Biology Chapter 3 Flashcards
What is the function of the cell surface membrane?
Regulates the movement of substances into and out of the cell. it also has receptor molecules on it, which allow it to respond to chemicals like hormones
What is the function of the nucleus?
Control’s the cell’s activities. DNA contains instructions to make proteins. The pores allow substances to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes
What is the function of the mitochondrion?
The site of aerobic respiration
Describe the structures in the mitochondria
Cristae = inner folds in the inner membrane
Matrix = inside the Cristal, contains enzymes involved in respiration
Double membrane
What is the function of the chloroplast?
The site where photosynthesis takes place
Describe the structures in the chloroplast
Stroma
Granum = stacked up thylakoid membranes
Lamella = thin, flat pieces of thylakoid membrane
What is the function of the Golgi apparatus?
Processes and packages new lipids and proteins. It also makes lysosomes
What is the function of the Golgi vesicle?
Stores lipids and proteins made by the Golgi apparatus and transports them out of the cell via the cell surface membrane
What is the function of lysosomes?
Contain digestive enzymes (lysozymes) which are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell
What is the function of ribosomes?
The site where proteins are made (protein synthesis)
What is the function of the rough endoplasmic reticulum?
Folds and processes proteins that have been made at the ribosomes
What is the function of the smooth endoplasmic reticulum?
Synthesises and processes lipids
What is the function of the cell wall?
Supports the cell and prevents the cell from changing shape
What is the function of the cell vacuole?
Helps to maintain the pressure inside the cell and keeps the cell rigid. It’s also involved in the isolation of unwanted chemicals inside the cell
Describe the structure of a prokaryotic cell
Cell surface membrane
Cell wall
Cytoplasm
Ribosomes (70s)
Flagellum (makes the prokaryotic cell move)
Circular DNA (floats free in the cytoplasm)
Plasmids (small loops of DNA)
Capsule (helps to protect the bacteria from attack by cells of the immune system)
Describe the process of binary fission
- The circular DNA and plasmids replicate. The main DNA loop is only replicated once, but plasmids can be replicated loads of times
- The cell gets bigger and the DNA loops move to opposite ‘poles’ of the cell
- The cytoplasm begins to divide (and new cell walls begin to form)
- The cytoplasm divides and 2 daughter cells are produced. Each daughter cell has 1 copy of the circular DNA, but can have a variable number of copies of the plasmids
Define acellular
Non-living
Describe the general structure of a virus
Core of genetic material (DNA or RNA)
Capsid (protein coat)
Attachment proteins
Describe viral replication
- Virus attaches to host cell receptor proteins
- Genetic material is released into the host cell
- Genetic material and proteins are replicated by host cell ‘machinery’
- Viral components assemble
- Replicated viruses released from host cell
How do you calculate magnification?
Size of image/ size of real object
What is the conversion from a millimetre to a micrometre?
x 1000
What is the conversion from a micrometre to a nanometre?
x 1000
What is resolution?
How well a microscope distinguishes between 2 points that are close together
What is magnification?
How much bigger the image is than the specimen
What is the difference between an optimal microscope and an electron microscope?
Optimal = lower resolution, lower magnification, coloured image
Electron = higher resolution, higher magnification, black and white image
How do TEMs work?
Electromagnets are used to focus a beam of electrons, which is then transmitted through the specimen. Denser parts of the specimen absorb more electrons, so they look darker on the image.
How do SEMs work?
Scan a beam of electrons across the specimen. This knocks off one electron from the specimen, which are gathered in a cathode ray tube to form an image
What is the difference between a transmission electron microscope and a scanning electron microscope?
TEM = higher resolution, can only be used on thin/dead specimens
SEM= lower resolution, can be used on thick/dead specimen, can be 3D
How do you prepare a microscope slide?
- Pipette small amount of water onto the centre of the slide
- Use tweezers to place a thin section of your specimen on top of the water drop
- Add a drop of a stain to highlight objects in the cell
- Add the cover slip
How do scientists distinguish between artefacts and cell organelles?
By repeatedly preparing specimens in different ways. If an object could be seen with one preparation technique, but not another, it was more likely to be an artefact than an organelle
Describe homogenisation
- Grind the cells in a blender to break up the plasma membrane and release organelles into the solution
- The solution must be kept cold, isotonic and buffered
Why must the solution during homogenisation be kept cold, isotonic and buffered?
