Cells Part 2—What Are Cells Made of?
Cells are mostly made of water.
The structure of the water molecule makes it ideal for dissolving other substances.
Cells are made of macromolecules—when many small molecules join together.
The four types of macromolecules are:
1.__________________________________
2.__________________________________
3,__________________________________
4.__________________________________
Nucleic acids form when long chains of molecules called nucleotides join together.
A nucleotide molecule contains a
phosphate group, sugar and base
Nucleotides are linked together to form chains
Nucleic acids are important in cells because they contain genetic information.
DNA contains two nucleotide chains
wound together in a helical shape
Each human chromosome is a single, long
DNA molecule compacted by proteins
Sub-Cellular Organizational Hierarchy of Life with Examples
Cell
neuron
Organelle
nucleus
genome
chomosome
gene
Macromolecule
DNA
Molecule
nucleotide
Atom
nitrogen
Sub-atomic particles
Protons, neutrons, electrons
The macromolecules that are necessary for nearly everything that cells do are proteins.
Proteins are long chains of amino acid molecules.
A lipid is a large macromolecule that does not dissolve in water.
Macromolecules that do not mix with water play an important role as protective barriers in
cells.
Sugar molecules make up carbohydrates.
Carbohydrates store energy and provide structural support. They are also used for
communication between cells.
Moving Cellular Material
Cell Membrane (Transport) Notes
Cell Membrane and Cell Wall:
ALL cells have a cell membrane made of proteins and lipids
•
SOME cells have cell membranes and cell walls – ex: plants, fungi and bacteria
protein channel
Layer 1
Cell
Membrane
Layer 2
lipid bilayer
protein pump
•
Plant cells have a cell wall made of cellulose – that cellulose is fiber in our diet
•
Bacteria and fungi also have cell walls, but they do not contain cellulose
•
Cell membranes and cell walls are porous allowing water, carbon dioxide, oxygen and nutrients to pass
through easily
Function of the Cell Membrane:
•
Cell membrane separates the components of a cell from its environment—surrounds the cell
•
“Gatekeeper” of the cell—regulates the flow of materials into and out of cell—selectively permeable
•
Cell membrane helps cells maintain homeostasis—stable internal balance
Passive Transport
A process that does not require energy to move molecules from a HIGH to LOW concentration
 Diffusion
 Facilitated Diffusion
 Osmosis
•
•
•
Diffusion is the movement of small particles across a selectively permeable membrane like the cell membrane
until equilibrium is reached.
These particles move from an area of high concentration to an area of low concentration.
outside of cell
inside of cell
Diffusion
HIGH to LOW concentration
• Osmosis is the diffusion of water through a selectively permeable membrane
like the cell membrane
Water diffuses across a membrane from an area of high concentration to an area
of low concentration.
Semi-permeable membrane is permeable to water, but not to sugar
•
Facilitated Diffusion is the movement of larger molecules like glucose through the cell membrane –
larger molecules must be “helped”
Proteins in the cell membrane form channels for large molecules to pass through
Proteins that form channels (pores) are called protein channels
outside of cell
Glucose molecules
inside of cell
Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's
cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to
shrivel.
Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's
cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to
swell and possibly explode.
Isotonic Solutions: contain the same concentration of solute as another solution (e.g. the cell's cytoplasm).
When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The
fluid that surrounds the body cells is isotonic.
Active Transport
Active transport is the movement of molecules from LOW to HIGH concentration.
Energy is required as molecules must be pumped against the concentration gradient.
Proteins that work as pumps are called protein pumps.
Ex: Body cells must pump carbon dioxide out into the surrounding blood vessels to be carried to the lungs for
exhale. Blood vessels are high in carbon dioxide compared to the cells, so energy is required to move the
carbon dioxide across the cell membrane from LOW to HIGH concentration.
outside of cell
inside of cell
Carbon Dioxide
molecules
ANALOGY
Weeee!!!
This is
gonna be
hard
work!!
high
high
low
•
low
Endocytosis and Exocytosis is the mechanism by which very large molecules (such as food and wastes)
get into and out of the cell
Food is moved into the cell by Endocytosis
Wastes are moved out of the cell by Exocytosis
Ex: White Blood Cells, which are part of the immune system, surround and engulf bacteria by endocytosis.
Cells and Energy
1. Cell Respiration
All living things need energy to survive.
Cellular respiration is a series of chemical reactions that convert energy in food
molecules into a usable form of energy called ATP.
First step is glycolsis which occurs in the cytoplasm of cells.
During glycolsis, glucose (a sugar) is broken into smaller molecules.
Step two requires oxygen and occurs in the mitochondria of eukaryotic cells.
The smaller molecules made during glycosis are broken down and large amounts
of energy, ATP, are produced.
Water and carbon dioxide are the two waste products given off.
2. Fermentation
Eukaryotic and prokaryotic cells use fermentation to obtain energy from food
when oxygen levels are low.
Fermentation occurs in the cell’s cytoplasm where glucose is converted into ATP
and a waste product called lactic acid.
Some types of bacteria and yeasts make ATP during alcohol fermentation. This
process produces ethanol and CO2.
3. Photosynthesis
Plants and some unicellular organisms obtain energy from light.
Light energy, water and CO2 are converted into glucose and oxygen.
In plants, light energy is absorbed by pigments such as chlorophyll.
The chemical reactions of photosynthesis occur in chloroplasts, the organelles in
plant cells that convert light energy into food.
Photosynthesis uses CO2 that is released during cellular respiration to make food
energy and release oxygen.