CELL BIOLOGY

Eukaryotic cell

  • animal cells and plant cells

  • They have their genetic info enclosed in a nucleus

  • cell membrane

  • cytoplasm

Prokaryotic cell

  • bacterial cell

  • genetic info not contained inside a nucleus

  • much smaller than eukaryotic

  • cell membrane and cell wall

  • cytoplasm

Sizes of cell

1cm = 1 × 10^-2m centimetre

1mm = 1 × 10^-3m millimetre

1μm = 1 × 10^-6m micrometre

1nm = 1 × 10^-9 nanometre

Order of magnitude

1 order of magnitude means 10x

2 order of magnitude mean 100x

3 order of magnitude mean 1000x

Animal cells

Nucleus - enclose genetic material

cytoplasm - where chemical reactions takes place

cell membrane - controls what enters and leaves

mitochondria - where aerobic respiration takes place

ribosomes - where protein synthesis takes place

Plant cells

nucleus

mitochondria

cytoplasm

cell membrane

ribosomes

chloroplasts - contain chlorophyll and where photosynthesis takes place

cell wall - strengthens the cell

permanent vacuole - contains cell sap which helps give the plant its shape

Sperm cell

  • To fertilise the egg cell

  • Sperm cells contain their genetic info in the nucleus

  • long tail to swim fast

  • mitochondria - provide energy for swimming

  • Enzymes- digest their way through the outer layer of the egg cell

Nerve cell

  • send electrical impulses

  • long axon - carries electrical impulses from one part to another

  • axon covered in myelin - insulates and speeds up transmission

  • end of the axon has synapses - allow impulses to pass from one nerve cell to another

  • Dendrites - increase surface area so that other nerve cells can connect more easily

Muscle cell

  • to contract

  • protein fibres - which can change their lengths, shorten decreasing the length of the cell

  • Mitochondria - provide energy for muscle contraction

Root hair cell

  • increase the surface area of the root to absorb water

  • do not contain chloroplasts because they are underground

Xylem cell

  • carry water and dissolve minerals

  • thick wall containing lignin- this provides support

  • since the plant is sealed with lignin it causes the Xylem cells to die

  • End walls between the cells have broken down- this forms a long tube so water and minerals can move easily

  • they have no nucleus, cytoplasm, vacuole or chloroplasts

Phloem cell

  • carry dissolved sugars up and down the plant

  • Phloem vessel cells have no nucleus and limited cytoplasm

  • The end wall of the vessel cells have pores called sieve plates

  • Both allow dissolved sugars to move through the cell

  • Connected to companion cells connected by pores

  • Mitochondria in the companion cell provide energy to the phloem vessel cell

Microscopes

  • place slide onto stage, and use clips to hold it in place

  • select the lowest power objective lens

  • position so it almost touched the microscope slide

  • slowly turn the coarse focussing dial

  • look down from the eyepiece

  • slowly turn the coarse focussing dial, this increases the distance between the objective lens and the slide, do this until the cells come into focus

  • use the fine focussing dial to bring the cells into a clear focus

magnification = image size/ actual size

Cell division by mitosis

  • Human body cells contain 23 pairs of chromosomes

  • Chromosomes contain genes

  • Stage 1- DNA replicates to form two copies of chromosomes, cell grows a copies its internal structures such as mitochondria and ribosomes

  • Stage 2- Mitosis takes place, one set of chromosomes it pulled to each end of the cell and the nucleus divides

  • Stage 3- Cytoplasm and cell membrane divide to form two identical daughter cells

  • mitosis is needed for growth and development of multicellular organisms

  • Mitosis takes place when an organism repairs itself

  • mitosis happens during asexual reproduction

Stem cells

  • undifferentiated cell which can differentiate into any other cell

  • embryonic stem cell - can differentiate into any type of cell

  • Adult stem cell- can differentiate into RBC, WBC, Platelets

Therapeutic cloning

  • an embryo is produced with the same gene as the patient

  • stem cells from the embryo can be transplanted into the patient without being rejected by the immune system

  • once differentiate to replace cells which have stopped working

plant meristem

  • can differentiate into any type of plant tissue

  • we can clone rare plant to stop it from going extinct using meristem

Diffusion

  • net movement of particles from an area of high concentration to an area of low concentration against the concentration gradient

  • higher temperatures speed up diffusion

  • larger surface area the greater rate of diffusion