Cells without a nucleus or membrane-bound organelles. They are much smaller than eukaryotic cells.
How do prokaryotic cells form new cells?
Binary fission
Describe DNA and function in prokaryotes
short, circular molecule of DNA, not associated with protein and free in cytoplasm which carries genetic codes for proteins
Describe Cell wall and function in prokaryotes
Contains murein (glycoprotein) and prevents osmotic lysis which is rigid and strengthening
Cytoplasm Prokaryotes
Solution where many dissolved molecules are found, no membrane bound organelles. Site of many metabolic reactions
Cell surface membrane prokaryotes
Phospholipid bilayer with embedded proteins. Controls passage of substances across exchange surfaces by passive or active transport
Small ribosomes prokaryotes
Small structures in cytoplasm 70s, protein synthesis
Which 3 structures are only found in pathogenic bacteria?
Simple flagellum, plasmids, capsule
Simple flagellum pathogenic bacteria
Thin rotating fibre which is responsible for movement of cell
Plasmids pathogenic bacteria
One or more small loops of DNA, can replicate independently. It can pass on genetic info via conjugation to other bacteria
Capsule pathogenic bacteria
Extra layer outside cell wall which protects cell from desiccation, phagocytosis and some pathogens
What are eukaryotes?
Extra features compared to prokaryotic cells. Have membrane bound organelles. Form new cells by mitosis and meiosis.
Plasma membrane (eukaryotic)
Double layered membrane found on cell surface and most internal organelles. Made of phospholipid belayer which contains embedded proteins. Selectively permeable which allows cell identification.
Nucleus
Contains chromosomes which are long, linear DNA molecules associated with histone protein. Surrounded by nuclear envelop, with nuclear pores. Has one or more nucleoli. DNA contains genetic code for making proteins. Nucleolus manufactures ribosomes.
Mitochondria
Oval shaped organelle surrounded by 2 membranes. Inner membrane folded & forms cristae. Fluid inside called matrix. Contains circular DNA like that in prokaryotes. Produces ATP from respiration, used in active transport.
Rough endoplasmic reticulum
Series of tubes in the cytoplasm of cell. Appears rough due to ribosomes attached to membranes. Synthesis & transport of proteins through cytoplasm
Ribosomes (eukaryote)
Small organelle made of RNA and protein, not surrounded by a membrane. 80s, larger than prokaryotic cells. Site of protein synthesis
Smooth endoplasmic reticulum
Series of tubes in cytoplasm, no ribosomes attached. Synthesises and transports lipids
Golgi body and vesicles
Stack of flattened sacs with vesicles continually budding off from the ends of these sacs. Modifies and processes proteins that are made in the cell and packages them into vesicles ready for export from the cell. Forms lysosomes
Lysosomes
Golgi vesicle, contains hydrolytic enzymes, called lysozymes. Digest unwanted material in cell like excess organelles or pathogens
Cytoplasm
Site of many metabolic reactions
What 3 structures do plant cells have which animal cells do not have
Cell wall, vacuole and chloroplast
Cell wall plant cell
Made of cellulose which provides high tensile strength that prevents osmotic lysis
What is the cell wall in fungi made from
Chitin
Vacuole
Filled with cell sap (solution of sugar and salts) which gives rigidity
Chloroplast
Found in plant and algal cells, in green plants most chloroplasts occur in the mesophyll cells of leaves. Site of photosynthesis
Envelope in chloroplast
Double membrane surrounding the chloroplast
Granum in chloroplast
A stack of membrane bound discs called thylakoids. The thylakoid membranes contain chlorophyll- the membranes provide a large surface area for light absorption (to maximise rate of photosynthesis)
Stroma
Contains enzymes needed for photosynthesis and stores starch grains
DNA in chloroplast
Short circular and not associated with proteins
Ribosomes in chloroplast
70s
Define tissue
Group of similar cells , e.g muscle, nervous and elastic tissue
Define organ
Group of different tissues e.g liver
Define organ system
Group of different organs working together to perform a complex function e.g digestive system
Describe viruses
Acellular, cannot undergo cell division so instead they attach to and enter a host cell and use that cell’s machinery to replicate.
What are the 3 components of viruses?
genetic material- either DNA or RNA
Capsid- protein coat
Attachment protein- allow virus to attach to a host cell (complementary to receptors on host cell membran)
Define magnification
How much bigger an image appears compared to its actual size
Define resolution
The ability to distinguish between two points so they can be seen as separate
Describe optical microscopes
Use light to illuminate the specimen and glass lenses are used to focus the light. There’s an eyepiece lens of fixed magnification and a selection of objective lenses of various magnification. Specimens must be thin enough to transmit the light e.g tissue should ideally be one cell thick