Topic 1 - Key Concepts Flashcards
State two types of cell
Eukaryotic, Prokaryotic
What is the difference between a eukaryotic and prokaryotic cell?
A eukaryotic cell contains a nucleus and membrane-bound organelles. A prokaryotic cell does not.
List components of both plant and animak cells?
Nucleus Cytoplasm Cell membrane Mitochondria Ribosomes
How is genetic information stored in a eukaryotic cell?
Within the nucleus, arranged in chromosomes
Other than storing genetic information, what is the function of the nucleus?
Controls celluar activities
Describe the structure of the cytoplasm
Fluid/jelly-like component cell
Contains organelles, enzymes and dissolved ions and nutrients
What is the function of the cytoplasm
Site of celluar reactions/chemical process
What is the function of the cell membrane?
Controls the entry and exit of materials into and out the cell
What is the function of the mitochondria?
Site of later stages of aerobic respiration in which ATP is produced
What is the function of the ribosomes?
Joins amino acids in a specific order during translation
Which organelles are found in plant cells only?
Large, permanent vacoule
Cell wall
Chloroplasts
What is the cell wall made of?
Cellulose
What is the function of the cell wall?
Provides structural integrity
Prevents the cell bursting when water enters by osmosis
What does the permanent vacoule contain?
A solution of salts, sugars and organic acids (cells sap)
What is the function of the permanent vacoule?
Supports the cell, maintaining its turgidity
What is the function of the chloroplasts?
Site of photosynthesis
When looking at a cell using a light microscope, why do chloroplast appear green?
Contain chlorophyll; a green pigment
List the organelles found in prokaryotic cell
Chromosomal DNA Plasmid DNA Cell Wall Cell membrane Ribosomes Flagella
How is genetic information stored in prokaryotic cell?
Found free within the cytoplams:
Chromosomal DNA (single large loop of circular DNA)
Plasmid DNA
What are plasmids?
Small, circular loops of DNA found free in cytoplasm and separate from the main DNA
Carry genes that provide genetic advantages e.g antibiotic resistance
What is a flagellum?
Long, rotating, “whip-like” protrusion
Enables bacteria to move
What is a haploid cell?
A cell that contains a single copy of each chromosome (half the number)
23 chromosomes in humans
What is a diploid cell?
A cell that contains two copies of each chromosome (full set of chromosomes)
46 chromosomes in humans
What are gametes?
Reproductive cells
They are haploid cells
Describe sexual reproduction in term of chromosome number?
Two haploid gametes fuse
Resulting embryo has two chromosomes for each gene and two copies for each allele
Describe how egg cells are adapted their function?
Haploid nucleus contains genetic material
Mitochondria in cytoplasm produce energy for the developing embryo
Cytoplams contains nutrients for the developing embryo
Cell membrane hardens after fertilisation, preventing the entry of other sperm and ensuring the zygote is diploid
Describe how sperm cells are adapted to their function?
Haploid nucleus contain genetic information
Tail enables movement
Mitochondria provide energy for tail movement
Acrosome contains enzymes that digest the egg cell membrane
Where are ciliated epithelial cells found?
Found lining the surface of structures such as the respiratory tract and uterus.
Describe the function of ciliated epithelial cells lining the airways
Move in sychronised waves to beat mucus (containing dirt and pathogens) up to the back of throat where it can be swallowed.
What is magnification?
The number of times bigger an image appears compared to the size of the specimal
How can the total magnification of an image be calculated from lens powers?
Total mag = eyepiece lens magnification x objective lens magnification
How can the magnification of an image be calculated?
Magnification = size of image / size of specimen
What is resolution?
The smallest distance between two obejcts that can be distinguished
How does a lighy microscope work?
Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed.
What are advantages of light microscopes?
Inexpensive
Easy to use
Portable
Observe both dead and living specimens
What is the disadvantage of light microscopes?
Limited resolution
How does an electron microscope work?
It uses a beam of electrons which are focused using magnets. The electrons hit a flourescent screen which emits visible light, producing an image.
Name two types of electron microscopes
Transmission electron microscopes (TEM)
Scanning electron microscope (SEM)
What is the advantage of electron microscopes?
Greater magnification and resolution
Which means some sub cellular structures e,g ribosomes can be seen
Why do electron microscopes and have a greater magnification and resolution?
They use a beam electrons which has a shorter wavelength than photons of light
How have electron microscopes enabled scientists to develop their understanding of cells?
Allow small sub-cellular structures to be observed in detail
Enable scientists to develop more accurate explanations about how cell structure relates to function
What are the disadvantages of electron microscopes?
Expensive
Large so less portable
Require training to use
Only dead specimens can be observed
Si Units
Mm: 10x-3
Um (micrometer):10x-6
Nm: 10x-9
Pm:10x-12
What are enzymes?
Biological catalyst that increase the rate of chemical reaction without being permanently altered themselves
What is an advantage of enzymes in body?
They enable cellular reactions to take place at lower temperatures
What is the active site of an enzymes?
The region of an enzyme to which a substrate molecule binds and the reaction takes place
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
1) substrate collides with the active site of an enzyme
2) Substrate binds, enzyme-substrate complex forms
3) Substrate converted to products
4) Products released from the active site which is now free to bind to another substrate
What factors affect the rate of an enzyme-controlled reaction?
Temperature
pH
Substrate concentration
Explaim how increasing temp intially affects the rate of enzyme-controlled reaction
As temperature increases molecules have more KE
Movement of molecules increase
Probability of a successful collision increases
More enzyme-substrate complexes form
Rate of reaction increases
Explain how increasing temperature above the optimum affects the rate of an enzyme-controlled reaction
Temperature increases above the optimum
Increased vibrations break bonds in enzyme structure
Active site changes shape, enzyme is denatured
No more enzyme-substrate complexes can form
Rate of reaction decreases
Explain how pH affects the rate of an enzyme-controlled reaction
Enzymes have an optimum pH
pH shifts from the optimum
Bonds in the enzyme’s structure are altered
Active site changes shape, enzyme is denatured
Rate of reaction decreases
Explain how the substrate concentration affects the rate of an enzyme-controlled reaction
Substrate concentration increases
Number of substrate molecules in the same volumes increases
Probability of a successful collisions increases
More enzyme-substrate complexes form
Rate of reaction increased
Once all active sites, become full, the rate of reaction plateaus
Draw a graph to show the effect of increasing substrate concentration on rate of an enzyme-catalysed reaction
How can the rate of an enzyme-controlled reaction be calculated when given a value for time?
Rate = 1/time
Units S^-1
Why must large organic molecules be broken down into smaller,simpler molecules in the body?
Large molecules are too big to absorbed across the surface of the gut wall
Large molecules are broken down into smaller molecules for absorption into the bloodstream
Give an example of the breakdown of large molecules into smaller molecules plants
Starch is broken down by enzymes into simpler sugars which are respired to release energy
What type of molecules are proteins and carbohydrates?
Polymers
What are the monomers of carbohydrates?
Simple sugars
Which group of enzymes catalyses the breakdown of carbohydrates?
Carbohydrases
Which type of carbohydrase catalyses the breakdown of starch?
Amylase
What are the monomers of proteins?
Amino acids
What type of enzyme catalyses the breakdown of proteins?
Proteases
What is the function of lipases?
Enzymes which catalyse the breakdown of lipids into fatty acids and glycerol
Why are small molecules synthesised into larger organic molecules in the body?
Large molecules are used for storage (glycogen) or are used to build structures (organelles)
Which enzyme catalyses the formation of glycogen from glucose
Glycogen synthase
