1.2 Ultrastructure of cells Flashcards
What is resolution?
The ability to distinguish between two points of an object.
When is resolution better?
When the wavelength of light is shorter
How are electron microscopes different?
- Uses electron beam as illumination
- Gives black and white image
- Higher resolution
- Cannot view any living material or processes due to vacuum
Ultrastructure
Architecture of cells and biomaterials that are only visible at high resolution
Prokaryotes
Single-celled organisms that lack a nucleus and membrane bound organelles
What does 70S mean?
It is the sedimentation rate in centrifugation
Pilli
Enable cell to attach to other surfaces and exchange DNA
Flagellum
Used for cell locomotion
Nucleoid/Plasmid
Contains DNA not enclosed by a nucleus
Process of binary fission
- Circular DNA is copied in response to replication signal
- 2 DNA loops attach to membrane
- Membrane elongates and pinches off to form 2 cells. Cytokinesis
Binary fission: Asexual or sexual?
Asexual as genetic content is exactly the same as circular DNA is replicated. (Except for mutations)
Eukaryote
Complex cell which contains a clearly defined nucleus
Advantages of compartmentalization
- Greater efficiency of metabolism as enzymes and substrates are enclosed in membrane for specific functions
- Internal conditions like pH and temp can be regulated separately
- Isolation of toxic or damaging substances in cytoplasm
- Flexibility in number and positions of organelles
Nucleus
Contains genetic material and controls cell activity.
Mitochondrion
Site of ATP production by aerobic respiration.
Nucleus structure
- Densely stained areas are chromatin
- Double membrane with pores in between
Mitochondria structure
- Smooth outer membrane
- Folded inner membrane
- Folds = cristae
- Matrix= Space in the middle of the cristae
Free ribosomes (80S)
Synthesizes protein and releases it into the cytoplasm as enzymes. Constructed in nucleolus
Ribosome structure
Usually appear as darkened granules in cytoplasm and not surrounded by a membrane. Often 20nm in diameter
Rough endoplasmic reticulum
Synthesizes protein for secretion from cell (Note: Doesn’t package or carry)
rER structure
- Cisternae: Flattened membrane sacs
- Ribosomes: Attached to cisternae
Golgi Apparatus
Processes proteins brought in by vesicles and sends to membrane for secretion
Golgi apparatus structure
- Cisternae: Not as long as rER, often curved
- No ribosomes
- More vesicles nearby
Vesicles
Small vacuoles that transport materials inside a cell
Vesicles structure
Small with single membrane and fluid inside. Often near Golgi apparatus
Lysosomes
Formed from Golgi vesicles and contain a lot of protein. Enzymes can be used to break down food, organelles or even entire cell
Lysosome structure
- Spherical with single membrane.
- Densely stained because of high conc. of proteins
Vacuoles
Used in plant cells for storage, in animal cells for digestion of absorbed food and in prokaryotes, maybe for expulsion of water
Vacuole structure
Often occupy more than half the space in plant cells. Most animal cells have tiny vacuoles
Cilia
Used for locomotion and can be used to create current in fluid next to cell
Cilia structure
Small and multiple present. Contain rings of nine double microtubules plus two central microtubules
Microtubules and centrioles
Cylindrical fibers that can be used in cell division and centrioles form anchor point for microtubules during division. Centrioles are combination of 9 microtubules and 2 extra microtubules
Chloroplast
Produce glucose and other organic compounds by photosynthesis
Chloroplast structures
- Double membrane
- Thylakoids: Flattened sacs of membranes, usually spherical or ovaloid
- Starch grains: Present when they photosynthesize rapidly
- Stroma: Fills center of chloroplast
Function of cell wall
They provide shape and structural support to cell. They also act as a filtering mechanism and are fully permeable
Are cell walls organelles?
They are not usually considered organelles as they are not specialized and only provide support
What is cell wall composed of?
Primarily made of cellulose fibers and pectin
Difference between animal and plant cell
- Plant cells have cell walls and chloroplast
- Plants cells have much larger vacuoles
- Plants have starch grains as glucose is converted to starch but in animal cells it is converted to glycogen
