Chapter 1 - Cell Structure Flashcards
What is a microscope?
A microscope is an object used to observe cell structure and to provide evidence to support hypotheses about the roles of cells and organelles.
What is magnification?
The number of times greater the size of the image is than the size of the real object.
Image size / Size of real object
What is resolution?
The ability to distinguish between two objects that are very close together - higher resolution means more detail.
What is the purpose of staining in microscopy?
Makes cells more visible
Increases contrast
Identify different cell components
e.g. Iodine
How can you measure a cell?
A stage micrometer - Slide with scales etched into it, used to calibrate an eye piece graticule.
Eye piece graticule - has arbitrary units and is used to measure the specimen, the actual measurement is calculated using the calibration data
What is the functions of a light microscope?
Magnification up to 2000x
Resolution to 200nm
Living and non-living specimens can be observed
What are the principles of a light microscope?
Uses light to form an image
Light that passes through or reflects from the surface of the specimen is seen
How does a transmission electron microscope (TEM) form an image?
Uses electrons to form an image
Electrons that pass through the specimen are detected
What is the functions of a transmission electron microscope (TEM)?
Magnification up to 1000000x
Resolution up to 0.2nm
Only dead or non-living specimens can be used
Creates 2D images
What are the principles of scanning electron microscopes (SEM)?
Uses electrons to form an image
Electrons that are reflected from the surface on the specimen are detected
What are the functions of a scanning electron microscope (SEM)?
Magnification up to 1000000x
Resolution to 3-20nm
Only dead or non-living specimens can be used
Creates 3D images
What are the principles of a laser scanning confocal microscope (LSCM)?
Uses a laser beam to scan an object pixel by pixel, creating a 3D image of the reflected photons. 2D imaged of higher resolution can also be produced.
What are the functions of a laser scanning confocal microscope (LSCM)?
Requires a compromise between resolution, scan time and photo-destruction of the specimen
High magnification
High resolution
Describe the structure of the Golgi apparatus.
Stack of membrane bound sacs (cisternae)
Secretory vesicles bring materials to and from the Golgi apparatus.
Describe the functions of the Golgi apparatus.
Modifies proteins and lipids from RER and prepares them for secretion
Responsible to synthesis of lysosomes
Describe the structure of the nucleus.
Large organelle surrounded by the nuclear envelope which contains many pores.
Contains chromatin and a structure called the nucleolus.
Describe the functions of the nucleus.
Controls cell activities
Control transcription of DNA
DNA contains instructions needed to make proteins
Chromatin is made from DNA and proteins and condenses into visible chromosomes
Describe the structure of the nuclear envelope.
Double membrane surrounding the nucleus
Has nuclear pores which are protein complexes with a channel through the center
Describe the functions of the nuclear envelope.
Separates nuclear contents from the rest of the cell
Nuclear pores allow larger substances to enter and leave the nucleus
Describe the structure of the nucleolus.
Dense spherical structure without a membrane
Composed of proteins and RNA
Describe the functions of the nucleolus.
RNA is used to produce ribosomal DNA - combined with proteins to form ribosomes needed for protein synthesis
Describe the structure of the rough endoplasmic reticulum (RER).
System of flattened membranes enclosing fluid filled cavities called cisternae
Surface coated with ribosomes
Describe the functions of the rough endoplasmic reticulum (RER).
Intracellular transport - cisternae forms channels to different regions of the cell
Large surface area for ribosomes to assemble amino acids into proteins for transport
Describe the structure of the smooth endoplasmic reticulum (SER).
System of flattened membranes enclosing fluid filled cavities called cisternae
Surface not coated with ribosomes
Describe the functions of the smooth endoplasmic reticulum (SER).
Makes lipids, including phospholipids for cell membranes
Contains enzymes to detoxify waste products
Describe the structure of the vesicle.
Small fluid-filled sac surrounded by single membrane
Describe the functions of the vesicle.
Transports substances in and out of the cell
Describe the structure of the mitochondria.
Surrounded by a double membrane
Inner membrane highly folded into cristae
Describe the functions of mitochondria.
Site of aerobic respiration
Where ATP is produced
Self replicates
Describe the structure of the chloroplast.
Double outer membrane
Complex internal arrangement that form thylakoids
Thylakoids are grouped into stacks called grana, joined by intergranal lamellae
Fluid filled matrix is called the stroma
Describe the functions of the chloroplast.
