Cells and Cell Structures

All animals are made up of millions of cells. The cells of most animals haveCell membrane- made mostly of fat, holds it all together and controls what can go in and out of the cell.Cytoplasm- watery substance surrounding the nucleus, in which many chemical reactions happen, which are controlled by enzymes.Organelles: Nucleus- controls the cells activities and contains DNA, which is needed so that the cell knows how to synthesise the chemicals needed. Mitochondria- use glucose in respiration to produce energy. Ribosomes- they synthesise proteins from amino acids. These are then used to make other parts of the cell and enzymes.

Nucleus- controls the cells activities and contains DNA, which is needed so that the cell knows how to synthesise the chemicals needed. Mitochondria- use glucose in respiration to produce energy. Ribosomes- they synthesise proteins from amino acids. These are then used to make other parts of the cell and enzymes.

Electron microscopes can magnify up to 500,000 times, and its with these that you can see the smaller organelles. These include mitochondria and ribosomes.

Cell Specialisation

Specialised cells have a specific shape which enables them to carry out their jobs efficiently.

Stores fat that can be used for energy. Has less cytoplasm and mitochondria. Can expand up to 1000x.

Large nucleus. Digestive enzymes in tip (to get to the egg). Many mitochondria, and a long tail (to help it to swim fast).

Long and thin. Branches of cytoplasm at each end allow it to pass impulses along to other nerve cells.

The cilia (tiny hairs can move particles along.

Large surface area but small diameter. No nucleus. Contain haemoglobin. Thin outer membrane.

Elongated. Contain many mitochondria. Have fibrils, so can shorten in length.

Large in diameter. Contains stored food that will allow a baby to grow if fertilised. Large nucleus.

Plant and Alga Building Blocks

As with animal cells, plant cells usually have

Cell membrane Cytoplasm Nucleus Mitochondria Ribosomes

However, they also have

A cell wall- made of cellulose, which strengthens the cell and gives it support.

Some plant cells have

Chloroplasts- contain chlorophyll, which is needed to absorb the Sun's light energy (and is therefore needed for photosynthesis. A vacuole- contains cell sap (a sugar and salt solution), but also helps keep the cell rigid.

Specialised Cells

Purpose is to absorb light and photosynthesise. Lots of chloroplasts. Large surface area.

Found in roots. Large surface area, to absorb water and minerals from the soil. Thin cell wall, so water can pass through more easily.

Hollow tubes, dead. Walls contain ligain.

Half-circle shape. Found in pairs. If the stomata are too big, water will be lost.

Bacteria

They are the most abundant cells on Earth.

Cell membrane- controls what goes in and out of the cell.Circular chromosome made out of DNA.Soft cell wall- holds it together and protects it.Cytoplasm- where the cell's reactions happen.Plasmids- small circles of DNA that also contain genes to make proteins.

Yeast

Yeast is a single-celled fungus. About 10 times bigger than bacterial cells.

Getting In and Out of Cells

Diffusion

Movement of a substance by random motion from a region of high concentration to a region of lower concentration.Net movement is the overall movement of particles from an area of higher concentration of one of lower concentration.Concentration gradient is the difference in the concentration of a substance in two different areas. (If you start with a much greater concentration gradient, diffusion will be faster.

Specialised Organ Systems

To begin with, we all came from a single fertilised cell. As we developed and grew, our cells started to differentiate. I.e. they adapted to serve different purposes. Similar cells group together as a tissue, like epithelial tissue or glandular tissue in animals, or epidermal tissue or mesophyll tissue in plants.Different tissues can work together as an organ. These have a certain purpose. E.g stomach, to store and digest food. Made up of glandular, epithelial and muscular tissues. Plants have organs too- like leaves (photosynthesis), roots (absorb water and minerals) and stems (holds leaf up).Different organs work together in a specialised organ system, like the digestive system.

Diffusion through Cell Membranes

All plant and animal cells have cell membranes, and they have tiny holes in them, which allow some particles to pass through by diffusion. Cells membranes are partially permeable membranes, because small particles can get through while big ones cannot.The net movement is always from the higher to lower concentration, when they are different.There are five cell membranes for an oxygen molecule to pass through from an alveolus in the lung to a red blood cell. Fast rate of diffusion keeps the cell alive and allows it to be transported around the body straight away.

Animal Building blocks

plant and alga building blocks

bacteria and yeast cells

getting in and out of cells

specialised organ systems