CP BIO Chapter 7 Cell Structure and Function

CP BIO: Chapter 7 Cell Structure and Function The cell is the basic unit of life 1

Discovery of the Cell • Robert Hooke 1660 s – cork “cells” • Anton von Leeuwenhoek 1660 s – first high-mag microscope – living cells, bacteria – Pond water, blood, saliva

All living things made of cells • Matthias Schleiden 1830 s – all plants made of cells • Theodore Schwann 1830 s – all animals made of cells • Rudolf Virchow 1850 s – new cells come from cell division 3

The Cell Theory 1. All organisms are made of one or more cells 2. The cell is the basic unit of life. Cells that form part of a larger organism still do their own life processes. 3. All cells come from pre-existing cells 4

Why are all cells small? Cells vary in size and shape • Must contain raw materials and molecules needed by cell • Must have fast exchange with environment Surface area must be large compared to volume 5

Cells have large Surface-to-Volume Ratio size increases (1 mm 2 mm) 2 X area increases (24/6) 4 X volume increases (8/1) 8 X 6 (1 4) 4 X (96/6) 16 X (64/1) 64 X

Two basic kinds of cells Prokaryotic small and simple no nucleus bacteria Eukaryotic larger and more complex nucleus all other organisms Both have: DNA & complex chemicals, cell membrane, cytoplasm, ribosomes

Two kinds of cells Bacteria (purple) in animal cell (pink) 8

Prokaryotes “before nucleus” 9

All prokaryotes have 1. Nucleoid • Region containing DNA, one chromosome 2. Cell (plasma) membrane • Encloses cytoplasm • Controls what enters and leaves cell 3. Cell wall • Outside membrane • Cell shape and protection 10

SOME prokaryotes have 4. Capsule – protective layer • Slimy or sticky coating, outside cell wall 5. Pili – extensions of cytoplasm • to attach to other cells, pass signals 6. Prokaryotic flagella – for movement 7. Plasmids – small rings of DNA • have special genes 11

Some prokaryotic cells Common shapes of bacteria 12

Eukaryotic Cells “true nucleus” Eukaryotes have membrane compartments – Larger than prokaryotes (10 -100 m) – Many organelles – tiny “organs”, with specific functions – Most organelles are enclosed by a membrane • Keeps chemistry inside organelle separate from rest of cell 13

7. 2 Cell Structure The cell is like a city – every part has a job to do. Together these parts keep the cell alive.

Cytoplasm • Watery solution outside nucleus • Has many dissolved substances for metabolism • Site for chemical reactions • Contains organelles, each has a function 15

Nucleus- control center of cell • Has most of the DNA • Chromosomes – structures containing DNA • Chromatin – loose, threadlike form of chromosomes when cell is not dividing • Nucleolus – makes ribosomes 16

Nuclear Envelope • Membrane surrounding nucleus • Many pores for molecules to pass through • Selectively permeable – controls what moves in and out of nucleus 17

Organelles that Build Proteins Ribosomes • Makes proteins, uses instructions in DNA • Made of RNA and protein • Made in nucleolus, move to cytoplasm and rough ER 18

Endoplasmic Reticulum - membrane channels throughout cell - make and transport materials - large surface area for reactions Rough ER - has ribosomes - makes and modifies proteins

Smooth ER • No ribosomes on membrane • Makes and transports lipids • Other functions in special tissues 20

Golgi Apparatus • Layers of membrane sacs • Receives proteins made in ER • Sorts and packages proteins into tiny vesicles • Final products may be used by cell (ex. lysosome) or exported from cell 21

Lysosomes Membrane sacs of digestive enzymes 1. Break down wastes and worn-out cell parts 2. Recycle molecules the cell can use 3. In one-celled, join to food vacuoles to digest food 4. In development, remove tissue no longer needed (ex. tadpole tail) 5. In defense, white blood cells digest bacteria 6. In Cell death – when cell is damaged beyond repair

Organelles that capture and release energy Mitochondria “Powerhouse of the cell” – site for cell respiration • Releases chemical energy from food and changes into energy cell can use ATP • ATP – energy molecule in all organisms 22

Plastids – in plants Chloroplasts • Site for photosynthesis: capture sun energy and change it into chemical energy of food • Layered membranes inside contain green pigment chlorophyll 23

Leukoplasts and Chromoplasts Leukoplasts store starch In potato Chromoplasts store other pigments -flowers, fruits, seeds 24 In red pepper

Mitochondria and Chloroplasts are different from other organelles 1. double-layered membrane organelles - inner membrane deeply folded/layered - large surface area for fast chemical processes 2. have their own DNA and ribosomes - can self-replicate as needed - make their own enzymes for reactions

Organelles that store and clean up Food vacuole in paramecium

Plant Vacuoles Stores water and substances needed for photosynthesis Also has enzymes to recycle molecules 27

Contractile Vacuole • In some one-celled organisms that live in fresh water • Water enters cell from environment • Vacuole pumps out excess water • Keeps homeostasis 28

Lysosomes are stained in this slide 30

The Cytoskeleton • Protein framework inside cell • Attach to cell membrane to keep cell shape • Anchor organelles • Transport materials inside cell Two kinds: microfilaments and microtubules 31

Microfilaments • Flexible, elastic threads • Support cell and help cells move – Move substances around inside cell – Cytoplasmic streaming – May form pseudopods Cytoplasmic streaming lets amoeba eat by encircling food 32

Microtubules • Hollow rigid tubes keep cell shape • Tracks for moving molecules in cell • Also found in cilia, flagella (for movement) and in centrioles and spindle fibers (for cell division) 33

Cytoskeleton and Cell Wall

Cilia and Flagella Extensions on cell surface • Cilia – short, many, like “oars” – Ex. line air passages in our body - cover Paramecium • Flagella – longer, one or a few, move like a “whip” – Ex. Human sperm, euglena 35

Centrioles and Spindle Fibers • Help in cell division • Centrioles (only in animal cells) – Organize spindle fibers • Spindle fibers (in all eukaryotic cells) • Organize and separate chromosomes when cell divides 36

Cell Boundaries Keep cell contents separated from surroundings Cell (plasma) membrane – in ALL CELLS • Selectively permeable • controls which substances move in or out of cell • Maintains homeostasis 37

The Cell Membrane Double layer of phospholipids and proteins

The Cell Wall • • • In many organisms, but NOT animals Outside cell membrane For shape, support, protection Some substances can pass through In plants – mostly cellulose Also in fungi, most bacteria, some protists

Cellulose fibers in cell wall 37

Cell Junctions • Connects cells to form tissues • Cells can communicate and share materials Gap junction anchoring junction tight junction

How do plant and animal cells differ? Plant cells also have: 1. rigid cell wall, contains cellulose 2. chloroplasts – do photosynthesis 3. large central vacuole – stores water and molecules for photosynthesis Animal cells have: 1. centrioles – for cell division 2. lysosomes – break down wastes 3. some have flagella or cilia 42

Endosymbiosis Theory for how eukaryotic cell evolved 1. Prokaryotes are different sizes 2. Larger prokaryotes ate smaller ones 3. Some were not digested, but became part of cell 4. Might have survival advantage – ex. make its own food; use energy efficiently

Endosymbiosis Theory

Evidence to support theory Chloroplasts and mitochondria a) have double membranes b) Have their own DNA and ribosomes c) Can self-replicate May have once been separate organisms