1. Cells and cell techniques Flashcards
What do all cells contain
- A cell-surface membrane
- Cytoplasm
-Genetic material, made of DNA
What are the two groups cells can be divided into
-Prokaryotic: Bacteria
- Eukaryotic: Cells found in plants, fungi, algae and animals that have internal membranes, forming organelles
What is an organelle
Small structure in cytoplasm that has a specific function
What are differences between prokaryotes and eukaryotes
Prokaryotes are much smaller
Prokaryotes don’t contain any membrane-bound organelles in their cytoplasm
How to prokaryotes from new cells
Binary Fission
What are the structures of a bacterium cell
Capsule (MBP)
Cell wall
Cell surface membrane
Cytoplasm
Small ribosomes
Plasmids (MBP)
DNA
Flagellum (MBP)
What is the DNA of a bacterium cell like
Short, circular molecule of DNA
Not associated with protein
Free in the cytoplasm
What is the function of DNA of a bacterium cell
Carries genetic codes for proteins
What is the cell wall of a bacterium like
Contains Murein - a glycoprotein
What is the function of the cell wall of a bacterium cell
Prevents osmotic lysis
Rigid - strengthening
What is cytoplasm in a bacterium cell like
A solution where many dissolved molecules are found
No membrane-bound organelles
What is the function of the cytoplasm in a bacterium cell
Site of many metabolic reactions
What is the cell surface membrane of a bacterium cell like
Phospholipid bilayer with embedded proteins
What is the function of the cell surface membrane in a bacterium cell
Controls passage of substances across exchange surfaces by passive or active transport
What is the function of the small ribosomes in a bacterium cell
Protein synthesis
What are simple flagellum like in a bacterium cell
Thin rotating fibres
What is the function of simple flagella in a bacterium cell
Responsible for movement of cell
What are plasmids like in a bacterium cell
One or more small loops of DNA
Can replicate independently
What is the function of Plasmids in a bacterium cell
Can pass on genetic info via conjugation to other bacteria
What is the capsule like in a bacterium cell
Extra layer outside the cell wall
What is the function of the capsule in a bacterium cell
Protects from desiccation, phagocytosis and some pathogens
How do we know that eukaryotes evolved from prokaryotes
Eukaryotes have extra features
What is the benefit of having membrane-bound organelles in eukaryotes
Allows chemical reactions to take place quickly and efficienctly
How to eukaryotes form new cells
Mitosis and meiosis
What is the plasma membrane like in a eukaryote
Found of cell surface and most internal organelles.
Made of a phospholipid bilayer which also contains embedded proteins
What is the function of the plasma membrane in eukaryotic cells
Selectively permeable
Allows cell identification
What is the nucleus like in eukaryotes
Contains chromosomes which are long, linear DNA molecules
Associated with histone protein
Has one or more neucleoli
What is the function of the nucleus in a eukaryote
DNA contains genetic code for making proteins
Nucleolus manufactures ribosomes
What is a mitochondrion like in a eurkaryote
Oval shaped organelle surrounded by 2 membranes.
Inner membrane folds and forms cristae
Fluid inside is called the matrix
Contains DNA like that in Prokaryotes
What is the function of mitochondria in eukaryotes
Produce ATP from aerobic respiration
ATP used by cell far active processes like protein synthesis
What is the Rough endoplasmic reticulum like in a eukaryote
A series of tubes in the cytoplasm of a cell.
Appears rough due to the ribosomes attached to the membranes
What is the function of the RER in a eukaryote
Synthesis and transport of proteins through cytoplasm
What are ribosomes like in a eukaryote
80s
Made of RNA and protein. Not surrounded by a membrane
What is the function of ribosomes in eukaryotes
Protein synthesis
what is the smooth endoplasmic reticulum like in a eukaryote
A series of tubes in the cytoplasm of cell
No ribosomes attached
What is the function of the SER in a eukaryote
Synthesises and transports lipids
What is the golgi apparatus and vesicles like in eukaryotes
Stacks of flattened sacs.
