Download The basic structural and functional unit of all organisms. A cell is the

Cells
The basic structural and functional unit of all organisms.
A cell is the smallest unit that can carry on all of the processes of life.
Discovery of Cells:
Scientists:
Robert Hooke (1665) – used an early
microscope to see cork cells. He
coined the word “cells”. He
mentioned that the cork cells
reminded him of “a great many little
boxes”.
Anton van Leeuwenhoek (1673) –
was the first to observe living cells.
(algae)
Discovery of Cells:
More Scientists:
Matthias Schleiden (1838) concluded that all plants were
composed of cells.
Theodor Schwann (1839) –
concluded that all animals were
composed of cells.
Rudolf Virchow (1821 – 1902) –
Observed that all cells come from
other cells
The Cell Theory:
These scientists’ discoveries led to the Cell Theory:
1. All living organisms are composed of one or
more cells.
2. Cells are the basic unit of structure and
function in an organism.
3. Cells come only from the reproduction of
existing cells.
I. Introduction:
A. Two types of cells:
1. Prokaryotes
• Generally single
celled organisms
like bacteria.
• Do NOT contain a
nucleus or other
membrane
organelles.
• Came about first
• DNA is in an area
called nucleoid
2. Eukaryotes
• Single or
multicellular
organisms
• Have nucleus and
membrane bound
organelles
I. Introduction
B. How many cells?
•
Some organisms are single cellular.
•
•
Bacteria
Some organisms are multicellular
•
75 trillion cells in the human adult.
C. How big are cells?
•
Different cells are different
sizes.
•
Basically, cells are just large
enough for their organelles
•
The average size is 10
microns
I. Introduction
Biggest reason for cell size:
SURFACE TO VOLUME RATIO
• In order for cells to survive, they must
constantly exchange ions, gases,
nutrients, and wastes with their
environment. These exchanges take
place at the cell’s surface. To perform
this function efficiently, there must be
an adequate ratio between the cell’s
volume and its surface area. As a cell’s
volume increases, its surface area
increases, but at a decreased rate. If you
continued to increase the cell’s volume,
it would soon be unable to efficiently
exchange materials and the cell would
die. This is the reason that the kidney
cell of an elephant is the same general
size as a mouse kidney cell.
I. Introduction
D. Cell Shapes
1. Most cells are cubodial or spherical.
2. SHAPE DETERMINES THE FUNCTION
•
•
•
•
Nerves Cells – elongated to reach out;
receive and transmit impulses
Epithelial Cells – thin and flattened to cover
the body
White Blood Cells – change shape to
surround infectious disease cells
Muscle cells – slender, rod-like to pull parts
closer.
Organelles
The following organelles are in both
prokaryotic and eukaryotic cells.
II. Cell Membrane
(also known as Plasma Membrane)
A. Cell Membrane Function
1. Separates cell from its external
environment
2. Gives cell its shape
3. Site of many metabolic reactions
4. Communication with other cells.
II. Cell Membrane
B. Cell Membrane Structure
1. Fluid Mosaic Model
a. lipid bilayer acts as a liquid
b. lipids and proteins change position
c. many different pieces make it up:
i. phospholipids
ii. Proteins
iii. Carbohydrates and lipids
2. Phospholipid bilayer
a. makes up a majority of the membrane
b. inside is hydrophobic (fatty acids)
c. outside is hydrophilic (phosphate group)
II. Cell Membrane
B. Cell Membrane Structure
3. Proteins
a. aid in communication
b. form pores, gates or channels to allow molecules or
ions to move in and out
II. Cell Membrane
B. Cell Membrane Structure
4. Carbohydrates
a. bound to protein
b. allows cells to recognize each other and communicate
III. Cytosol & Cytoplasm
A. Cytosol:
• Jelly-like material
inside the cell.
• Surrounds organelles
B. Cytoplasm:
• All organelles and cytosol in the
cell except nucleus and plasma
membrane.