Site of photosynthesis
Grana - light energy is trapped by chlorophyll and used to make ATP and water is split into ions
Stroma - energy from ATP is used to make carbohydrates
Describe the structure of the vacuole.
Surrounded by a membrane called the tonoplast contains fluid
Describe the functions of the vacuole.
Filled with water and solutes and maintains cell stability
Describe the structure of the lysosome.
Round organelle surrounded by a single membrane
Small bags formed by the Golgi apparatus
Describe the functions of the lysosome.
Contains powerful hydrolytic enzymes
Can engulf old cell organelles and recycle material, often abundant in phagocytic cells that ingest pathogens
Describe the structure of the plasma membrane.
Membrane on the surface of an animal cells
Just inside the cell wall of plant cells and prokaryotic cells
Mainly made of lipids and proteins
Describe the functions of the plasma membrane.
Acts like a barrier to the cell
Controls what enters and leaves due to differential permeability
Describe the structure of the cilia.
Small hair-like structures found on the surface membrane of the surface membrane of some animal cells
Cross-section shows they have an outer membrane and a ring of 9 pairs of protein microtubules, with a single pair of microtubules in the middle.
Describe the functions of the cilia.
Microtubules allow cilia to move
Movement of cilia pushes substances along the cell surface
Occur in large numbers along the cell surface
Nearly all body cells have at leave one cilia, which contains receptors to detect environment
Describe the structure of the undulipodia.
Also known as the flagellum
Similar to cilia but longer
Surrounded by plasma membrane
Describe the functions of undulipodia.
Microtubules contract to make the flagellum move and propel forwards
Describe the structure of the ribosomes.
Small spherical organelles
Consists of two small subunits
Made of proteins and rRNA
Not surrounded by a membrane
Describe the functions of the ribosomes.
Site where proteins are made
Ribosomes attached to the RER exterior make proteins to be exported out the cell
Free-floating ribosomes in cytoplasm make proteins to be used inside the cell
Describe the structure of the centriole.
Consists of two bundles of microtubules at right angles to each other
Microtubules made of tubulin protein sub-units and arranged to form a cylinder
Describe the functions of the centriole.
Involved in the separation of chromosomes during cell division
Chromosomes attach to middle of spindle and motor proteins walk along the tubulin threads, pulling chromosomes apart
Involved in the formation of cilia and undulipodia
Describe the structure of the cellulose wall.
A rigid structure that surrounds plant cells
Made from bundles of cellulose fibers
Describe the functions of the cellulose wall.
Strong and can prevent plant cells from bursting
Provides strength and support
Maintains cell shape
Permeable due to plasmodesmata (pores within walls) and allow solutions through
What is the cytoskeleton?
A network of protein structures within the cytoplasm
What 4 structures make up the cytoskeleton?
Microfilaments
Intermediate filaments
Microtubules
Motor proteins
What are the 3 functions of the cytoskeleton?
Cellular movement
Intracellular movement
Strength and support
What is the function of microfilaments?
Give support and mechanical strength
Keep the cell’s shape stable and allow movement
What is the function of intermediate filaments?
Anchor nucleus within cytoplasm
Allow cells to adhere to a basement membrane, stabilizing tissues
What is the function microtubule?
Provide shape and support
Help transport substances and organelles through the cytoplasm
Form the spindle for mitosis
Make up cilia and flagella
What is a eukaryotic cell?
Has a true membrane bound organism
What is a prokaryotic cell?
A single cells organism that doesn’t have a nucleus or membrane bound organelles
How are the organelles of a eukaryotic cell involved in the production of proteins?
Proteins are synthesised on ribosomes bound to the RER
They then pass into the cisternae and are packaged into transport vesicles
These vesicles go to the Golgi apparatus by the cytoskeleton
The vesicles fuse to the cis face of the golgi and proteins enter
Proteins are structurally modified before leaving through the trans face in a vesicle
The secretory vesicle secretes the protein out of the cell
What are the structural differences between prokaryotic and eukaryotic cells?
Prokaryotes only have a loop of DNA that isn’t membrane bound whereas eukaryotes have a membrane bond nucleus
Ribosomes in prokaryotes are smaller than in eukaryotes
Plant cells have a cell wall made out of cellulose fibres whereas in prokaryotic cells it is made up of peptidoglycan
Flagella is thinner in prokaryotes and doesn’t have the 9+2 arrangement
What is the difference between reproduction in prokaryotic and eukaryotic cells?
Prokaryotes - binary fission
Eukaryotes - asexual or sexual (asexual for single cells, sexual for multicellular organisms)
