Biology B5

An unspecialised cell is a stem cell

Specialised Cells

• nerve cells
• heart cells
• red and white blood cells
• cartilage cells
• bone cells

Cells form tissues

Tissues form organs

Tissue - group of specialised cells of the same type working together to do a particular job

Organ - part of a plant or animal made up of different tissues

Phloem - the tissue in a plant that transports sugar

Xylem - the tissue in a plant that transports water and dissolved nutrients

Cortex - tissue immediately below the epidermis of a stem or root and act as storage tissue

Cambium - a cellular plant tissue from which phloem, xylem or cork grows by division

Epidermis - an outer layer of tissue in a plant

• Meristem - Animal
• Stem - Plant
• Plant - where: tip of stem, tip of the root, cambium
• Animals - where: everywhere
• Plants grow throughout their whole lives
• Animals don't grow throughout their whole lives

Phototropism - the bending of growing plant shoots towards the light

Double helix (helix - spiral) Four Bases

• A (paired with T)
• T (paired with A)
• C (paired with G)
• G (paired with C)

Sugar involved - Deoxyribose

Mitosis - used to make body cells

Meiosis - used to make gametes (sex cells)

Cell Cycle

• DNA replication
• mitosis
• specialisation
• cell enlargement and making more organelles

Chromosomes in parent cell - 46

Chromosomes in daughter cells - 46

Only human cells

Animal gametes - sperm and ovum (eggs)

3 bases -> 1 amino acids

DNA -> mRNA (m = messenger) -> protein molecule

mRNA bases -> AUCG (U replaces T)

Totipotent - these are cells which are fully unspecialised and can produce any type of protein (all genes switched on) e.g. embryonic stem cells

Pluropotent - these are cells where some genes are switched off but the cell still has the abolity to specialise into certain other types of cells e.g. bone marrow cells