Topic 1: Key concepts in biology Flashcards
State the two types of cells
Prokaryotic and Eukaryotic
What is the difference between a Eukaryotic and Prokaryotic cell?
Eukaryotic cell has a nucleus and membrane-bound organelles, unlike a Prokaryotic cell
List the components of both animal and plant cells
Mitochondria
Nucleus
Cytoplasm
Ribosomes
Cell membrane
How is genetic information stored in a Eukaryotic cell?
In the nucleus, arranged in chromosomes
What is the function of the nucleus?
Contains genetic information and controls cellular activity
Describe the structure of the cytoplasm
Fluid gel-like substance containing enzymes
What is the function of the cytoplasm?
Site where chemical reactions take place (respiration)
What is the function of the cell membrane?
Holds cell together and controls movement of substances in and out of the cell
What is the function of the Mitochondria?
Site where energy is released for respiration
What is the function of the ribosomes?
Join amino acids in a specific order during translation
What is the cell wall made of?
Cellulose
Which 3 organelles are only found in plant cells?
Cell wall
Vacuole
Chloroplasts
What is the function of the cell wall?
Provides strength and structural support
What does the vacuole contain?
Cell sap, a weak solution of sugars and salts
What is the function of the vacuole?
Maintains internal pressure to support cell
What is the function of the chloroplasts?
Site of photosynthesis
Why do chloroplasts appear green under a light microscope?
Contain the green pigment chlorophyll
List the six organelles found in prokaryotic cells
Plasmid DNA
Chromosomal DNA
Ribosomes
Cell wall
Cell membrane
Flagella
How is genetic information stored in a Prokaryotic cell?
Found free within the cytoplasm as chromosomal or plasmid DNA
What are plasmids?
Small circular loops of DNA which are separate from the main DNA. They carry genes that provide genetic advantages such as antibiotic resistance
What is the Prokaryotic cell wall composed of?
Peptidoglycan
What is a flagellum?
Long, rotating, ‘whip like’ protrusion that enables bacteria to move
What is a haploid cell?
A cell with a single copy of each chromosome (23 chromosomes)
What is a diploid cell?
A cell with two copies of each chromosome (46 chromosomes)
What are gametes?
The reproductive cells: egg and sperm cell which are haploid cells
Describe sexual reproduction
Two haploid gametes fuse to produce a fertilised egg which develops into an embryo. It will be a diploid cell as it will have two chromosomes for each gene, therefore, two copies of each allele.
How are egg cells adapted to their function?
1) Haploid nucleus contains genetic material
2) Nutrients in cytoplasm to feed embryo
3) Cell membrane hardens after fertilisation, preventing other sperm entering, ensuring zygote is a diploid
How are sperm cells adapted to their function?
1) Haploid nucleus contains genetic material
2) Long tail enables movement
3) Mitochondria in middle section provide energy for tail movement
4) Acrosome contains enzymes to digest egg cell membrane
Where are ciliated epithelial cells found?
Lining the surface of structures such as respiratory tract and uterus
Describe the function of ciliated epithelial cells lining airways
Move in synchronised waves to beat mucus (full of dirt pathogens) to the back of the throat to be swallowed
What is magnification
The number of times bigger an image appears compared to the size of the specimen
How do you calculate total magnification?
total magnification = eyepiece lens magnification x objective lens magnification
How can magnification of an image be calculated?
Magnification=image size/actual size
Define resolution
The smallest distance between two points that can be distinguished
How does a light microscope work?
Beam of light passes through specimen and travels through eyepiece lens allowing specimen to be observed
List four advantages of light microscopes
1) Inexpensive
2) Easy to use
3) Portable
4) Can view living and dead specimens
What is a disadvantage of light microscopes?
Limited resolution
How does an electron microscope work?
Uses a beam of electrons which are focused using magnets. Electrons hit a flourescent screen which emits visible light, producing image
Name both types of electron microscopes
TEM= Transmission electron microscope
SEM= Scanning electron microscope
What is the advantage of electron microscopes?
Higher resolution and magnification
Why do electron microscopes have a higher resolution and magnification?
Beam of electrons has a shorter wavelength than photons of light
How have electron microscopes allowed scientists to develop their understanding of cells?
Allow small sub-cellular strucutres such as mitochondria and ribosomes to be obseved in detail. Therefore, enables scientists to develop more accurate explanations about how cell structure relates to cell function
What are the disadvantages of electron microscopes?
1) Expensive
2) Difficult to use
3) Large so less portable
4) Only dead specimens can be observed
What are enzymes?
Biological catalysts that speed up the rate of reaction without getting used up
What is the advantage of enzymes in the body?
Enable cellular reactions to take place at lower temperatures
What is the active site of an enzyme?
The region of the enzyme where the substrate molecule binds to catalyse the reaction
Why are enzymes described as having a “high specificity” for their substrate?
Only substrates with a specific, complementary shape can fit into an enzyme’s active site
Describe the Lock and Key model
The substrate collides with the active site of the enzyme. binding to it, thus forming the enzyme-substrate complex. Bonds are broken as substrate is converted into products. Products are released from active site as they no longer fit, leaving active site free to bind
What 3 factors affect enzyme rate of reaction?
Temperature
PH
Substrate Concentration
Explain how temperature increase affects rate of reaction
Initially, as temperature increases, rate of reaction also increases. However, as optimum temperature is surpassed, bonds of the enzyme break, becoming denatured. The active site changes shape so the substrate no longer fits, decreasing rate of reaction.
Draw graph to show the effect of increasing temperature on an enzyme-catalysed reaction
(refer to google doc)
Explain how PH affects rate of reaction
Bonds of enzymes are altered is PH is too high or low from optimum. Active site changes shapes, thus, denaturing enzyme, thus, decreasing rate of reaction
Draw graph to show the effect of increasing PH on an enzyme-catalysed reaction
(refer to google doc)
What is the usual optimum PH of enzymes and describe an anomaly
Optimum PH=7
Pepsin breaks down protein in the stomach. Since it’s suited to acidic conditions its optimum PH is 2
Explain how substrate concentration affects rate of reaction
As substrate concentration increases, rate of reaction increases as probability of successful collision increases so more enzyme-substrate complexes will form. Once all active sites are full, rate of reaction plateaus.
Draw graph to show the effect of increasing substrate concentration on an enzyme-catalysed reaction
(refer to google doc)
Describe how you can investigate the effect of PH on enzyme activity using the reaction of amylase and starch
Amylase catalyses breakdown of starch to maltose. Iodine solution is used to detect the starch, if starch is present the solution will turn from browny-orange to blue-black
Describe the method for investigating the effect of PH on enzyme activity using the reaction of amylase and starch
1) Set up heating apparatus using bunsen burner, heatproof mat, gauze and tripod. Place beaker of water on tripod and heat to 35 degrees keeping this constant throughout the experiment
2) Fill each depression of spotting tile with iodine solution
3) Use syringe to add 2 cm3 of amylase solution and 1cm3 of buffer solution into boiling tube and place boiling tube into water and wait 5 min
4) Using a different syringe add 2cm3 of starch solution into boiling tube, mix contents and start stopwatch
5) Use continuous sampling to record how long it takes amylase to breakdown all starch . Taking fresh samples from boiling tube using pipette every 10 seconds , transferring to tile unitl solution remains brown (all starch is broken down)
What are the control variables for reaction of amylase and starch necessary for a fair test?
Volume and concentration of amylase solution
Temperature of water
Time intervals between testing solution
