Unit 3 Obj. 1.1.1, 1.1.2. ___ flowers___ hamburger___ leaf ___ skin___ DNA___ seeds ___...
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Transcript of Unit 3 Obj. 1.1.1, 1.1.2. ___ flowers___ hamburger___ leaf ___ skin___ DNA___ seeds ___...
Cell Structure
Unit 3Obj. 1.1.1, 1.1.2
Place an “X” next to the things you think are made of cells
___ flowers ___ hamburger ___ leaf
___ skin ___ DNA ___ seeds ___ proteins ___ calcium ___ water ___ rocks___ apples ___ sugar ___ milk ___ sand ___ blood ___ bone ___ worms ___ saliva ___ lungs ___ bacteria ___
mushroom
What is a cell?
The smallest unit of life; the smallest thing biologists study
RECALL: Organization of Living Things:
Cell Tissue Organ Organ system Organism
What is a cell?
Cells have smaller parts inside of them called organelles
This means “little organ.” They perform special functions for the cell to keep it (and the organism) alive.
What is a cell?
Cells were discovered in 1665 by Robert Hooke
He thought they looked like the rooms monks lived in, so he called them “cells”
What is a cell?
Anton van Leeuwenhoek was the first to see living cells. He used a hand held microscope to look at pond scum and scrapings from his teeth in 1673.
He thought they look like little animals.
Cell Theory
Contributed to by Theodor Schwann and Matthias Jakob Schleiden in 1839 and Rudolf Virchow in 1858.
Three main ideas: 1. All living things are made of one or more
cells.▪ Unicellular = one-celled organism▪ Multicellular = organism made from many cells
2. Cells are the basic unit of structure and function in all living things.
3. All new cells come from pre-existing cells.
Types of cells
1. Prokaryotic (means “before nucleus”)
No nucleus, unbound DNA
No membrane-bound organelles
Small and simple; “older” type of cell
Examples: Bacteria
2. Eukaryotic (means “true nucleus”)
Has a nucleus, DNA is inside nucleus
Has organelles Larger and more
complex; “younger” type of cell
Examples: Plants and Animals
Cell Membrane
Aka “plasma membrane” Provides protection, helps cell communicate,
transports substances in and out of cell, keeps the cell together
Made of a phospholipid bilayer (phosphate head, lipid tail, two layers)
The head is hydrophilic (loves water), the tails are hydrophobic (fears water)
Selectively permeable Found in all cells
Cell Wall
Only found in plant cells Shapes and supports the cell Provides additional protection Made of cellulose = humans cannot
digest
Nucleus
Contains the genes that control the cell = DNA
Chromatin = uncoiled DNAChromosomes = coiled DNA Surrounded by nuclear envelope =
double membrane The “information center” of the cell
Nucleolus
Makes rRNA and assembles ribosomes
Not surrounded by a membrane Cells can have 1-3 Disappears when the cell divides
Mitochondria
Where the cell performs respiration makes ATP, a molecule the cell can use as energy for work
Major site of metabolism Folded inner membrane (cristae)
more surface area for chemical reactions
Chloroplast
Found only in plant cells Contains chlorophyll = pigment
that gives plants their green color Traps sunlight to make glucose
(food) Site of photosynthesis
Ribosomes
Protein synthesis = making proteins using RNA from the nucleus to assemble amino acids into proteins
Can be floating in cytoplasm or attached to a membrane
Vacuole
Stores water, sugar, salts, nutrients, wastes, etc.
Large and central in plant cells Small or not present in animal cells
Cytoplasm
Jelly-like substance that helps fill up the cell and suspend organelles
Site of many metabolic reactions
Centriole
Only found in animal cells Made of microtubules Help the cell divide
Golgi Apparatus
Processes and packages macromolecules that are synthesized by the cell in vesicles (membrane bound packages)
Secretion Found in eukaryotes only
Rough endoplasmic reticulum
Rough ER Called “rough” because it is studded
with ribosomes Makes proteins The “highway” of the cell
transports proteins
Smooth endoplasmic reticulum
Smooth ER Lacks ribosomes Makes lipids Also the “highway” of the cell an
interconnected network of tubules and vesicles
Cytoskeleton
Made of protein – microtubules and microfilaments
“Framework” of cell Provides structural support
Lysosomes
Contain digestive enzymes Digest food, worn out organelles,
viruses, etc. Can also act as a “self-destruct
button” and cause the cell to lyse itself apoptosis
The “janitor,” “hit man,” and “suicide bomber” of the cell
Flagellum
Tail-like projection from cell Helps cell move by whipping around
in a circle similar to helicopter blade
Cilia
Small, hair-like projections Used to help cell move and sense
environment
Pseudopodia
“False foot” Temporary projections of eukaryotic
cells Usually found in amoeba Cells use extension and contraction
to move around
Plasmid
DNA molecule that is separate from and can replicate independently from chromosomal DNA
Usually found in prokaryotes
Eyespots
Photoreceptive organelle = can sense light
Usually found in unicellular photosynthetic cells, like green algae
Allows the organism to respond to light and swim towards it or away from it
Plant cells vs. Animal cells
Plant Cells Animal Cells
Membrane surrounding cytoplasm
Yes Yes
Nucleus Yes, near cell wall
Yes, near center of cell
Mitochondria Yes Yes
Chloroplast Yes No
Vacuole Yes, large and central
Small or absent
Cell Wall Yes No
Centrioles No Yes
Food storage Starch Glycogen
To be or not to be… multicellular What are some advantages?
Differentiation More control over internal conditions Greater motility able to move around and
avoid predators and find more food Genetic diversity greater chance for
positive traits What are some disadvantages?
Harder to reproduce must find a mate first Need more resources
Cell Specialization
When cells have different jobs or functions
Only multicellular organisms can have specialized cells
Specialized Animal Cells
Muscle, bone, brain, nerve, skin, hair= all different cells with different functions
Muscle cells: have more mitochondria than other cells= more metabolism!
Cool fact: Muscle cells have more than one nucleus!
Red Blood Cells: lose their nucleus and are donut-shaped to carry oxygen molecules
Remember: Hemoglobin is a protein
How do you get specialized cells?
Start as a stem cell = has the ability to become any cell in the body a “blank slate”
Gets signals (usually hormones) to become a certain cell type (this is called differentiation)
Cell Communication - Chemical Hormones = proteins that are used by both
plant and animal cells to send messages Produced in large amounts, usually in
response to something environmental Travel slowly throughout the organism Endocrine system (thyroid, testes, ovaries,
pituitary gland, etc.) releases hormones into the blood stream
Affects only those cells with the right receptors = has effects on certain cells in the body
Cell Communication - Electrical Neurons = cells in the
nervous system that transmit information throughout the body. Animals only!
Sends messages that can be voluntary or involuntary
Send out neurotransmitters that get passed from neuron to neuron
Neurons have two main parts: dendrite and axon