Cell Structure Flashcards
How to calculate magnification?
Magnification = image size/object size
Define resolution.
Resolution is the ability to see more detail/ separate two objects.
Describe light microscopes.
Light microscopes use light to view whole cells and tissues which are living specimens. They are cheap and easy to use but have limited resolution.
Describe the use of scanning electron microscopes.
Scanning electron microscopes (SEM) use a beam of electrons to scan the surface of the specimen and a reflected beam is detected. They are used for viewing cell surface and providing depth in 3D images.
Describe the use of transmission electron microscopes.
Transmission electron microscopes pass a beam of electrons through a specimen to look at organelle detail. The specimen must be thin to prevent deflection of electrons.
State the uses of staining.
Stains bind to chemicals on the specimen enabling the specimen to become visible. Improve contrast. More internal structures are visible. Clearer images can be obtained.
Describe the function of the nucleus.
Contains genetic material (chromosomes), controls cell’s activities, site of RNA synthesis.
Describe the function of the nucleolus.
Assembles the ribosomes.
Describe the function of the nuclear envelope.
Separates the genetic material from the cytoplasm, nuclear pores allow molecules of mRNA to pass from the nucleus to the ribosomes in the cytoplasm.
Describe the function of the Rough endoplasmic reticulum.
Holds many ribosomes, provides large surface area for protein synthesis.
Describe the function of the smooth endoplasmic reticulum.
Site of lipid and hormone production.
Describe the function of the Golgi Apparatus.
Modifies proteins made in the ribosome, often adding a carbohydrate group, repackages proteins into secretory vesicles.
Describe the function of the ribosomes.
Site of protein synthesis; where mRNA assembles proteins from amino acids.
Describe the structure of the mitochondria.
Site of aerobic respiration - ATP produced which is needed for active transport, DNA replication, protein synthesis and enables faster chemical reactions. Made up of two membranes separated by a fluid filled space known as the matrix, the inner membrane is folded into cristae, contain 70s ribosomes, contain their own DNA in the form of plasmids.
Describe the function of the lysosome.
Contain hydrolytic enzymes involved in digestion.
Describe the structure of the chloroplast.
Site of photosynthesis, have 2 membranes separated by a fluid filled space; inner membrane is continuous with a network of flattened disks called thylakoid where chlorophyll is found, have their own circular DNA.
Describe the function of the centrioles.
Involved in the organisation of microtubules that make up the cytoskeleton, form the spindle fibres used to move chromosomes in nuclear division.
Describe the function of the flagella.
Enables cell movement, powered by chemiosmosis.
Describe the structure of the vacuole.
Membrane bound organelle found in plant cells, membrane is known as the tonoplast, filled with water and enzymes, involved in removing water and unwanted substances from the cell and altering the cell shape by changing the amount of water in the vacuole.
Describe the function of the vesicle.
A membrane-bound organelle which is used to transport substances.
State all the cellular components which are membrane-bound.
- Nucleus
- Mitochondria
- Rough and smooth endoplasmic reticulum
- Golgi apparatus
- Vacuole
- Lysosome
- Chloroplast
- Flagella
- Cilia
- Vesicle
Outline the functions of the cytoskeleton.
- Formation of microtubules which form the spindle fibres to move chromatids during mitosis and meiosis
- Mechanical strength to cells
- Cell support
- Formation/movement of flagella/cilia
- Holding organelles in position/movement of vesicles
- Cell movement
Describe the differences between eukaryotic and prokaryotic cells.
- Prokaryotic cells have cytoplasm that lacks membrane-bound organelles
- Ribosomes are 70s compared to eukaryotic cells which are 80s
- No nucleus - circular free DNA molecule which is not wrapped around histone proteins
- Reproduce using binary fission unlike eukaryotic cells which reproduce using mitosis
- Cell wall made from peptidoglycan (murien) unlike eukaryotic cells which is made from cellulose.
Explain the role of the membrane in the rough endoplasmic reticulum.
- Compartmentalisation
- Separate proteins (synthesised) from cell cytoplasm
- Hold ribosomes/enzymes in place.
Describe the steps used to stain a sample.
- Place stain at the edge of sample not at centre
- Lower cover slip at an angle/use mounted needle
- Use blotting paper to remove excess stain/pull stain through
- Use more than one stain to improve contrast.
Outline the rules needed to be followed for a biological drawing.
- No shading
- Add a scale/magnification
- Add a title
- Label lines should not cross
- No arrowheads.
Give two structural features of mitochondria that suggest they may have evolved from bacteria.
- Length/size is similar to that of a bacterium
- Contain DNA
- Contain 70s ribosomes
- May have plasmids
- Have double membrane.
State the path taken by proteins that are exported out of the cell.
Rough endoplasmic reticulum then Golgi Apparatus then secretory vesicle.
Describe how a molecule is prepared and secreted after translation has taken place.
- Transport vesicle from Rough endoplasmic reticulum
- Modification at Golgi apparatus
- Packaged into a secretory vesicle
- Vesicle moves along the cytoskeleton
- Vesicle fuses with plasma membrane
- Secretion occurs by exocytosis.
Explain the function of epithelial cells in the airways of mammals in the defence against pathogens.
- Goblet cells secrete mucus
- Mucus traps pathogens
- Phagocytes
- Cilia sweep/waft mucus.
Suggest the importance of the cytoskeleton in carrying out the function of epithelial cells.
Cytoskeleton moves up the cilia.
How to analyse standard deviation?
- When the standard deviation bars overlap, there is no significant difference between the two data sets.
- When the standard deviation bars don’t overlap, there is a significant difference between the two data sets.
- If the standard deviation is really large, then mean is not appropriate measure of central location.
Describe the role of acetic orcein.
Acetic orcein binds to DNA and stains chromosomes dark red.
Describe the role of Iodine.
Iodine stains cellulose yellow and starch blue/black.
Describe the role of eosin.
Eosin stains cytoplasm.
Define differential staining.
Differential staining is when you use more than one type of stain to distinguish between different types of cells/organelles/organisms.
