Biology Unit 2
Animal and plant cells.
Animal and plant cells have some structures in common; they have:
- A nucleus to control the cell's activities
- Cytoplasm where many chemical reactions take place
- A cell membrane that controls substances coming in and out of the cell
- Mitochondria where most of the energy during respiration is released
- Ribosomes where protein synthesis takes place
Plant cells also have: (NOT all plants cells have chloroplasts or a vacuole)
- A rigid cell wall for support
- chloroplasts that contain chlorophyll for photosynthesis
- A permanent vacuole containing cell sap.
Key words: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, chloroplasts, vacuole.
- Yeast is a single-celled organism
- The cells have a nucleus, cytoplasm and a membrabe surronded by a cell wall
- Bacterium is a single-celled organism.
- A bacterial cell consists of cytoplasm and a membrane surroded by a cell wall
- The genes are not in a distinct nucleus.
Cells may be speacialised to carry out a particular function. (Need to know how structure makes them suitable to carry out the job it does.)
- Root hair cell- has a large surface area to absorb water and minerals easily. Close to xylem tissue that carries water to the rest of the plant
- Plisade cell- Column shaped cells canbe packed tightly together at upper surface of leaf. Packed with chloroplasts for photosynthesis.
- Sperm cell- Large nucles (for genetic info). Long tails allow sperm to swim to the egg. Middle section contains many mitochondria to provide the energy to move the tail.
- Fat cell- Small volume of cytoplasm leaves more room for fat. Few mitochondria present (un-needed). Fat cells can expand as they fill with fat.
- Cone from the human eye- Outser sement contains visual pigment which breaks down into ligh. Mitochondria in middle section provide energy to remake visual pigment.
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
Factors affection diffusion.
- Surface area: The larger the surface area, the faster the diffusion.
- Temperature: Higher temperature. the faster the diffusion
- Distance: The shorter the distance, the faster the dffusion.
- Steep concentration gradient, big diffusion. (shallow concentration gradient, small diffusion)
Tissues, Organs and Organ systems.
The cells of multicellular organisms may differentiate and become adapted for specific functions. Tissues are aggrergatioms (a collection) of similar cells; organs are aggregations of tissues performing specific physiological functions. Organs are organised into organ systems, which work together to form organisms.
Examples of animal tissues include:
- Muscular tissue, which can contract to bring about movement
- Glandular tissue, which can produce substances such as enzymes and hormones.
- Epithelial tissue, which covers some parts of the body.
The stomach is an organ that contains:
- Muscular tissue, to churn the contents
- Glandular tissue, to produce digestive juices
- Epithelial tissue, to cover the outside and the inside of the stomach
The digestive system
- Glands, such as the pancrease and salivary glands, which produce digestive juices
- The stomach and small intestine, where digestion occurs