biology paper 1

• nucleus - contains genetic material and controls cell activities, controls cell division and growth, controls cell specialisation
• mitochondria - site of aerobic respiration, where most of the energy is released
• cytoplasm - medium for chemical reactions,
• cell membrane - semi permeable, controls what goes in and out of the cell
• ribosome - where protein synthesis occurs
• prokaryote is a cell with no nucleus e.g. bacteria. also unicellular
• eukaryote is a cell with a nucleus e.g. plant and animal cells. also multicellular
• plant cell wall is made up of cellulose. it supports and strengthens the cell.
• plant cell vacuole contains cell sap and maintains internal pressure to support the cell
• plant cell chloroplasts is the place where photosynthesis occurs. contains chlorophyll which makes the plant green
• chromosomal dna in a bacterial cell controls the cells activity, replication and floats in the cytoplasm freely
• plasmid dna in a bacterial cell is small parts of seperate dna and contains genes like drug resistance
• flagellum - a structure (e.g. in a sperm cell) rotating around the cell to make it swim
• egg cell adaptations are nutrients in cytoplasm to feed the embryo, haploid nucleus and after fertilisation, the membrane changes structure so it gets the correct amount of dna
• sperm cell adaptations are a long tail to swim, lots of mitochondria that releases energy, acrosome with digestive enzymes and a haploid nucleus
• ciliated epithelial cell adaptations are cilia on the surface that pump substances in one direction
• light microscopes use light to form an image of the specimen. they have a lower magification and resolution, are cheaper, let you see images in 3d and in colour.
• electron microscopes use electrons to let you see the specimen. they have a higher magnification and resolution, are more expensive and let you see the specimen in 2d and in black and white
• image size = magnification x real size
• total magnification = eyepiece lens mag x objective lens mag
• enzymes are biological catalysts that speed up chemical reactions in the body without being used up. every enzyme has an active site that fits a specific substrate. they fit together and this is called the lock and key mechanism. they have an optimum temperature, ph and substrate concentration. if it doesnt have these needs it will denature (change active site so it can no longer catalyse)
• starch is broken down by the amylase enzyme into maltose

  proteins are broken down by protease enzymes into amino acids

  lipids are broken down by lipase enzymes into glycerol and fatty acids
• diffusion is the overall movement of particles from an area of high concentration to an area of low concentration.
• active transport is the movement of particles across a membrane from an area of low concentration to an area of high concentration. it uses energy.
• osmosis is the overall movement of water molecules from a region of high water concentration to a region of low water concentration
• interphase - the cell is growing and preparing for mitosis

  prophase - chromosomes condense and nucleus breaks down

  metaphase - chromosomes line up in middle of cell

  anaphase - spindle fibres pull chromosomes apart

  telophase - the cell divides into two
• mitosis happens with all cells (other than gametes) e.g. animal cells. at the end of mitosis, youll end up with 2 diploid daughter cells that are genetically identical.
• meiosis is the same as mitosis except for the fact it happens twice and produced 4 genetically variated haploid daughter cells. meiosis only happens for gametes (sperm and egg)
• stem cells are unspecialised cells that can differentiate into any type of cell in the body. they are produced from either bone marrow (which are versatile) or from the embryo of an unborn child. you can also get them from meristem cells in plants.
• the nervous system:

  stimulus - receptor - sensory neuron - cns - motor neuron - effector - response
• sensory neuron : carries nerve impulses from receptor cells to cell body

  motor neuron : carries nerve impulses from cns to cell body

  relay neuron : carries nerve impulses from sensory neuron to cell body to motor neuron
• cerebrum - the largest part of the brain, responsible for conscious thought and memory

  cerebellum - responsible for muscle coordination and balance

  medulla oblongata - controls unconscious activities like breathing and heart rate
• ct scanning (computed tomography) is used to look at the brain. it shows the main structures and whether it has any damage or diseases it may have.

  pet scanning (positron emmision tomography) uses radioactive chemicals to show which parts of the brain are active. it can be useful in seeing if someone has any brain disorders
• cornea - refracts light to focus it on the retina

  iris - controls the amount of light let into the eye

  lens - refracts light onto retina

  retina - covered in cones (colour) and rods (dim light)

  optic nerve - converts light into electrical impulses that are carried to the brain
• colour blindness is cause by a defect in the cone cells of the retina, resulting in a lack of colour vision.

  a cataract is a cloudy patch on the lens which causes blurred vision. can be treated by replacing the faulty lens with an artificial one
• long sighted people cant focus on near objects. the eyeball is too short so the light rays meet past the retina. you can use a convex (diverging) lens to fix it

  short sighted people cant focus of distant objects. the eyeball is too long so the light rays meet before the retina. you can use a concave (converging) lens to fix it
• asexual reproduction : produces offspring quickly and only one parent is needed but no genetic variation

  sexual reproduction : creates genetic variation, leads to natural selection and evolution but it requires energy and time finding a mate, and two parents are needed.
• dna is made up of nucleotides (sugar phosphate backbone and a base) there are four bases : adenine, thymine, cytosine and guanine and they are joined together by weak hydrogen bonds. dna is a double helix.
• transcription: 2 dna strands are unzipped by breaking the hydrogen bonds. rna polymerase attaches to the dna strand and moves along. thymine binds with adenine but adenine binds with uracil on the mrna. a copy of the original dna is made but the thymine is uracil. the new mrna leaves the nucleus and goes to the ribosome
• translation: the mrna strands move through the cytoplasm and attaches to the ribosome. the ribosome lines up with 3 complementary molecules of trna. trna molecule transports specific amino acids to the ribosome. 3 mrna bases for each of the trna molecule. used trna molecules exit the ribosome and get another amino acid. a chain of lots of amino acids in the order of the original dna is made. this is called a polypeptide. the polypeptide folds into the correct shape and becomes a protein