Biology Paper 1: Topics 1-5 Flashcards
What are eukaryotic cells?
Complex cells. All plant and animal cells
What are prokaryotic cells?
Smaller, simpler. Bacteria. Prokaryotes are single celled organisms
What’s the nucleus?
Contains genetic material arranged in chromosomes, controls activities of the cell
What’s a cytoplasm
Contains enzymes which Control chemical reactions that take place here
What’s a cell membrane?
Holds cell together, controls what goes in and out
What’s mitochondria
Where reactions for respiration (transfer energy cells need to work) occur
What are ribosomes?
Involved in translation of genetic material in synthesis of proteins
What’s a rigid cell wall
Made of cellulose, supports and strengthens cell
What’s a large vacuole
Contains cell sap (weak solution of sugar and salts) and maintains internal pressure of cell
What are chloroplasts
Where photosynthesis occurs. Contain green chlorophyll
What’s chromosomal dna
Controls activities and replication, floats free in cytoplasm.
What’s flagellum
Rotates to move bacterium away from harmful and towards good substances
What’s plasmid dna
Small loops of extra dna, can be passed between bacteria, contain genes
What’s a specialised cell
Cell with a structure adapted to its function
What’s resolution
How well microscope distinguishes between two points that are close together
What are the two types of microscope
Light microscope - pass light through specimen
Electron microscope - pass electrons though specimen, cant be used on living cells
What is magnification
How many times bigger the image is
What are the two equations for magnification
Total magnification = eyepiece lens magnification x objective lens magnification
OR
Magnification = image size / real size
Put the four measurements smaller than cm in size order, and how do you convert between them?
Millimeter, mm
Micrometer, um
Nanometer, nm
Picometer, pm
Milli to micro = x1000
What an enzyme? What’s their job?
A biological catalyst. Speed up useful chemical reactions in the body without being changed. Enzymes have a high specificity for their substrate because substrate must fit the active site (lock and key mechanism)
Enzymes break big molecules (proteins, lipids, carbohydrates) into smaller components, so they can be used for growth and life processes. Enzymes are also used to synthesise carbohydrates, proteins and lipids from their smaller components
Enzymes break down starch (a carbohydrate) in plants into smaller molecules that can be respired to transfer energy to be used by cells
What’s substrate
Molecule changed in the reaction
What’s an active site
Where enzyme joins onto substrate
How do temperature, ph and substrate concentration affect rate of enzyme controlled reaction?
Temperature = higher temp increases rate until enzyme denatures. Optimum temperature is different for all enzymes
pH = too high or too low pH denatures the enzyme. Optimum pH often 7
Substrate concentration = higher substrate concentration > faster reaction, because more likely an enzyme will encounter a substrate molecule. When all active sites full, further increase in substrate concentration makes no difference
What’s denaturing of enzyme?
Some bonds holding enzyme together break, causing shape of enzyme’s active site to change. Substrate will no longer fit.
What’s an experiment to investigate effect of pH on enzyme activity?
Use continuous sampling to time how long it takes amylase to break down all starch solution, when mixed with buffer solutions of various pHs. Detect starch using iodine solution, changes from orange to black if starch present
What’s the two equations for rate of reaction?
If experiment is measuring how much something changes over time:
Rate of reaction = change / time
OR
Rate of reaction = 1000 / time
What do digestive enzymes do?
Break down food into smaller, soluble molecules that can then easily pass through walls of digestive system, so can be absorbed into bloodstream, then pass into cells for use in the body
What are the big molecules carbohydrates, proteins and lipids broken down into and how?
Carbohydrates > simple sugars, by carbohydrase enzymes.
Eg: starch (amylase enzyme) > maltose + other sugars
Proteins > amino acids, by protease enzymes
Lipids > glycerol + fatty acids, by lipase enzymes
What’s glycogen and hows it made?
Chains of glucose molecules broken down into glycogen using glycogen synthase enzyme.
Glycogen is a molecule used to store energy in animals
What’s diffusion?
The net (overall) movement of particles from an area of higher concentration to an area of lower concentration.
