Knowt
Paper 1 Notes
Key Concepts in Biology
Cells
Organelles - subcellular structures
Eukaryotic - with nucleus:
Animal cells
Nucleus - DNA, controls
Cytoplasm - contains enzymes, where most reactions happen
Mitochondria - respiration
Ribosome - protein synthesis
Cell membrane - controls what goes in and out of the cell
Plant cells
Nucleus - DNA, controls
Cytoplasm - contains enzymes, where most reactions happen
Mitochondria - respiration
Ribosome - protein synthesis
Cell membrane - controls what goes in and out of the cell
Cell wall - strengthens cell
Vacuole - sac filled with cell sap
Chloroplasts - photosynthesis, contains chlorophyll
Prokaryotic - without nucleus:
Bacterium
Plasmid - where DNA is held since the cell has no nucleus
Flagellum - movement
Cell membrane - controls what goes in and out of the cell
Cytoplasm - contains enzymes
Ribosomes - protein synthesis
Chromosomal DNA - contains most of the genes
Mesosome
Specialised Cells
A cell that goes through differentiation to be able to carry out one specific purpose
Examples:
Sperm
Flagellum - tail to swim
Nucleus
Long mitochondria - needs energy to swim to the egg
Acrosome - helps sperm penetrate the egg’s jelly coat
Plasma membrane
Egg
Cell membrane
Mitochondria
Cytoplasm
Haploid nucleus
Thick jelly coat that hardens when a sperm gets in so that no more can enter
Ciliated cells
Red blood cells
Nerve cell
Xylem cell
Root hair cell
Microscopes
Magnification = objective lens x eyepiece lens
Micrograph - image that a microscope creates
Stage - what the slide sits on
Coarse adjustment - higher dial that roughly makes the image clearer
Fine adjustment - lower dial that makes the image fully clear
Eyepiece lens - smaller magnification
Objective lens - larger magnification
How many um are there in a mm?
1000um
How many nm are there in a um?
1000nm
How to Prepare a Slide
Place sample on the slide
Stain with iodine
Place coverslip on sample
Place slide on stage
Select objective lens
Use rough focus knob
Use fine focus knob
Enzymes
Made of protein
Biological catalyst
Substrate - what it works on
Active site - what the substrate binds to to break it down
Catalyst - something that speeds up a reaction
Biological catalyst - something that speeds up a reaction without being used up itself
Lock and Key Mechanism:
Substrate enters active site
Enzyme-substrate complex formed
Reaction happens
Product leaves active site
Digestive enzymes - break down large food molecules down to ones small enough to absorb
Amylase - starch (carbohydrate) → glucose
In saliva, small intestine, pancreas
Protease - protein → amino acids
In stomach, small intestine, pancreas
Lipase - fat → fatty acids and glycerol
In small intestine, pancreas
Denaturing - active site has changed shape
Caused by → high temperature, low/high pH
Experiment to see what happens when different pHs are used:
Warm one test tube of starch solution and one test tube of amylase and pH buffer to 40 degrees
Mix tubes and start timer
Every 30s, remove a small sample, put it in one well of a spotting tile and test the pH with iodine
Record time when no colour change
Repeat with different pHs
Diffusion, Osmosis, Active Transport
Concentration - number of particles in a given volume
Diffusion - when molecules move from a high concentration to a low concentration (down a concentration gradient)
Osmosis - diffusion of water across a partially permeable membrane
Active Transport - movement of any substance from a low to high concentration (up a concentration gradient)
Investigating Osmosis:
Cut potatoes into cylinders of equal size
Blot them dry
Measure them
Record mass
Place them in sucrose solutions of different concentrations
Leave for 15 mins
Blot them dry
Reweight them
Calculate the percentage change
Cells and Control
Cell Division
The process of making 2 cells
Diploid - contains 23 pairs of chromosomes
Haploid - contains 23 chromosomes
Mitosis:
One diploid parent cell
Two genetically identical daughter cells
Asexual reproduction
Growth and repair
Makes all cells except gametes
Interphase (before mitosis) - copying chromosomes and cell grows - preparation for mitosis
Prophase - nucleus breaks down, spindle fibres form
