Unit 3: Cell structure and function Mrs. P Biology Unit 3: Cell structure and function

Cell Theory In 1665, Englishman Robert Hooke used an early light microscope to look at a thin slice of cork. Under the microscope, cork seemed to be made of thousands of tiny, empty chambers. Hooke called the chambers “cells”.

Cell Theory By 1855, it was clear that cells were the basic units of life, and the Cell Theory was born. The cell theory states: All living things are made of cells Cells are the basic units of structure and function in living things. New cells are produced from existing cells.

LEVEL OF ORGANIZATION The levels of organization in multicellular organisms: Cells g tissues g organs g organ systems g organism

TWO MAJOR TYPES OF CELLS Cells fall into 2 major categories: prokaryotes and eukaryotes.

Prokaryotes (pro = before, karyon = nucleus, so literally “before nucleus” Generally smaller than eukaryotes. Lack a nucleus and membrane bound organelles.

Prokaryotes Store genetic material in one circular DNA molecule called a nucleoid. Have a cell wall made of peptidoglycan.

Eukaryotes eu = true, karyon = nucleus, so literally “true nucleus” Generally bigger than prokaryotes Have a nucleus and cytoplasm (gel like material inside)

Eukaryotes Have membrane bound organelles (literally “little organs”) that carry out different functions. Store genetic material in the nucleus.

PARTS OF THE CELL A eukaryotic cell is like a microscopic factory. It is filled with organelles, each of which has its own job. Most biologists divide the cell into two major parts: the nucleus and the cytoplasm. The cytoplasm is the part of the cell outside of the nucleus.

All cells except prokaryotes Cell Structure Type of Cell Structure Function Nucleus All cells except prokaryotes In the center of the cell, surrounded by a nuclear envelope. Envelope has pores, which allow things to move in and out of the nucleus. Controls all of the cell’s activities Contains the genetic material for the cell (chromatin/chromosomes) Plasma Membrane

Regulates what enters and leaves the cell. Cell Structure Type of Cell Structure Function Plasma Membrane ALL cells Made of a lipid bilayer, with proteins embedded inside and carbs attached to the proteins. “Fluid Mosaic Model” Regulates what enters and leaves the cell. Provides protection and support. Cell wall

Regulates what enters and leaves the cell. Cell Structure Type of Cell Structure Function Plasma Membrane ALL cells Made of a lipid bilayer, with proteins embedded inside and carbs attached to the proteins. “Fluid Mosaic Model” Regulates what enters and leaves the cell. Provides protection and support. Cell Wall Plants Fungi Prokaryotes Outside of the plasma membrane. Made of cellulose in plants, chitin in fungi, peptidoglycan in prokaryotes. Structural support (grow tall) Protection allows H2O, O2, CO2 to diffuse in & out of cell

Synthesize (make) proteins. Cell Structure Type of Cell Structure Function Ribosome ALL cells Small particles of RNA and protein found throughout the cytoplasm or attached to the Rough ER. Synthesize (make) proteins. Mitochondria

Synthesize (make) proteins. Cell Structure Type of Cell Structure Function Ribosome ALL cells Small particles of RNA and protein found throughout the cytoplasm or attached to the Rough ER. Synthesize (make) proteins. Mitochondria All eukaryotic cells Shaped like a peanut, it has a double membrane, the inner membrane has folds called cristae. Converts energy stored in food into energy used in the body (ATP) in a process called cellular respiration.

Rough ER has ribosomes attached to its surface, smooth ER does not. Cell Structure Type of Cell Structure Function Endoplasm Reticulum Eukaryotic cells Rough ER has ribosomes attached to its surface, smooth ER does not. Helps with protein synthesis Where lipids in the cell are made Golgi Apparatus

Rough ER has ribosomes attached to its surface, smooth ER does not. Cell Structure Type of Cell Structure Function Endoplasm Reticulum Eukaryotic cells Rough ER has ribosomes attached to its surface, smooth ER does not. Helps with protein synthesis Where lipids in the cell are made Golgi Apparatus Stacks of flattened sacs Modifies, sorts, and packages proteins and other materials made in the cell. Helps to “ship” materials out of the cell.

Plant cells have one big vacuole Cell Structure Type of Cell Structure Function Vacuoles Plant cells have one big vacuole Animal cells have smaller vacuoles (called vesicles) Fluid filled sacs Largest organelle in plant cells Store materials like carbohydrates water, salt, and proteins. Structural support in plants. Chloroplasts

Plant cells have one big vacuole Cell Structure Type of Cell Structure Function Vacuoles Plant cells have one big vacuole Animal cells have smaller vacuoles (called vessicles) Fluid filled sacs Largest organelle in plant cells Store materials like carbohydrates water, salt, and proteins. Structural support in plants. Chloroplasts Plant cells Contain chlorophyll (green) Have small stacks of thylakoids called grana Capture energy from sunlight and convert into chemical energy (photosynthesis)

Small organelles filled with enzymes Cell Structure Type of Cell Structure Function Lysosomes Eukaryotic cells Small organelles filled with enzymes Breaks down large food molecules into smaller molecules for the cell Breaks down old cell parts Cytoskeleton

Small organelles filled with enzymes Cell Structure Type of Cell Structure Function Lysosomes Eukaryotic cells Small organelles filled with enzymes Breaks down large food molecules into smaller molecules for the cell Breaks down old cell parts Cytoskeleton Made of protein filaments Microfilaments (actin) and microtubules (tubulin) helps the cell to maintain its shape helps with cell division

Cell Specialization Organisms that are made up of many cells are called multicellular Gene expression is especially important in shaping the way a multicellular organism develops.

Each of the specialized cell types found in the adult develops from the same fertilized egg cell.

Cells throughout an organism develop in different ways to perform different tasks. This process is called cell specialization.

Different types of cells have different types of shapes and parts so that they can perform different functions.

A series of genes called the HOX genes control the differentiation of the cells and tissues in the embryo.

During the process of differentiation, only specific parts of the DNA are activated. Different parts of the genetic instructions are used in different types of cells (this is influenced by the cell’s environment)

Because all the cells in an organism contain the same DNA, they initially have the potential to become any type of cell; however, once a cell differentiates, the process cannot be reversed.

SPECIALIZED CELLS Neuron – cells that carry messages throughout the nervous system. Have an axon to send electrical impulses over long distances and dendrites to pass and receive messages from other nerve cells.

Red Blood cells – have a small disc like shape to increase the surface area for oxygen absorption; hemoglobin binds and carries oxygen; no nucleus to make more space for the hemoglobin

Muscle cells - A muscle cell is generally elongated and elastic containing mitochondria in large number. The elongated and elastic feature helps muscle tissues to contract; the mitochondria make more ATP for the cell.

Xylem – have a thick cell wall and hollowed center; used to transport water upward from the roots of a plant

Phloem – a specialized plant tissue used for transporting nutrients and glucose; made of specialized cells called sieve tube cells and companion cells.

Stomata – Where transpiration occurs in a plant Stomata – Where transpiration occurs in a plant. Guard cells surround the stoma and open and close to let water in or out.

Stem Cells Stem cells – unspecialized cells that continually reproduce. Stem cells can be turned into different specialized cells. Sources of stem cells include:

Embryonic stem cells – found in an embryo; controversial because have to destroy the embryo; are pluripotent (can turn into almost any type of cell)

Adult stem cells – found mostly in bone marrow, but also in liver, brain, skin, and some muscle cells; not as useful as embryonic stem cells.

Umbilical cord/placenta – doctors can now collect an infant’s cord blood; can be used to cure some cancers, blood disorders, and immune disorders. (636) 733-4100 (636) 733-4100