Cellular Life Processes Biology 2.4 Cellular Life Processes
Bio 2.4 Cell Bits Biological ideas, as they relate to each of the life processes at the cellular level, are selected from: • reasons for similarities and differences between cells such as cell size and shape, type and number of organelles present. Limited to plant and animal cells
Cell wall A rigid structure made of cellulose surrounding plant cells. This provides shape and strength.
Cell membrane A layer that encloses the cell contents. Plant cell A layer that encloses the cell contents. Controls what enters and exits the cell. Animal cell
Cell membrane Is made of two layers of lipid (fat) molecules with proteins for cell identification, active transport and communication.
Cytoplasm fills the interior of the cell. It consists of a liquid (called the cytosol that contains water, proteins and dissolved ions) and cell organelles. It is used to transport substances throughout the cell and create internal pressure and is where most chemical reactions occur.
Nucleus Contains the genetic material which controls the cells activities. nucleoplasm Nucleolus: round structure inside nucleus: produces the ribosomal RNA
Nuclear membrane Separates the contents of the nucleus from the cytoplasm. Perforated by pores and continuous with ER.
Chromosomes Structures made of DNA and protein containing genes for protein synthesis.
Mitochondria Organelles within the cytoplasm for cell respiration - where food molecules are broken down to release energy.
Chloroplast Starch granule Membrane Stroma Grana Organelles in plant cells containing chlorophyll for photosynthesis.
Centriole Mostly present in animal cells for cell division. Produces spindle fibres for separating chromosomes. Centrioles
Vacuole Liquid-filled organelle in cytoplasm for creating pressure and storing water and dissolved substances.
Ribosome Organelle found free in the cytoplasm or attached to ER. Used for protein synthesis. <> <>
Endoplasmic reticulum Is a system of membranes and connecting tubes that provide a surface for chemical reactions and a pathway for moving material within the cell. Smooth ER Rough ER
RER vs SER RER Produces proteins (both secreted & part of cell membrane) SER Produces lipids, steroids Metabolises carbohydrates Regulates calcium levels
Lysosome Membrane-bound sac containing digestive enzymes. Breaks down food and worn out cell parts.
Golgi body a series of membrane-bound sacs for producing and releasing secretions.
Plant Cells have: rigid cell walls giving the plant cells a geometric shape; chloroplasts (usually); starch granules large central vacuole They are usually larger than animal cells.
Become specialised to perform support, absorption of water, conduct liquids, allow gases in and out, manufacture food, form protective surfaces and reproduction.
Animal Cells don’t have a cell wall and have centrioles and an irregular shape. Become specialised to perform specific tasks. Humans have over 200 different kinds of cells.
Similarities and differences
Cell size
Cell size is limited by the rate at which essential nutrients and oxygen can diffuse into a cell and waste products can be removed.
Cell shape is determined by the role of the cell. Nerve cells are long and thin to conduct neural messages around the body. Intestinal cells have frilly edges to increase surface area for rapid diffusion.
Egg cells are spherical and large to contain organelles and nutrients for the zygote. Sperm cells have a long flagellum and many mitochondria for fast movement.
RBC’s are disc-shaped with rounded edges for easy passage through blood vessels. Many cells are flat to increase the surface area, reduce travelling distance and increase diffusion rates
Relative numbers of organelles present Secretory cells (e.g. glands) have large numbers of golgi bodies. Highly active cells (e.g. muscle) have larger numbers of mitochondria.
Leaf cells contain large numbers of chloroplasts. Root cells have a large surface area for efficient water absorption.