cell structure Flashcards
what’s the difference between eukaryotic cells and prokaryotic cells?
eukaryotic cells are complex and include all animal and plant cells whereas prokaryotic cells are smaller and simpler (bacteria)
what are the 4 organelles that the plant cell has that an animal cell does not?
cell wall, plasmodesma, vacuole, chloroplast
description and function of a plasma membrane
D- surface of animal cells made of lipids and proteins.
F- regulates the movement of substances in and out of the cell
description and function of a cell wall
D-made of cellulose
F-supports the plant cell
description and function of the nucleus
D-surrounded by a nuclear envelope which contains pores and the nucleus contains chromatin which is made from DNA and proteins and nucleolus.
F-controls the cells activities, nucleolus makes ribosomes, pores allow movement of substances between nucleus and cytoplasm, DNA has instructions to make proteins.
description and function of lysosome
D-round organelle surrounded by a membrane
F-contains digestive enzymes which break down work out components of cells or digest invading cells.
description and function of ribosome
D-small organelle that is made up of proteins and RNA, NOT SURROUNDED BY MEMBRANE.
F-site where proteins are made.
description and function of the rough endoplasmic reticulum.
D-a system of membranes enclosing a fluid filled space, surface covered with ribosomes.
F-folds and processes proteins
description and function of the smooth endoplasmic reticulum
D- similar to REM but with NO RIBOSOMES
F-synthesis and processes LIPIDS
description and function of a vesicle
D-a small fluid filled sac surrounded by a membrane
F-transports substances in and out of cell and between organelles.
description and function of a golgi apparatus
D-a group of fluid filled, membrane bound, flattened sacs
F-processes and packages new lipids and proteins, makes lysosomes
description and function of a mitochondrion
D- have a double membrane
F- site of aerobic respiration, where ATP is produced. Found in large numbers is cells that are very active and requires lots of energy
Description and function of a chloroplast
D- surrounded by a double membrane and has membranes inside called thylakoid membranes.
F-site of photosynthesis
description and function of a centriole
D-small, hallow cylinders made of microtubules
F-involved in the separation of chromosomes during cell division
description and function of cilia
D-small hair like structures, cross section have a ring of nine pairs of protein microtubules (tiny protein cylinders) with one pair in the middle. 9+2 formation
F-the microtubules allow cilia to move, this movement is used by the cell to move substances along the cell surface
description and function of flagellum
D-like cilia but longer. stick out from cell surface and surrounded by plasma membrane. have formation like cilia too.
F-the microtubules contract to make the flagellum move. flagella are used like outboard motors to propel cells forward.
describe the process of protein production.
1- mRNA copy of the instructions for insulin is made in nucleus
2-mRNA leaves the nucleus through nuclear pore
3-mRNA attaches to ribosome and ribosome reads the instructions to assemble the protein
4-insulin molecules are pinched off in vesicles an travel towards golgi apparatus.
5-vesicles fuse with golgi apparatus
6-golgi apparatus processes and packages insulin molecules ready for release
7- packaged insulin molecules are pinched off in vesicles from golgi apparatus and move towards plasma membrane
8-vesicles fuse with plasma membrane
9-plasma membrane open to release insulin molecules outside
what is cytoskeleton?
a network of protein threads, microtubules and microfilaments
what are the four main functions of cytoskeleton?
1-strenghten the cell and maintain its shape
2-supports cells organelles keeping them in position
3-responsible for the movement of materials
4-can cause the cell to move
compare and contrast eukaryotic and prokaryotic cells
prokaryotic- DNA is circular, no nucleus, cell wall is made of polysaccharides, small ribosomes, divide by binary fission, have linear chromosomes so cant carry out mitosis
eukaryotic- DNA is linear, nucleus is present, no cell wall, cellulose cell wall of chitin cell wall (FUNGI), larger ribosomes, divide by mitosis
define magnification
how much bigger the image is then the specimen
define resolution
is how detailed the image is, how well a microscope distinguishes between 2 points that are close together.
magnification equation
mag= I/A
um to mm
divide by 1000
light microscope magnification and resolution and what they look at (light)
Mag- x1500
res-0.2 micrometres, um
whole cells/tissues
A-cheap, portable
D- low mag and res
Laser scanning confocal microscope resolution and magnification and what they look at (light)
use laser beams and fluorescent dye, produce a much clearer image. used to look at objects at different depths in thick specimens, 3d
A-3d images, high res and mag
D-cannot be used on live specimen
transmission electron microscope resolution and magnification and what they look at
provide high resolution images but they can only be used on thin specimen and they can be used to look at a range of organelles, 2D images
mag-more than 1000000
res-0.0002um
A-high mag and res
D-expensive and training is required
scanning electron microscope resolution and magnification and what they look at
the images produced show the surface of the specimen and can be 3D. they give lower resolution images than TEMs
mag-0.002um
res-less than 500000
The angle at which specimens are cut can affect how they appear
A-3D image, high mag and res
D- need training, black and white images
why does an object need to stained?
sometimes an object is entirely transparent, this makes the whole thing look white as the light rays or electrons just pass straight through. SOME PARTS ABSORB MORE LIGHT THAN OTHERS
staining samples for light microscopes
methylene blue-stains DNA
eosin-stain cell cytoplasm
contrast makes the different parts show up
staining samples for electron microscopes
objects are dipped in a solution of heavy metals (lead). the metal ions scatter the electrons creating contrast. they are STILL BLACK AND WHITE, but artificial colour can be added.
how to prepare a dry mount microscope slide under a light microscope
light needs to be able to get through so u need a thin slice of specimen to use on your slide, use tweezers to pick up the specimen and put it in the middle of a clean slide, pop a cover slip on top
how to prepare a wet mount microscope slide under a light microscope (looking at tiny organisms that live in water)
pipette a small amount of water onto the slide, use tweezers to place specimen on water drop, add cover slip by stand upright next to water droplet and slowly and carefully tilt it. try to not get any air bubbles as they will obstruct your view. once in position u can get a stain, put a drop of stain next to one edge of cover slip then put a bit of paper towel next to opposite edge, the stain will get drawn under the slip across the specimen.
how to use a light microscope
start by clipping the slide containing the specimen you want to look at onto the stage
select the lowest powered objective lens (lowest mag)
use the coarse adjustment knob to bring the stage up to just below the objective lens
look down the eyepiece (containing the ocular lens)
use the coarse adjustment knob to move the stage downwards away from the objective lens until the image is roughly in focus
adjust the focus with the fine adjustment knob until u get a clearer image of what is on the slide.
if you need to see the slide with greater magnification, swap to a higher powered objective lens and refocus.
what is an eyepiece graticule?
is fitted onto the eyepiece, its like a transparent ruler with numbers but no units
what is a stage micrometre?
is placed on the stage and it is a microscope slide with an accurate scale and its used to work out the value of divisions on the eyepiece graticule at a particular magnification
