Cell structure and microscopy Flashcards
What are cells?
The basic unit of all living organisms. They contain genetic information in a nucleus or nuclei, a cytoplasm and ribosomes
What is a tissue?
A group of similar cells which work together to perform a specific function
What is an organ?
A group of tissues which work together to perform a specific function
What is an organ system?
A group of organs that work together to perform a particular function
State 8 organelles found in animal cells
Nucleus, mitochondria, ribosomes, rough endoplasmic reticulum, smooth endoplasmic reticulum, centrioles, golgi body, lysosomes
What is the function of the nucleus?
To store and transmit genetic material
What is the function of nuclear pores?
To allow substances to enter and exit the nucleus
What is chromatin?
DNA wrapped around histone proteins
Describe the structure and function of the rough endoplasmic reticulum
Studded with ribosomes, made up of membranes folded into cisternas. It synthesizes proteins destined to be secreted
Describe the structure and function of mitochondria
Double membrane folded into chrisae. There’s fluid with matrix inside. It contains its own DNA (mDNA). It’s a site of ATP production through aerobic respiration
What is the function of lysosomes? What do they contain?
They break down substances so they can be used. They contain hydrolytic enzymes that break down waste
What is the function of vesicles?
To transport substances within cells
What is the structure and function of ribosomes?
Two units made of protein and rRNA. They synthesize proteins
Describe the structure of the Golgi body
It’s a membrane-bound organelle folded into cisternae
What is the function of the Golgi body?
It modifies and processes lipids and proteins and packages them into vesicles.
Describe the structure and function of lysosomes
Membrane-bound vesicles that contain hydrolytic enzymes that break down waste and toxins.
Describe the structure of centrioles
A cylindrical bunch of protein called tubules. They’re often found in pairs which make up a structure called centrosome.
Name the components of a chloroplast (7)
Inner membrane, outer membrane, grana, stroma, ribosome, thylakoid, intergranal lamellae
What is an intracellular enzyme?
An enzyme that acts within cells. Ex catalase
What is an extracellular enzyme?
An enzyme that is secreted by cells and functions outside of cells. Ex amylase
Describe the steps involved in the production of an extracellular enzyme
- DNA transcribed to produce mRNA in the nucleus
- mRNA exits the nucleus and travels to a ribosome on the rER
- Enzyme synthesized by the ribosomes in translation
- Enzyme is packaged into a vesicle and sent to the Golgi apparatus where it’s repackaged and modified
- The enzyme leaves the Golgi apparatus enclosed in a vesicle and undergoes exocytosis to exit the cell
What is the function of the flagellum?
To move the cell
What is the function of the pili?
They allow the bacteria to adhere to other cells or surfaces
What is the function of plasmid DNA?
To provide beneficial genes which aid in the survival of the prokaryote.
What is the function of the bacterial capsule?
It protects the cell from dry environments and it acts as a virulence factor which helps resist phagocytosis
What is the magnification of a microscope the measurement of?
How many times bigger the image appears compared to the original object
What is the formula for calculating magnification?
image size = actual size x magnification
actual size = image size / magnification
magnification = image size / actual size
What is the purpose of staining specimens?
To visually distinguish different parts of a specimen and to increase contrast. Lots of cellular components are transparent
What is differential staining?
A form of staining used to distinguish between different parts of the specimen using different stains
How do light microscopes work?
They use lenses to magnify visible light passed through a specimen
What is resolution?
A measurement of the clarity of an optical instrument. The minimum distance which two separate points can be distinguished by an optical instrument
Describe how a Transition Electron Microscope works
High energy beam of electrons passed through a thin slice of specimen. More dense structures absorb more electrons so they appear darker. The image is focussed onto a fluorescent screen or photographic plate using magnetic lenses
Describe how a Scanning Electron Microscope works
Beam of electrons focused on the surface of a specimen using electromagnetic lenses. Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
Why do electron microscopes have a higher resolution than light microscopes?
Electrons have a much shorter wavelength than light and so can distinguish much smaller structures
What type of microscope typically produces naturally colored images?
Light microscope
What type of electron microscope produces 2D images?
Transmission electron microscope because the electrons are passed through the specimen
Give 5 advantages of light microscopes
-cheap
-easy to use
-can visualize living cells
-portable and don’t always require electricity
-can visualize whole specimens
Give 2 advantages of electron microscopes compared to light microscopes
They have much higher resolution and depth of field. They have much higher magnification.
