B1 cell biology Flashcards
Animal cell
Nucleus
Cell membrane
Cytoplasm
Plant cell
Nucleus Cell membrane Cytoplasm Vacuole Chloroplasts Cell wall
Nucleus
Controls activities of cell
Contains DNA
DNA organised into chromosomes
Cell membrane
Controls passage of substances into and out of the cell
Cytoplasm
Is where most chemical reactions take place. (Aerobic Respiration)
Vacuole
Surrounded by a membrane and fluid filled
Fluid is called cell sap
Vacuoles are permanent structures in plants
Chloroplasts
Found in plant cells above ground
Contain chlorophyll that absorbs the light the plant needs for photosynthesis
Cell wall
Is an additional layer outside the cell membrane
Is made from cellulose fibres
Contains fibres that provide strength
Doesn’t regulate what enters or leaves the cell
Cell size
0.01-0.10 mm
Total magnification
Total magnification= mag of eyepiece x mag of object lens
Magnification of image
Mag of image=size of image/size of real object
Resolving power/resolution
Ability to distinguish 2 points
Mitochondria
Where aerobic respiration takes place. It has a double membrane although the internal membrane is folded.
Ribosomes
Tiny structures where protein synthesis takes place. They either lie free in the cytoplasm or be attached to an internal network of channels within the cytoplasm
TEMs
X1000000
SEMs
Reveal shape of structures
Electron microscope
Colour images
Required practical- using a light microscope to observe and record animal and plant cells
Mount live cells on a slide using a drop of water
Cover with a glass coverslip and avoid air bubbles
Start looking at it on low power and then swap to high power for more detail
Sketch the cell you saw, label and identify it as animal or plant
Eukaryotic
Have cell membrane, cytoplasm containing sub-cellular structures called organelles and a nucleus containing DNA
Prokaryotic
Ribosomes Cytoplasm Plasmids- small ring of DNA Cell membrane Cell wall (may be surrounded by a capsule) Flagellum Single loop of DNA not enclosed in a nucleus Smaller cells
Classification domains
Bacteria
Archaea
Eukaryota (animals,fungi,plants,protists)
Archaeans
Live in extreme environments eg.hot springs and salt lakes
Ribosomes are similar size and structure of bacteria.
Nucleic acid is closer to eukaryotes
2/3 of DNA are unfamiliar
How many chromosomes do we have
46 and 23 pairs
Mitosis
DNA molecule in nucleus
DNA replicates to form a double chromosome each half has an identical set of genes
DNA condenses to form a recognisable chromosome. The DNA is now compacted into 1/50000 of it original length
The cell cycle
- The cell grows. No. Of sub cellular structures increases
- DNA replicates to form 2 copies of each chromosome
- Further growth and cell checked for errors
- Mitosis- the chromosomes move apart and 2 nuclei form
- Cytoplasm divides to make 2 identical cells
- Temporary cell resting period, doesn’t divide
Differentiation
As cells divide, new cells acquire certain features for their specific function.
A cells shape,size and internal structure are adapted for its role. Most animal cells differentiate at an early stage
Sperm cell
Head Acrosome- contains enzymes to penetrate the egg Nucleus- 23 chromosomes Mitochondria- in spiral for energy Tail for movement Cell membrane 55 nano metres long 3 nano metres wide
Nerve cell
Extensions that communicate with other nerve cells Nucleus Fatty covering- the myelin sheath Main part of cell(cell body) Gap I'm myelin sheath- the nerve impulses jumps from one gap to the next making it quicker. Branches that connect with a muscle Motor nerve cell length 1m diameter 1-20 nano metres
Muscle cell
Mitochondria- provide energy for muscle contraction
Protein filaments- slide over each other to produce muscle contraction
The cells that make up a skeletal muscle fibre physically join together during their development
Protein filaments
Give the cells of a heart and skeletal muscle a striped appearance. In smooth muscle, found in the circulatory system, there are fewer filaments, which are thinner and less well organised
Cells, tissues and organs
Cell
Tissue - lots of cells
Organs- tissue grouped together
Organ system- organs working together
What is cancer?
A damaged cell that divides uncontrollably.
Benign tumour
Slow growing
Often have capsule around so easy to remove
Not cancerous and rarely spread
Can press on other body organs and look unsightly
Malignant tumour
Grow faster
Can spread to other body tissues
As it grows, cancer cells detach and can form secondary tumours in other parts of the body.
What triggers cancer?
Chemicals and other agents that cause cancer called carcinogens
They damage the DNA causing mutations
If it isn’t discover in the cell cycle it continues to spread.
