name the four types of eukaryote
Plants, animals, fungi and protists
What is the average diameter of an eukaryotic cell?
50µm (micrometers)
Which molecule is the cell membrane mainly made from, and what configuration are they in?
Phosphlipids, in a bilayer
Describe the function of the cell membrane
To separate two aqueous environments. To control what goes into and out of the cell.
What does the nucleus contain?
Chromosomes and a nucleolus inside the nucleoplasm
What other organelle is the nuclear envelope continuous with?
RER
Describe the structure of the nuclear membrane
It is a double phospholipid bilayer with nuclear pores
What is contained inside the nucleolus
Ribosomes and rRNA
Describe the function of the nucleus
To store chromosomes
Describe the function of the nucleolus
To assemble ribosomes
Which type of ribosomes are found in eukaryotic cells?
80s ribosomes (larger)
Describe the two places ribosomes are found in eukaryotic cells
Free ribosomes in the nucleus, and ribosomes bound to the RER
Describe the function of free ribosomes found in the cytoplasm
To synthesise proteins for use inside the cell
Describe the function of the ribosomes bound to the RER
To synthesise proteins that will be released out of the cell (e.g. enzymes, hormones etc)
RER are made of a stack of membrane folds. What are these membrane folds called?
Cisternae
Describe the function of the RER
To synthesise proteins that will be released out of the cell (e.g. enzymes, hormones etc)
Once proteins have been synthesised in the RER, which organelle are they transported to?
Golgi apparatus
SER are made of a stack of membrane folds. What are these membrane folds called?
Cisternae
Describe the function of the SER
To synthesise, store and transport lipids and carbohydrates
Once lipids and carbohydrates have been synthesised in the RER, which organelle are they transported to?
Golgi apparatus
Describe the structural difference between the RER and SER
The RER have ribosomes bound to the cisternae and the SER does not
Golgi apparatus are made from stacks of layers of membrane. What are these layers of membrane called?
Cisternae
Describe the function of the Golgi apparatus
To modify and package proteins, carbohydrates and lipids into vesicles
What comprises the outside of vesicles?
A single phospholipid bilayer
What is a lysosome?
Vesicles containing lysozymes (enzymes)
Describe the function of vesicle
To transport molecules outside the cell
Mitochondria are surrounded by an double membrane. The inner membrane is folded. What are these folds called?
Cristae
What is the jelly-like substance inside a mitochondria called?
Matrix
Describe the function of the mitochondria
It is the site of respiration and therefore where ATP is produced
Which cellular process are centrioles involved in?
Cell division
Which polysaccharide are plant cell walls made from?
Cellulose
Which polysaccharide are fungi cell walls made from?
Chitin (chi-a-tin)
Which biological molecule do algae cell walls also contain?
Glycoproteins
Describe the function of the cell wall
Maintainsthe shape of a plant cell,prevents lysis, and provide strength andsupport
Name the single membrane that surrounds the vacuole
Tonoplast
Describe the function of the vacuole
To provide turgidity and store food
Name the individual discs found inside a chloroplast
Thylakoid
What is a stack of thylakoids called?
Grana (singular granum)
Name the structures that connect grana
Lamellae
Name the fluid found inside a chloroplast
Stroma
Describe the function of chloroplasts
The site of photosynthesis (production of carbohydrates)
Which polysaccharide can be found inside chloroplasts?
Starch (grains)
Describe a adaptation a cell would have to carry out more active transport
More mitochondria
Describe an adaptation a muscle cell would have to enable it to contract more
More mitochondria
How might the mitochondria in muscle cells be adapted to enable the muscle cell to contract more?
They would have more cristae
Explain why muscle cells and mitochondria have these adaptations (more cristae)
For an increased surface area for more respiration and therefore more contraction
Describe an adaptation a palisade mesophyll cell might have to photosynthesis more
More chloroplasts
How might the chloroplasts in palisade mesophyll cells be adapted to enable the cells to photosynthesise more?
More thylakoids
Explain why palisade mesophyll cells and thylakoids might have these adaptations (more chloroplasts so more thylakoids)
An increased surface area for more photosynthesis
Which three organelles might a glandular cell have more of?
More ribosomes (on the RER), more golgi apparatus, and more ATP
Why might glandular cells have more ribosomes on their RER?
To synthesise more proteins for secretion
Why might glandular cells have more golgi apparatus?
To package more proteins for secretion
Why might glandular cells have more mitochondria?
To produce more ATP for more vesicle transport
What is the average diameter of an prokaryotic cell?
