chapter 7: cell structure and function honors biology/chemistry

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Chapter 7: Cell Structure and Function Honors Biology/Chemistry

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Page 1: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Chapter 7: Cell Structure and Function

Honors Biology/Chemistry

Page 2: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

The Discovery of the Cell• In 1665, Robert Hooke used an early

compound microscope to look at a thin slice of cork, a plant material.

• Cork looked like thousands of tiny, empty chambers.

Page 3: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Hooke called these chambers “cells.”• Cells are the basic units of life.

Page 4: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Overtime, the discoveries of multiple scientists were summarized in a single cell theory. The cell theory states:– All living things are composed of cells.– Cells are the basic units of structure and

function in living things.– New cells are produced from existing

cells.

Page 5: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Prokaryotes and Eukaryotes• Cells come in a variety of shapes and

sizes.• All cells:

– Are surrounded by a barrier called a cell membrane.

– At some point they contain the nucleic acid, DNA.

Page 6: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Cells are classified into two categories, depending on whether they contain a nucleus.

• The nucleus is a large membrane-enclosed structure that contains the cell's genetic material in the form of DNA.

• The nucleus controls many of the cell's activities.

Page 7: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Prokaryotic cells:– Have genetic material that is not

contained in a nucleus.

• Do not have membrane-bound organelles.

• Are generally smaller and simpler than eukaryotic cells.

• Bacteria are prokaryotes.

Page 8: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Eukaryotic cells:– Contain a nucleus in which their genetic

material is separated from the rest of the cell.

– Are generally larger and more complex than prokaryotic cells.

– Generally contain dozens of structures and internal membranes.

– Many eukaryotic cells are highly specialized.

– Plants, animals, fungi, and protists are eukaryotes.

Page 9: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 10: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Eukaryotic Cell Structure• Structures within a eukaryotic cell

that perform important cellular functions are known as organelles.

• Cell biologists divide the eukaryotic cell into two major parts: the nucleus and the cytoplasm.

• The Cytoplasm is the portion of the cell outside the nucleus.

Page 11: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 12: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

The Nucleus• The nucleus is the control center of the cell.

– The nucleus contains nearly all the cell's DNA and with it the coded instructions for making proteins and other important molecules.

Nuclear envelope

Nuclear pores

Nucleolus

Chromatin

The nucleolus is inside the nucleus and synthesizes ribosomes.

Page 13: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Ribosomes• One of the most important jobs

carried out in the cell is making proteins.

• Ribosomes are the organelles where protein synthesis takes place.

• Ribosomes are small particles of RNA and protein found throughout the cytoplasm.

Page 14: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Ribosomes can be either free (floating in the cytoplasm) or attached (found attached to the folded membranes of the endoplasmic reticulum.)

Page 15: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Golgi Apparatus• Appears of stacks of flattened

membranes.• The Golgi Apparatus modifies,

sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or secretion outside of the cell.

Page 16: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 17: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Endoplasmic Reticulum• There are two types of Endoplasmic

Reticulum:– Rough: Covered in ribosomes

• Synthesis of proteins – Smooth: Lacking ribosomes

• Synthesis of lipids for the cell membrane

– Both types of Endoplasmic Reticulum help to transport materials throughout the cell.

Page 18: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 19: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Lysosomes

• Small organelles filled with enzymes.• Lysosomes function to digest

macromolecules, old organelles, and other unwanted material.

Page 20: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Vacuoles• Store materials such as water,

salts, proteins and carbohydrates.

Page 21: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Mitochondria• Organelles that convert the

chemical energy stored in food into compounds that are more convenient for the cell to use.

Page 22: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Chloroplasts• Organelles that capture the energy

from sunlight and convert it into chemical energy in a process called photosynthesis.

Page 23: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Cytoskeleton• A network of protein filaments that helps

the cell to maintain its shape. • Also involved in movement.• Centrioles: small structures found in animal cells

that assist in cell division.

Page 24: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Plant vs. Animal Cells• Eukaryotic cells can be divided into Plant and

Animal cells.• Plant cells:

– Have chloroplasts– Have a rigid cell wall outside of their cell membrane.– Lack centrioles– Have a single, large vacuole (central vacuole)

• Animal cells:– Lack chloroplasts– Lack cell walls– Have centrioles– Have several small vacuoles (if any)

Page 25: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 26: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 27: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Cell Boundaries• All cells are surrounded by a thin,

flexible barrier called a cell membrane.

