A2.2 Cell structure Flashcards
Cells as the basic structural unit of all living organisms (A2.2.1)
All living things are composed of cells.
Cells come from preexisting cells.
The cell is the basic unit of life.
Microscopy skills (A2.2.2)
Magnification = size of image/actual size of specimen
Make sure all units are the same.
Milimetres to micrometres (A2.2.2)
x1000 (and vice versa)
Stains and fluorescence (A2.2.3)
Stains: coloured substances that bind to some chemicals but not others.
Fluorescence: when a substance absorbs light then re-emits it at a longer wavelength.
Fluorescent microscopes and immunofluorescence (A2.2.3)
Microscopes have intense light sources (LEDs/lasers) which emit single wavelength. Light absorbed + re-emitted by sample -> generates bright images.
Immunofluorescence: Antibodies that bind to particular antigens in cell are produced. Fluorescent markers of diff. colours linked to antibodies. Multicoloured fluorescent image produced -> shows chems located.
Freeze-fracture electron microscopy (A2.2.3)
Produce images of surfaces within cells.
Sample rapidly freezed (liq propane). Steel blade fractures sample between membrane. Then etched: ice at surface removed by vaporization -> enhance texture.
Vapour platinum/carbon fired onto surface at 35° to form coating. Creates a replica.
Cryogenic electron microscopy (A2.2.3)
For researching the structure of proteins.
Thin layer protein solution flash-frozen on grid (using liq ethane) + put in electron microscope -> detectors capture electron transmission patterns of individual proteins.
Patterns combined using computer algorithm-> 3D image of protein at freezing.
Structures common to cells in all living organisms - plasma membrane (A2.2.4)
Outer boundary, controlls entry + exit of substances, prevents unwanted/toxic ones entering.
Can pumps substances in against a conc. gradient + helps maintain concs. different from surrounding environment.
Structures common to cells in all living organisms - cytoplasm (A2.2.4)
Water = main component, many substances
dissolved/suspended. Enzymes catalyse diff chem reactions -> metabolism.
Metabolism provides cell w/ energy, produces all proteins + substances that make up cell structure.
Structures common to cells in all living organisms - DNA (A2.2.4)
DNA can be copied + passed on to daughter cells + generations = heritable. Genes contain info for cell to carry out functions.
Plant + animal cells have a nucleus, bacteria store DNA in cytoplasm.
Prokaryote cell structure - cell wall (A2.2.5)
Thicker + stronger than membrane. Protects cell, maintains shape + supports membrane to prevent bursting. Contains peptidoglycan.
Prokaryote cell structure - cytoplasm/ribosome (A2.2.5)
Cytoplasm w/ no compartmentalization. No cytoplasmic organelles apart from 70S ribosomes.
Electron micrographs darker region of cytoplasm = contain ribosomes, enzymes + other proteins.
Prokaryote cell structure - DNA storage (A2.2.5)
Only single “naked” DNA molecule that forms a loop or circle.
Electron micrographs lighter region of cytoplasm = nucleoid (has DNA).
Eukaryote cell structure - cell wall, cytoplasm divison. (A2.2.6)
Some eukaryotes have a cell wall. Have a compartmentalized cytoplasm, separated by single or double membranes.
Eukaryote cell structure - nucleus (A2.2.6)
Compartment holds cell’s chromosomes. Double membrane w/ pores through it.
Chromosome = one long DNA molecule attached to histones. DNA is linear.
Eukaryote cell structure - ribosomes (A2.2.6)
80S ribosomes, larger in size and more mass. Sink quicker than when centrifuged.
Eukaryote cell structure - mitochondria (A2.2.6)
In cytoplasm. Has double membrane. Inner membrane folded inwards = increase SA.
Produces ATP (cell’s energy currency) by converting glucose in aerobic cell resp.
Processes of life - homeostasis (A2.2.7)
Maintenance of a constant internal environment in an organism.
Processes of life - metabolism (A2.2.7)
The sum of all the biochemical reactions that occur in a living organism.
Processes of life - nutrition (A2.2.7)
Supplying the nutrients required for energy, growth and repair in an organism.
