Topic 1 - Key Concepts In Biology Flashcards
State the 2 types of cell
Eukaryotic (animals and plants) and prokaryotic
Whats the difference between a eukaryotic and prokaryotic cell?
A eukaryotic cell contains a nucleus and membrane-bound organelles. A prokaryotic cell does not.
List the components of both plant and animal cells (5)
Nucleus Cytoplasm Cell membrane Mitochondria Ribosomes
How is genetic info stored in a eukaryotic cell?
Within the nucleus, arranged in chromosomes
Other than storing genetic info, what is the function of the nucleus?
Controls cellular activities
Describe the structure of the cytoplasm
Fluid component of the cell
Contains organelles, enzymes and dissolved ions and nutrients
Whats the function of the cytoplasm?
Site of cellular reactions. Eg: first stage of respiration
Whats the function of the cell membrane?
Controls the entry and exit of materials into and out of cell
Whats the function of mitochondria?
Release energy through 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
Chloroplasts
Whats the cell wall made of?
Cellulose
Whats the function of the cell wall?
Provides strength
Prevents cell bursting when water enters by osmosis
What does permanent vacuole contain
Solution of salts, sugars and organic acids
What is the function of the permanent vacuole?
Supports 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 chloroplasts appear green?
Contain chlorophyll, a green pigment
List the organelles found in prokaryotic cells (6)
Chromosomal DNA Plasmid DNA Cell wall Cell membrane Ribosomes Flagella
How is genetic info stored in a prokaryotic cell?
Found free within the cytoplasm as:
Chromosomal DNA (single large loop of circular dna)
Plasmid DNA
What are plasmids
Small circular loops of DNA found free in the cytoplasm and seperate from the main DNA
Carry genes that provide genetic advantages eg antibiotic resistance
Whats the prokaryotic cell wall composed of?
Peptidoglycan
What is a flagellum
Long rotating ‘whip like’ protrusion
Enables bacteria to move
What is a haploid cell?
A cell containing a single copy of each chromosome (half the no of chromosomes)
Eg 23 in humans
Whats a diploid cell
A cell containing 2 copies of each chromosome (full set)
Eg 46 in humans
What are gametes
Reproductive cells (eg egg and sperm cells) They are haploid cells
Describe sexual reproduction in terms of chromosome number
2 haploid gametes fuse
Resulting embryo has 2 chromosomes for each gene and 2 copies of each allele : diploid
Describe how egg cells are adapted to their function
- Haploid nucleus contains genetic material
- Mitochondria produce energy for developing embryo
- Cytoplasm contains nutrients for developing embryo
- Cell membrane hardens after fertilisation, preventing entry of other sperm and ensuring zygote is diploid
Describe how sperm cells are adpated to their function
- haploid nucleus contains genetic info
- tail enables movement
- mitochondria provide energy for tail movement
- acrosome contains enzymes that digest egg cell membrane
Where are ciliated epithelial cells found?
Found lining surface of structures such as respiratory tract and uterus
Describe 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
No 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 mag = eyepiece lens mag x objective lens mag
How can magnification of an image be calculated?
Mag = size of image / size of specimen
What is resolution?
Smallest distance between 2 objects that can be distinguished
How does a light microscope work?
Passes beam of light through specimen which travels through eyepiece lens, allowing specimen to be observed
What are 4 advantages of light microscopes
Inexpensive
Easy to use
Portable
Observe both dead and living specimens
Whats the 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 fluorescent screen which emits visible light, producing an image
Name the 2 types of electron microscopes
Transmission electron microscope (TEM)
Scanninf electron microscope (SEM)
Whats the advantage 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 (eg mitochondria/ribosomes) 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? (4)
Expensive
Large so less portable
Require training to use
Only dead specimens can be observed
How do you convert m to mm
x1000 (x10³)
How do you convert m to um
x 1 000 000 (x10⁶)
How do you convert m to nm
x 1 000 000 000 (x10⁹)
How do you convert m to pm
x 1 000 000 000 000 (x10¹²)
Convert 1.527m to um. In standard form.
1.527 x 10⁶
What are enzymes?
Biological catalysts that increase the rate of a chemical reaction without 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 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 enzymes active site
Describe the lock and key model
- Substrate collides with active site of enzyme
- Substrate binds, enzyme-substrate complex forms
- Substrate converted to products
- Products released from 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
Explain how increasing temperature initially affects the rate of an enzyme controlled reaction
As temp increases, molecules have more KE
Movement of molecules increases
Probability of successful collision icreases
More enzyme-substrate complexes form
Rate of reaction increases
Explain how increasing temperature above the optimum affects the rate of an enzyme controlled reaction
Temp increases above optimum
Increased vibrations break bonds in enzyme structure
Active sit changes shape, enzyme 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 optimum pH pH shifts from optimum Bonds in enzyme structure altered Active site changes shape, enzyme denatured Rate of reaction decreases
Explain how substrate concentration affects rate of an enzyme controlled reaction
Substrate concentration increases
No of substrate molecules in same vol increases
Probability of successful collision increases
More enzyme-substrate complexes form
Rate of reaction increases
Once all active sites become full, rate of reaction plateaus
How can rate of enzyme controlled reaction be calculated when given a value for time
Rate = 1/time
What are units for rate
s⁻¹
Why must large organic molecules be broken down into smaller simpler molecules in the body
Large molecules are too big to be absorbed across surface of gut wall
Large molecules are broken down into smaller for absorption into bloodstream
Give an example of the breakdown of large molecules into smaller molecules in plants
Starch is broken down by enzymes into simpler sugars which are required to release energy
What type of molecules are proteins and carbohydrates
Polymers
What are 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
Which 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 (eg glycogen) or are used to build structures (eg organelles)
Which enzyme catalyses the formation of glycogen from glucose?
Glycogen synthase
What is simple diffusion
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 eg oxygen, water, glucose, amino acids
What factors affect rate of diffusion (3)
Temp
Concentration gradient
Surface area of cell membrane
Define osmosis
Net movement of water molecules from area of high water concentration to area of low water concentration through a partially permeable membrane
What is active transport
Movement of molecules across a cell membrane from area of low concentration to area of high concentration, against the concentration gradient, using energy
How is a percentage change is mass calculated
% change = (final mass - initial mass / initial mass) x 100
