Section 2 Flashcards
Cells
Fill in the gaps
What extra organelles do plant cells have compared to animal cells?
Cell wall
Vacuole
Chloroplasts
What organelles do algea and fungi cells have?
Algea - the same as plant
Fungi - the same as plant apart from their cell wall is made from chitin not cellulose and they don’t have chloroplasts
What is the structure and function of the cell membrane?
Found on the surface of animal cells and just inside the cell wall in plant cells
Made of lipids and proteins
Regulates movement of substances in and out of the cell
Has receptor molecules on it so it can respond to chemicals like hormones
What is the structure and function of the nucleus?
Surrounded by a nuclear envelope which has pores
Contains chromosomes which are protein bound and linear and a nucleolus
Controls the cells activities and contains instructions to make proteins
The pores allow substances to move in
The nuclelous makes ribosomes
What is the structure and function of the mitochondira?
Double membrane, the inner one is folded to form cristea
Inside is the matrix which contains enzymes invloved in respiration
Site of aerobic respiration which produced ATP
What is the structure and function of the chloroplasts?
Double membrane and has membranes inside called thylakoid membranes. These are stacked up to form grana which are linked together by lamellae - thin flat pieces of thylakoid membrane
Stroma - fluid inside
The site where photosynthesis takes place
What is the structure and function of the golgi apparatus?
Fluid filled membrane bound flattened sacs
Vesicles are at the edges
It processes packages new lipids and proteins
Makes lysosomes
What is the structure and function of the golgi vesicle?
Small fluid filled sac produced by golgi apparatus
Stores lipids and proteins made by the golgi and transports them out of the cell
What is the structure and function of the lysosome?
Contains hydrolytic enzymes which are kept seperate from the cytoplasm by the membrane can be used to digest invading cells or worn out components of the cell
What is the structure and function of the ribosomes?
Free floating or attached to rough endoplasmic reticulum
Made up of proteins and RNA
No membrane
Site where protiens are made
What is the structure and function of the rough endoplasmic reticulum?
a system of membranes enclosing a fluid filled space covered in ribosomes
Folds and processes proteins that have been made at the ribosomes
What is the structure and function of the smooth endoplasmic reticulum?
Similar to RER but no ribosomes
Synthesis and processes lipids
What is the structure and function of the cell wall?
Rigid structure made of celluloes or chitin
Supports cells and stops it from changing shape
What is the structure and function of the cell vacuole?
membrane bound organelle found in the cytoplasm containing cell sap - sugar and salt solution
The surrounding membane is called the tonoplast
Helps to maintain pressure inside the cell and keeps the cell rigid
Isolated unwatned chemicals inside the cell
How are epithilial cells adapted to their function?
Lots of vili which increase surface area for absorption which also have mircovilli
Lots of mitochondria to provide energy for the transport of digested food molecules into cell
How are RBC adapted to their function?
No nucleus to create a concave shape so more room for haemoglobin which carries oxygen
How are sperm cells adapted for their function?
Lots of mitochondria which provide them with lots of energy needed to propel themselves towrads the egg
Describe the process of replication in prokaryotes
Binary fission
1) Circular DNA and plasmids replicate. The DNA loop is replicated once but plasmids can be replicated multiple times.
2) The cell gets bigger and the DNA moves to oppostie poles of the cell
3) The cytoplasm divides
4) Two daughter cells are produced. Each cell has one copy of circular DNA and a varied amount of plasmids
Describe the structure of a virus
DNA/ RNA
capsid (protein coat)
attachment proteins
Describe viral replication
1) Using attachment proteins they bind to complimentary receptors on a host cell to inject their DNA/ RNA
2) Genetic material and proteins are replicated by host cell
3) viral components are assembled
4) and released from host cell
What is magnification?
how much bigger the image is than the real specimen
What is the equation for magnification and the units?
magnification = image size/ real size
All units need to be the same e.g mm
(I = AM)
How do you convert from millimeter to micrometer to nanometer and vice versa?
Measurments getting smaller = x1000
Measurements getting bigger = divide by 1000
What is resolution?
How well a microscope can distinguish between two objects that are close together
A microscope can’t distinguish two between objects which are smaller than its resolution
Describe optical microscopes
Use light to form an image
Lower magnification and resolution
Pictures can be in colour
Specimen can be alive
Can only see a nucleus no other organelles
Describe electron microscopes
Use electrons to form an image
Higher magnification and resolution
Pictures in black and white
Specimen has to be dead
Can see all organelles
Describe a transmition electron microscope (TEM)
Use electromagnets to focus a beam of electrons through the specimen
Denser parts of the specimen absorb more electrons which makes them appear darker
Describe scanning electron microscopes (SEM)
Scan a beam of electrons across the specimen knocking off electrons from the specimen which are gathered in a cathode ray tube to form an image. Can be 3D so can be used on thicker specimens but have a lower resolution than TEMs
How do you prepare a temporary mount?
