Cells -B5 Flashcards
What does ATP consist of and what is it used for?
ATP consists of a nitrogenous organic base and three phosphate groups and is used as the energy source in plants and animals to carry out essential life processes.
What is endosymbiosis?
Cells engulfing each other for a mutual benefit
How is ATP produced?
ATP is produced by joining ADP(adenosine diphosphate) and inorganic phosphate.
Why is ATP hydrolysed?
ATP is hydrolysed to provide energy for cell reactions i.e. active transport, muscle contraction, and protein synthesis.
What is the journey of a protein?
-nucleus: DNA codes for mRNA(protein) > RER: proteinsynthesis - ribosomes(in vesicle) > Golgi : package, identify, modify the protein > exocytosis - leave cell > vesicle breaks down +protein released
-mitochondria - ATP - protein synthesis, vesicle and transportation
What are the sub-cellular structures of an epithelial cell?
1)mitochondria
2)cell membrane
3)cytoplasm
4)ribosomes
5)rough endoplasmic reticulum
6)golgi apparatus
7)smooth endoplasmic reticulum
8)lysosomes
9)nuclear envelope/membrane
10)nucleus
11)chromatin
12)centrioles/centrazone
13)microtubules
What happens in the mitochondria?
-where aerobic respiration takes place. they have a double membrane.
-ATP is formed in the mitochondria - respiration
-inner membrane forms cristae
-matrix> contains enzymes - outer membrane
-have their own DNA due to endosymbiosis
What happens in the ribosomes?
-small structures which are found in cytoplasm and RER
-contain ribosomal RNA
-size: 80s. -eukayotic, 70s. prokaryotic
-function: carry out proteinsynthesis
What happens in the RER?
-transports proteins throughout the cell
-has ribosomes on outer surface(proteinsynthesis)
-cells which makes lots of proteins have lots of RER
-cisternae and ribosomes
What happens in the golgi apparatus?
-sorts, modifies and packages molecules, such as proteins produced by the cell, into vesicles(may be used to form lysosomes)
-composed of flattened cysternae sacs made of membranes. The sacs are fluid filled and pinch off vesicles at their ends.
-usually only one golgi body in each cells, as large molecules must be packaged in vesicle to be transported out of cell.
-sort, label, and package proteins
What happens in the SER?
-function: synthesises lipids, carbohydrates and steroids.
-no ribosomes on outer surfaces
-cisternae and flat sacs
What happens in lysosomes? What is the structure like?
-used to breakdown unwanted structures within the cell
-similar in size to mitochondria. They are bound by a single membrane and have no internal structure.
-contain a large no. of hydrolytic enzymes, which must be kept separate from rest of cell contents to avoid damage
-digestive enzymes
What happens in the nuclear envelope?
-let mRNA through
What happens in the nucleus?
-production of mRNA
-hereditory information
-retain genetic material in the form of DNA
What happens in the microtubles?
-provides structure for cell
-used for transportation
What are the centrioles?
Hollow tubes made of microtubules.
What is chromatin?
A mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms.
What is the nucleolus?
Small areas within the nucleus where ribosomes are made.
What is the nuclear membrane?
Perforated by nuclear pores to allow the exit of mRNA.
holes mRNA can fit, DNA doesn’t.
What is the function of the lysosomes?
Used to breakdown unwanted structures within the cell.
What is the smooth endoplasmic reticulum?
A system of membranes lacking adjoining ribosomes which synthesises lipids and carbohydrates.
What is the function of the cytoskeleton?
A structure that helps cells maintain their shape and internal organisation.
-It’s everywhere(not in images)
What is the function of mitochondria?
The site of ATP formation by aerobic respiration.
What is the cell membrane?
The outer barrier of the cell made of a phospholipid bilayer.
What are the ribosomes?
Small structures made up from two subunits which are used to synthesise proteins.
What is the rough endoplasmic reticulum?
A system of membranes with attached ribosomes which synthesises many of the cells’ proteins.
What is the golgi apparatus?
System of flattened membranes that processes, modifies and packages molecules, such as proteins and lipids, into vesicles for transport.
What are the sub-cellular structures of bacteria, and what is their function?
-cell wall: physical barrier that protects against mechanical damage
-capsule(slime): protects bacteria from other cells and helps groups of bacteria stick together for protection
-cell surface membrane: acts as a partially permeable membrane
-flagellum: aids movement due to it’s rigid corkscrew shape and rotating base to help the cell spin through fluids.
-circular DNA: genetic information for the replication of bacterial cells
-plasmid: posses genetic genes that aid the survival of bacteria
-ribosomes(70s size-they’re smaller)
-nucleoid: circular DNA
-cell wall: made from peptidoglycan
-capsule: slime allows to stick to surfaces- stops from drying out
-pili: (pilus) allow to attatch to other bacteria- surfaces
What is the replication of bacteria called?
