Topic 1: Key Concepts Flashcards
What are the two types of cells?
Eukaryotic (animals and plants) and prokaryotic
What is the difference between an eukaryotic and prokaryotic cell?
An eukaryotic cell contains a nucleus and membrane-bound organelles, a prokaryotic cell doesn’t
What are the components of both plant and animal cells? (5)
Nucleus, cytoplasm, cell membrane, mitochondria and ribosomes
How is genetic information stored in an eukaryotic cell?
Within the nucleus, arranged in chromosomes
What is the function of the nucleus?
Storing genetic information and controls cellular activities
What is the structure of the cytoplasm?
Fluid component of the cell and contains organelles, enzymes dissolved ions and nutrients
What is the function of the cytoplasm?
Site of cellular reactions
What is the function of the cell membrane?
Controls the entry and exit of materials into and out of the cell
What is the function of the mitochondria?
Site of later stages of aerobic respiration
What is the function of the ribosomes?
Joins amino acids in a specific order during translation
Which organelles are found in plant cells only? (3)
Large permanent vacuole, cell wall and chloroplast
What is the cell wall made of?
Cellulose
What is the function of the cell wall?
Provides strength and prevents the bursting when water enters by osmosis
What does the permanent vacuole contain?
A solution of salts, sugars and organic acids
What is the function of the permanent vacuole?
Supports the cell, maintaining its turgidity
What is the function of the chloroplasts?
Site of photosynthesis
Why do chloroplast appear green?
Contain chlorophyll which is a green pigment
What organelles are found in prokaryotic cells? (6)
Chromosomal DNA, plasmid DNA, cell wall, cell membrane, ribosomes and flagella
How is genetic information stored in a prokaryotic cell?
Found free within the cytoplasm as chromosomal DNA or plasmid DNA
What are plasmid?
Small, circular loops of DNA found free in the cytoplasm and separated from the main DNA, they also carry genes that provide genetic advantages
What is the prokaryotic cell wall composed of?
Peptidoglycan
What is a flagellum?
Long, rotating ‘whip-like’ protrusion and enables bacteria to move
What is a haploid cell?
A cell that contains a single copy of each chromosome
What is a diploid cell?
A cell that contains two copies of each chromosome
What are gametes?
Reproductive and haploid cells
What is sexual reproduction in terms of chromosome number?
Two haploid gametes fuse resulting embryo has two chromosomes for each gene and two copies of each allele
How are egg cells adapted to their function? (4)
Haploid nucleus contains genetic material, mitochondria in cytoplasm produce energy for the developing embryo, cytoplasm contains nutrients for the developing embryo and cell membrane hardens after fertilisation, preventing the entry of other sperm and ensuring the zygote is diploid
How are spermicide cells adapted to their function? (4)
Haploid nucleus contains genetic information, tail enables movement, mitochondria provide energy for tail movement and acrosome contains enzymes that digest the egg cell membrane
Where are ciliated epithelial cells found?
Found lining the surface
What is the function of ciliated epithelial cells lining the airways?
Move in synchronised waves to beat mucus (containing dirt and pathogens) up to the back of the throat where it can be swallowed
What is magnification?
The number of times bigger an image appears compared to the size of the specimen
How can the total magnification of an image be calculated from lens powers?
Total magnification = eyepiece lens magnification x objective lens magnification
How can the magnification of an image be calculated?
Size of image / size of specimen
What is resolution?
The smallest distance between two objects that can be distinguished
How does a light microscope work?
Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
What are the advantages of light microscopes? (4)
Inexpensive, easy to use, portable and 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 fluorescent screen which emits visible light, producing an image
What are the two types of electron microscope?
Transmission electron microscope (TEM) and scanning electron microscope (SEM)
What are the advantages of electron microscopes?
Greater magnification and resolution
Why do electron microscopes have a greater magnification and resolution?
They use a beam of 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 and enable scientists to develop more accurate explanations about how cell structures relates to function
What are the disadvantages of electron microscopes?
Expensive, large so less portable, require training to use and only dead specimens can be observed
How do you convert meters to millimetres?
x 1000
How do you convert meters into micrometers?
x 1,000,000
How do you convert meters to nanometers?
x 1,000,000,000
What is simple diffusion?
The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient
What molecules enter and leave cells via simple diffusion through the cell membrane?
Small molecules e.g oxygen, water, glucose and amino acids
What factors affect the rate of diffusion?
Temperature, concentration gradient and surface area of cell membrane
What is osmosis?
The net movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane
What is active transport?
The movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, again the concentration gradient, using energy
How is the percentage change in mass calculated?
Percentage change = (final mass - initial mass) / initial mass x 100
What are enzymes?
Biological catalysts that increase the rate of a chemical reaction with being permanently altered themselves
What is an advantage of enzymes in the body?
They enable cellular reactions to take place at lower temperatures
What is the active site of an enzyme?
The region of an enzyme to which a substrate molecule binds and the reaction takes place
Why are enzymes described as having a ‘high specific’ for their substrate?
Only substrates with a specific, complementary shape can fit into an enzyme’s active site
What is the ‘lock and key’ model?
Substrate collides with the active site of an enzyme, substrate binds, enzyme-substrate complex forms, substrate converted to products, 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 and substrate concentration
How does increasing temperature initially affect the rate of an enzyme-controlled reaction?
As temperature increases molecules have more KE, movement of molecules increases, probability of a successful collision increases, more enzyme-substrate complexes form and rate of reaction increase
How does increasing temperature above the optimum affects the rate an enzyme-controlled reaction?
Temperature increases above the optimum, increased vibration break bonds in enzyme’s structure, active site changes shape, enzyme is denatured, no more enzymes-substrate complexes can form and 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 change shape, enzyme is denatured, rate of reaction decreases
How does the substrate concentration affects the rate of an enzyme-substrate?
Substrate concentration increases, number of substrate molecules in the same volume increases, probability of a successful collision increases, more enzymes-substrate complexes form, rate of reaction increases and once all the active sites become full, the rate of reaction plateaus
How can the rate of an enzyme-controlled reaction be calculated when given a value for time?
1/time
What are the units for rate?
S-1
Why must large organic molecules broken down into smaller, simpler molecules in the body?
Large molecules are too big to be absorbed across the surface of the gut wall and large molecules are broken down into smaller molecules for absorption into the bloodstream
What type of molecules are proteins and carbohydrates?
Polymers
What are the monomers of carbohydrates?
Simple sugars
Which group of enzymes catalysts the breakdown of carbohydrates?
Carbohydrases
Which type of carbohydrases catalysts the breakdown of starch?
Amylase
What are the monomers of proteins?
Amino acids
Which group of enzymes catalysts the breakdown of protein?
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 or are used to build structures
Which group of enzymes catalysts the formation of glucogen from glucose?
Glycogen synthase
How can the amount of energy contained in food be measured?
Measured using calorimetry
What is calorimetry?
A method of measuring the heat transfer during a chemical reaction
What is the method used to measure the amount of energy in a sample of food?
Add a set volume of water to a boiling tube, record initial temperature, record the mass of a small sample of food, stick the sample onto a mounted needle, using a bunsen burner light the food sample. Hold the sample under the boiling tube until it burns up, record the maximum temperature reached by the water and record the final mass of the food sample
How can the amount of energy in the food sample be calculated?
Energy in food = mass of water x temperature change of water x 4.2
