1 Cell Structure & Function

It wasn’t until the 1600s that scientists were able to use microscopes to observe living things.

Cells In 1665, Robert Hooke observed cork cells under the microscope. He called them cells. This is a drawing he made of the cork cells.

Leeuwenhoek’s Microscope Anton Van Leeuwenhoek used a single- lens microscope to view pond water and other things.

Use light to view objects Magnify up to 2000 times Able to view living or preserved specimens

Electron Microscope Magnify up to 200,000 Takes place in a vacuum Not able to view live specimens

Cells Smallest unit of life that can carry on functions of life Diverse in size and structure Shape is related to its function

Living Things can be Multicellular or Unicellular Unicellular: made up of one cell Multicellular: made up of many cells

The Cell Theory Cells are the basic unit of life Cells are the basic unit of life All organisms are made of one or more cells All organisms are made of one or more cells All cells arise from existing cells All cells arise from existing cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Size The logistics of carrying out cellular metabolism sets limits on the size of cells Small cells function more efficiently than large cells because they have a higher surface-area- to-volume ratio Large cells would take too long to exchange need materials – Diffusion & Osmosis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Size Surface area increases while total volume remains constant Total surface area (height  width  number of sides  number of boxes) Total volume (height  width  length  number of boxes) Surface-to-volume ratio (surface area  volume)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Common Features to All Cells Some cell parts are common to all types of cells – Cell Membrane – Cytosol (Cell Fluid) Cytoplasm – Ribosomes – Chromosomes (DNA)

Types of Cells Cells are classified as prokaryotic or eukaryotic. Prokaryotic cells have genetic material that is not inside a nucleus (no nucleus). Eukaryotic cells have genetic materials in a nucleus. (“true” nucleus)

Two Major Classes of Cells  Prokaryotic cells The smallest, most simple cells. They live in a broad range of environments. Lack a nucleus and other organelles. Have a single chromosome in a region called the nucleoid Have a cell wall outside the membrane that provides structure and support. Many use flagella (long, tail-like structures) for locomotion Ex. Bacteria

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic Cells Gram-positive – Thick single layer wall that retains a violet dye from Gram stain procedure Gram-negative – Multilayered wall does not retain dye Susceptibility of bacteria to antibiotics depends on cell wall structure.

Cell Structures Cells contain small structures called organelles. Each organelle has a specific task it performs in the cell.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) A thin section through the bacterium Bacillus coagulans (TEM) Pili: attachment structures on the surface of some prokaryotes Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane) Ribosomes: organelles that synthesize proteins Plasma membrane: membrane enclosing the cytoplasm Cell wall: rigid structure outside the plasma membrane Capsule: jelly-like outer coating of many prokaryotes Flagella: locomotion organelles of some bacteria (a) A typical rod-shaped bacterium 0.5 µm Bacterial chromosome Figure 6.6 A, B

Two Major Classes of Cells  Eukaryotic cells More complex, organized cells. Posses a true nucleus and other organelles. Ex. - plant and animal cells The cells in our bodies are EUKARYOTIC!

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A animal cell Rough ERSmooth ER Centrosome CYTOSKELETON Microfilaments Microtubules Microvilli Peroxisome Lysosome Golgi apparatus Ribosomes In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) Nucleolus Chromatin NUCLEUS Flagelium Intermediate filaments ENDOPLASMIC RETICULUM (ER) Mitochondrion Nuclear envelope Plasma membrane Figure 6.9

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A plant cell In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata CYTOSKELETON Ribosomes (small brwon dots) Central vacuole Microfilaments Intermediate filaments Microtubules Rough endoplasmic reticulum Smooth endoplasmic reticulum Chromatin NUCLEUS Nuclear envelope Nucleolus Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Golgi apparatus Peroxisome Tonoplast Centrosome Plasma membrane Mitochondrion Figure 6.9

Basic Cell Structures

Separates cells contents from its environment Made up of 2 layers of phospholipids Controls what enters and leaves the cell Proteins are embedded in the membrane

The cytoskeleton is a network of protein filaments that helps the cell maintain its shape. It is also involved in movement.

Cytoplasm The cytoplasm (AKA cytosol) is the fluid outside the nucleus. It contains the organelles. Many chemical reactions occur here.

Control center of the cell Contains genetic material Surrounded by the nuclear envelope Nucleolus: darkly stained portion of the nucleus that produces ribosomes

Ribosomes are protein assembly organelles. The ribosome connects the amino acids. Ribosomes can be “free” in the cytoplasm or on the endoplasmic reticulum.

The endoplasmic reticulum is the site where lipids of the cell membrane are assembled, along with proteins and other materials. It can contain ribosomes and be Rough ER or have no ribosomes and be Smooth ER

The golgi apparatus modifies, sorts, and packages proteins and other materials from the ER. These materials are then stored or secreted.

Lysosomes Lysosomes are small organelles that contain enzymes. These enzymes breakdown lipids, carbohydrates, and proteins into small molecules that can be used by the cell. Lysosomes also remove “junk and clutter” in the cell.

Mitochondria The mitochondria is the organelle that converts chemical energy from food into ATP to power cell processes.

Inflexible structure that surrounds the plasma membrane Made of different substances in different organisms Found in plants, algae, and some bacteria and fungi

Central Vacuoles Vacuoles are storage organelles. They store water, salts, proteins, etc. Plants have a large Central Vacuole that helps plants support leaves and stems.

Chloroplasts are organelles that capture sunlight energy and convert it into chemical energy in a process known as photosynthesis.