5µm
On average, how many times bigger is a eukaryotic cell compared to a prokaryotic cell?
10 x
Describe the structure of the free DNA in prokaryotes
It is circular and not associated with histone proteins
Describe the function of the free (circular) DNA in prokaryotes
It codes for the structural and functional proteins within the prokaryote
Describe the function of plasmids in prokaryotes
Carry the genes that give the cell an evolutionary advantage, e.g. antibiotic resistance
What is the difference between the cytoplasm in a eukaryote and a prokaryote?
The cytoplasm in a prokaryote lacks membrane-bound organelles, whereas the cytoplasm in a eukaryote contains membrane-bound organelles
Name the glycoprotein the cell wall of a prokaryote is made from
Murein (mure-rain)
What is the capsule in a prokaryote?
A slime layer surrounding the cell
Describe the function of the capsule in a prokaryote
To protect the bacteria from environmental dangers
Describe the function of the flagella in a prokaryote
Locomotion
What is the average diameter of a virus?
20nm
Viruses are non-living. They also contain no organelles. Therefore they cannot carry out their own ……………… ……………
Metabolic processes
In which two forms can viral genetic material be in?
DNA or RNA
What surrounds the viral genetic material?
Capsid
Where are the attachment proteins found?
On the outside of the virus
Describe the function of the attachment proteins
To allow it to attach to and infect host cells
Name the two main type of microscopes
Optical (light) and Electron
What is the maximum resolution of an optical microscope?
0.2µm
What is the maximum resolution of an electron microscope?
0.0002µm
Why is the resolution of an electron microscope higher than that of a light microscope?
Because electrons have a smaller wavelength than light
Name the two types of electron microscope
Transmission (TEM) and Scanning (SEM)
Describe how a TEM works
Uses electromagnets to focus a beam of electrons which is then transmitted through the specimen. Denser parts of the specimen absorb more electrons which makes them look darker on the image.
Describe two advantages of TEMs
Can see the internal structures of the specimen
Highest resolving power
Describe 3 limitations of a TEM
Specimens must be dead (viewed in a vacuum), image is 2D, specimen must be very thin and stained – both are complex processes and can form artefacts
Describe how an SEM works
A beam of electrons is scanned acrossthe specimen. This scatters electrons from the specimen, which is gathered in a cathode ray tube to form an image.
Describe two advantages of SEMs
The image is 3D, the specimen can be thicker (as the electrons do not need to penetrate), therefore less artefacts are produced
Describe two limitations of a SEM
Specimens must be dead (viewed in a vacuum), only the surface of the specimen can be observed (cannot see internal structures), and a lower resolution than TEMs
Describe two advantages of light microscopes
The image is in colour, live specimens can be used
When using a light microscope, why must our specimen be thin?
To allow light to pass through the sample
Why do we stain our specimens?
To make the organelles more visible
Once our specimen is mounted on the microscope slide, why should we press down firmly on the cover slip?
To ensure the sample is thin enough for light to pass through
When producing biological drawings, the lines should be …………….
Unbroken
When producing biological drawings, there should be no hatching or …………..
Shading
The large and small details of our biological drawings should be the same ………. and ………… as the image
Size and shape
How should we draw label lines on biological drawings?
Straight and parallel with no arrowheads
What kind of scale must always be present on a biological drawing?
A magnification scale
Recall the equation to calculate magnification
Magnification = Image size / Actual size
What is the conversion between cm and mm?
1cm = 10mm
What is the conversion between mm and µm?
1mm = 1000µm
What is the conversion between µm and nm?
1µm = 1000nm
What is cell fractionation?
The process of breaking up cells and separating out their organelles
Recall the three stages of cell fractionation
Homogenisation, Filtration and Ultracentrifugation
Describe how tissues are homogenised
In a blender
What is the purpose of cell homogenisation?
To break up the plasma membranes and release the organelles
During cell fractionation, the tissue must be kept in a solution. What three properties should this solution have?
Ice cold, isotonic and buffered
Why should this solution be ice cold?
To reduce enzyme activity so organelles are not broken down
Why should this solution be isotonic?
To prevent osmosis to prevent lysis, crenation or plasmolysis
Why should the solution be buffered?
To maintain the pH
What is the purpose of filtration during cell fractionation?
To remove large debris
In ultracentrifugation, the organelles are separated by their what?
(Decreasing) mass
Which organelles should be separated first, second and third in ultracentrifugation?
Nucleus first, then chloroplasts and then mitochondria
