GCSE BIOLOGY PAPER 1
TOPIC - CELLS
MICROSCOPY
Light microscope – image is formed using light, cheap, views live specimens, 2000x magnification, low
resolution.
Electron microscope – image is formed using electrons, expensive, doesn’t view live specimens, very
expensive, high resolution, 2,000,000x magnification
ANIMAL AND PLANT CELLS
ANIMAL CELL – Nucleus – controls cell activity
Cell membrane – controls what enters cell
Cytoplasm - where chemical reactions happen
Mitochondria – where aerobic reparation occurs
Ribosome – where protein synthesis takes place
PLANT CELL - Nucleus – controls cell activity
Cytoplasm - where chemical reactions happen
Mitochondria – where aerobic reparation occurs
Ribosome – where protein synthesis takes place
Cell membrane – controls what enters cell
Chloroplast – contains chlorophyll, absorbs light for photosynthesis
Vacuole – holds cell sap
Cell wall – holds structure
EUKARYOTIC AND PROKARYOTIC CELLS
Animal cells and plants cells and fungi are eukaryotic cell because they all have a nucleus
Bacteria are prokaryotic because their genetic info is not in the nucleus
SPECIALISED CELLS
Initially all cells are undifferentiated (the same)
, As organism grows, the cells differentiate (specialised cells)
Specialised cells are cells that have a specific job
Sperm cell – function is to fertilise egg cell, has tail, mitochondria, large DNA
Muscle cell – function is contract and relax, has mitochondria, proteins
Nerve cell – carries electrical impulses around body,
Root hair cell – absorbs water and mineral from soil, large surface area, mitochondria
Xylem – function is to send water and minerals from roots to plant
Phloem – function is to send sugar to where is needed
DIFFUSION
Diffusion is spreading out particles from high to low concentration. (Passive process)
3 factors that influence rate of diffusion
temperature – higher temp = faster diffusion
Concentration gradient – greater difference of concentration = faster diffusion
Surface area – bigger SA = faster diffusion
OSMOSIS
Osmosis is movement of water particle through a semi permeable membrane (high to low) +passive
ACTIVE TRANSPORT
Movement of substances from low-high conc through semi permeable membrane (against
concentration gradient) + requires energy
MITOSIS AND CELL CYCLE
Nucleus has 23 pairs of chromosomes, made up of DNA.
DNA codes for genes
Cell cycle stages
Stage 1 – cell grows, and increases number of sub cellular structures, and DNA replicates to form
2 copies of each chromosome, so the cell contains 92 chromosomes
Stage 2 - (MITOSIS) one set of chromosomes is pulled to each end of cell. Nucleus divides in 2.