Cells Flashcards
Nucleus
Largest organelle
Present in all plant and animal cells (not RBCs/Phloem sieve tubes)
Double membrane - nuclear envelope
Envelope has gaps - nuclear pores
Mitochondria
Double membrane (outer and inner)
Site of aerobic respiration - makes ATP
Muscles and sperm cells have lots of mitochondria - require more energy
ATP made on inner membrane - Cristae
Golgi
Stack of flattened , curved sacs
Sacs are made of membranes
Processes and packs proteins
- When proteins are ready the ‘bud’ off from the Golgi as Golgi Vesicles
Move to cell membrane and empty their contents out of the cell when they get there
Lysosomes
Tiny bags of membrane of digestive enzymes
Endoplasmic Recticulum
Network of membranes
Interconnected membranous sacs and tubules
Rough endoplasmic recticulum
When ribosomes are attached
Site of protein synthesis
Proteins sent to Golgi for processing and packing
Smooth endoplasmic reticulum
Has a different role depending on cell its in
Ovaries and Testes - makes steroid horemones
Liver cells - breaks down toxins into harmless substances
Cell Wall
Always present in plant cells
Gives support
Made of cellulose (criss cross of cellulose fibres allows cell to swell not burst)
Chloroplast
Plant cells only (only those that absorb light)
Sight of photosynthesis - makes ATP
Vacuole
Permanent in plant cells - not in animal
Membrane bound organelle full of liquid
Forms in membrane called a Tonoplast
Contains water, sugars and enzymes
Cytoskeleton
Network of microfilaments
Helps support the cell - keep its shape
Gives cell mechanical strength
Acts as a pulley - moves organelles through the cytoplasm
Centrosomes and Centrioles
Animal cells only
Present in mitosis and meiosis
Light microscope
Long wavelength of light rays - can only distinguish between 2 objects if they are 0.2um or further apart
Strenghts of the light microscope
Specimens can be living or dead
Original colour can be viewed
Quite cheap to buy and operate
Limitations of the light microscope
Low magnification
Low resolution
Electron microscope
Light microscopes have a poor resolution as a result of a long wavelength
1930s - microscope developed that used a beam of electrons - not light
Advantages to electron microscope
Short wavelength = higher resolution
Electrons are negatively charged so the beam can be focused using electromagnets
Transmission electron microscope
Cosists of an electron gun that produces a beam of electrons that is focused onto the specimen by an electromagnet
Beam passes through thin section of specimen
Advantages of TEM
Powerful magnification
Greater resolution
Short wavelength
Limitations of TEM
Requires dead/dehydrated specimens - must be extremely thin
Does not show colour
Requires more time consuming preparations
Advantages of Scanning electron microscope
High resolution
Very accurate measuring
Limitations of SEM
Expensive
Requires skill
Prokaryotic cell
Single
Smaller than eukaryotes
No nucleus or nuclear envelope + membrane bound organelles
Ribosomes in a Prokaryotic cell
Site of protein synthesis
Not attached to membranes and smaller than eukaryotes
70s Ribosomes
Cell walls in prokaryotes
Always have a clue wall
Made of Murein
Flagella
Whip like structure
Rotates - allowing bacterium to move
Not all bacteria have a flagella - some have more than one
Slime layer
Some bacteria have this outside cell wall
Used for protection and helps group of bacteria stick together
DNA in prokaryotes
Plasmids
Separate tiny circles of DNA carrying only a few genes which occur throughout the cytoplasm
Virus
Acellular - not made of or able to be divided into cells
Non living - unable to exist/ reproduce without a host cell
Virus
Acellular - not made of or able to be divided into cells
Non living - unable to exist/ reproduce without a host cell
Phagocytosis
- Phagocyte detects the pathogen
- Phagocyte moves towards it and engulfs the pathogen - forms a phagosome
- Lysosomes within the phagocyte release digestive enzymes and break the pathogen down
- The phagocyte places the antigens from the pathogen on its cell surface membrane - Antigen presenting cell
Cellular immune response
T cells and cells in the immune system they react with eg. Phagocytes
Humoral response
B cells , clonal selection and production of monoclonal antibodies
T Cells
Type of WBC
Activated by phagocytes
Have receptor proteins which bind to antigens
Helper T cell - release chemical signal to stimulate phagocytosis (and B cells)
Cytotoxic T cell - kill abnormal and forgein cells
B cells
- When the antibody on the B cells finds a complementary antigen , it binds to it
- This together with the substances released from helper T cells activates the B cell (clonal selection)
- Activated B cell divides into plasma cells
