Chapter 2 Basic Components Of Living Systems Flashcards
State the different techniques of preparing slides
Wet mount
Dry mount
Squash slide
Smear slide
How is a dry mount slide prepared?
Specimen is thinly sliced and placed onto the slide with a cover slip over the top
Eg, hair, muscle, plant tissue
How is a wet mount prepared?
Specimen is suspended in a liquid
A cover slip is placed at an angle reducing air bubbles
A stain can be added by placing a drop next to the cover slip
Place a paper towel on the opposite end to draw the dye under
Eg, aquatic organisms
How is a squash slide prepared?
Wet mount prepared first
Lens tissue used to press down cover slip
The sample is squashed between the slides
Eg, root tip samples
How is a smear slide prepared?
Edge of slide smears sample onto another slide creating a thin even coating
Cover slip placed over sample
Eg, blood
Why is staining used to view biological specimens?
Increases visibility
Improves contrast
What is differential staining?
Techniques which involves many chemical stains being used to stain different parts of a cell in different colours.
Give examples of stains that are used to stain negatively charged materials
Positively charged
Crystal violet
Methylene blue
Give examples of stains used to stain the backgrounds of cells
Negatively charged cannot enter cells as cytosol repels them
Nigrosin
Congo red
What is resolution?
The ability to distinguish between two close together objects
What is the equation for magnification?
Size of image / actual size of object
State the two types of electron microscopes
Transmission electron microscope
Scanning electron microscope
State the microscope with the highest resolution
TEM
State the microscope with the lowest resolution
Light microscope
State the microscope with the highest magnification
TEM
State the microscope with the lowest magnification
Light microscope
How does a TEM work?
Electromagnets focus a beam of electrons which are transmitted through the specimen.
Denser areas of specimen absorb more electrons and appear darker.
What image does a TEM create?
Black and white
2D
How does a SEM work?
Scans a beam of electrons across a specimen
Beam is reflected and the electrons are detected forming the image.
What image does a SEM create?
Black and white
3D
Give examples of stains used for electron microscopes
Samples are coated in heavy metals such as lead
Evaluate the use of TEM
Strength
Higher resolution- internal structures visible
Weakness
Live specimen cannot be viewed due to vacuum
Artefacts can distort viewing
Black and white image
Only thin specimens viewed
Evaluate use of SEM
Strength
View thick specimens
3D image
Weakness
Lower resolution
Live specimen cannot be observed
Black and white image
What are artefacts?
A detail caused by the preparation of a specimen, not an actual feature.
Why are artefacts more likely to occur using electron microscopes?
Longer preparation process than light microscopes- more likely to damage specimens
State the function of the plasma membrane in cells
Controls the movements of substances into and out of the cell
Contains receptors which have a role in cell signalling
State the function of the cell wall
Provides structural support to plant cells
Describe the structure of the Nucleus
Organelle surrounded by a double membrane nuclear envelope containing pores.
Contains chromatin and nucleolus
State the function of the nucleus
Controls cells activities - eg, controlling transcription of DNA
Contains coded genetic information in form of DNA
State the function of the nuclear pores
Allow substances to move between the nucleus and cytoplasm
State the structure of the nucleolus
Made from proteins and RNA
State the function of the nucleolus
Produces ribosomes
State the structure of a lysosome
A round organelle surrounded by a membrane with no internal structure
State the function of the lysosome
Contains hydrolytic enzymes used to digest invading cells or breaking down waste material.
Also involved in apoptosis.
State the structure of the ribosome
Organelle not surrounded by a membrane that is found in the cytoplasm or is bound to the RER.
Made up of proteins and RNA
State the function of ribosomes
Site of protein synthesis
Describe the structure of the RER
Contains a series of connected flattened membrane bound sacs called cisternae studded with ribosomes
State the function of the RER
Folds and processes proteins that have been synthesised at ribosomes
Describe the structure of the SER
Series of connected flattened membrane bound sacs called cisternae that have no ribosomes
State the function of the SER
Lipid and carbohydrate synthesis and storage
State the structure of a vesicle
Fluid filled membrane bound sac
State the function of vesicles
Transports substances into and out of the cell and between organelles.
