2.1.1 Cell Structure Flashcards
A)What are the microscopes you need to know
- light/optical microscopes
- Transmission electron microscopes
- Scanning electron microscopes
A)what does a light ( optical ) microscope do
- they helps to understand cell structure
- optical microscopes uses light (wavelength 400-700 nm) which is focused by glass.
- the photo of the image produced is called a photomicrograph
A) what are the advantages of using a light / optical microscopes
- linear magnification (x50 means 50 times larger)
- cheap
- easy to use
- portable
- stains are not necessary
A) what are the disadvantages of a light/optical microscope
- limited resolution so some organelles cannot be seen ( eg ribosomes)
A) how does a transmission electron microscope work
- a beam of electron ( wavelength 0.004nm) from a cathode passes through the specimen and are focused by magnets onto a screen/photographic plate
- produces a 2B black and white photomicrograph
A) what are the advantages to transmission electron microscopes
- very high magnification ( x2 000 000 max)
- 0.1 nm resolution
- Ultrastructure seen
A) what are the disadvantages of transmission electron microscopes
- large
- expensive
- needs skills and training to use
- specimen needs to be in a vacuum
-specimens needs to be dehydrated and stained with metal salt (may be dangerous)
A) How does a scanning electron microscope work
- use of a beam of electrons from a cathode ( 0.004nm wavelength) that bounces of a specimen and then focussed by magnets.
- this makes a 3D black and white electron micrograph ( colour can be added by computer)
A) what are the advantages of using a scanning electron microscope
- high magnification achieved (x15 - x200,000)
- 0.1 nm resolution
- whole specimen can be used
A) what are the disadvantages of scanning electron microscopes
- large
- expensive
- need skill and training to use
- cannot be used to study living organisms
- specimen needs to be viewed while in a vacuum
B) how do you prepare the wet mount slide for light microscopes
- place a drop of water on the slide
- place your sample specimen in your drop of water
- set a cover slip over the sample specimen at a 45 degree angle
B) how do you prepare the stained slides for light microscopes
- Set a cover slip over the sample specimen at a 45o angle.
-Place 1 drop stain on the other side of the cover slip.
-The staining agent will begin to seep under the cover slip as the paper towel draws water out from the other side.
B) what and how does an eye piece graticule work
- an eye piece graticule is a small transparent ruler used to see the size of the object you are looking at
B) what is a stage micrometre
a microscope slide with a slide divided scale marked on the surface used to calibrate the eye piece graticule
(c) what are stains
stains are coloured chemicals that bind to molecules which allows the different structures in specimens to become more visible
(C) what is meant by differential staining
using different stains which are used so different tissues are stained different colours
what are the conversions between cm, mm, micrometres, nanometres
cm -> mm x10
mm -> micrometre x1000
micrometre -> nanometres x1000
what should biological drawing include and not include
Biological drawings should not:
Include shading or colouring
Include arrow heads for labels
Involve lines overlapping each other
Biological drawings should:
Include a title
State the magnification or scale
Be drawn with a sharp pencil
Include smooth, continuous lines
Include labels
Include accurate sizes of observable structures
what is the magnification formula
image size= magnification x actual size
i = am
define resolution
Resolution is the ability to distinguish between two separate points (or how detailed the image is).
define magnification
Magnification is how many times larger an image is than the object.
what are the components of a eukaryotic cell
-nucleus
-nucleolus
-nuclear envelope
-rough and smooth endoplasmic reticulum (ER)
-Golgi apparatus
-ribosomes
-mitochondria
-lysosomes
-chloroplasts
-plasma membrane
-centrioles
-cell wall
-flagella
-cilia
what are eukaryotes
multicellular organisms made up of eukaryotic cells like animals, plants, fungi, and protists.
what are prokaryotes
These are single-celled organisms made up of prokaryotic cells like bacteria.
what is the structure and function of the nucleus, nucleolus and nuclear envelope
Animal+plant
Structure
- surrounded by a nuclear envelope ( double membrane) containing pores
- contains genetic information in the form of chromosomes
- contains the nucleolus
Function
- Controlling the cell’s activities - It contains DNA with instructions to produce proteins.
- Synthesis of ribosomes - The nucleolus makes ribosomal RNA
- substances can enter and leave the nucleus via the pores in the nuclear envelope
- stores organisms genome and transmits genetic information
what is the structure and function of the rough endoplasmic reticulum
animal+plant
Structure
- a system of membrane with fluid-filled cavities ( cisternae) that is continuous with the nuclear envelope and is coated with ribosomes
function
- RER is used as a transport system where ribosomes make the proteins and the cavities transport the proteins
- provides a large surface area for the ribosomes for protein synthesis
what is the structure and function of the smooth endoplasmic reticulum
animal+plant
Structure
- system of cisternae continuous with the nuclear envelope but no ribosomes
- contains enzymes that catalyse reactions involved with lipids
Function
- used for the synthesis, storage and transport of lipids and carbohydrates
- for example: cholesterol and steroid hormones
what is the structure and function of the Golgi apparatus
animal+plant
Structure
- contains fluid filled, membrane bound sacs know as cisternae, and contains smaller vesicles
- the vesicles being substances to and from the Golgi apparatus
Function
- Process and package lipids and proteins - Carried out by the cisternae.
