Cells and Their Functions

What is a cell?

Here’s what a “cell” is! Cell - the smallest unit of an organism that carries on the functions of life A cell can perform all the processes of life.

Comparing cells Many Sizes: nerve cells - up to a meter long human egg cell - dot of an i bacteria - 80,000 could fit in the dot of an i

Comparing cells Different shapes: Related to their function (job)

Comparing cells Cell types: Prokaryotic cell - very simple; no membrane-bound structures (ex: bacteria) Eukaryotic cell - more advanced; has (ex: animal cells, plant cells)

Early Cell Scientists Robert Hooke (1665) An English scientist who looked at slices of cork under a crude compound microscope and saw “a great many little boxes” that he called “cells.” First person to see cells. “Cell” comes from the Latin word for “little room.”

Anton van Leeuwenhoek (1673) Early Cell Scientists Anton van Leeuwenhoek (1673) A Dutch shopkeeper who looked at pond water using a simple microscope and saw what he called “animalcules.” Today, we call them single-celled organisms. An Early Simple Microscope

Early Cell Scientists Matthias Schleiden (1838) A German botanist who discovered that all plants are made up of similar units, or cells.

Theodor Schwann (around 1830) Early Cell Scientists Theodor Schwann (around 1830) A German scientist who stated that all plants and animals are made up of building blocks, or cells. He also observed that there are similarities and differences between plant and animal cells.

Early Cell Scientists Rudolph Virchow (1858) This German physician also reported that every living thing is made of up vital units, known as cells. He also predicted that cells come from other cells.

Cell Theory 1. All living things are made up of one or more cells. 2. Cells are the basic unit of structure and function in living things. 3. All cells come only from other living cells.

Cell Structure Animal Cell Plant Cell

Cell Structure A cell is like a small town: Different parts have different and specialized jobs. Plant cells and animal cells have many similar structures, but have several important differences.

Cell Membrane Structure: Outer boundary of the cell Double lipid membrane Selectively permeable

Cell Membrane Function (job): Protects inside Supports/gives shape Controls what enters/leaves - “gatekeeper” Helps maintain homeostasis (ability to keep a stable environment) Analogy: Townline

Cell Wall Structure: ONLY IN PLANTS Made of cellulose Strong & rigid Dead layer

Cell Wall Analogy: Castle Wall Function (job): Protects/support Gives shape Analogy: Castle Wall

Cytoplasm Structure: Jelly-like substance 80% water

Cytoplasm Function (job): Organelles float in cytoplasm Materials for growth are found in cytoplasm Expels waste through cell membrane Analogy: Town property

Nucleus Structure: Surrounded by nuclear membrane Usually round/oval Near center

Nucleus Function (job): Control center of cell Controls cell activities Contains chromosomes Analogy: Mayor and city council

Mitochondria Structure: Has an outer membrane and an inner folded membrane Rod shaped

Mitochondria Function (job): Cellular respiration Turns food into useable energy (ATP) Analogy: Power house (powerplant)

Ribosomes Structure: Tiny, round, dark Can be free floating or attached to endoplasmic reticulum

Ribosomes Function (job): Protein factories Assembles proteins used in growth, repair and control Analogy: Factory

Endoplasmic Reticulum Structure: Network of tubes and canals Smooth ER - no ribosomes attached Rough ER - ribosomes are attached

Endoplasmic Reticulum Function (job): Transports materials “intracellular highway” Analogy: Roads and highways

Golgi Bodies Structure: Series of flattened sacs

Golgi Bodies Function (job): Processes, packages and secretes material Materials that are transported by the ER usually stop first at the Golgi bodies where they are stored or altered before moving to other parts of the cell Analogy: Center for Manufacturing and shipping (UPS)

Lysosomes Structure: ONLY IN ANIMALS Contains powerful digestive chemicals

Lysosomes Function (job): Contains digestive enzymes (chemicals), breaks things down “suicide sac” Analogy: Garbage collectors

Vacuoles Structure: Fluid-filled sacs that float in the cytoplasm

Vacuoles Function (job): Stores water and food materials Stores waste and helps the cell get rid of waste Plant cells contain a large central vacuole - filled with water - helps give shape Analogy: Storage warehouse

Chloroplast ONLY IN PLANT CELLS Structure: Green, oval-shaped Contains green pigment chlorophyll

Chloroplast Function (job): Site of photosynthesis Traps the sun’s energy to make glucose Analogy: Greenhouse or solar cell

How are plant and animal cells different? PLANT CELLS: Have cell walls, chloroplasts, large vacuoles

How are plant and animal cells different? Have lysosomes

How are different cells adapted to their functions? Plant Cells: Rigid cell walls allow plants to grow upright. Muscle Cells: Have large quantities of mitochondria for energy.

How are different cells adapted to their functions? Red Blood Cells: Thin, flexible discs allow them to squeeze through tiny blood vessels. Nerve Cells: Have long projections through which messages are sent throughout the body.

Vocabulary Permeable Diffusion Osmosis Mitosis Chromosome Centriole Centromere

Organization of Living Things

Organization of Living Things Five main levels of organization 1. Cell 2. Tissue 3. Organ 4. Organ System 5. Organism

Tissue Example: Muscle Tissues are made of specialized cells.

