Cells (Cells Structure) Flashcards
Microscopy
The technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye
Magnification
How many times bigger the image is when compared to the object
Size of real object =
Size of image/Magnification
Resolution
The minimum distance apart that two objects can be in order for them to appear as separate items
Cell fractionation
The process where cells are broken up and the different organelles they contain are separated out
Homogenation
Cells are broken up by a homogeniser, this releases the organelles from the cell
Ultracentrifugation
the process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge
Transmission Electronic Microscope
Consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet
Photomicrograph
An image that is produced on a screen and this can be photographed to give a photomicrograph
The Scanning Electron Microscope
All the limitations of the TEM also apply to the SEM, except that specimens need not be extremely thin as electrons do not penetrate.
Eyepiece Graticule
Is a disc placed in the eyepiece with 100 divisions and has no scale
Stage Micrometer
A microscope slide with a finely divided scale marked on the surface
Eukaryotic Cell
A cell that has a membrane-bound nucleus and chromosomes.
Prokaryotic Cell
A cell of an organism belonging to the kingdom Prokaryotae by lacking a nucleus and membrane-bound organelles
Ultrastructure
The internal structure of the cell that suite it for its job
The nucleus
The most prominent feature of a eukaryotic cell
Nuclear Envelope
A double membrane that surrounds the nucleus, controls entry and exit of materials in and out of nucleus
Nuclear Pores
Allows the passage of large molecules, such as messenger RNA, they are typically around 3000 pores in each nucleus, each 40-100nm in diameter
Nucleoplasm
The granular, jelly-like material that makes up the bulk of the nucleus
Chromosomes
Consist of protein-bound, linear DNA
Nucleolus
A small spherical region within the nucleoplasm, that manufactures ribosomal RNA and assembles the ribosomes
Mitochondrion
The sites of the aerobic stages of respiration (Krebs cycle and the oxidative phosphorylation pathway), production of ATP
Double Membrane
Controls the entry and exit of material. The inner of the two membranes is folded to form extols known at the cristae
Cristae
Extensions of the inner membrane, provides large surface area for the attachment of enzymes and other proteins involved in respiration
Matrix
Remainder of the mitochondrion, contains protein, lipids, ribosomes and DNA (allows mitochondrion to control the production of their own proteins
ATP (Adenosine Triphosphate)
An activated nucleotide found in all living cells that acts as an energy carrier
Active Transport
Movement of a substance from a region of low concentration to a region of high concentration
Chloroplasts
Carry out photosynthesis in plants
The chloroplast envelope
Double plasma membrane that surrounds the organelle, is highly selective in what it allows to enter and leave the chloroplast
The Grana
Are sacks of up to 100 disk-like structures called thylakoids
Thylakoids
Disk-like structures that contain photosynthetic pigment called chlorophyll
Chlorophyll
Absorbs the light energy, gives plants their green colour
The Stroma
Fluid-filled matrix where the second stage of photosynthesis takes place, starch grains are also in here
Endoplasmic Reticulum
3D system of sheet-like membranes, spreading through the cytoplasm of the cells, network of tubules and cisternae
Rough ER
Has ribosomes present on the outer surfaces of the membranes, provide a large surface area for the synthesis of proteins and glycoproteins
Smooth ER
Lacks ribosomes on its surface and is often more tubular in appearance. Synthesise, store and transport lipids and carbohydrates
Golgi Apparatus
Horse shoe shaped, sacks of membranes that make up flattened sacs or cristernae, with small rounded hollow structures called vesicles. Proteins from ER pass through Golgi as they are modified and labeled, then transported to golgi vesicles which are regularly pinched off from the ends of the golgi cisternae.
