Cell Biology Flashcards
Cell membrane
Holds cell together and controls what can enter and leave the cell
Cytoplasm
A jelly-like substance where the chemical reactions inside the cell occur
DNA
Genetic material that controls the activities of a cell
Ribosomes
Site of protein synthesis in the cell
What are the 2 distinct types of cell
Prokaryotic and Eukaryotic
What are eukaryotic cells?
Cells which have a nucleus, (eg. Plant and animal cells)
What are prokaryotic cells?
A cell WITHOUT a nucleus, DNA is a single loop within the cytoplasm, eg. Bacteria
Which (prokaryotic or eukaryotic) is bigger?
Eukaryotic cells are far bigger than prokaryotic
What are the main subcellular structures in animal cells?
- Nucleus
- Cell membranes
- Mitochondria
- Ribosomes
- Cytoplasm
Nucleus
Contains genetic material that controls the activities of the cell
Mitochondria
Organelle which releases energy and conducts respiration for the cell
What do plant cells often have?
- Nucleus
- Cell membranes
- Mitochondria
- Ribosomes
- Cytoplasm
- Cell wall
- Permanent vacuole
Cell wall
Made of cellulose and gives extra support to the plant cell
Chloroplasts
Contains enzymes needed for photosynthesis and chlorophyll to absorb light energy
Permanent vacuole
Contains cell sap and used for storage of certain materials and helps support shape of the cell
What is a specialised cell?
A cell which has a particular structure and composition of subcellular organelles and is adapted to do specific things
What is a nerve cell?
A specialised cell adapted to conduct impulses from nerve to nerve.
Adaptations -
- Dendrites (receive signals) and axons (transmit signal) allow the neurone to COMMUNICATE with other nerve and muscle cells
- Axon is covered with a fatty sheath to speed up nerve impulses
What are muscle cells?
Cells containing layers of fibres allowing them to CONTRACT for MOVEMENT. There are 3 different types of muscles in animals - Skeletal, smooth and cardiac
Adaptations -
- Layers of protein filaments which slide over each other causing contraction
- High density of mitochondria to provide sufficient energy (via respiration)
What is a sperm cell?
The reproductive male cell containing the genetic code within a nucleus with 13 chromosomes
Adaptations -
- Acrosome in the head contains digestive enzymes to break down the outer layer of an egg cell
- Has a tail to swim towards the egg
What is a root hair cell?
Absorbs water and mineral ions from the soil in a plant.
Adaptations -
- Root hairs increase surface area so the rate of water uptake by osmosis is greater
- Thinner walls so water has a shorter diffusion distance
- Lots of mitochondria present for active transport of mineral ions
What is a xylem vessel?
A transport tissue for water and dissolved ions with a thickened wall of lignin to support the continuous column of water
Adaptations -
- Cells are essentially dead without organelles or cytoplasm to allow free passage of water
- Outer walls are thickened with lignin to support the plant
What is a phloem cell?
Transports dissolved foods around the plant, and the tube is made of living cells
Adaptations -
- Cells have very few subcellular structures to aid the flow of materials
What is cell differentiation?
An important process early on in the cell’s stages of development by which a cell changes to become SPECIALISED.
Once a cell has differentiated it would have developed structure and a composition of specific subcellular structures enabling it to carry out a certain function
After differentiation, cells lose their ability to differentiate again once they have become specialised
However some cells retain the ability to differentiate throughout the life of the animal, and they are called STEM CELLS, which are mainly involved in replacing and repairing cells
Plants differ from animals because many types of plant cells retain the ability to fully differentiate throughout its life and not just during early stages
When were the first light microscopes developed and how has it changed over time?
17th Century
Design of the light microscope has evolved where magnification has increased and resolution has increased too, enhancing the detail of what we can see
What are electron microscopes?
Use beams of electrons rather than light to visualise specimens, and were developed in the first half of the 20th century.
The wavelength of the electron beam is much smaller than visible light so electron microscopes have a much higher resolution and magnification
What is the equation for magnification?
Magnification = Drawing size / Actual size
Remember “I AM” triangle
Magnification notes -
1m = 1000mm
1mm = 1000μm
1μm = 1000nm
Look at required practical on microscopy
To use a light microscope to observe, draw and label a section of plant and animal cells including a magnification scale
What is binary fission?
A type of simple cell division in prokaryotes, primarily BACTERIA
It occurs in the right conditions where a bacteria cell prepares to divide by replicating its genetic material before it increases in size
When its genetic material has doubled the cell splits and forms two identical daughter and the number of cells increases by a power of 2 every time it occurs
Why can we only use temperatures below 25°C in school labs?
Because harmful pathogens are likely to grow
How can we prepare to culture microbes in the lab? (aseptic technique)
- Work should be carried out in front of a lit Bunsen burner (prevents airborne contamination)
- Hot agar jelly is poured into a sterilised petri dish (high temperatures kill microbes that could contaminate experiment)
- Inoculating loop is passed through a hot flame before used to transfer bacteria to the culture (microbes on loop killed preventing contamination)
- Petri dish should only be open as little as possible and near the Bunsen burner (decreases risk of contamination)
- Lid of petri dish taped, but so oxygen can get in so bacteria can respire and grow (decreases risk of contamination)
- Cultures should NOT be incubated above 25°C in school labs (reduces chances of harmful pathogens growing)