Cells- Topic 2 Flashcards
Magnification
how much the microscope can
increase the image size.
Resolution
how well you can determine the
difference between two points.
1m =
1,000mm = 1,000,000µm =
1,000,000,000nm. (x 1000)
Magnification =
size of image/ size of real object
Light microscope resolution
Low resolution due to comparatively large wavelength of light
Light microscope limitations
Samples are generally dead, Very thin sample slices are needed, The sample may have to be stained to show up important features eg, nucleus
of cell, The image is 2D
Transmission electron microscope
Highest resolution, 2D image, electron beam passes through a thin sample
Transmission Electron microscope limitations
Sample must be dead, complex staining process, thin sample, vacuum needed, complex staining process.
Scanning electron microscope
3D image, electrons bounce off sample
Scanning electron microscope limitations
lower resolution and magnification than TEM, vacuum needed, complex staining process.
Cell fractionation
the process by which cells are broken up and the different organelles they contain are separated out
Before homogenisation the sample is placed in a solution which is:
Cold, Isotonic and Buffered
Homogenisation
Blending the sample to release the cells contents
Filtration
Removes impurities from the sample
Ultracentrifugation
Spun to form sediment pellets of heaviest component and supernatant which can be respun
Nuclear envelope
a double membrane surrounding the nucleus with nuclear pores to control the exit of substances
nucleoplasm
semifluid matrix which contains chromatin (less condensed form of DNA)
Nucleolus
Centre of the nucleus, produces ribosomes
Nucleus function
Controls functions of the cell
Mitochondria function
Site of aerobic respiration, produces ATP
Mitochondria double membrane
Inner and outer membranes, Controls entry and exit of material
Mitochondria Cristae
Extensions of inner membrane (folds), Provide large surface area (attachments of
enzymes and proteins)
Matrix (Mitochondria)
Space between cristae, Contains protein, lipids, ribosomes, DNA, enzymes.
Chloroplasts function
Site of Photosynthesis
Chloroplast envelope
double plasma membrane: outer and inner
membrane, selective, choose what can enter and leave
Thylakoids (chloroplasts)
Membranous sacs which contain photosynthetic pigment called chlorophyll (capture light), ATP is made here,
Grana (chloroplasts)
stacks of up to 100 disk like thylakoids,
lamellae (chloroplasts)
connecting tubes between thylakoids
Stroma (chloroplasts)
fluid-filled matrix where sugars are made from carbon dioxide
Rough Endoplasmic Reticulum structure
A system of membranes enclosing a fluid-filled space studded with numerous ribosomes
Rough Endoplasmic Reticulum function
pathway for transport of materials (proteins) folds and processes proteins that have been made at the ribosomes
Smooth Endoplasmic reticulum structure
A system of membranes enclosing a fluid-filled space, no ribosomes
Smooth Endoplasmic reticulum function
synthesise, processes, store and transport lipids and carbohydrates
Golgi apparatus structure
A group of fluid-filled, membrane-bound
flattened sacs. Vesicles are often seen at the edges of the sacs
Golgi apparatus function
processes and packages new lipids and
proteins, forms glycoproteins. It also makes lysosomes
Golgi Vesicle structure
small fluid-filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus
Golgi Vesicle function
Stores lipids and proteins made by
the Golgi apparatus and transports
them out of the cell (via the
cell-surface membrane)
Lysosome structure
Formed when vesicles from Golgi body contain enzymes (protease and lipase and lysozyme)
Lysosome function
Hydrolyse material ingested by phagocytic cells (white blood cell, bacteria), Release enzymes to the outside of cell (exocytosis) to destroy material around the cell, Digest worn out organelles, Autolysis – completely break down cells after they have died
Ribosomes structure
Made of proteins and rRNA, Two subunits – large and small. 80s in eukaryotes, 70s in prokaryotes
Ribosome function
Site of protein synthesis
Cell wall structure and function
Microfibrils of polysaccharide embedded in a
matrix, provides mechanical strength
Cell membrane function
selectively permeable barrier
Vacuole structure and function
membrane-bound organelle found in the cytoplasm of plant cells containing cell sap. surrounding membrane is called a tonoplast. Helps to maintain pressure inside the cell and keep the cell rigid, isolates unwanted chemicals.
substance in bacterial cell wall
murein
DNA store in prokaryotes
circular strand of DNA and plasmids
How do bacteria divide
binary fission
flagella
tail that some bacteria have
Capsule
Outer layer of bacterial cells
viruses
acellular, non living particles
virus structure
Contain nucleic acids, DNA and RNA, enclosed within a protein coat called the capsid
G1 of cell cycle
cell contents duplicated
S of cell cycle
DNA duplicates
G2 of cell cycle
checking DNA replication and preparing to divide
centromere
where 2 sister chromatids are joined
interphase
chromosomes duplicate so there is double the amount of genetic information
Prophase
prepare. DNA super coils and chromosomes become visible. Nuclear membrane breaks down. Centrioles divide (to form 4) and spindle is assembled
centriole
organises the spindle fibres
Metaphase
middle. Chromosomes line on equator of cell Spindles fibres attach to centromeres
anaphase
apart. Centromere splits Chromatids are pulled to opposite poles as spindle
fibres contract
telaphase
two. Nuclear membranes reform Chromosomes uncoil Cytokinesis begins
Cytokinesis
cell divides to form 2 daughter cells
what causes tumours and cancer
uncontrolled cell division
how do viruses replicate
by injecting their nucleic acid into host cells
mitotic index
the proportion of cells (in a group of cells or a
sample of tissue) that are undergoing mitosis. The more rapidly the cells are dividing, the higher the index
mitotic index calculation
number of cells in mitosis/ total number of cells
