B1 Cell Biology Flashcards
Eukaryotic cells
Found in plants, animals, fungi and protists
10 - 100 μm
Eukaryote
An organism made up of eukaryotic cells
Prokaryotic cells
Found in bacteria and archaea
0.1 - 5.0 μm
Prokaryote
An organism Made up f prokaryotic cells
Plasmid
Small rings of DNA
Found in prokaryotic cells
Can replicate and move between cells to share genetic information
DNA loop
Prokaryotic cells do not have a nucleus
Most genetic material is stored in a single loop in the cytoplasm
Standard form
x * 10^n
when 1.0 <= x > 10.0
Adding and subtracting standard form
- Convert to non-standard form
- Add/subtract
- Convert to standard form
Multiplying standard form
- Multiply x
- Add n
- Concatenate
Dividing standard form
- Divide x
- Subtract n
- Concatenate
Animals cells
10 - 50 μm
Animals cells have: Cell membrane Nucleus Ribosomes Mitochondria Cytoplasm
Cell membrane
Separates the interior of the cells from the environment
Selectively permeable
Controls what enters and exits the cell
Nucleus
Control centre of the cell
Contains chromosomes which hold genetic material
Ribosomes
Responsible for synthesising proteins
Mitochondria
Produce the cell’s energy through aerobic respiration
Aerobic respiration
A process that uses sugar and oxygen to release energy
Cytoplasm
Jelly-like fluid that fills the cell
Where most of the cell’s chemical reactions take place
Plant cells
10 - 100 μm
Plant cells have:
Permanent vacuole
Chloroplasts
Cell wall
Vacuole
Fluid-filled sac that stores water
Enclosed in a membrane
Can make up as much as 90% of a plant cell’s volume
Chloroplasts
Contain chlorophyll, a pigment needed for photosynthesis
Cell wall
A structure made of cellulose that surrounds the cell
Increases the structural strength of the cell
Differentiation
A process where cell acquire different subcellular structures
Can happen at different stages of development in plants and animals
Differentiation in plants
Many plants can differentiate throughout their whole live
This means plants are always able to create new tissues
Differentiation in animals
Most animal cells differentiate early in their development
In mature animals, cells mostly divide to replace cells and repair tissues that are already present
New tissues rarely created by cell differentiation
Instead, cells divide to replace or repair existing tissue
Bacteria cells
Examples of prokaryotic cells
Include: Flagella Cell wall and membrane Cytoplasm Plasmids
Flagella
Whip-like structures used for movement
Some bacteria have flagella
Differentiation in embryos
Cells that form the embryo differentiate to produce cells that can perform all of the body’s functions
Sperm cells
Specialised to fertilise egg cells
Sperm cells have: Flagella Acrosome Head Middle section
Acrosome
Found as the tip of the sperm’s head
Contains digestive enzymes that are used to penetrate an egg cell
Sperm head
Contains the sperm cells’ nucleus
Sperm is haploid
This means a sperm’s nucleus only contains half of an organism’s genetic material
This combines with the egg cell’s half of genetic material to fertilise the egg
Sperm middle section
Filled with mitochondria to provide it with enough energy for it to travel a long distance to reach the egg cell
Neurones
Specialised to transmit electrical signals around the body
Neurones have:
Axon
Myelin sheath
Dendrites
Axon
A long tail that the electrical signal travels along in a neuron
Myelin sheath
A sheath that surrounds the axon
Prevents the signal from leaking out of the neuron and increases the speed of the transmission
Dendrites
Branches of a neuron
Transfer electrical signals to other neurons
Synapse
The site of transmission of electric signals between neurons
Myocytes
Specialised to produce force and motion
Muscle cells have:
Mitochondria
Protein fibre
Mitochondria in myocytes
Contain lots of mitochondria to generate energy for motion
Protein fibre in myocytes
Contract to move the muscle
Root hair cells
Specialised to absorb water and minerals
Root hair cells have:
Long projection
No chloroplasts
Long projections in root hair cells
Increases surface area
Allows them to absorb more water and minerals
Lack of chloroplasts in root hair cells
Do not contain chloroplasts as there is no light for photosynthesis
Xylem cells
Dead cells specialised to transport water up the stem of a plant to the leaves
Xylem cells have:
Open ends
Lignin
Open ends in xylem cells
End walls of xylem cells are broken to allow water to move through them
Lignin in xylem cells
Lignified to strengthen cell walls
Phloem cells
Living cells specialised to transport food in the plant
Phloem cells have:
Cell wall holes
Cell walls in phloem cells
End walls of phloem cells contain small holes to allow food products to move up and down the vessels
Microscope magnification
How many times larger an image seen through a microscope is compared to the real object
Equation for magnification
Magnification = image size / actual size
Magnification = magnification of eyepiece * magnification of objective lens
Resolution
The ability to see and distinguish between fine detail
Light microscope
Passes light through a specimen and creates a magnified image using lenses
The first light microscope was made using two lenses towards the end of the 16th century
This microscope had a resolution better than the human eye
Objective lens
The lens closest to the specimen
Short focal length
Produces a magnified image of the specimen
Discoveries from light microscopes
Visual distinction of plant and animal cells
View of bacteria
Electron microscope
Electrons are passed through the specimen instead of light.
First used in 1933
Can resolve distances of 1nm
Magnifications of ×500,000.
Discoveries from electron microscopes
Clear view of subcellular structures
Allowed the study of the function of structures like mitochondria, chloroplasts and ribosomes
Uses of microorganism cultures
Used to investigate the effects of antibiotics and disinfectants
Growing media of cultures
Cultures can be grown in one of two mediums:
Nutrient broth
Agar gel
Nutrient broth
Liquid medium for growing microorganisms containing carbohydrates, minerals and sometimes other chemicals
Agar gel
Solid, jelly-like medium for growing microorganisms
Contamination
The growth of bacteria not being investigated in an investigation
Risks of contamination
Jeopardising the results of the investigation,
Serious health and safety risk
Sources of contamination
Potential sources of contamination are: Skin Soil Air Water
Aseptic Technique
Techniques used on apparatus to kill and prevent the entry of unwanted bacteria
Aseptic techniques include: Boiling Flames Lids Temperature
Boiling as an aseptic technique
Solutions and agar must be boiled for sterilisation
Flames as an aseptic technique
Inoculation loops must be passed through a flame for sterilisation
Lids as an aseptic technique
Lids must be rapidly taken off and put back on when using the inoculating loop to add bacteria to the agar
Lids should be taped on and the dish should be stored upside down to prevent condensation forming on the lid and then dripping onto the agar
Temperature as an aseptic technique
In schools, the maximum temperature at which cultures should be incubated is 25 degrees Celsius
This precaution reduces the risk of harmful bacteria growing
Bacterial growth
Bacteria multiply through simple cell division (binary fission), in which one cell divides to produce two cells
Mean division time
The average time for bacteria to divide
Estimation of bacteria populations
A future population of bacteria can be estimated by multiplying the current population by two for every mean division time that passes
Divisions can happen as fast as every 20 minutes when the conditions are ideal
Equation for bacteria population size
Future population = current population * 2 ^ (time passed / mean division time)
