B1 - Cell biology Flashcards
Define Eukaryotic Cell
Contain their genetic material enclosed in a nucleus
Define Prokaryotic cell
Genetic material not enclosed in a nucleus:
It is a single DNA loop & there may be small rings of DNA called plasmids
Prokaryotic cells are (…) in comparison to eukaryotic cells
Much smaller
Give the prefixes in standard form:
1) Centi
2) Milli
3) Micro
4) Nano
1) 1 x 10^-2 m
2) 1 x 10^-3 m
3) 1 x 10^-6 m
4) 1 x 10^-9 m
Order of Magnitude
Every order of magnitude is 10x greater than before.
10x = 1 order of magnitude
100x = 2 orders of magnitude
1000x = 3 orders of magnitude
Function of the Nucleus
To enclose the genetic material
Function of the Cytoplasm
Watery solution where chemical reactions take place
Function of the Cell Membrane
Controls the molecules that can enter and leave the cell
Function of the Mitochondria
Mitochondria are where aerobic respiration takes place
Function of the Ribosomes
Sites of protein synthesis
Function of the Chloroplasts
Contain chlorophyll & are the sites of photosynthesis
Function of the Cell wall
Made from cellulose.
Strengthens the cell.
Function of the Vacuole
Filled with a fluid called cell sap.
Helps give the plant cell its shape.
How are Sperm cells specialised to carry out their functions?
Genetic information contained in the nucleus - located in the head of the sperm cell.
Long tail + Streamlined - Allows them to swim to the ovum
Midpiece packed full of mitochondria - provide energy for swimming
Enzymes in the head of sperm cell - digest through outer layer of the ovum
How are Nerve cells specialised to carry out their functions?
Axon - Carries electrical impulses from one part of the body to another
Myelin - insulates the axon and speeds up transmission of nerve impulses
Synapses - Junctions which allow impulse to pass from one nerve cell to another
Dendrites - Increase surface area so other nerve cells connect more easily
How are Muscle cells specialised to carry out their functions?
Muscle cells can contract - Contain protein fibres which can change their length
Packed full of mitochondria to provide energy for muscle contraction
Work together to form muscle tissue
How are root hair cells specialised to carry out their functions?
Increases surface area of the root.
Do not contain chloroplasts as they are underground.
How are xylem cells specialised to carry out their functions?
Thick walls containing lignin - provides support to the plant.
End walls between cells broken down to form a long tube so water & dissolved minerals can flow easily.
No internal structures - easier for water & minerals to flow.
How are Phloem cells specialised to carry out their functions?
Phloem vessel cell & sieve plates allow dissolved sugars to move through the cell interior.
Companion cell - mitochondria provides energy to the phloem vessel cell.
Describe the advantages of an electron microscope over a light microscope
• Much greater magnification & resolution than light microscopes
• Enabled biologists to see & understand many more sub-cellular structures
What is the equation for number of bacteria after a certain time?
Number of bacteria = 2*(n)
(n) = number of rounds of division
Why must Petri dishes & culture media be sterilised before use?
To kill any unwanted microorganisms & it prevents contamination
Explain why the lid of the Petri dish should be secured with adhesive tape & stored upside down
To stop the lid from falling off & any unwanted microorganisms entering.
Placed upside down - stops moisture from dripping down onto the bacteria & disrupting the colonies.
Explain why in school laboratories, cultures should be incubated at a maximum temperature of 25 C
Reduces the chances that harmful bacteria will grow
What is meant by “Zone of inhibition”
A region where the bacteria have not grown
Describe the stages of the cell cycle involving mitosis
• DNA replicates to form 2 copies of each chromosome
The cell also grows & copies its internal structures.
• Mitosis - 1 set of chromosomes pulled to each end of the cell. Nucleus also divides.
• The cytoplasm & cell membrane divide to form 2 identical cells.
Describe the importance of mitosis
• Essential for growth & development of multicellular organisms
• Mitosis takes place when an organism repairs itself
• Mitosis happens during asexual reproduction
What is meant by a stem cell?
An undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, from which certain other cells can arise from differentiation.
Function of stem cells in embryos:
Can be cloned & made to differentiate into most different types of human cells.
Function of stem cells in adult animals:
Stem cells from adult bone marrow can form many types of cells including blood cells.
Function of stem cellls in plants:
Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
Describe how stem cells can be used for medical treatment
Therapeutic cloning - embryo is produced with the same genes as the patient.
Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.
Risks of the use of stem cells for medical treatment
• Transfer of viral infection
• Ethical & religious objections
Describe how stem cells can be used for plant cloning
Stem cells from meristems in plants can be used to produce clones of plants quickly & economically.
• Rare species can be cloned to protect from extinction
• Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
What is meant by diffusion?
The spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration.
Describe the factors which affect the rate of diffusion
• Difference in concentrations (concentration gradient)
• Temperature
• Surface area of the membrane
Explain the need for exchange surfaces & a transport system in multicellular organisms
• Their surface area is not large enough for their volume
• Cells on the surface get enough oxygen by diffusion however not enough oxygen can diffuse into the cells in the centre of the organism. They are too far away from the surface.
Describe how gills increase the rate of transport of gases into & out of the fish
• Oxygen-rich water passes into mouth, then flows over gills where oxygen is transported into bloodstream.
• Gills covered in a very large number of fine filaments where gases pass in & out of the blood.
• Deoxygenated blood passes into filament. Oxygen diffuses from water into blood. Oxygenated blood returns to body.
Adaptations of the filaments to increase rate of diffusion
• Massive surface area.
• Thin membrane - short diffusion pathway.
• Efficient blood supply - concentration gradient always high.
How is the effectiveness of an exchange surfaces increased
• large surface area
• thin membrane for short diffusion path
• (in animals): efficient blood supply
• (in animals, for gaseous exchange): being ventilated
What is meant by osmosis
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
Describe the effects of osmosis on animal cells
• If cell placed in water, osmosis takes place - water moves by osmosis from outside cell to inside cell.
The cell will expand or could burst.
• If cell in concentrated solution, water moves out of cell by osmosis & the cell will shrink.
Describe the effects of osmosis on plant cells
• Place plant cell in water - water moves into cell by osmosis & cell will expand.
Cell wall prevents cell from bursting so cell become swollen (turgid)
• Place cell in concentrated solution - water moves out of plant cell by osmosis.
Causes cell to shrink (becomes flaccid)
Equation for % change
% change = change in value
________________ X 100
Original value
What is active transport?
Moves substances from a more dilute solution to a more concentrated solution (against the concentration gradient).
This requires energy from respiration.