It moves down the concentration gradient therefore is passive movement, happens in liquids and gases. Only small molecules can dissolve through cell membranes
What’s osmosis?
The net movement of water molecules across a partially permeable membrane (membrane with small holes in), from a region of higher water concentration to a region of lower water concentration (water can be replaced by ‘solute’)
Solute solution will become more dilute with osmosis
What’s active transport
Movement of particles across a membrane against a concentration gradient (lower to higher) using energy transferred during respiration
What’s an experiment for investigating osmosis
Put potato cylinder groups of 3 in sucrose solutions of different concentrations, then calculate percentage change in mass for each cylinder group before and after going into sucrose. Negative result means cylinders lost mass
Percentage change in mass = ((final mass - initial mass) / initial mass) x 100
On a graph plotted for the ‘investigating osmosis’ experiment, what do __ mean:
- points above x axis
- where curve crosses x axis
- points below x axis
Above; water concentration of sucrose solution is higher than in cylinders. Cylinders gained mass, water drawn in by osmosis
Curve crosses x axis; fluid inside cylinders and sucrose solution are isotonic = have same wate concentration
Points below x axis; water concentration of sucrose solutions lower than in the cylinders. Cylinders lose water, so mass decreases
What are chromosomes
Coiled up lengths of DNA molecules. A diploid cell has two copies of each chromosome
Whats the cell cycle
Body cells in multicellular organisms undergo the cell cycle
It’s mitosis and cytokinesis, and then interphase
Mitosis: stage of cell cycle when the cell divides. Organisms use mitosis to grow or replace damaged cells, or to asexually reproduce. Mitosis produces two genetically identical diploid cells.
Interphase: DNA is spread out in long strings, cell growing to increase number of sub cellular structures. DNA duplicates and forms x shaped chromosomes (with identical left and right arms)
Describe what happens in each cell of the cell cycle
Interphase: DNA duplicates forming x-shaped chromosomes
Mitosis and cytokinesis:
Mitosis:
1 Prophase: chromosomes condense, lie free in cytoplasm as membrane around nucleus breaks down
2 Metaphase: chromosomes form a line at centre of cell (equator)
3 Anaphase: Cell fibres (formed by centrioles) pull chromosomes apart at the centromeres (middle bits of chromosomes), each arm (chromatid) of each chromosome go to opposite ends of cell
4 Telophase: Membranes form around each of the sets of chromosomes (these become nuclei of new cells)
Cytokinesis: Before Telophase ends cytoplasm and cell membrane divide to form two separate ends
Whats equation to calculate number of cells after multiple divisions of a cell by mitosis
Number of cells = 2^n, n being the number of divisions by mitosis
What’s ‘cell growth’ defined as
An increase in size or mass. All growth in animals is done by cell division, plants grow by cell elongation, with cell division happening at tips of roots and shoots.
What’s cell differentiation?
Cell changes to become specialised, allowing multicellular organisms to work more efficiently.
On a growth percentile chart, what does the 50th percentile for eg weight tell you?
Shows weight that 50% of babies will have reached at a certain age
What are stem cells? What are the different types?
Undifferentiated cells. Can divided by mitosis to become new cells that then dissociate.
Embryonic stem cells = found in embryos, have potential to divide and become any type of cell. Essential for growth and development of organisms
Adult stem cells = only found in certain places, eg bone marrow. Can only produce certain cell types, use to replace damaged cells
In plants, stem cells found in meristem tissue, which is found in areas of plant that are growing. Can divide into any cell type.
What’s the nervous system made of?
Neurones (nerve cells)
What are sensory receptors?
Group of cells that detect stimulus, a change in environment. Different receptors detect different stimulus. When stimulus detected by receptors, it’s converted to a nervous electrical impulse, sent along sensory neurones to CNS
What’s the CNS made of
CNS = central nervous system, made of brain and spinal cord. It coordinates response, as impulses travel through CNS along relay neurones. CNS sends information to an effector (muscle or gland) along motor neurone. Effector responds accordingly
Whats reaction time?
Time taken to respond to stimulus