1) Pipette small drops of water onto the slide
2) Using tweezers place a thin section of the specimen on top
3) Add a drop of stain e.g iodine/ eosin
4) Add the coverslip by lowering it slowly at an angle so it covers the specimen with no air bubbles
What are artefacts?
Things seen down the microscope which aren’t part of the specimen e.g air bubbles, dust, fingerprints
They are usally made during the preperation of the slide
Can be distingushed by doing multiple images and seeing if its still there - if its not its likely an artefact
Describe cell fractionation
1) Homogenisation - breaking up the cells
Grind the cells up in a blender to break open the membrane and put the organelles into solution
The solution must be ice cold to reduce enzyme activity, isotoic to prevent damage by osmosis and buffered to maintain pH
2) Filtration
Filter through a gauze to seperate large cell debris
3) Ultracentrifugation
Put solution into a tube into a centrifuge spin at a low speed to get the heaviest organelle - nucleus at the bottom of the tube (the pellet) the rest of the organelles are floating in the supernatant which is drained off and poured into another tube and spun at a faster speed and the process repeates
Order of organelles in supernatant - nuceli, chloroplasts, mitochonria, lysosomes, ER, ribosomes
What are the stages in the cell cycle?
Mitosis
Interphase –>
Gap phase 1 - cells grows and new organelles and proteins are made
Synthesis - cell replicates its DNA
Gap phase 2 - cell keeps growing and proteins needed for cell division are made
End of interphase
Mitosis again
What happenes in interphase?
DNA unravels and replicates
Organelles replicate
ATP increase
Describe the structure of a chromosome in mitosis
Two chromatids joined by a centromere
Two strands on the same chromosome are called sister chromaids
Describe prophase
Chromosomes condense and bundles of proteins called centrioles move to opposite ends of the cell forming spindle fibers
Nuclear envelope breaks down and chromosomes are free in the cytoplasm
Describe metaphase
Chromosomes line up along the middle of the cell and attach to the spdinle fibers by their centromere
Describe anaphase
Centromeres divide seperating each pair of sister chromatides
Spindle fibers contract pulling chromatids to opposite poles by the centromere
Describe telophase
Chromatids uncoil and become long and thin again (not condensed) and are chromosomes again
Nuclear envelope forms around each group of chromosomes
Cytokinesis finished forming two daughter cells that are genetically identical
What are the stages of mitosis?
Interphase
Prophase
Anaphase
Metaphase
Telophase
How does cancer treatment affect the cell cycle?
Chemical drugs prevent the synthesis of enzymes needed for DNA replication
Radition and drugs damage DNA and if the cell detects it it will kill itself
Describe how to prepare a root rip cell squash (RP)
1) Add HCl to a boiling tube and heat in a water bath
2) Cut the tip of a growing room with a scaple
3) Put it tube and incubate for 5 min
4) Use tweezers to remove it and rinse with cold water. Leave to dry on a paper towel
5) Place on microscope slide
6) Use a needle to break open the tip and spead out cells thinly
7) Add stain
8) Put cover slip on and fliter paper on top and squash the cells
9) Look through a microscope
How do you set up and use an optical microscope?
1) Clip the slide onto the stage
2) Select the lowest powered objective lense (lowest mag)
3) Turn the coarse adjustment knob to bring the stage up to the lense
4) Look down the eyepiece with the ocular lense inside and move the stage down until the image is in focus
5) Ajust the focus with the fine adjustment knob
6) Can swap to a higher powered objective lense and refocus
What is mitotic index?
The proportion of cells in a tissue smaple that are undergoing mitosis - how quickly the tissue is growing
Whats the equation for mitotic index?
mitotic index = number of cells with visible chromosomes / total number of cells observed
What is an eyepiece graticule?
A transparent ruler with no units that fits onto the eyepiece
What is a stage micrometer and what is it used for?
A microscope slide with an accurate scale (units) and is used to work out the divisions on the eyepice graticule at a certain magnification
What is the general structure of a cell membrane?
