Chapter 3 Flashcards
What is a buffered solution used for?
To resist small changes in pH which denature proteins in the membranes of cell organelles
Why should a buffered solution for cell fractionation be cold?
To reduce the effect of enzymes that would digest the cell organelles
What does isotonic mean for a cell?
Means that the solution outside the cell is the same concentration as the in solution inside the cell. Means that they have the same water potential
What does hypertonic mean for a cell?
Means that the solution outside the cell is a higher concentration than the in solution inside the cell. Means that the cell has a low water potential.
What does hypotonic mean for a cell?
Means that the solution outside the cell a lower concentration than the in solution inside the cell. Means that the cell has a high water potential
Define homogenate
A fluid in which everything is evenly distributed
What is the effect of ultracentrifugation?
During spinning the heaviest organelles will separate out and the the lightest organelles will separate out last
State the equation for magnification
Magnification = size of image / size of object
Define resolution
The minimum distance apart that 2 objects can be in order for them to appear as 2 distinct items
The greater the resolution the greater the ________ of the image
Clarity
What controls the resolving power of a microscope?
The wavelength size and the form of radiation used
What is cell fractionation?
The process where cells are broken up and the different organelles they contain are separated out
What is ultracentrifugation?
The process in which the fragments in a filtered homogenate are separated out in a machine called a centrifuge
Describe the process of ultracentrifugation in animal cells
The homogenate is spun at a low speed and the heaviest organelles are forced to the bottom via centrifugal force. The supernatant is then removed and placed into a different tube and spun faster than before to separate out mitochondria which are then forced to the bottom This process is continued for more organelles
Why do light microscopes have poor resolutions?
Due to the long wavelength of light
When was the electron microscope developed?
In the 1930s
Name 2 advantages of electron microscopes over light microscopes
Higher resolving power due to a short electron wavelength (0.1nm) Electrons can be focused using electomagnets
What does TEM stand for?
Transmission electron microscope
What is the resolving power of a tem?
0.1nm
Why might the resolution of a tem be altered?
A high electron beam could destroy the specimen The specimen may be prepared wrong
What kind of image is produced by a tem? What is this projected on?
2D A fluorescent screen
Does a TEM make a colour image?
No
How does a TEM work?
An electron beam is passed through a v thin layer of specimen and some parts absorb electrons and some pass them through making darker and lighter spots which make the image
List 5 limitations of a TEM
Vaccuum needed - specimen is not alive Complex staining process Image not coloured Specimen must be extremely thin - not whole view Artefacts may appear and confuse or distort the image
How does an SEM work?
A beam of electrons is sent to the specimen but instead of penetrating the object the electrons are scattered and the pattern of the scatter and the secondary electrons make the image
What is a limitation of a SEM that a TEM doesnt have
The resolving power is lower - 20nm not 0.1nm
What is a limitation that a TEM has that an SEM doesnt?
The specimen has to be thin and the image is 2D
What is the the magnification of a Light microscope TEM SEM
400x 150,000x 100,000x
When is a vaccum required ?
SEM TEM
What is the resolving power of a light microscope?
200nm
Why do light microscopes have poor resolutions?
Due to the long wavelength of light
When was the electron microscope developed?
In the 1930s
Name 2 advantages of electron microscopes over light microscopes
Higher resolving power due to a short electron wavelength (0.1nm) Electrons can be focused using electomagnets
What does TEM stand for?
Transmission electron microscope
What is the resolving power of a tem?
0.1nm
Why might the resolution of a tem be altered?
A high electron beam could destroy the specimen The specimen may be prepared wrong
What kind of image is produced by a tem? What is this projected on?
2D A fluorescent screen
Does a TEM make a colour image?
No
How does a TEM work?
An electron beam is passed through a v thin layer of specimen and some parts absorb electrons and some pass them through making darker and lighter spots which make the image
List 5 limitations of a TEM
Vaccuum needed - specimen is not alive Complex staining process Image not coloured Specimen must be extremely thin - not whole view Artefacts may appear and confuse or distort the image
How does an SEM work?
A beam of electrons is sent to the specimen but instead of penetrating the object the electrons are scattered and the pattern of the scatter and the secondary electrons make the image
What is a limitation of a SEM that a TEM doesnt have
The resolving power is lower - 20nm not 0.1nm
What is a limitation that a TEM has that an SEM doesnt?
The specimen has to be thin and the image is 2D
What is the the magnification of a Light microscope TEM SEM
400x 150,000x 100,000x
When is a vaccum required ?
SEM TEM
What is the resolving power of a light microscope?
200nm
What is an eyepiece graticule?
A glass disk that is placed in the eyepiece of a microscope which has a scale etched onto it which is visible when looking down the eyepiece
What is an eyepiece graticule?
A glass disk that is placed in the eyepiece of a microscope which has a scale etched onto it which is visible when looking down the eyepiece
The scale on the eyepiece graticule _______ _________ the _____ when the objective lens is changed so the graticule must be calibrated for a ________ lens
Doesnt remain Same Particular
To calibrate an eyepiece graticule you need to use a special slide called a __________ that has a _________ etched onto it which is usually 2 mm long with _____ divisions
Stage micrometer Scale 200
What is cellulose made of?
Fully permeable long, straight cellulose molecules which lie side by side to form microfibrils
What is the function of the cell wall?
Maintains the shape of the cell, allowing it to become turgid without bursting Provides mechanical support and protection
Describe the function of the plasma membrane
Boundary between the cell and its environment Partially permeable and controls what enters and exists Acts as a receptor bc has receptor molecules
What is the plasma membrane made of ?
Consists of phospholipids and proteins Has receptor molecules on the surface
How big is the nucleus?
10 micrometers Largest organelle
What is the purpose of the nucleus?