Metaphase - spindle fibres are fully formed and are lined up along the equator
Anaphase - pairs pulled to opposite poles
Telophase - new nucleus forms around each end, cell pinches in the middle
Cytokinesis (after mitosis) - separation of cells is completed
Meiosis:
Two haploid parent cells
Four genetically different daughter cells
Sexual reproduction
Used to make only gametes
Starts in a similar way to mitosis
Daughter cells split without replicating chromosomes
Egg - ovum
Egg + sperm → zygote → embryo → fetus → baby
Stem Cells
Stem cells - cell that can differentiate
Differentiation - when a cell divides to produce 2 types of specialised cell
Nervous System
Sensory - carries impulse to central nervous system
Relay - makes decisions
Motor - carries impulse from central nervous system to muscle
Reflex Arc:
stimulus → receptor → sensory → relay → motor → muscle
Allows an automatic reaction to keep us safe - doesn’t involve the brain - relay neurone makes decision
DNA
Chromosome - large piece of DNA
Gene - section of DNA
Structure:
Double helix
Complementary base pairs
Sugar phosphate backbone
Bases are held together by weak hydrogen bonds
Bases attached to sugar
Alleles
Can be:
Dominant - one copy needed to show feautre
Recessive - 2 copies needed to show feature
Homozygous - 2 of the same allele
Heterozygous - different alleles
Phenotype - what you see
Genotype - genes you have
Capital letter shows dominant allele
Lowercase letter shows recessive allele
Each parent gives one allele
Variation
Differences between members of a species - effects chances of survival
Discontinuous - genes
Continuous - genes and environment
Natural Selection and Genetic Modification
Selective Breeding
Improving characteristics of crops or animals
Select individuals with the best characteristics
Breed them
Raise their offspring
Breed the best of those together
Repeat
Can lead to issues with inbreeding
Genetic Engineering
Inserting genes from one organism into another
Remove desired gene from the chromosome
Cut organism’s chromosome open using a restriction enzyme
Insert into organism using DNA ligase
Breed organism (offspring will contain new gene)
Evolution
Theory by Charles Darwin
Radiometric dating gives an age in years for rocks by measuring carbon-14, which is radioactive
Common ancestor - ancestor shared by 2 or more other organisms
Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Makes genetically modified organism (GMO)
Health and Disease
Non-communicable Diseases
Malnutrition - getting too much/too little of certain nutrients
Obesity - too much nutrients
Too much fat/carbohydrates
Nutrient deficiency - too little nutrients
Kwashiorkor
Scurvy - lack of vitamin C (swollen, bleeding gums, bone issues)
Rickets - softens bones and curves them - lack of vitamin D or calcium
Anaemia - caused by lack of iron (lightheadedness)
Liver disease
Caused by alcohol abuse
Cirrhosis - liver starts to break down
Causes death
Only cure is to get a liver transplant
Cardiovascular Disease
Caused by obesity
Non-communicable disease
Heart disease
Determine obesity by BMI
BMI = mass (kg)/height^2 (m)
Heart attacks - inside arteries, plaque builds up, blocks arteries, blood can’t get through, body doesn’t get as much nutrients, heart can die and the rest of the body stops getting nutrients
Prevented by exercise and healthy lifestyle
Communicable Diseases
Pathogens - microorganisms that cause disease
Types of Pathogen:
Bacteria
Virus
Protist
Fungus
Cholera - bacteria (vibrio cholera) - waterborne
TB - bacteria (mycobacterium tuberculosis) - airborne
Malaria - protist - vector (mosquitos)
Chalara ash dieback - fungus - airborne
Cold/flu - virus - airborne
Food poisoning - bacteria - oral route
HIV - virus - sexually transmitted
Ebola - virus - direct contact
Immune System
Kills/destroys pathogens
Immune response:
Antigens are on pathogens
Antibody has a shape that matches antigens and marks it
Antitoxin finds antibody and kills pathogen
Lymphocyte produces antibodies
Phagocyte - phagocytosis (engulfing of pathogens)
Most lymphocytes will die
Memory lymphocytes will remain to remember the pathogen when it returns - making you immune