Vesicles are continually budded off from the ends of the sacs
What is the function of the Golgi apparatus and vesicles in a eukaryote
Modifies proteins that are made in the cell e.g coverts them to glycoproteins
Packages them into vesicles
Forms lysosomes
What is a lysosome like in a eukaryote
Golgi vesicle
Contains hydrolytic enzymes, sometimes known as lysozymes
What is the function of lysosomes in a eukaryote
Digest unwanted material in the cell like pathogens or unwanted organelles
What structures do plant cells have that animal cells dont
Cell wall
Vacuole
Chloroplasts
What is the function of a plant cell wall
Made of cellulose
Provides high tensile strength that prevents osmotic lysis
Cell wall in Fungi is made of Chitin
What is the function of a vacuole in a plant cell
Filled with cell sap
Gives rigidity
What is the function of chloroplasts in a plant cell
Site of photosynthesis
Where are chloroplast cells found
The mesophyll cells of leaves of green plants
What are the structures of a chloroplast
Envelope
Granum
Stroma
DNA
Ribsomes
What is the function of a chloroplast envelope
A double-membrane surrounding the chloroplast
What is the function of Granum in chloroplasts
A stack of membrane-bound discs called thylakoids
Thylakoid membranes contain chlorophyll
Membranes provide large SA for light absorption to maximise photosynthesis
What is the function of the Stroma in chloroplasts
Contains enzymes needed for photosynthesis and stores starch grains
What is the function of DNA in chloroplasts
Short, circular and not associated with proteins
What size are the ribosomes in a chloroplast
70s
What is a tissue
A group of similar cells
What is an organ
A group of tissues
What is an organ system
A group of interacting, interrelated, or independent organs forming a complex functional whole
What are viruses
They’re not cells and so are non-living.
Acellular
Cant undergo cell division - need to attach and enter a host cell and use that cell’s machinery
What components are viruses made up of
Genetic material
Capsid
Attachment protein
What is the genetic material of a virus
either DNA or RNA
What is a capsid in a virus
A protein coat
What is an attachment protein in a virus
Allows the virus to attach to host cell
Complementary to receptors of host cell membrane
What is magnification
The number of times bigger the image appears compared to its actual size
What is resolution
The minimum distance between 2 objects / points at which they can be seen as separate
What does an optical microscope consist of
Use light to illuminate and glass lenses to focus light
Eyepiece lens of fixed magnification and selection of objective lenes of various magnifications
One-cell-thick specimen
What resolution for light microscopes have
Have a relatively long wavelength so the resolution is low
What does an electron microscope consist of
Beam of e- which are focused using a series of electromagnets
What is the resolution of an electron microscope
e- have a smaller wavelength so resolution is higher
What are the different types of electron microscopes
Transmission electron microscope (TEM)
Scanning electron microscope (SEM)
What is a transmission electron microscope
The beam of electrons is transmitted through a very thin specimen
What can be looked at under a TEM
The greater resolution means smaller organelles such as ribosomes can be observed as well as internal details of organelles
What is a scanning electron microscope
Used to study 3D objects. The e- are reflected off the surface rather than passing through
What are the advantages of using light microscopes
Colour of images
Living specimens
Prep of specimens is simple
What are the limitations of using light microscop[es
Lower resolution
Limited by wavelength of light
Lower magnification
What are the advantages of using an electron microscope
Higher resolutionas e- beam wavelength is shorter than light.
Higher magnification
Finer detail can be seen
What are the limitations of using electron microscopes
Black and white images only
Vacuum is needed so only dead specimens
Complex preparation of specimens often results in artefacts
TEM require thin specimen
What is an artefact
Something that results from the way a specimen is prepared. May appear on micrograph but not be part of the natural specimen.
How do you convert between mm-um-nm
mm-x10^3-um-x10^3-nm
How do you calculate magnification and how is it measured
I=AM (mm)
How can you determine an organelle function
Must be isolated from the cell by cell fractionation and ultracentrifugation
What happens in cell fractionation
- Cells broken pen using homogeniser - breaks cell membranes and allows the organelles to be released
- Cell debris and whole cells are filtered off to leave a suspension
What happens during ultracenrtifugation
-Resultant suspension is centrifuged at a low speed
-The most dense organelle (Nucleus) separates out at the bottom of the tube. The rest of the organelles are still suspended in the supernatant
-Supernatant is poured into fresh tube and spun at a higher speed to separate (chloroplasts) mitochondria
-Process is repeated at increasing speeds to separate off the less dense organelles. A very high speed will be needed for ribosomes
What conditions are held during the separation of organelles
Cold temperature
Buffer
Isotonic
Why are cold temperatures needed when separating organelles
Reduces enzyme activity so no digestion of organelles by lysozymes
Why is a buffer needed in organelle separation
Maintains constant pH to prevent denaturation of proteins including enzymes
Why does organelle separation need to be kept isotonic
Same as water potential as organelles to prevent osmotic lysis or shrinking of organelles