Function:
Add carbohydrate to proteins to form glycoproteins
Produce secretory enzymes, such as those secreted by the pancreas
Secrete carbohydrates, such as those used in making cell walls
Transport, modify and store lipids
Form lysosomes
Cristernae
Any of the flattened disks of the ER and Golgi
Lysosomes
Formed when vesicles produced by the Golgi contains proteases and lipases. Also contain lysozymes that hydrolyse cell walls of some bacteria. 50 such enzymes in one lysosome.Lysosomes isolate these enzymes from the rest of the cell before releasing them, either to the outside or into a phagocytic vesicle with the cell
Function:
Hydrolyse material ingested by phagocytic cells, such as white blood cells and bacteria
Release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell
Digest worn out organelles so that the useful chemicals they are made of can be re-used
Completely break down cells after they have died
Phagocyte
A type of cell that is able to ingest, and sometimes dies, foreign particles, such as bacteria, carbon, dust or dye
Ribosomes
Small cytoplasmic granules found in all cells, occur in cytoplasm (free) or be associated with RER
80S
Found in eukaryotic cells, is around 25nm in diameter
70S
Found in prokaryotic cells, mitochondria and chloroplasts, is slightly smaller
Cell Wall
Consists of microfibrils, embedded in a matrix, they consist of a number of polysaccharides, such as cellulose there is a thin layer, called the middle lamella, which marks the boundary between adjacent cell walls and cements adjacent cells together
Function:
Provide mechanical strength in order to prevent the cell bursting under the pressure created by the osmotic entry of water
To give mechanical strength to the plant as a whole
To allow water to pass along it and so contribute to the movement of water through the plant
Middle Lamella
Layer made up of pectins and other substances found between the walls of adjacent plant cells
Chitin
A large, structural polysaccharide made from chains o modified glucose, found in exoskeletons of insects and cell wall of fungi
Cell Surface Membrane
Two layers of phospholipids containing other molecules particularly proteins, partially permeable, controls the passage of substances into and out of the cell
Phospholipids
Triglyceride in which one of the tree fatty acid molecules is replaced by a phosphate molecule
Cholestrol
Lipid that is an important component of cell-surface membranes
Gylcolipids
Serve to stabilise the cell membrane, responsible for cell to cell interactions
Proteins
Complex polymers that are made up of amino acids
Vacuoles
Fluid filled sac bounded by a single membrane
Function:
They support herbaceous plants, and herbaceous parts of woody plants, by making cells turgid
The sugars and amino acids may act as a temporary food store
The pigments may colour petals to attract pollinating insects
Tonoplast
The single membrane that surrounds that vacuole
Exocytosis
The bulk transport of materials through the cell-surface membrane out of the cell
Endocytosis
The cellular process in which substances are brought into the cell
Autolysis
The destruction of cells or tissues by their own enzymes
Centrioles
Small hollow cylinder, occur in pairs near nucleus in animal cells, Help to form spindle in nuclear division
Spindle fibres
Form a protein structure that divides the genetic material in a cell
Tissues
A collection of similar cells that perform a specific function
Cell specification
Each cell of multicellular organisms are each specialised in different ways to perform a particular role
Organs
A combination of tissues that are coordinated to perform a variety of functions
Organ systems
Many organs that are working together as a single unit
Bacterial cell wall
Physical barrier that excludes certain substances and protects against mechanical damage and osmotic lysis
Bacterial cell capsule
Protects bacterium from other cells and helps groups of bacteria to stick together for further protection
Bacterial cell-surface membrane
Acts as a differentially permeable layer, which controls the entry and exit of chemicals
Bacterial circular DNA (nucleoid)
Possesses the genetic information for the replication of bacterial cells
Bacterial plasmid
Possesses genes that may aid the survival of bacteria in adverse conditions, eg (antibiotics)
Bacterial flagellum
There may be one or more, used to propel cell
Viruses
Non-living, contain NUCLEIC ACIDS, much smaller than bacteria
Capsid
Encloses the nucleic acid (protein coat)
Attachment proteins
Allow the virus to identify and attach to a host cell
Cell division
The behaviour of chromosomes during interphase and the stages of mitosis
Mitosis
A process where a single cell divides into two identical daughter cells
Interphase
G1 = biosynthesis organelles replicate proteins and other molecules made S = chromosomes replicate to form sister chromatids G2 = further cell growth
Prophase
Chromosomes visible, shorten and thicken (super-coil)
Centrioles move to poles of the cell
Spindle fibres start to develop from centrioles
Nucleolus and nuclear membrane disintergrate
Metaphase
Spindle fibres attach to centromere holding the chromatids together
Chromosomes are pulled towards the centre of the cell where they line up along the equator
Anaphase
Centromeres divide in two
Spindle fibres contract and pull chromatids
Chromosomes move to opposite poles of the cell
Telophase
Chromosomes unravel and become longer and thinner - once widespread this material is called chromatin
Spindle fibres disintegrate
Nucleolus and nuclear membrane form at each pole
Cytocenises in animal cells
Ring of contractile protein (actin and myosin)
Contract to pull plasma membrane inwards to form cleavage furrow
Cytokinesis in plant cells
Vesicles move to equator and fuse to form tubular structures
Vesicles deposit pectin in between cells by exocytosis = middle lamella
Vesicles deposit cellulose next to pectin = cell walls
Haploid
Cells that contain only a single copy of each chromosome
Diploid
Cells in which the nucleus contains two sets of chromosomes
Replication of Viruses
Attach to host cell with attachment proteins
Inject their nucleic acid
Provides instructions for host cell’s metabolic processes to start producing viral components
Cancer and controls of mitosis
Caused by a growth disorder in cells
Cells divide and increase size of mutated cells
Caused by mutation in two genes
Treatment of cancer
Blocking part of the cell cycle
