B2.1 Cells, Tissues and Organs

BOTH Plants and Animal cells contain:

• Nucleus - Contains genetic material, which controls the activities of the cell
• Cytoplasm - Most chemical processes take place here, controlled by enzymes
• Cell Membrane - Controls the movement of substances into and out of the cell
• Mitochondria - Most energy is released by respiration here
• Ribosomes - Protien synthesis happens here 

ONLY Plant cells also contain:

• Cell Walls - Strenghtens the cell
• Chloroplasts - Contains chlorophyll, which absorbs light energy for photosynthesis 
• Permenant Vacuole - Filled with cell sap to help keep the cell turgid 

Bacteria:

• A bacterium is a single-celled organism.
• A bacteria cell has a different structure to an  animal or plant cell
• It consists of a cytoplasm and a membrane surrounded by  a cell wall
• The genetic material in a baterium is not in a distinct nucleus 

Yeast

• Is a single-celled organism
• They have a nucleus, cytoplasm and a membrane surrounded by a cell wall
• (They are the same as bacteria cells but with a nucleus)

CellFunctionAdaption

Leaf cell

Absorbs light energy for photosynthesis Packed with chloroplasts. Regular shaped, closely packed cells form a continuous layer for efficient absorption of sunlight.

Root hair cell

Absorbs water and mineral ions from the soil Long 'finger-like' process with very thin wall, which gives a large surface area.

Sperm cell

Fertilises an egg cell - female gameteThe head contains genetic information and an enzyme to help penetrate the egg cell membrane. The middle section is packed with mitochondria for energy. The tail moves the sperm to the egg.

Red blood cells

Contains haemoglobin to carry oxygen to the cells.Thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus, so the whole cell is full of haemoglobin.

Dissolved substances can move in and out of cells by diffusion 

Diffusion is the spreading of the particles of gas or any substance in solution from a region where they are of a higher concentration to a region with a lower concentration.

The greater the difference in concentration the faster the rate of diffusion 

Examples:

LocationParticles moveFromTo Gut Digested food products Gut cavity Blood in capillary of villus Lungs Oxygen Alveolar air space Blood circulating around the lungs

Multicellular organisms develop sustems for exchanging materials. During the development of a multicellular organism, cells differentiate so they can perform different functions.

During the development of a multicellular organism, cells differentiate so that they can carry out different functions. Differentiation is the process by which a cell becomes a specialised type of cell.

Tissues -

A tissue is a group of specialised cells that have a similar structure and function.

Types of tissues and their functions:

• Muscular Tissue - Contracts, bringing about movement
• Glandular Tissue - Produces substances such as enzymes and hormones
• Epithelial Tissue - Covers some parts of the body 

Cells - Tissues - Organ - Organ System 

Organs are made of tissues. A particular organ may contain several different tissues.

E.g. In the stomach there is....

• Muscular tissues - To churn the food and other contents of the stomach 
• Glandular tissue - To produce digestive juices such as acids and enzymes
• Epithelial Tissue - To cover the inner and outer surfaces of the stomach 

The four main organ systems in the body....

• The nervous system
• The respitory system
• The reproductive system
• The digestive system

Parts and functions of the parts of the digestive system:

• Glands - Such as the pancreas and salivary glands which produce digestive juices
• The stomacha and small intestine - Where digestion occurs
• The liver - Which produces bile
• The small intestine - Digest and absorb soluable foods 
• The large intestine - Absorbs water from undigested food, producing faeces.

Plant organs include...Stems, roots and leaves
.

Tissues-

• Epidermal tissues - Cover the plant
• Mesophyll - Carries out photosynthesis
• Xylem and phloem - Transport substances around the plant 

Leaves- Adapted for absorbing sunlight through photosynthesis

Adaptation and Purpose 

• Chlorophyll - Absorb sunlight
• Large surface area - To absorb more light
• Stomata - To let carbon dioxide diffuse into the leaf
• Thin - Short distance for carbon dioxide to diffuse into leaf cells
• Network of veins - To support the leaf and transport water and carbohydrates

AdaptionPurpose Thin, waxy cuticlemade of wax To protect the leaf without blocking out light Thin, transparentepidermis To allow more light to reach the palisade cells Layer of palisade cells on the top surface To absorb light Many chloroplasts in the palisade cells To increase absorption of light Spongy mesophyllinside the leaf Air spaces allow carbon dioxide to diffuse through the leaf, and increase the surface area

AdaptionPurpose Thin, waxy cuticlemade of wax To protect the leaf without blocking out light Thin, transparentepidermis To allow more light to reach the palisade cells Layer of palisade cells on the top surface To absorb light Many chloroplasts in the palisade cells To increase absorption of light Spongy mesophyllinside the leaf Air spaces allow carbon dioxide to diffuse through the leaf, and increase the surface area