Contains chromosomes, containing genes made of DNA Has a nucleolus Surrounded by double nuclear membrane with nuclear pores
Explain the function of the nucleus
Cell division and protein synthesis Makes rRNA Assembles ribosomes Controls entry and exit of materials
Explain the function of chloroplasts
Trap light energy and produces carbohydrates from CO2
How big are chloroplasts?
5 micrometers
What is the shape of chloroplasts?
Cigar shape
Explain the structure of chloroplasts
Double membrane Own DNA thylakoid membrane containing chlorophyll molecules - form stacks called grana linked together by lamellae
How big are mitocondria?
2-5 micrometers
What is the function of the mitocondria?
Site of aerobic respiration where cells ATP is made
Explain the structure of the mitocondria
Smooth outer and highly folded inner membranes with folds called Matrix Have their own DNA, ribosome and enzymes
Describe the function of the endoplasmic reticulum
Storage and transport
What does the Rough ER transport ?
Proteins made in the ribsomes
What does the Smooth ER transport?
Lipids
Explain the structure of the endoplasmic reticulum
A network of membranes running through the cytoplasm made up of tubes and cavities containing fluid filled spaces Rough ER has ribosomes on the outside
Explain the function of ribosomes
Act as giant enzymes that are the site of translation (protein synthesis)
Explain the function of the golgi apparatus and vesicles
Makes lysosomes Processing and packaging area - receives vesicles of RER which fuses together to form the flattened sacs Proteins are processed and packaged into enzymes, glycoproteins and released on the other side
Describe the structure of the golgi apparatus
Stack of flattened membrane discs of variable size
Explain the function of lysosomes
Responsible for destroying worn - out organelles and for digesting the contents of vacuoles formed by phagocytosis
Explain the structure of lysosomes
Small spheres surrounded by a membrane with no clear internal structure
Describe the function of a vacuole
Stores waste products and other substances and changes the volume affect the turgidity of the cell
Describe the structure of a vacuole
A sac bounded by a single membrane. Contains cell sap which is a solution of mineral salts, pigment, organic acids and other substances
Describe the structure of the centriols
A pair of short cylinders. Each cylinder is made if 9 fibres
Describe the function of lysosomes
Form spindle shaped structure of protein fibres on which the chromosomes move during nuclear division
Every cell contains the ———- needed for it to develop into ——— one of the different cells in an organism. Only some are ________ in any one cell at any one time.
Genes Any Expessed
True or false All bacteria possess a cell wall made up of kertin
False All bacterial cells possess a cell wall made up of murein
What do all bacterial cells contain
Cell surface membrane Circular DNA Cytoplasm Ribosomes Cell wall
What do only some bacterial cells contain Explain the functions of these
A slime capsule - protects bacterial cells and helps them to clump together Plasmids- possesses the genetic information for the replication of bacterial cells Pili - attached to surfaces of other bacteria - used for communication Flagellum- used for movement
Explain 5 differences between prokaryotic and eukaryotic cells
1).Pro - no nucleus - euk - nucleus 2) Pro - dna not associated with proteins - euk- associated with histone proteins 3) pro -dna stored circularly euk- dna stored linearly 4) pro - ribsomes are smaller 70s euk- ribsokes are 80s 5) pro - cell wall made of murein - euk - cell wall made of cellulose
How small are viruses?
20-300 nm
How do viruses multiply?
They contain nucleic acid and multiply within living host cells
What are viruses nucleic acid enclosed in
A protein coat called a capsid
What do attachment proteins do?
Allow the virus to identify and attach to host cells
How many cells are produced from mitosis? Are they identical? Is it somatic or gametic? Haploid or diploid?
2 Yes Somatic Diploid
How many cells are produced via meiosis? Haploid or diploid? Genetically identical? Gametic or somatic?
4 Haploid No Gametic
What are the functions of mitotic cells?
Growth, repair and differentiation
What are the functions are meiosis cells?
Reproduction
What is a period when a cell is not dividing called?
Interphase
What is the phase of mitosis when the chromosomes become visible as a distinct structures is called ….
Prophase
What happens in prophase?
Chromosomes become visible Centrioles move to opposite poles of the cells Spindle fibres develop - spindle apparatus The nucleolus disappears Nuclear envelope breaks down
What happens in metaphase?
Chromosomes can be seen to be made up of 2 chromatids Chromatids are joined by the centromere Microtubules from the pole are attached to the centromere and pull the chromosomes along the spindle apparatus
What happens in anaphase?
The centromeres divide in 2 and the spindle fibres pull the individual chromatids apart The chromatids move rapidly to opposite poles of the cells
What happens in telophase?
The chromatids reach their perspective poles and become longer and thinner and disappear all together The fibres disintegrate and the nuclear envelope and nucleolus reform
What happens in cytokenisis
The cytoplasm divides
Define mitotic index
The number of cells undergoing mitosis in proportion with all of the cells (including the ones undergoing mitosis)
What is cancer?
Cancer is a group of diseases caused by growth disorders in cells.
What causes cancer?
A mutation in one of the genes that controls mitosis can cause uncontrolled mitosis
What are tumour suppressor genes?
Genes that inhibit the cell cycle If mutated the genes stop working so there will be too much mitosis
What are proto-oncogenes?
Genes that promote the cell cycle If mutated the genes cannot stop working so there will be too much mitosis
List 7 types of cancer
Lungs Prostate glands Breast and ovaries Large intestine Stomach Oesophagus Pancreas
How do treatments work?
By preventing DNA from replicating Inhibiting the metaphase stage of mitosis by interfering with the spindle formation
What is the problem with cancer treatments?
Normal body cells that divide rapidly, such as hair and skin are also at risk
