Science - Grade 10 Biology - Cells

Cells

The Cell

• The basic unit of life
• Self-replicating
• Bound by a membrane
• May contain organelles with specific structures and functions
• Contains biological molecules like DNA, proteins and sugars

Cell Theory

• All living things are made up of one or more cells and the products of those cells
• Cells are the functional units of life
• All cells come from pre-existing ones

Types of Cells

Prokaryotic Cells

• Simple Cells
• No nucleus
• No organelles
• e.g. bacteria

Eukaryotic Cells

• More complex cells
• Nucleus
• Membrane-bound organelles
• e.g. plant cells, animal cells, protists and fungi

Specialized Animal Cells

• Red blood cells
• Cheek cells
• Sperm and egg cells
• Brain cells

Organelles

• Little “organs” of cells
• Membrane-bound
• Allow for cellular functions like:
  • DNA replication
  • cell division
  • excretion of wastes

Cell Wall

• Protects the cell
• Gives shape
• Made of cellulose
• Found in plants, algae, fungi, & most bacteria

Cell Membrane

• Outer covering, protective layer around ALL cells
• For cells with cell walls, the cell membrane is inside the cell wall
• “selectively permeable”
  • Allows food, oxygen, and water into the cell and waste products out of the cell
  • Diffusion and Osmosis

Cytoplasm

• Gelatin-like inside cell membrane
• Constantly flows
• Holds organelles in place

Cytoskeleton

• Scaffolding-like structure in cytoplasm
• Helps the cell maintain or change its shape
• Made of protein

Nucleus

• Directs all cell activities
• Contains DNA – hereditary instructions for everything the cell does
• Usually the largest organelle

Nucleolus

• Aka “little nucleus”
• Found in the nucleus
• Makes components of ribosomes

Endoplasmic Reticulum

• Network of tubes or membranes
• Carries materials through cell
• Can be
  • Smooth (no ribosomes on the surface)
  • Rough (ribosomes on the surface)

Ribosome

• Small bodies free or attached to the endoplasmic reticulum
• Their function is to produce proteins

Mitochondrion

• Bean-shaped with inner membranes
• Place where sugar molecules are broken down into ENERGY - called “cellular respiration“

Golgi Bodies

• Stack of membrane-bound vesicles
• Packages, modifies and sorts substances to be transported around the cell

Vacuoles

• Fluid-filled sacs found in both plants and animals
• Storage site for food, water, waste

Lysosomes

• Small, round structures with a membrane
• Digestion -breaks down larger food molecules into smaller molecules
• Protection
  • Attack “foreigners”

Chloroplasts

• Green, oval structures found in plant cells ONLY
  • Contain the green pigment chlorophyll
• Place where energy from sun is utilized to make food for the plant
  • called “photosynthesis”

Centrioles

• Cylindrical structures found only in animal cells
• Produce spindle fibres
  • Important for moving chromosomes during cell division

Flagellum

• Found in animal cells
• A projection of the cell that helps with locomotion

Comparison of Plant and Animal Cells

Animal Cell

• Only a cell membrane
• No chloroplasts
• Centrioles
• Lysosomes present
• Irregular shape
• Many tiny vacuoles

Plant Cell

• Cell wall and cell membrane
• Chloroplasts
• No centrioles
• Lysosomes uncommon
• Regular shape
• Usually only one large vacuole