Processes of life - excretion (A2.2.7)
Removal of waste products of metabolism from an organism.
Processes of life - growth (A2.2.7)
An increase in size or number of cells.
Processes of life - response to stimuli (A2.2.7)
Perception of stimuli and carrying out appropriate actions in response.
Processes of life - reproduction (A2.2.7)
Production of offspring, either sexually or asexually.
A2.2.8 Differences in eukaryotic cell structure (animals, fungi, plants) - Plastids
Organelles with two outer membranes and internal membrane sacs. Only plants have them (e.g. chloroplast).
A2.2.8 Differences in eukaryotic cell structure (animals, fungi, plants) - cell wall
Rigid layer outside plasma membrane to strengthen and protect the cell.
Fungi = composed of chitin
Plants = composed of cellulose
A2.2.8 Differences in eukaryotic cell structure (animals, fungi, plants) - vacuole
A flexible fluid-filled compartment, has a single membrane.
Animals = temporary, expel excess water, or digest food/pathogens from endocytosis.
Plants, fungi = large, permanent, for storage of substances and pressurising the cell.
A2.2.8 Differences in eukaryotic cell structure (animals, fungi, plants) - centrioles
Cylindrical organelles that organize microtubules (the cell’s skeletal system), determining nucleus placement.
Animals = important to mitosis and cilia/flagella base structure.
Plants, fungi = absent, except in swimming male gametes
A2.2.8 Differences in eukaryotic cell structure (animals, fungi, plants) - Undulipodia
Cilia and flagella generate cell movement or fluid movement around the cell.
Animals = in many animal cells.
Plants, fungi = absent, except male gametes that swim using flagella.
A2.2.9 Atypical cell structure in eukaryotes - Skeletal muscle cells
Cells divide into columns, then fuse, meaning the cell has more than one nucelus. This forms a synctium.
A2.2.9 Atypical cell structure in eukaryotes - Red blood cells
Lack a nucleus. When developing in bone marrow, nucleus moves to the edge of the cytoplasm, is pinched off, and destroyed by phagocytes. Cell is smaller + more flexible, but can’t repair damage. Life: 100-120 days.
A2.2.9 Atypical cell structure in eukaryotes - Aseptate fungal hyphae
Aseptate hyphae are not made of clearly defined individual cells, resulting in a continuous cytoplasm along the length of the hyphae.
A2.2.9 Atypical cell structure in eukaryotes - Phloem sieve tube elements
Sieve tube elements in plant phloem are anucleate, with little cytoplasm and few organelles, resulting in low resistance to substance movement.
A2.2.12 (HL) Origin of eukaryotic cells by endosymbiosis - defenition endosymbiosis
Whereby one cell is engulfed by another and becomes assimilated into its cellular structure.
A2.2.12 (HL) Origin of eukaryotic cells by endosymbiosis - mitochondria
Prokaryotic ancestor engulfed an aerobic bacterium, which over time lost its independent utility and developed into the mitochondria.
A2.2.12 (HL) Origin of eukaryotic cells by endosymbiosis - chloroplast
Prokaryotic ancestor engulfed a photosynthetic cyanobacterium, which over time lost its independent utility and developed into the chloroplast.
A2.2.12 (HL) Origin of eukaryotic cells by endosymbiosis - evidence
Have double membrane (outer may have vesicular origin).
Both organelles susceptible to certain antibiotics (target prokaryotic features). Have their own DNA, naked and circular. Both have 70S ribosomes.
Divide similar to binary fission (bacterial).
A2.2.13 (HL) Cell differentiation as the process for developing specialized tissues in multicellular organisms
Cell differentiation is when unspecialized cells become specialized. This is guided by gene activation and extracellular signals. Specialized cells combine into tissues to perform essential functions.
A2.2.14 (HL) Evolution of Multicellularity - survival advantages
Allows an organism to exceed size limits imposed by SA:Vol ratio limitations.
Have longer lifespans as the organism can survive the death of an individual cell.
Fosters complexity through differentiation of cell types within an organism.
