Cell Structure and Function Chapter 2

Lesson 1: Cells and Life

Understanding Cells People didn’t always know about cells Too small to be seen without proper tools Robert Hooke (English Scientist) 300 years ago he built a microscope Used his microscope to look at cork (from oak tree) Small openings he saw reminded him of the rooms that Monks live in called “cells”

Cell Theory After Hooke’s discovery, microscopes were improved Scientists began looking for cells in many other places (pond water, blood) The newer microscopes enabled scientists to see structures inside of cells. Matthias Schleiden, a German scientist, used the microscope to look at plant cells. Theodor Schwann used the microscope to study animal cells Both scientists realized that plant and animal cells have similar structures.

Cell Theory Rudolf Virchow, a German doctor proposed that all cells come from previously existing cells. The observations of these scientists were combined to form THE CELL THEORY 1 2 3

Basic Cell Substances Cells are made of smaller parts that are joined together, called macromolecules Macromolecules form by joining many small molecules together. The main ingredient of macromolecules is water More than 70% of a cell is water Water surrounds cells This surrounding water helps insulate your body This helps your body maintain homeostasis, or a stable internal environment

There are 4 types of macromolecules: Nucleic Acids Contain genetic information (make up your DNA) Proteins-Amino acids Communication, Transport, Chemical Breakdown, and Structural Support Lipids-Fats Energy Storage, protective membranes, and communication Carbohydrates –sugars and starches Energy storage, structural support and communication

Macromolecules

Lesson 2: The Cell

Cell Shape and Movement Cells come in many shapes and sizes The size and shape of the cell relate to it’s function Cell structures that make up a cell also have unique functions In a cell, the different structures perform different functions that keep a cell alive They work together!

Cell Membrane vs Cell Wall All cells are surrounded by a protective covering called a membrane. A Cell Membrane is a flexible covering that protects the inside of a cell from the environment outside. Membranes are mostly made up of proteins and lipids Some cells are also surrounded by a structure called a cell wall A Cell Wall is a stiff structure outside the cell membrane. Cell Walls protect against harmful attacks, as well as help with shape and support

Cell Membrane vs Cell Wall

Cell Appendages Arms and legs are appendages on an organism Cells can have Flagella or Cilia to help them move

Cytoplasm and Cytoskeleton Most of the Cells water is in the Cytoplasm Cytoplasm: a fluid inside of a cell that contains salts and other molecules. The cytoplasm also contains a Cytoskeleton Cytoskeleton: a network of threadlike proteins that are joined together in a framework This helps give the cell it’s shape

Cytoplasm and Cytoskeleton

Prokaryotic Cells vs. Eukaryotic Cells Prokaryotic – Genetic material (DNA) is not surrounded by a membrane (nucleus) Most Prokaryotic cells are unicellular organisms called Prokaryotes Eukaryotic – Genetic material (DNA) is surrounded by a membrane Has many other structures called organelles, each having their own function

Cell Organelles Nucleus Largest organelle Directs cell activities Contains Genetic information (DNA)

Manufacturing Molecules Proteins are made in tiny structures called a Ribosome Ribosomes don’t have membranes surrounding them. Ribosomes are round floating in the Cytoplasm as well as attached to a web like structure called the Endoplasmic Reticulum

Manufacturing Molecules Endoplasmic Reticulum Rough E.R. – with ribosomes attached to the side Where proteins are manufactured Smooth E.R. – without ribosomes Where lipids such as cholesterol are made Helps remove harmful substances from the cell

Processing Energy - Mitochondria Mitochondria are surrounded by two membranes Energy is released during a chemical reaction that takes place in the mitochondria This energy is stored in high- energy molecules called ATP ATP is fuel for cellular processes

Processing Mitochondria - Chloroplasts Chloroplasts are found in plant cells and some protists Chloroplasts use light energy and make food-a sugar called glucose- from water and carbon dioxide in a process called photosynthesis This sugar glucose, contains energy that can be released when the plant cell needs it

Golgi Apparatus Golgi apparatus Prepares proteins for their specific jobs or functions Then it packages the proteins into tiny, membrane bound, ball like structures called vesicles Vesicles are structures that transport substances from one area of a cell to another area of a cell. Some Vesicles in an animal cell are called lysosomes Lysosomes contain substances that help break down and recycle cellular components

Golgi Apparatus, Vesicles, and Lysosomes

Storing Molecules Vacuoles Saclike structures Stores food, water, and waste material Plant cells usually have one very large vacuole that stores water and other substances

Lesson 3: Moving Cellular Material

Passive Transport A cell membrane is semipermeable Semipermeable means that the membrane only allows certain substances to enter or leave the cell