Fluid (constantly moving phospholipids bilayer)
Mosaic - protiens are scattered through the bilayer
Channel proteins and carrier proteins - allow larger molecules and ions to pass
Receptor proteins - detect chemicals from other cells
The chemicals signal the cell to respond in some way
Proteins with a carbohydrate attached are glycoproteins and lipids with carbohydrates attached are glycolipids
+ Cholesterol
What are the role of phospholpipids in the membrane?
Form a barrier to water soluble substances
Hydrophillic head and hydrophobic tail so the center of the bilayer is hydrophobic and doesn’t allow water soluble substances like ions and polar molecules to diffuse through
Small non polar substances and water (osmosis) can diffuse through the membrane
What is the role of cholesterol in the membrane?
Gives the membrane stability, fits between the phospholipids and binds to the hydrophobic tails causing them to pack more closely together restricting the movment
How does temperature affect the membrane?
Below 0 degreese
Phospholipids don’t have much energy so can’t move much. Chennal and carrier proteins denature increasing the permability.
Between 0 and 45
Phospholpipids can move around as they have more energy this increases the permability of the membrane
Above 45
Phospholipid bilaye starts to break down becoming more permable. Water inside the cell expands putting presure on the membrane. Channel and carrier proteins denature increasing permability
How do you investiagte the affect of temperature on cell membrane permability (RP) ?
1) Use a scaple to cut five equal sized pieces of beetroot and rinse to remove extra pigment
2) Add to five different test tubes with 5cm of water in
3) Place each tube in a water bath at 10, 20, 30.. etc degreese for the same amount of time
4) Remove the beetroot
5) Use a colourimeter
6) Turn on and leave for five min to stablise and set up a blue filter
7) Add water to a cuvette so its 3/4 full and put in colourimeter and cailbrate to 0
8) Repeate for the other solutions
9) Higher absorbance = more pigment released = higher permability of membrane
What is water potential?
The likelihood of water molecules to diffuse out of or into a solution
Pure water has a water potential of zero - adding solutes lowers its water potential so the water potential of any solution is always negative
What does isotonic, hypertonic and hypotonic mean?
Isotonic - same water potential so no net movement of water
Hypertonic - Solution with a lower water potential than inside the cell (the cell will shrink as water moves out by osmosis)
Hypotonic - Solution with a higher water potential than inside the cell (the cell will swell as watre moves in by osmosis)
How do you investigate water potential (RP) ?
1) Make a serial dilution series (decreasing in conc by the same amount each time)
2) Measuring changes in masses -
Cut equal chips of potatoes and put them into equal groups and measure the mass of each group
Place one group into each sucrose solution and leave for 20 min
Remove and pat dry weight each group again and calculate percentage change
3) Producing a calibration curve -
Plot percentage change in mass against conc of sucrose solution and use it to find the water potential of the potatoe cells (when mass change = 0)
How do you make a serial dilution series?
e.g starting with an inital sucrose conc of 2 M and diluting each solution by a factor of 2
1) Line up 5 test tubes in a rack
2) Add 10cm of the initial 2 M sucrose solution to the first tube and 5cm of wter to the other four tubes
3) Using a pipette draw 5cm of the solution from the first tube and add to the water in the second tube to make a 1 M conc
4) Draw 5cm from the 1 M conc and add it to the third pipette to make a 0.5 M conc
5) repeate for all tubes
How would you make a 15cm of 0.4 M sucrose solution?
1) Start with a solution of a known conc e.g 1 M
2) Find the scale factor by dividing the conc of this solution by the conc of the solution you want
so 1M / 0.4M = 2.5M
3) This means the solution you want is 2.5 times waker than the one you have. To make it 2.5 times weaker use 2.5 times less of it
15cm / 2.5 = 6cm transfere this into a tube
5) top up with water to get the volume you want
15 - 6 = 9
so add 9 of distilled water
Describe the process of active transport in the absorption of glucose
1) Sodium ions are actively transported out of the epithelial cells in the ileum into the blood by the sodium potassiu pump. This creates a conc gradients - there is no a higher conc of sodium ions in the lumen of the ileum than inside the epithelial cell
2) This casues sodium ions to diffuse from the lumen of the ileum into the epithelial cell down the conc gradient via sodium- glucose co-transporter proteins. The protein carrier sodium and glucose into the cell so the conc of glucose increases
3) Glucose diffuses out of the cell into the blood down conc gradients through a protein channel by facilitated diffusion
What affects the rate of active transport?
speed of carrier proteins
number of carrier proteins
rate of respiration (ATP)
NOT conc gradient