Binary fission
What are the steps in the process of binary fission?
1) DNA and plasmids from the parent cell replicate and duplicate
2)the cytoplasm splits/ divides into two daughter cells
-the no. of plasmids each daughter cell gets is random
-“daughter cells” > not genetically identical
How much smaller are viruses than animal and bacterial cells?
-on average, 10x smaller than animal cells, 100x smaller than bacterial cells > significantly smaller
Why are viruses unable to replicate independently?
They have no organelles. They require a living cell to replicate inside.
Viruses are acellular. What does this mean?
They are not living things.
What is the structure of a virus, and what are it’s subcellular structures?
For all viruses:
-protein capsid
-DNA/RNA : one or another, not both. Single or double stranded.
For some viruses:
-receptors: to bind and enter cells
-nuclear envelope(from a cell)
-reverse transcriptase : enzyme.
What is the function of chloroplasts?
contains chlorophyll which absorbs light/where photosynthesis occurs.
Why do chloroplasts have their own DNA ?
They used to be prokaryotic
What are the sub-cellular structures in a chloroplasts?
Thylakoids discs, stroma, granum
What is the function of thylakoids discs?
In stacks, they have chlorophyll and absorb light
What is the function of the stroma?
It’s the liquid found within thylakoid discs, enzymes, light independent reaction.
What is the granum?
Used for light dependent reactions
What is cell fractionation?
the separation of cell organelles
What are the three stages of cell fractionation?
1)homogenization
2)filtration
3)ultracentrification
What is homogenisation?
-blend/break up cells
-release organelles from cells by breaking plasma membrane
-this can be done either by vibrating the cells or grinding the cells in a blender which breaks the plasma membrane
-solution its done in must be cold, isotonic, and have a buffered pH
Why must the solution be cold in homogenisation?
to reduce enzyme activity(which could break down cells)
Why must the solution be a buffered pH in homogenisation?
resist pH change and prevent enzymes denaturing
Why must the solution be isotonic in homogenisation?
stops osmotic effects(bursting)
-no osmosis
-water potential is even
-no movement of water
Why is the solution filtered in cell fractionation?
-to remove cell debris and tissue and any complete cells(not broken up)
-cell debris and unbroken cells are removed
What is ultracentrifugation?
spun at low speed in a centrifuge, heaviest organelles to the bottom
-add supernatant and then spun at a faster and longer so smaller organelles go to the bottom
-then again for smaller organelles
-centrifuge has to be balanced
-heaviest thing falls to the bottom first
-remove supernatant each time, place in new test tube, leaving oher organelles there
-spin faster > next heaviest
What is supernatant?
liquid containing other organelles
What is the order of density cell structures are separated by in cell fractionation?
cell wall
nucleus
chloroplast
mitochondria
ribosomes
Define magnification.
How much bigger you’re making the image/sample -> making things bigger
Define resoution.
the ability to distinguish between two separate points close together
With light microscopes, can specimens be living or dead?
specimens can be both, but often need to stained.
Specimens are illuminated with light
What is the magnification limited to on a light microscope?
The mag. is limited to x1500. This allows individual cells and some large structures to be observed, but none of the smaller structures
Why does light have a poorer resolution?
light has a poorer resolution as it has a longer wavelength - the wavelength is longer than the sample
How do electrons increase resolution?
electrons are used to increase resolution as they have a much shorter wavelength than light so have a higher resolution
What do electron microscopes use instead of light?
uses a beam of electrons to produce an image instead of light
What does a vacuum pump do in an electron microscope?
a vacuum pump removes all air to stop air molecules getting in the way of the beam of electrons
What is the benefit of electrons being negatively charged in an electron microscope?
the beam can be focused using electromagnets
What are the advantages of using electron microscopes?
-higher resolution
-higher magnification
-shorter wavelength
What are the disadvantages of using electron microscopes?
-can’t look at living cells
-must be in a vacuum
-no colour images
-specimens must be thin
-artefacts may end up in the image
What is a transmission electron microscope used for?
mainly used for studying the internal structures of a cell(2D)
What is a scanning electron microscope mainly used for?
mainly used to study the surface of cells(3D)
What are the advantages of transmission electron microscopes?
-higher resolution
-see internal structures
What are the disadvantages of transmission electron microscopes?
-only see samples in 2D
-samples must be thin
What are the advantages of scanning electron microscopes?
-can see in 3D
-can see the surface
What are the disadvantages of scanning electron microscopes?
-poorer resolution
What are the limitations of light microscopes?
poor resolution(long wavelength)
What is the equation for magnification?
magnification= image size/actual size
What do you do when converting from big units to small units?
multiply
What do you do when converting from small units to big units?
divide
