- Created by: suhayb
- Created on: 03-12-18 01:17
biology paper 1 revision
nucleus - controls activities of the cell
cytoplasm - where most of the chemical reactions take place
cell membrane - controls what goes in and out of a cell
mitochondria - where most of the energy is released in respiration
ribosomes - where protein synthesis takes place
chloroplasts - absorb light energy to make food
Magnification = size of image / size of real object
chromosomes - The nucleus of a cell contains chromosomes made of coiled DNA molecules, they are the genetic information. Each chromosome carries a large number of genes. In body cells, the chromosomes are normally found in pairs. Models and analogies can be used to develop explanations of how cells divide.
Cells divide into a series of stages called the cell cycle. There are several stages of the cell cycle, including mitosis.
During the cell cycle, the genetic material is doubled and then divided into two identical cells.
Before a cell can divide it needs to grow and increase the number of subcellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.
In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
Finally, the cytoplasm and cell membranes divide to form two identical cells.
Cell division by mitosis is important in the growth and development of a multicellular organism
transport in cells
Dissolved substances move by diffusion and by active transport.
Water often moves across boundaries by osmosis. Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules.
Differences in the concentrations of the solutions inside and outside a cell cause the water to move into or out of the cell by osmosis.
Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.
This process enables cells to absorb substances from very dilute solutions.
Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Plants require ions for healthy growth.
It also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
the digestive system
The digestive system is an example of an organ system in which several organs work together to digest and absorb food.
The digestive system includes:
Glands, such as the pancreas and salivary glands, which produce digestive juices
Stomach and small intestine, where digestion occurs
Liver, which produces bile
Small intestine, where the absorption of soluble food occurs
The large intestine, where water is absorbed from the undigested food, producing faeces.
The heart is an organ that pumps blood around the body in a double circulatory system. Much of the wall of the heart is made from muscle tissue.