• Is in constant motion
(Cytoplasmic Streaming)
IV. Ribosomes
• Most numerous organelle
• Site of proteins synthesis
• Round, granular structures
Last slide
Organelles
The following organelles are in eukaryotic
cells… Both plant & animal cells.
V. Endoplasmic Reticulum (ER)
• Membrane network of folded &
connected sacs and tunnels
• Act as a transport system inside the cell.
• Found in both plant & animal cells
• Two Types
1. Rough ER:
a. has ribosomes
b. produces and transports
proteins
2. Smooth ER:
a. no ribosomes;
b. absorbs fat
c. metabolizes drugs
VI. Golgi Apparatus
1. Flat stacks of membranes that are
unconnected.
2. Modifies proteins from the ER by adding
lipids and carbohydrates
3. Packages the modified protein
4. Secretes the proteins outside the cell.
5. Found in both plants & animal cells.
VII. Mitochondria
1. Carries out cell aerobic respiration
2. Release energy from glucose
3. Makes Adenosine Triphosphate (ATP)
•
ATP provides energy for all cell reactions.
i. Plants get glucose by making it
themselves during photosynthesis.
ii. Animals must eat plants or other
animals to get glucose to make ATP
4. Large, elongated bean shape
• Has 2 membranes an inner & outer
• Inner membrane has many folds called cristae.
i. These improve surface area to volume ratio
for the cell respiration rxn’s that happen
in the mitochondria.
5. Found in both plants & animals.
VIII. Chloroplasts
*Found in plant cells only!
A. Football shaped structure
B. Traps light energy from the sun and
converts it to glucose during
photosynthesis.
C. Key Parts
1. Has 3 membranes:
a. inner & outer like mitochondria.
b. membrane around thylakoids.
2. Chlorophyll: green pigment that
absorbs light energy.
3. Stroma: Fluid inside chloroplasts
inner membrane.
4. Thylakoid: membrane sac
5. Grana: stack of thylakoids
IX. More Plant Cell Only Structures
1. Cell Wall
• Composed of cellulose
• Supports and protects
the plant
2. Central Vacuole
• Large fluid filled
structure
• Contains:
Enzymes, wastes (toxic),
Water, ions, other nutrients
• Provides pressure on the
cell wall that keeps
plants upright.
X. Lysosomes & Vacuoles
*Found in both plant & animal cells
A. Lysosomes
1. Small, round organelles that
contain digestive enzymes.
2. Digests food particles, bacteria
trapped by white blood cells, and
broken cell parts
3. Clean up and waste
management
B. Vacuoles
1. Saclike structures
2. store water, salts, and proteins
3. In animal cells it assists in
endocytosis & exocytosis.
4. Plant cells have a large central
vacuole.
XI. Microtubules and Microfilaments
A. Make up cytoskeleton:
• Shape and support cell
B. Move cellular material
C. Make up centrosomes:
• Found only in animal cells
• Two hollow cylinders at
right angles
• Help distribute
chromosomes during cell
division.
XII. Cilia and Flagella
A.
B.
C.
Function: Cell movement
Structure: Both made of
microtubules
Differences
1. Cilia:
a. Short, hair-likestructures
b. ex.: Cells in nose & throat
2. Flagella:
a. Long, whip-like structures
b. ex. Sperm cells
XIII. Nucleus
A. Controls all cell activities
B. Site where nucleic acids are
made
C. Parts of nucleus
1. Nuclear Envelope w/ pores:
surrounds entire nucleus
2. Chromatin: Fine strands
of DNA and protein (histones)
3. Chromosome: Strand of
chromatin that coils up
during cell division
4 . Nucleolus: Site where
ribosomes are made
Tissues
Groups of cells that carry out a particular
function
XIV. Tissue
Human tissue is organized into 4 categories:
XV. Organ Systems
A. Organs:
Groups of tissue that perform
a specific function
B. Organ Systems:
Groups of organs that perform
a set of related tasks
Remember from simplest to most complex level of organization:
cells  tissues organs  organ systems  organisms