Mutations
Viruses
Chemicals in the home,industry or environment
Ionising radiation
Ultraviolet radiation
Lifestyle choices eg. Alcohol, smoking, diet
Stem cells
Unspecialised cells that can produce many different types of cells
How stem cells could help
Injuries eg. Spinal injuries leading to paralysis
Conditions in which the body cells degenerate eg. Alzheimer’s disease, diabetes and multiple sclerosis
Cancers, or following treatments for cancer such a chemotherapy or radiation eg. Leukaemia
Produce red blood cells
Embryonic stem cells
Removed from a living human embryo
Religion doesn’t agree with this as life starts at contraception
Law says embryos can be created purely for scientific research
Rejection of stem cell transplants
If a stem cell is taken from a bank to which other people have contributed the patients body may reject it.
A current solution is to find a close match between donor and patient.
Or give drugs to suppress Immune system.
A possible source is blood left in the umbilical cord and placenta after baby is born. It is easy to collect and store.
Therapeutic cloning
Producing stem cells with the same genes as the patient. So it wouldn’t be rejected.
Requires nuclear transfer.
Nuclear transfer
Human egg has nucleus removed and combined with the nucleus of the patient. Cell is simulated to divide Embryo produced is grown. After 4-5 days stem cells are removed Stem cells from the embryo are cultured
Scientific, ethical and social questions of stem cells
How successful would it need?
After 60 divisions mutations have been observed
Virus could transfer with stem cell leading to infection
Is it morally right to create an embryo with the intent of destroying it
Could an embryo simple be a resource for researchers
Are there more positives than negatives
Does it give patients false hope
Cells
Protein molecule- helically coiled nucleic acid molecule with protein coat.
Virus- has lipoprotein envelope around it.
Mitosis occurs when…
Cells die or become damaged
A eukaryotic organism reproduces by asexual reproduction
Cancer cells divide
Eukaryotic cells are cloned
Organisms need energy to…
Drive chemical reactions needed to keep them alive, including building large molecules
For movement ( make our muscles contract)
For keeping warm
Cell division
Maintain constant environment
Active transport
Transmit nerve impulses
Aerobic respiration
Uses glucose to create heat (ectothermic reaction)
Glucose+oxygen}carbon dioxide + water
C6H12O6+6O2}6CO2+6H2O
Starts in cytoplasm then in mitochondria
Respiration with oxygen
Anaerobic respiration
Respiration without oxygen
In cytoplasm of cell
Anaerobic respiration in yeast cells and other micro organisms is called fermentation
Fermentation
Glucose} ethanol+carbon dioxide
Anaerobic isn’t as efficient a as aerobic
Oxygen debt
Glucose}lactic acid
Incomplete oxidisation cases a build up of Latin acid and oxygen debt.
The acid is taken to the liver by the blood where it is oxidised to co2 and waterproof converted to glucose then glycogen. Glycogen levels in the muscles and liver are then restored
Needs oxygen to repay debt
Culturing bacteria
Best to grow them in large numbers to study them.
Bacteria grow in culture, in or on a culture medium
This is either a liquid nutrient broth or a gel agar
How to stop bacteria being infected
All equipment must be sterilised
The inoculating loop must be sterilised by passing it through a Bunsen flame before and after use
The lid of the agar plate must be secured, but not sealed using adhesive tape
Agar plates must be sterilised in an autoclave before disposal
This is an aseptic technique
Binary fission
Prokaryotes divide into 2 rapidly to form a colony
Bacteria growth curves
Lag phase- no reproduction. Bacteria copying DNA and proteins within their cell
Exponential growth phase
Stationary phase- resources become scarce so bacteria dies at same rate produced
Death phase- bacteria poisoned by build up of toxins in the culture
Antibiotic testing
Disc diffusion technique
Agar plate inoculated with bacterium being tested (spread over plate evenly)
A disc of antibiotic is placed on the plate
Different concentrations are put on plate as well
Lab vs school
Lab- mueller-Hinton agar with blood
For human pathogens
37 degrees Celsius
School- normal agar plate
Bacteria (don’t want to grow pathogens)
25 degrees Celsius
Validity of testing Antibiotics
A sample bacteria for testing must be representative of the population of bacteria
Clear zones will be uniformly circular
Measurements made with ruler or callipers
If there is poor growth becomes anomalies
Required practical- investigating disinfectants
Agar plate inoculated with bacteria with different disks with different disinfectants and a control
Inoculate at 25 degrees Celsius
See which has the biggest clear zone as it is most effective for bacerierium staphylococcus aureus in hospitals