-Store and transport lipids and proteins - Carried out by the vesicles.
-Synthesise lysosomes - Specialised vesicles.
what is the structure and function of the ribosomes
animal+plant
Structure
- made up of proteins and ribosomal RNA
- consists of a large and small subunit
- not surrounded by a membrane
Function
- site of protein synthesis - involved in the process of translation
what is the structure and function of the mitochondria
animal+plant
Structure
- contains an enzyme - rich liquid known as the matrix
- surrounded by a double membrane in which the inner membrane is folded to form structures known as cristae
- contains their own DNA and ribosomes
Function
- site of aerobic respiration - produces ATP
what is ATP used for
it is used for energy in process such as ion transport, muscle contraction and nerve impulse propagation
what is the structure and function of lysosomes
Animal
Structure
- Round organelles with no clear internal structure
- contains hydrolytic enzymes
- surrounded by a membrane to keep enzymes separate from the cytoplasm of the cell
Function
- Digest pathogens - using enzymes
- break down waste material ( including old organelles and cells)
what is the structure and function of chloroplast
plant
Structure
-found in the green parts of plants
- contains fluid - filled sacs known as thylakoid which are stacked up to form grana
- surrounded by a double membrane, enclosing a fluid known as stroma
- contains its own DNA and ribosomes
Function
- a site of photosynthesis - reactions take place in the grana and stroma
what is the structure and function of the cell surface membrane/ plasma membrane
animal+plant + bacteria
Structure
- found on the surface of animal cells
- mainly made up of lipids and proteins
Function
- controls the movement in and out of the cell as the membrane is partially permeable
- cell signalling - receptors can detect signals from other cells
what is the structure and function of centrioles
animal
Structure
- they are hollow cylinders containing a ting of microtubules arranged at right angles to each other
- spindle fibres form the centrioles
Function
- involved in cell division, when the cell is dividing the centrioles go to opposite ends of the nucleus
what is the structure and function of the cell wall
plant + bacteria
Structure
- made up of cellulose
- contains channel ( gaps_ known as plasmodesmata
Function
- supports the cell, contents of the cell press against the cell wall to make it rigid
- prevents the cell from bursting as the cell wall can withstand high osmotic pressure
- allows exchange of substances between cells as the channels connects to neighbouring cells
what is the structure and function of the vacuole
plant
Structure
- Contains cell sap ( salt and sugar solution)
- surrounded by selectively permeable membrane known as tonoplast
Function
- Helps to maintain pressure within then cell, which keeps the cell rigid and stops the plant from wilting
what is the structure and function of the flagella
Bacteria
Structure
- a long, hair - like structure
Function
- attached to the cell membrane and rotates to push the cell around its environment
what is the structure and function of the cilia
animal
Structure
- protrusions from the cell surface membrane containing microtubules
Function
- to sweep substances along
what is the relationship between some o the organelles involved in the production and secretion of protiens
- mRNA copy of the gene is made in the nucleus and leaves via the nuclear envelopes nuclear pores
- the mRNA attaches to a ribosome connected to RER
- the ribosome reads instructions to assemble amino acid chains
- proteins are then transported from the RER to the golgi apparatus in vesicles.
- they are then modified in the Golgi apparatus
- vesicles pinched off to the plasma membrane where it fuses with the membrane and the contents are releases via exocytosis
what is the cytoskeleton
- it is present in the cytoplasm and gives structure and support to the cell
what is the importance of the cytoskeleton
- made of microfilaments which is involved in cell movement and locomotion such as muscle contraction
- made of microtubules which form a scaffold structure throughout the cell and acts as tracks for intracellular transport of vesicles and organelles
- made of intermediate filaments which is responsible for the mechanical strength of certain tissues such as skin and hair
what are the similarities and differences in structure and ultrastructure of eukaryotic and prokaryotic cells
Organism
prokaryotes - bacteria cells
eukaryotes - animal, plant
size
prokaryotes - 0.1 - 0.5 micrometres
eukaryotes - 10 to 100 micrometres
DNA
prokaryotes -circular DNA free in the cytoplasm
eukaryotes - linear DNA in the nucleus
Ribosomes
prokaryotes - smaller ribosomes (70s ribosomes)
eukaryotes - bigger ribosomes (80s ribosomes)
Organelles
prokaryotes -contains a few non membrane-bound organelles
eukaryotes - contains membrane-bound and non-membrane bound organelles
Cell walls
prokaryotes - made up of murein
eukaryotes - made up of cellulose (plants) or chitin ( fungi)
