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)
How can we determine effectiveness of different antibiotics, antiseptics and disinfectants?
By calculating the area of an INHIBITION ZONE around a disc of the substance being tested
Revise REQUIRED PRACTICAL 2
To investigate the effect of antiseptics or antibiotics on bacterial growth using agar plates and measuring zones of inhibition
What are the 3 transport processes that living organisms use for exchange?
Diffusion, osmosis and active transport
What is diffusion?
Diffusion is the spreading of particles in any substance in solution resulting in a net movement from an area of higher concentration to an area of lower concentration
What substances can enter AND leave cells by diffusion?
- Oxygen (animal cells)
- Carbon Dioxide (plant cells)
- Urea (excreted by kidneys)
- Carbon Dioxide (must diffuse out of cells after aerobic respiration)
How is the movement of diffusion driven in a cell?
A concentration gradient existing between the cell and its immediate environment
What factors affect the rate of diffusion?
- Difference in concentration gradient
- Temperature
- Surface are of a membrane
How does temperature affect the rate of diffusion?
- Higher temperature means more movement of particles
- They will therefore spread faster and increase rate of diffusion
How does a higher concentration affect the rate of diffusion?
The greater the difference in concentration between TWO REGIONS, the FASTER the overall RATE OF DIFFUSION
How does a larger surface area of the membrane affect rate of diffusion?
Greater surface are means greater rate of diffusion because there is MORE AREA for a particle to CROSS the membrane
What does the small intestine do?
Where most absorption of digested food molecules INTO the bloodstream occurs in the body
How is the small intestine adapted to its role?
- Highly folded surface
- Lined with specialised cells
- Contains villi (which also have good blood supply (CONCENTRATION GRADIENT))
How are lungs adapted to their roles?
- Millions of alveoli with high SA
- Walls of alveoli are one cell thick, so small diffusion distance
- Excellent blood supply (maintaining concentration gradient)
How are gills adapted to their role?
- Covered in filaments so increased surface area
- Good blood supply (maintains concentration gradient)
Role of root hair cells?
Absorbs water and mineral ions in the roots from soil
Adaptations of root hair cell?
- Slightly branched (increases surface area)
- Millions of root hair cells (increased surface area)
Role of leaves?
- Contains most of a plant’s photosynthetic cells
- Allows gas exchange to take place through membrane
How are leaves adapted to their roles?
- Stomata decreases diffusion distance for gases
- Lower layer of leaf made of spongy mesophyll so air can circulate inside the leaf
To summarise, what are some common adaptations of organisms to maximise efficiency of transport?
- Large surface area
- Thin membranes to provide short diffusion distance
- Efficient blood supply (maintains concentration gradient)
- Ventilation (gas exchange)
What is osmosis?
The diffusion of water molecules from a dilute solution to a concentrated solution through a PARTIALLY PERMEABLE MEMBRANE
Required 3 practical on Osmosis
Investigate the effect of a range of concentrations of salt or sugar solutions on the mass of a plant tissue
What is active transport?
Active transport move substances from a more DILUTE SOLUTION to a more CONCENTRATED solution, which is against a concentration gradient so requires energy from respiration
What are examples of active transport in plants?
Allows mineral ions from the soil to diffuse into the plant through root hairs from VERY DILUTE SOLUTIONS in the soil
What are examples of active transport in animals?
Allows sugar molecules to be absorbed from LOWER CONCENTRATIONS in the gut into the BLOOD which has a higher sugar concentration
What is an Isotonic sports drink?
A drink containing SIMILAR CONCENTRATIONS of SALT and SUGAR as the human body are are primarily used for HYDRATION and fluid replenishment
What are Hypertonic sports drinks?
- Contain concentrations of SALT and SUGAR which are HIGHER THAN TYPICAL BLOOD LEVELS
- This provides high salt and sugar levels for absorption from the small intestine
What are hypotonic sports drinks?
- A drink containing concentrations of salt and sugar lower than the typical blood levels
- Drinking this creates a concentration gradient between the bloodstream and small intestine
- Suitable for rapid rehydration as water is drawn into the bloodstream by OSMOSIS
What are chromosomes?
Chromosomes are thread like structures of DNA (carrying genes) which are based in the nucleus of EUKARYOTIC CELLS
How many chromosomes do humans have?
46 chromosomes found in pairs in the human body
What is mitosis?
Mitosis is the stage in the cell cycle where the nucleus DIVIDES
What occurs during the GROWTH PHASE of the cell cycle?
The genetic material of the cell (chromosomes) is doubled
What needs to happen before a cell can divide?
DNA must replicate to form two copies of each chromosome
What is cytokenesis?
Cytoplasm and cell membranes divide, which forms the two genetically identical daughter cells
Why is mitosis so important to multicellular organisms?
It is essential for growth and development
What are stem cells?
An UNDIFFERENTIATED cell of an organism which is capable of dividing into identical stem cells
Embryonic stem cell (learn)
- Found on inside layer of an embryo
- Undifferentiated
- All different types of specialised cells can be made from these
Adult stem cell (learn)
- Found in bone marrow, skin, organs such as the liver or brain, umbilical chord
- Limited ability to differentiate and partially specialised
- Cells in bone marrow (produces RBCs and cells of the immune system)
- Cells in Skin (produces cells found in skin such as hair follicles)
- Other organs (cells found respectively in these organs)
- Umbilical chord (produces RBCs, muscles, nerve tissue, etc)
Meristem cells (learn)
- Found in tips and of roots and shoots
- Fully undifferentiated
- One cell has the ability to divide to produce a whole new plant
How can we obtain embryonic stem cells?
Growing human embryos in the lab and extracting embryonic stem cells from them, which can differentiate into most types of cells
How can embryonic stem cells be used?
- Repairing damaged organs
- By growing new tissue from embryonic stem cells
What diseases can stem cells treat?
Diabetes and paralysis
What is therapeutic cloning?
- Where embryos are produced with the same genes as the patient
- Less likely to be rejected by the body so can be used for medical treatment
Benefits of using stem cells
- Great potential to treat lost of diseases
- Adult stem cells successfully treat some diseases already
Risks of using stem cells
- During culturing can be infected by virus and transmitted to patient
- Risks of cultured stem cells mutating and developing into cancer cells
- Few stem cell donors
Social issues of stem cells
- Expensive to collect embryonic stem cells before birth
- Lack of evidence to prove treatment is 100% safe
- Educating the public about stem cells
Ethical issues of stem cells
- Morality problems, such as consent of the baby
- Does an embryo have rights?
- Is it okay that cloned embryos are destroyed?
How can we use meristem cells?
To clone plants quickly and economically
- Rare species cloned to prevent extinction
- Crops with resistance can be cloned which increases yield