Cold = to reduce enzyme activity that break down organelles
Isotonic = same concentration/water potential of chemicals as the cells being broken down, to prevent damage to the organelles through osmosis and to prevent organelles from shrinking to bursting
Buffered = to maintain the pH and to prevent proteins from denaturing
Why do TEMs have to kept under near-vacuum conditions?
To prevent bits of dust and molecules in the air from absorbing the electrons
Describe filtration during cell fractionation
Homogenised cell solution is filtered through a gauze to separate large cell debris or tissue debris, like connective tissue, from the organelles. The organelles are much smaller than the debris, so they pass through the gauze
Describe ultracentrifugation
- Cell fragments poured into a tube. Tube put into a centrifuge and is spun at low speed. Heaviest organelles get flung to the bottom of the tube by the centrifuge. They form a thick sediment at the bottom of the pellet. The rest of the organelles stay suspended in the fluid above the sediment (supernatant)
- Supernatant is drained off and poured into another test tube and spun at medium speed. Same thing re-occurs.
- This process is repeated at higher and higher speeds, until all the organelles are separated out
Describe the order of organelles from heaviest to lightest during ultracentrifugation
Nucleus (chloroplasts) Mitochondria Lysosomes Endoplasmic reticulum Ribosomes
Describe the 3 growth stages of interphase
Gap 1 phase = cell grows and new organelles and proteins are made
Synthesis = cell replicates its DNA, ready to divide by mitosis
Gap 2 phase = cell keeps growing and proteins needed for cell division are made
What are the 4 stages of the cell cycle?
Gap 1 phase
Synthesis
Gap 2 phase
Mitosis
Describe interphase
The cell’s DNA is unravelled and replicated, to double its genetic content. The organelles are also replicated so it has spare ones, and its ATP content is increased (which provides energy for cell division)
Describe prophase
Chromosomes condense
Centrioles start moving to opposite end of the cell, forming the spindle
The nuclear envelope breaks down and the chromosomes lie free in the cytoplasm
Describe metaphase
Chromosomes line up along the middle of the cell and become attached to the spindle by their centromere
Describe anaphase
The centromeres divide, separating each pair of sister chromatids
The spindles contract, pulling chromatids to opposite poles of the spindle, centromere first
Chromatids appear V-shaped
Describe telophase
Chromatids reach opposite ends of the poles on the spindle
Chromatids uncoil and become long and thin again to become chromosomes again
Nuclear envelope forms around each group of chromosomes, so there are now 2 nuclei
The cytoplasm divides (cytokinesis)
2 genetically identical daughter cells are produced
What is cancer?
A tumour that invades surrounding tissue (due to uncontrolled cell division)
What are cancer treatments directed at and why do they cause side effects such as hair loss?
Controlling the rate of cell division and because rapidly dividing cells such as hair cells and cells that line the gut are also affected
Describe how to prepare a root tip cell squash
- Add hydrochloric acid to boiling tube and put the tube in water bath and warm
- Use scalpel to cut tip of growing root because that’s where mitosis occurs
- Transfer the root tip into the boiling tube containing the acid. Incubate for about 5 minutes
- Use tweezers to remove the root tip from the tube and use a pipette to rinse it well with cold water. Leave the tip to dry on a paper towel
- Place the root tip on a microscope slide and cut a bit of the tip
- Use a mounted needle to break the tip open and spread the cells out thinly
- Add a few drops of stain to make the chromosomes easier to see under a microscope
- Place a cover slip over the cells and put a piece of folded filter paper on top. Push down firmly to squash the tissue, which would allow light to pass through it
- Look at the stages of mitosis under a microscope
Describe how to set up and use an optical microscope
- Clip the slide you’ve prepared onto the stage
- Select the lowest-powered objective lens
- Use the coarse adjustment knob to bring the stage up to just below the objective lens
- Look down the eyepiece. 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 you get a clear image of what’s on the slide
- If you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus
How do you calculate the mitotic index?
Number of cells with visible chromosomes/ total number of cells observed
What is an eyepiece graticule?
A transparent ruler with numbers, but no units
What is a stage micrometer?
A microscope slide with an accurate scale used to work out the value of the divisions on the eyepiece graticule at a particular magnification
