Cell Biology Revision (Part 1) Flashcards
The Plasma Membrane
The Plasma Membrane controls what enters and leaves the cell. It is made of a double layer of phospholipids and proteins.The phospholipids are not bound together but instead arrange the selfs by attraction. The phospholipids heads ‘love’ water (+) and the phospholipids tails ‘hate’ water (-).
Cell Structure
Nucleus - Controls cell activities and contains genetic information
Cytoplasm - Site of chemical reactions (e.g respiration)
Cell Membrane - Controls what passes in and out of the cell
Cell Wall - Supports cell
Vacuole - Stores sugar and salt solution
Chloroplasts - Contains photosynthetic pigment which traps light
energy for photosynthesis
Ribosomes - Where proteins are made
Mitochondria - Site of aerobic respiration
Fungal cells have similarities to plant cells but their cell wall is made of Chitin instead of Cellulose.
Transport across the membrane
Diffusion: The movement of molecules from a high area of concentration to an area of low concentration down the concentration gradient.
Osmosis: The movement of water from a high water concentration (HWC) to low water concentration (LWC) through a selectively permeable membrane.
Active Transport: the movement of charged particles (ions) across plasma membrane from low to high concentration against the concentration gradient.
DNA
DNA (deoxyribose nucleic acid) is a large molecule found in the nucleus of all plants and animals. DNA molecules are arranged into a double helix structure which coils around to form larger structures called chromosomes. In almost all human cells there are 23 pairs of chromosomes. You have two copies of each chromosome, one from your mum and one from your dad. These little differences in our genes are what make us all unique.The double helix consists of 2 strands made up of sub units called nucleotides.
Adenine always pairs with Thymine
Guanine always pairs with Cytosine
The weak hydrogen bonds between the base pairs hold the 2 stands of the DNA double helix together.
Protein synthesis
DNA carries the instructions (genes) a cell needs to correctly make proteins e.g. Hormones, Enzymes. Proteins have a variety of jobs within cells and in large multicellular organisms like us, these proteins distinguish our characteristics e.g. Hair colour.
Cell division
Cell division is essential to allow organisms to grow new cells and repair damaged cells e.g. Cuts and broken bones. Cell division is the process of one cell dividing into two daughter cells that are identical to the original cell. This process is called MITOSIS. Some animal cells are capable of regenerating damaged tissues. The degree of regeneration depends on the species of animal. Some animals can heal whole limbs but humans are only capable of healing wounds and broken bones. Cancer is the uncontrolled division of mutant cells in the body. Cells growth is affected by oxygen concentration, temperature and pH.