Passive Transport 2 water molecules Passive transport is the movement of substances through a cell membrane without using the cell’s energy Molecules must be small to pass through membranes Such as Oxygen or Carbon Dioxide molecules Passive transport depends on the amount of a substance on each side of a membrane Example: Suppose there are more Oxygen molecules (O2) outside of a cell than inside it Will the O2 molecules move? Which direction will they move? Yes, the O2 molecules will move into that cell until the amount of O2 is equal on both sides of the cell’s membrane 8 water molecules 5 Oxygen molecules 4 Oxygen molecules

Passive Transport The concentration of substance is the amount per unit volume Diffusion The movement of substances from an area of higher concentration to an area of lower concentration Usually, diffusion will continue through a membrane until the concentration of a substance is the same on both sides of the membrane

Passive Transport Osmosis-The Diffusion of water Diffusion refers to the movement of any small molecules from higher to lower concentrations Osmosis is the diffusion of only water molecules through a membrane Example: Water diffusing out of a plant cell Concentration of water in air is less than water in vacuoles of plant cell Water continues to diffuse into the air until the concentrations of water inside the plant’s cells and in the air are equal If plant is not watered to replace the water it loses, what will eventually happen? It will wilt and eventually die Salt Molecules Water Molecules

Facilitated Diffusion Some molecules are too large or chemically unable to travel through a membrane by diffusion Facilitated diffusion happens when molecules pass through a cell membrane using special proteins celled transport proteins Like diffusion, no energy is required for facilitated diffusion Channel proteins form pores through the membrane Carrier Proteins carry large molecules such as sugar through the membrane

Active Transport The movement of substances through a cell membrane only by using the cell’s energy is Active Transport When substances move from a low concentration to a higher concentration it requires energy

Endocytosis & Exocytosis When a substance is too large to enter a cell membrane by diffusion or by using a transport protein they must enter by another process called Endocytosis: The process during which a cell takes in a substance by surrounding it with the cell membrane is called Endocytosis When a substance is too large to leave a cell it leaves through a process called Exocytosis Exocytosis: The process during which a cell’s vesicles release their contents outside the cell

Cell Size and Transport Remember: the movement of nutrients, waste materials and other substances into and out of a cell are very important for survival For Movement to happen, the area of cell membrane must be large compared to the volume of the cell Area of cell membrane = Cell’s Surface Area Amount of space inside cell = Cell’s Volume

Cell Size and Transport As the cell grows, both volume and surface area grow Volume of cell increases faster than the cell’s surface area Why is this a problem? As cell grows it needs larger amounts of nutrients and create more waste material. But the surface area of the cell’s membrane is too small to move enough nutrients and wastes into or out of cell for it to survive

Lesson 4: Cells and Energy

Cellular Respiration All living things need energy to survive Cellular Respiration is a series of chemical reactions that convert the energy in food molecules into a usable form of energy called ATP

Cellular Respiration Glycolysis: The first Step Occurs in the cytoplasm Process in which glucose, a sugar, is broken down into smaller molecules Produces some ATP, but Glycolysis also needs ATP to happen

Cellular Respiration 2nd Step: Occurs in the Mitochondria Requires Oxygen (O2) The smaller molecules made from Glycolysis are broken down

Cellular Respiration Large amounts of ATP – usable energy- are produced Cells use this ATP to power ALL cellular processes Two waste products – water (H2O) and Carbon Dioxide (CO2) – are given off during this step

Fermentation A reaction that both eukaryotic and prokaryotic cells can use to obtain energy from food when oxygen levels are too low Takes place in the cell’s cytoplasm Produces less ATP than cellular respiration because no oxygen is used

Fermentation Lactic Acid fermentation: When Glucose is converted into ATP and produces Lactic Acid as a waste product Muscle cells in humans and other animals use lactic- acid fermentation to produce energy during excercise

Fermentation Some types of bacteria make ATP through a process called Alcohol Fermentation Instead of producing lactic acid, an alcohol called ethanol and CO2 are produced. Some bread is made using yeast The CO2 produced during alcohol fermentation makes the dough rise

Photosynthesis Plants and some unicellular organisms obtain energy from light Photosynthesis is a series of chemical reactions that convert light energy, water and CO2 into the food energy molecule glucose and give off Oxygen Photosynthesis requires light energy. In plants, pigments such as chlorophyll absorb the light energy Green light is reflected as green color seen in leaves. Plants also reflect other colors we see such as red and yellow. Light energy powers chemical reactions that take place in the chloroplasts of plant cells.

The Photosynthesis & Cellular Respiration Relationship Photosynthesis uses CO2 that is released during cellular respiration to make food energy and release oxygen

The Photosynthesis & Cellular Respiration Relationship When an organism eats plant material, it takes in food energy. An organism’s cells use oxygen released during photosynthesis to convert food energy into usable energy.