topic 1 Flashcards
What are the 2 types of cells and how are they different?
Prokaryotic and eukaryitic. Eukaryotic cells are complex and include all animal and plant cells. Prokaryotic cells are smaller and simpler. Eukaryotes are organisms made of eukaryotic cells. A prokaryote is prokaryotic cell (single-celled organism).
What does the nucleus, mitochondria and ribosomes contain?
Nucleus-genetic material controls activities of cell
Mitochondria-where most of reactions for aerobic respiration takes place. Respiration transfers energy that cell needs to work.
Ribosomes-where proteins are made in cell.
What is the cell wall made from and what is the permanent vacuole?
Cell wall- made of cellulose, supports and strengthens cell.
Permanent vacuole-contains cell sap, weak solution of sugar and salts.
What is in bacteria?
No chloroplasts or mitochondria, has cytoplasm, cell membrane, cell wall. Don’t have nucleus but single strand circular strand of DNA that floats freely in cytoplasm. May contain 1 or more small strands of DNA called plasmids.
What are light and electron microscopes?
Light: use light and lenses to form image of specimen and magnify it. Let us see individual cells and larger subcellular structures.
Electron: use electrons instead of light to form image. Have much bigger magnification and resolution than light microscopes.
What is resolution?
Ability to distinguish between 2 points. Higher resolution gives sharper image.
What is the formula for magnification?
magnification=image size/real size. Sometimes useful to write magnification in standard form.
How do you prepare a slide to view onion cells?
Add drop of water in middle of clean slide, cut onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from bottom of one of layers. Using tweezers, place epidermal tissue into water on slide.
What do you do after the epidermal tissue has been placed into water on slide?
. Add drop of iodine solution. Iodine solution is stain. Stains are used to highlight objects in cell by adding colour to them. Place cover slip (square of thin transparent plastic or glass) on top. To do, stand cover slip upright on slide, next to water droplet. Then carefully tilt and lower it so it covers specimen. Try not to get any air bubbles under there-they’ll obstruct view of specimen
How do you prepare a light microscope?
Clip slide prepared onto stage, select lowest-powered objective lens, use coarse adjustment knob to move stage up to just below objective lens, look down eyepiece. Use coarse adjustment knob to move stage downwards until image is roughly in focus, adjust focus with fine adjustment knob, until get clear image of what’s on slide, if need to see with greater magnification, swap to higher-powered objective lens and refocus.
What are undefined cells called?
Stem cells.
How are sperm cells specialised for reproduction?
Function: to get male DNA to female DNA. Has long tail and streamlined head to help it swim to egg. Lot of mitochondria in cell to provide energy needed. Also carries enzymes in its head to digest through egg cell membrane.
How is the nerve cell specialised for rapid signalling?
Function: to carry electrical signals from 1 part of body to another. Long cells and have branched connections at ends to connect to other nerve cells from network throughout body.
How are muscle cells specialised for contraction?
Function: to contract quickly. Long cell (to have space to contract) contain lots of mitochondria to generate energy needed for contraction.
how are root hair cells specialised for absorbing water and minerals?
Are on surface of plant cells, which grow “hairs” which stick out into soil. Gives plant big surface area for absorbing water and mineral ions from soil.
How are Phloem and xylem cells specialised for transporting substances?
Phloem and xylem tubes, which transport substances e.g. food and water around plants. To form tubes, cells are long and joined end to end. Xylem cells are hollow in centre and phloem cells have few subcellular structures, so stuff can flow through them.
What are chromosomes and where are they found?
coiled up lengths of DNA molecules, found in nucleus. Each chromosome has large number of genes. Different genes control development of different characteristics. Body cells normally have 2 copies of each chromosome, 1 from its mother and 1 from its father. 23 pairs of chromosome for each cell.
What is the stage of cell cycle when cells divide called?
mitosis. Multicellular organisms use mitosis to grow or replace cells that have been damaged.
When is the end of cell cycle?
When 2 identical cells to original cell with same number of chromosomes divide.
What happens in the growth and repair stage of cell cycle?
In cell that’s not dividing, DNA is all spread out in long strings. Before divides, cell has to grow and increase amount of subcellular structures e.g. mitochondria and ribosomes. Then duplicates its DNA-so is 1 copy for each new cell. DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of chromosome is exact duplicate of other.
What happens in binary fission?
circular DNA and plasmid(s) replicate. Cell gets bigger and circular DNA strands move to opposite ‘poles’ of cell. Cytoplasm begins to divide and new cell walls begin to form, cytoplasm divides and 2 daughter cells are produced. Each daughter cell has 1 copy of circular DNA, but can have variable number of copies of plasmid(s).
How does bacteria divide?
Divide quickly in right conditions (e.g. warm environment). Some bacteria such as E. coil, can take as 20 minutes to replicate in right environment. However, if conditions become unfavourable, cells will stop dividing and eventually begin to die.
How do you find the number of bacteria in a population?
Mean division time is just average time it takes for 1 bacteria cell to divide into 2. If know mean division of cell, can work out how man times has divided in certain amount of time, and do number of cells it has produced in that time.
What does a “culture medium” contain?
Carbohydrates, minerals, proteins and vitamins. Can be a nutrient broth solution or solid agar jelly.
How does bacteria grow?
To make agar plate, hot agar jelly is poured into shallow round plastic dish called Petri dishes. When jelly’s cooled and set, inoculating loops (wire loops) can be used to transfer microorganisms to culture medium. Alternatively a sterile dropping pipette and spreader can be used to get an even covering of bacteria, microorganisms then multiply.
How do you know bacteria has grown?
On agar ‘plates’. Will form visible colonies on surface of jelly or will spread out to give even covering of bacteria.
What are the correct conditions for growing bacteria?
In lab or school cultures of microorganisms are kept above 25 degrees Celsius because harmful pathogens are more likely to grow above this temperature. In industrial conditions, cultures are incubated at higher temperatures so they can grow a lot faster.
What are the preparation steps for investigating the effects of antibiotics on bacterial growth?
Place discs soaked in different types (or different concentrations) of antibiotics on agar plate that has an even covering of bacteria. Leave some space between discs.
What happens after the antibiotics diffuse into the agar jelly?
Antibiotic-resistant bacteria will continue to grow on agar around paper discs, but non-resistant strains will die. Clear view will be left where bacteria have died-called inhibition zone.
