Chapter 3: Cell Structure

Question 1

Cell Theory

Answer 1

• the cell is the smallest unit of life
• all living things are made of cells
• every cell comes from a pre-existing cell

Question 2

Why are cells small?

Answer 2

-Small cells have a larger amount of surface area compared to volume.

An increase in surface area allows:

• more nutrients to enter a cell wastes to exit a cell
• There is a limit to how large a cell can be and still be efficient and metabolically active. Metabolism requires nutrients to enter the cell and wastes to exit the cell.

Question 3

All Cells Contain

Answer 3

• plasma membrane: separates the living part of a cell from the non-living environment
• Cytoplasm
• DNA
• Ribosomes: not surrounded by a membrane

Question 4

The Endosymbiont Theory

Answer 4

Primitive Eukaryotes engulfed bacteria which eventually lost the ability to live on their own and became organelles

Which organelles evolved in this manner?

• Mitochondria
• Chloroplasts

Question 5

organelle

Answer 5

Small membranous structure in the cytoplasm of eukaryotic cells having a specific structure and function.

Question 6

Mitchondria (heterotrophic cells)

Answer 6

originated from purple nonsulfur bacteria (aerobic, heterotrophic cells).

Advantage: allows cell to carry out aerobic respiration which produces much more energy than anaerobic cells

Question 7

Chloroplasts

Answer 7

originated from cyanobacteria (autotrophic cells).

Advantage: cell can produce its own sugar/ food by photosynthesis

Question 8

Plasma Membrane

Answer 8

Plasma Membrane
Structure:
phospholipid bilayer with proteins attached and embedded in it.
heads face the watery sides of the membrane
polar heads oriented to the outside and inside of the cell
hydrophobic tails oriented inward toward each other
aquaporins: proteins channels involved in the transport of lipids

Function:regulates entry into and out of the cell

The phospholipid bilayer contains cholesterol to give it strength.

Some proteins and lipids have sugars attached to them. A protein with a sugar attached to it is called a glycoprotein .

The plasma membrane is selectively permeable/ semipermeable. This means that: only certain substances can pass directly through the lipid bilayer by themselves

Question 9

what can and cant pass through the plasma membrane

Answer 9

What kind of molecules can pass through the plasma membrane by themselves (without using a transport protein)?
water
small, uncharged

What kind of molecules can’t pass through the plasma membrane by themselves (they need to use a transport protein in order to cross the membrane)?
charged ions
charged molecules
large molecules

Question 10

How do things move across the plasma membrane?

Answer 10

Diffusion/ simple diffusion 
osmosis 
facilitated transpost 
active transport 
endocytosis & exocytosis

Question 11

diffusion

Answer 11

Direction of movement: substance moves from an area of higher concentration to an area of lower concentration.
Movement is down the concentration gradient. (like rolling downhill)

Does the cell need to spend energy to move the substance across the membrane? no

Question 12

osmosis

Answer 12

• the diffusion of water.

Water moves from an area of higher concentration of water to an area of lower concentration of water.

Does the cell need to spend energy to move the water across the membrane?
no energy input is needed

Question 13

What is the difference between osmosis and diffusion?

Answer 13

Diffusion is the movement of solute molecules from a higher concentration to a lower concentration.

b Osmosis is the movement of water molecules from a high concentration to a low concentration.

Question 14

Diffusion across a membrane

Answer 14

Direction of movement: solute will move from an area of high concentration to an area of low concentration

Does the cell need to input energy to move a substance across a membrane by diffusion? no energy input needed 

 Does movement of the solute across a membrane require the use of a transport protein? no

Question 15

Facilitated Diffusion

Answer 15

Direction of movement: solute will move from an area of high concentration to an area of low concentration

   Does the cell need to input energy to move a substance across a membrane by Facilitated Diffusion? no 
  Does movement of the solute across a membrane require the use of a transport protein? yes

Question 16

Active Transport

Answer 16

Direction of movement: solute will move from an area of low concentration to an area of high concentration

Does the cell need to input energy to move a substance across a membrane by Facilitated Diffusion? yes, ATP

Does movement of the solute across a membrane require the use of a transport protein? yes

Question 17

Endocytosis

Answer 17

Endocytosis
a The cell transports substances into the cell .

b The substance to be moved is packed into a membrane encased sac called a vesicle .

Question 18

Exocytosis

Answer 18

Exocytosis
a The cell transports substances out of the cell.

b The substance being moved is packed into a vesicle.

  When the vesicle reaches the plasma membrane it fuses with the plasma membrane and the substance being transported is released out of the cell.