• Plant and bacterial cells also have a strong protective layer surrounding the cell membrane called a cell wall.

Page 28: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 29: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Cell Membrane• Regulates what enters and leaves

the cell and also provides protection and support.

• Known as a lipid bilayer because it is made of 2 layers of lipids.

Page 30: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• In addition to lipids, cell membranes contain protein molecules that are embedded throughout the bilayer. – These proteins act as channels and pumps that

move materials across the membrane.• Carbohydrates are found on some proteins

and help cells to identify one another.

Page 31: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• We say that the cell membrane is “selectively permeable” or “semi-permeable” because it controls what can enter and leave the cell.

Page 32: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Phospholipids• The lipids in the cell

membrane are called phospholipids. – Contain a phosphate head

and fatty acid tails.

• The “head” of the phospholipid is polar, or hydrophilic, and the “tail” is non-polar, or hydrophobic.

Page 33: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 34: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Cell Walls• Provide support and protection for

the cell.• Found in plants, bacteria, and fungi.

Page 35: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Diffusion Through Cell Boundaries

• Measuring Concentration– A solution is a mixture of two or more

substances.– The substances dissolved in the solution

are called solutes. – The concentration of a solution is the

mass of solute in a given volume of solution, or mass/volume.

Page 36: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• If you dissolved 12 grams of salt in 3 liters of water, the concentration would be 12g/3L, or 4 g/L.

• If you dissolved 12 grams of salt in 6 liters of water, the concentration would be 2 g/L.

• The first solution is twice as concentrated as the second solution.

Page 37: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Food Coloring Demo!

Page 38: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Diffusion– Particles in a solution tend to move from

an area where they are more concentrated to an area where they are less concentrated. (Down the concentration gradient

– This process is called diffusion. – When the concentration of the solute is

the same throughout a system, the system has reached equilibrium.

– Animation

Page 39: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

–Diffusion happens randomly, and does not require energy. Therefore, diffusion is called a passive process.

Page 40: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Cucumber Demo

Page 41: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Osmosis– Some substances are too large or too

strongly charged to pass through the lipid bilayer.

– When the solute cannot pass through the membrane (the membrane is impermeable to the solute), water passes though the membrane in order to reach equilibrium.

Osmosis is the diffusion of water through a selectively permeable membrane.

Page 42: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Sugar is too large to fit through the selectively permeable membrane.

In order to reach equilibrium, water moves from an area of high water concentration (low solute concentration) to low water concentration (high solute concentration)

Page 43: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• When the concentration of water and solute are the same on both sides of a membrane, we describe the two solutions as being isotonic.

• Before osmosis occurs, we describe one solution as being hypertonic (higher concentration of solute - sugar) and one solution as being hypotonic (lower concentration of solute - sugar).

• Water moves from a hypotonic solution (low sugar and high water) to a hypertonic (high sugar and low water) solution.

Page 44: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Which side of the beaker is hypertonic? Hypotonic? In which direction will water move across the membrane in order to reach equilibrium?

Page 45: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 46: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Facilitated Diffusion– Some large molecules can actually pass

through the membrane.– Cell membranes have substance-specific

protein channels acting as carriers allowing (or...”facilitating”) certain molecules to pass through.

– This process moves solute from high to low concentration and does not require energy.

Page 47: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 48: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Learning Check

• Compare and contrast the 3 types of passive transport:– Diffusion– Osmosis– Facilitated Diffusion

Page 49: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Active Transport– Sometimes cells must move materials

against the concentration gradient.• From low to high solute concentration

– This process usually utilizes protein pumps throughout the membrane and requires energy.

Page 50: Chapter 7: Cell Structure and Function Honors Biology/Chemistry
Page 51: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Larger molecules or even clumps of material may be transported by movements of the cell membrane as a whole unit.

• Endocytosis: process of taking material into the cell by folding the cell membrane inward and forming pockets.

Page 52: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• There are two types of endocytosis:– Phagocytosis: “Cell eating”; taking in

solid materials.– Pinocytosis: “Cell drinking”; taking in

liquid materials.

Page 53: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

• Exocytosis– The membrane of a vesicle filled with

material fuses with the cell membrane, forcing the material out of the cell.

Page 54: Chapter 7: Cell Structure and Function Honors Biology/Chemistry

Learning Check

• In what two ways does active transport differ from passive transport?