Describe the structure of the Golgi Apparatus
Group of fluid filled flattened membrane bound sacs
Vesicles often seen at the edges of the Golgi apparatus
State the function of the Golgi apparatus
Processes and packages new lipids and proteins into vesicles
Also forms lysosomes
Describe the structure of the mitochondria
Surrounded by a double membrane
The inner membrane is folded (for a large surface area) to form cristae.
Also contains a fluid interior known as the matrix which contains enzymes used in aerobic respiration and mitochondrial DNA.
State the function of mitochondria
Site of aerobic respiration where ATP is produced.
Found in large numbers in cells that are active and require a lot of energy.
Describe the structure of the cytoskeleton
Network of fibres that make up the shape and stability of the cell.
State the components of the cytoskeleton
Microfilaments
Microtubules
Intermediate fibres
State the function of the cytoskeleton
-Providing mechanical strength to cells to maintain its shape
-Transport of materials within the cell
- Proteins of the cytoskeleton can cause the cell to move- eg, cilia and flagella
-Microtubules and microfilaments support the cells organelles keeping them in position.
What are Microtubules?
Protein cylinders
-determine shape of cell
-aid movement of organelles including vesicles
What are Microfilaments?
Contractile fibres
-Cell movement and cell contraction (cytokinesis)
What are intermediate fibres?
Give mechanical strength to cells and maintain integrity
What are spindle fibres made from?
Microtubules
State how Microtubules and Microfilaments can be prevented from functioning
Respiratory inhibitors as they requires energy from respiration
Describe to structure of the chloroplast
Small flattened structure surrounded by a double membrane.
Contains fluid interior of stroma
Contain internal membranes called thylakoids, several thylakoids stack to form grana.
Grana are linked by lamellae membranes which are thin, flattened pieces of thylakoid membranes.
State the function of chloroplasts
Site of photosynthesis
Some parts of photosynthesis happen in Grana, other happen in stroma
State the structure of the cell wall
Plant cell walls are composed of cellulose
Fungi cell wall composed of chitin
Bacteria cell wall composed of Peptidoglycan
Freely permeable
State the structure of centrioles
Small, hollow cylinders made of Microtubules
Occur in pairs to form a centrosome
State the function of the centriole
Involved in the production of spindle fibres to organise the positioning of chromosomes
Position flagella and cilia
Describe the structure of cilia
Small hair like structures found on the surface membranes of animal cells
Cross section consists of an outer membrane and a ring of 9 pairs of protein Microtubules with two Microtubules in the middle
9 + 2 formation
State the function of cilia
Microtubules allow cilia to move
Cilia help to move substances along cell surface by moving in a rhythmic wafting motion
Describe the structure of the flagella
Cross section has a ring of 9 pairs of protein Microtubules with two at the centre which stick out from cell surface
Surrounded by a plasma membrane
State the function of flagella
Microtubules contract making flagellum move
Propel the cell forward
State the organelles involved in protein synthesis
Ribosomes/ RER
Vesicles
Golgi apparatus
Describe the process of protein synthesis
Proteins are synthesise at the ribosomes
Proteins produced at the RER are folded and processed in the RER
They are transported from the RER to the Golgi apparatus in vesicles
At Golgi apparatus the proteins are modified and packaged into secretory vesicles
The vesicles are carried to the cell surface membrane where it fuses and releases the protein by exocytosis.
What type of proteins are made at the RER?
Proteins which are excreted or attach to cell membrane
What type of proteins are made at free ribosomes?
Proteins which stay in the cytoplasm
What are prokaryotes?
Single celled organisms without a nucleus and no membrane bound organelles
What are eukaryotes?
Make up multicellular organisms, contain a nucleus and membrane bound structures
Describe the differences between eukaryotes and prokaryotes
Prokaryotic cell are extremely small while eukaryotic cells are much larger
Prokaryotes have circular DNA while eukaryotic cells have linear DNA
Prokaryotes have no nucleus (DNA free in cytoplasm), eukaryotes have DNA enclosed in a nucleus
Prokaryotes have a cell wall composed of peptidoglycan, eukaryotes have no cell wall in animals, cellulose in plants and chitin in fungi
Prokaryotic cells have small 70s ribosomes while eukaryotic cells have 80s ribosomes
Prokaryotes have a flagella made of protein flagellin arranged in a helix, in eukaryotes flagella is made of Microtubules proteins arranged in 9 + 2
Describe the similarities between prokaryotes and eukaryotes
Both have a plasma membrane
Both have cytoplasm
Both have ribosomes
