Cell Structure and Function

Cells
• Smallest living unit
• Most are microscopic

Cell Size

Cells Have Large Surface
Area-to-Volume Ratio

Characteristics of All Cells
• Cell Membrane (Plasma Membrane)
• Cytoplasm – cell contents in thick fluid
• Control center with DNA

• Prokaryotic
• Eukaryotic
Cell Types

Prokaryotic Cells
• First cell type on earth
• Cell type of Bacteria and Archaea

Prokaryotic Cells
• No membrane bound nucleus
• Nucleoid = region of DNA concentration
• Organelles not bound by membranes

Eukaryotic Cells
• Nucleus bound by membrane
• Include fungi, protists, plant, and animal cells
• Possess many organelles
Protozoan

Representative Animal Cell

Representative Plant Cell

Cytoplasm
• Viscous fluid containing organelles
• components of cytoplasm
– Interconnected filaments & fibers
– Fluid = cytosol
– Organelles (not nucleus)
– storage substances

Nucleus
• Double membrane filled with nucleoplasm
• Control center of cell
• Houses and protects cell’s genetic info
• Control’s cells functions

DNA
• Hereditary material
• Chromosomes
– DNA and protein
– Only visible when cell is dividing (but present all the time)

Nuclear Envelope and Pores
• Double membrane
• Separates nucleus from rest of cell
• Has pores
• Allows only certain materials to enter and exit nucleus

Nucleolus
• Dark dense area inside nucleus
• Where DNA is concentrated when making ribosomal RNA

Cell (Plasma) Membrane
• Double layer of phospholipids, proteins and cholesterol
• Contains cell contents
• Controls what enters/exits the cell

Endoplasmic Reticulum
• Helps move substances within cells
• Network of interconnected membranes
• Two types
– Rough endoplasmic reticulum
– Smooth endoplasmic reticulum

Rough Endoplasmic Reticulum
• Ribosomes attached to surface
• Helps to move proteins around cell
• May modify proteins from ribosomes

Smooth Endoplasmic Reticulum
• No attached ribosomes
• Helps to make lipids
• Detoxifies and breaks down harmful chemicals

Ribosomes
• Attached to ER or free floating in cytoplasm

Golgi Apparatus
• Stack of flattened membranes
• Packaging & shipping station of cell
• Proteins go here after leaving ER and are modified and shipped out of cell in small sacs called vesicles

Lysosomes
• Small sac-like structures
• Contain digestive enzymes
• Functions
– Recycling centers
– Break down old cell parts
– Digests invaders
• Found in animal cells

Peroxisomes
• Small sac-like structures
• Abundantly found in liver and kidneys
• Help to detoxify
• Names for the hydrogen peroxide they produce as a waste from their reactions .

Mitochondria
• Break down sugars and fats in cellular respiration and release energy in the form of
ATP
• Cells that need more energy have more

Mitochondria
• Has its own DNA
(endosymbiotic theory)

Cytoskeleton
• Filaments & fibers
– Microfilaments
– Microtubules
– Intermediate filaments
• 3 functions:
– mechanical support
– anchor organelles
– help move substances
• Include cilia, flagella and centrioles

Centrioles
• Pairs of microtubular structures
• Play a role in cell division
• Found only in animal cells

Cell Walls
• Found in plants – composed of cellulose
• Surrounds plasma membrane
• Provides support, strength and protection

Central Vacuoles
• Membrane bound storage sacs
• In plants
• Very large
• Contents
– Water
– Food
– Wastes
*animals have small vacuoles throughout cell

Chloroplasts
• Solar energy capturing organelle – carry out photosynthesis
• Contain chlorophyll and are green
• Have their own DNA

Chromoplast
• Contain pigments
• Help capture more light energy for photosynthesis
• Help to make other parts of the plants other colors
(fruits, flowers, roots etc.)

End Chapter 5