Cell Biology (1) Flashcards
Sub-cellular structures of an animal cell and plant cell (eukaryotic cells)
Animal:
nucleus- controls the cell, contains DNA stored in chromosomes
cytoplasm- where most chemical reactions occur
cell membrane- controls substance movement in and out of cells
mitochondria- where aerobic respiration occurs
ribosomes- where protein synthesis occurs
Plant: (all of the above plus…)
vacuole- stores liquids and provides structure to the cell
chloroplasts- contains green pigment chlorophyll which absorbs
sunlight for photosynthesis
cell wall- maintains the cell shape
What is a prokaryotic cell and what is its structure
prokaryotic cells are much smaller than eukaryotic cells
They have cytoplasm and a cell membrane surrounded by a cell wall
The genetic material is not enclosed in a nucleus It is a single DNA loop and there may be one or more small rings of DNA called plasmids.
Onion cell microscopy RP
- add a drop of water onto a clean glass slide
- use tweezers to remove some epidermal tissue from an onion
- place tissue in water and stain with iodine to highlight the sub-cellular structures
- place a cover slip on top and ensure no air bubbles have formed
- Observe cell through a microscope
Light Microscope:
Eyepiece-
Objective lens-
Stage-
Coarse adjustment-
Fine adjustment-
Light source-
Eyepiece- what you look through when viewing samples, changeable magnification
Objective lens- three lenses with different magnifications
Stage- platform where samples are placer to view
Coarse adjustment- moves the stage up and down to focus on the sample
Fine adjustment- focuses on the object
Light source- illuminates the sample
Differences between a light and electron Microscope
resolution-
magnification=
A light microscope is cheaper and portable making it more convenient and practical for most use cases
An electron microscope is a lot more powerful with greater magnification and clarity. However, they’re extremely expensive and immobile
Resolution- the ability to distinguish between two points, so a higher resolution gives a clear image
Magnification= image size/real size
Specialised cells-
Unspecialised cells-
Specialised cells- cells that are optimised to do a certain function
(sperm cell, nerve cell, root hair cell etc)
Unspecialised cells-
Adult Stem cells- cells found in bone marrow that can specialise into a certain amount of cells
Embryonic stem cells- cells from embryos that can specialise into any other type of cell
Meristem cells- plant cells capable of developing into any type of
plant cell. They’re small, densely packed and have a thin cell wall Found in roots, shoots and in between the xylem and phloem
Mitosis-
- The cell first doubles its number of sub-cellular structures, then the number of chromosomes
- The chromosomes and other structures align in the middle of the cell
- Spindle fibres pull them apart to opposite sides of the cell
- A new membrane forms around each set of genetic material to form the new nucleus
- the cytoplasm and cell membrane divide to form two identical, haploid daughter cells (cytokinesis)
Binary Fission-
- the circular DNA and plasmids replicate
- the cell gets bigger and the circular DNA strands move to opposite ends of the cell
- the cytoplasm begins to divide and a new cell wall begins to form
- The cytoplasm divides and two identical daughter cells are produced. Each daughter cell has one copy of circular DNA but can have a varying number of copies of the plasmids
Culturing microorganisms and testing antibiotics RP
- sterilise the inoculating loop by passing it through a blue flame
- fill a petri dish with hot agar jelly
- transfer some microorganisms from a sample to the petri dish using the loop
- Place 4 different paper disks of the same size in the dish. 3 are coated with different antibiotics and one is a test. Ensure you can identify which disk is which
- lightly tape a lid on the dish so oxygen can enter but other microorganisms cant
- store the dish upside down in a room of 25*c for two days (upside down prevents condensation from dripping onto the agar jelly)
- Measure the zone of inhibition for each sample by using the equation area = π r². The largest zone of inhibition is the most effective antibiotic
transportation processes in organisms:
Diffusion:- movement of solutions and gas particles from an area of high concentration to lower concentration down a concentration gradient
- It is a passive process so requires no energy
- The rate is increased by a higher temperature as the particles have more kinetic energy
- cell membranes control diffusion
Osmosis: -movement of water through a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
-It is a passive process so requires no energy
Active Transport- -movement of substances from an area of low
concentration to an area of high concentration against the concentration gradient (eg, nutrients going from the blood to the gut)
- Carrier proteins bind to the substance to be transported.
-ATP energy moves the substance
-energy is needed from respiration
How does surface area to volume ratio change with object size?
Adaptations of exchange surfaces (5)-
larger object has a smaller surface area to volume ratio
-One cell thick membrane
-Large surface area to volume ratio
-Lots of blood vessels for a good blood supply to maintain a concentration gradient
-Well ventilated
-Partially permeable membrane
Examples of substance exchanges (4)
Alveoli in lungs- gas exchange
Villi in small intestine- nutrient exchange
Leaves- gas exchange
Fish Gills- water enters the fish’s mouth, oxygen diffuses into the gills and CO2 diffuses out
Osmosis RP
- Cut the potato into equal-sized cylinders or chips using a knife and ruler. Measure the initial mass of each potato sample.
-Prepare several different concentrations of sucrose solution
-Place each potato sample into a separate beaker containing one of the sucrose solutions.
-Leave the potato samples in the solutions for a set period
-After the set time, remove the potato samples, blot them dry with a paper towel, and measure their final mass.
-Calculate the percentage change in mass for each sample.
-In dilute solutions, potatoes may gain mass due to water entering the cells.
-In concentrated solutions, potatoes may lose mass due to water moving out of the cells.
-The point at which there is no change in mass indicates that the concentration of sucrose inside the potato is equal to the concentration of sucrose outside, which is the isotonic point.
Factors affecting the rate of diffusion (7)
Concentration Gradient – A steeper gradient increases the rate of diffusion.
Temperature – Higher temperature increases kinetic energy, speeding up diffusion.
Surface Area – A larger surface area increases the rate.
Distance for Diffusion – A shorter diffusion distance increases the rate.
Size of Particles – Smaller particles diffuse faster than larger ones.
State of Matter – Diffusion is fastest in gases, slower in liquids, and slowest in solids.
Permeability of Membrane – More permeable membranes allow for faster diffusion.
Factors affecting the rate of osmosis (5)
Water Potential Gradient – A larger difference in water potential increases osmosis.
Temperature – Higher temperatures increase kinetic energy, making osmosis faster.
Surface Area – A larger surface area increases the rate of osmosis.
Thickness of the Membrane – A thinner membrane allows faster osmosis.
Permeability of the Membrane – the membrane permeability increases osmosis.
Factors affecting the rate of active transport (6)
Availability of ATP – More ATP energy increases active transport.
Number of Carrier Proteins – More carrier proteins in the membrane increase the rate.
Speed of Carrier Proteins – Faster functioning proteins speed up active transport.
Temperature – Higher temperatures increase kinetic energy but too high temperatures denature proteins.
Oxygen Availability – More oxygen allows more respiration, producing more ATP.
Concentration of Substances – A higher concentration difference requires more ATP for transport.
Why do plant cells not burst when water enters
Cell wall prevents bursting