Organ Examples: Heart, Lung, Brain Found in both plants and animals. Composed of tissue that is organized into groups that work together to perform special functions.

Organ System Example: Circulatory System A group of organs that work together.

10 Organ Systems in complex organisms (humans, dogs, birds, etc.) 1. Circulatory 2. Digestive 3. Nervous 4. Respiratory 5. Skin 6. Skeletal 7. Muscular 8. Reproductive 9. Excretory 10.Endocrine

ORGANISMS Different organ systems work together to keep the organism alive.

QUESTION: Classify the following as a tissue, organ, or organ system. a. Brain, spinal cord, and nerves b. Heart c. Group of muscle cells

QUESTION: Can a single-celled organism contain tissue? Explain.

QUESTION: Give one example of each: a. Cell c. Tissue b. Organ d. Organism

Cell Processes

Cell Processes Think of the cell membrane as being like a gatekeeper at an ancient castle. It was the gatekeeper’s job to decide when to open the gate and allow people to pass into and out of the castle. The gatekeeper controlled the permeability of the castle walls.

Permeable If the gatekeeper allowed friendly folk to enter, he or she was allowing the castle walls to be permeable. Permeable means that in cells certain substances can move freely through the membrane.

Impermeable If the gatekeeper prevented enemies from entering, he or she was allowing the castle walls to be impermeable. Impermeable means that in cells substances cannot pass freely through the membrane.

Selectively Permeable Because the gatekeeper can select those that can enter the castle, he or she was allowing the castle walls to be selectively permeable. Because the cell membrane allows some materials to pass through and is impervious to others it is selectively permeable.

Substances that move into or out of a cell do so by one of three methods: Diffusion Osmosis Active Transport

Diffusion This is the main way by which substances move into and out of cells. The process by which molecules tend to move from an area of higher concentration to an area of lower concentration. Eventually there is an equal concentration of molecules inside and outside of the cell.

……is the diffusion of water molecules through a permeable membrane. Osmosis ……is the diffusion of water molecules through a permeable membrane. Osmosis is important to cells because cells cannot function properly without adequate water.

Osmosis In osmosis, water molecules move by diffusion from an area where they are highly concentrated…through the cell membrane…to an area where they are less concentrated.

Passive transport Osmosis & Diffusion *The cell doesn’t need to use energy to move materials across the membrane. Osmosis & Diffusion

Active Transport Requires the cell to use energy to let things pass through the membrane. Large proteins in the cell membrane are involved in active transport.

Cell Division

Cell Division The cells in your body are constantly changing. Most new cells replace damaged or dead cells. These new cells are made during a process called cell division. When cell division takes place two identical cells are produced.

Cell Division In single celled organisms, cell division results in the formation of two new organisms. Dividing Paramecium

Cell Division Feeling Fine In many celled organisms, cell division increases the number of cells making up the organism. As the cells increase in number, the organism grows. Feeling Fine

This cycle may take a few hours or a few days! Cell Cycle The cell grows and develops. The cell divides. The cell prepares for division. This cycle may take a few hours or a few days!

Cell Cycle of Human Liver Cell Mitosis: Cell Division 1 hour Growth 9 hours Preparation for Division 2 hours DNA Replication 10 hours

This process by which a cell’s nucleus divides into two identical nuclei is called Mitosis

Mitosis Mitosis occurs in several phases. Most of a cell’s life is spent in the growth and development phase, called ‘interphase.’

Interphase What's Happening? The cell is making enough protein, mitochondria, and other substances for two cells. In the nucleus, each chromosome is forming an exact copy of itself. In animal cells, two pairs of centrioles are forming in the cytoplasm.

Prophase What's Happening? The nuclear membrane dissolves. The centrioles migrate to opposite sides of the cell. Spindle fibers form between the centrioles. Chromatid pairs are pulled to the center of the cell by the spindles.

Metaphase What's Happening? The chromosomes align across the center of the cell. Each chromosome attaches to a spindle fiber at its centromere.

Anaphase What's Happening? The centromeres split and the chromatids become two identical chromosomes. The spindle fibers shrink, pulling the chromosomes to opposite sides of the cell. The cell stretches out to prepare for division.

Telophase What's Happening? The chromosomes reach opposite ends of the cell. The spindles disintegrate. A nuclear membrane forms around each set of chromosomes, forming two new nuclei. A furrow forms in the cell membrane, deepens, and divides the cell completely.

Mitosis in Plants ....is different! Plants do not have centrioles. But they do have spindle fibers. The rigid cell wall can’t form a furrow in the middle, so a cell plate forms across the middle.

Mitosis in Plants ....is different! After the cell divides into two new cells, each forms its own cell wall.

During what phase of mitosis does a cell divide into two new cells? QUESTION: During what phase of mitosis does a cell divide into two new cells? Answer: During telophase!

How does mitosis differ in plants and animals? QUESTION: How does mitosis differ in plants and animals? Answer: Plants do not have centrioles. Plants form a cell plate before dividing.