Question 19

Nucleus

Answer 19

Nucleus
describe the structure of the nucleus (or draw a diagram in your notes)
double membrane, nuclear pore, nucleolus,
DNA in chromatin

Function: stores DNA, DNA replication, RNA synthesis

Question 20

Ribosome

Answer 20

Ribosome
Structure: large subunit & small subunit, made of 50% rRNA and 50% protein; Ribosomes are organelles composed of proteins and rRNA.

Function: makes proteins or protein synthesis

Location: free in cytoplasm or on rough ER

Ribosomes are often attached to the endoplasmic reticulum, but they also may occur free within the cytoplasm, either singly or in groups called polyribosomes. Proteins synthesized at ribosomes attached to the endoplasmic reticulum have a different destination from that of proteins manufactured at ribosomes free in the cytoplasm

Is the ribosome surrounded by a membrane (membrane-bound)? No

Question 21

What is the difference between Prokaryotic and Eukaryotic ribosomes?

Answer 21

Prokaryotic ribosomes: have small 60s ribosomes

Eukaryotic ribosomes: have large 80s ribosomes

Question 22

The Endomembrane System

Answer 22

What is the Endomembrane System?
-a series of membranes in the cytoplasm of the cell
Proteins and lipids are made in some of these membranes and transported to other membranes

The endomembrane system consists of:
the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, and vesicles (tiny membranous sacs)

This system compartmentalizes the cell so that chemical reactions are restricted to specific regions. The vesicles transport molecules from one part of the system to another.

Question 23

Name the 5 structures/ organelles that are part of the Endomembrane System

Answer 23

• Smooth Endoplasmic Reticulum = SER
• Rough Endoplasmic Reticulum = RER
• Vesicles
• Golgi
• Lysosomes

Question 24

Smooth Endoplasmic Reticulum (SER)

Answer 24

Structure: tubular sheets of membrane continuous with RER, no ribosomes

Function:
*main function: lipid and membrane synthesis 
Ca++ storage
detoxification
carbohydrate metabolism

Question 25

Rough Endoplasmic Reticulum (RER)

Answer 25

``` Structure: sheets of membrane, contains ribosomes on surface. RER is continuous with nuclear membrane Protein synthesis occurs on Ribosomes on RER ``` Function: insertion of proteins into membrane After a protein is made in the RER where does it go next? golgi How does it get there? vesicles

Question 26

Golgi apparatus

Answer 26

Structure: stack of membranes Function: proteins and lipids from the RER have sugars attached to them. This is called glycosylation . Proteins are sorted , packed into vesicles and are then are either sent to their final location or are secreted out of the cell.

Question 27

What is a vesicle?

Answer 27

small membrane sacs that transport substances between membranes or organelles

Question 28

Lysosome

Answer 28

How do substances get to the lysosome? Vesicles transport substances to be broken down What happens to these substances once they are inside the lysosome? Contains digestive enzymes that break down macromolecules, nutrients and cell parts so they can be used/ recycled in the cell Lysosomes, membranous sacs produced by the Golgi apparatus, contain hydrolytic enzymes. Lysosomes are found in all cells of the body but are particularly numerous in white blood cells that engulf disease-causing microbes. When a lysosome fuses with such an endocytic vesicle, its contents are digested by hydrolytic enzymes into simpler subunits, which then enter the cytoplasm. In a process called autodigestion, parts of a cell may be broken down by the lysosomes.

Question 29

Cytoskeleton

Answer 29

What is the cytoskeleton? network of molecules inside the cell What is the cytoskeleton made of? - actin microfilaments - intermediate filaments - microtubules Function: - gives structure to the cell and organelles - involved in intracellular transport - involved in cell movement

Question 30

Cilia and Flagella

Answer 30

cilia and flagella are made of: microtubules Function: - to move a cell through a liquid - to move air/ water across a surface Structure of cilia and flagella - microtubules - plasma membrane

Question 31

Mitochondria

Answer 31

Structure: the liquid part is called the: matrix the inner membrane is called the: cristae Function: cellular respiration During respiration food molecules are broken down to make ATP. The cell uses this molecule as energy to carry out enzyme reactions and metabolism.

Question 32

What is Aerobic Cellular Respiration?

Answer 32

Function: production of ATP from the breakdown of sugar or other food molecules ``` Part 1: Glycolysis Where does this process occur in the cell? cytoplasm Does this process require O2? NO ``` ``` Part 2: Citric Acid Cycle Where does this process occur in the cell? mitochondria Does this process require O2? NO ``` ``` Part 3: Electron transport Chain Where does this process occur in the cell? mitochondrial membrane Does this process require O2? YES ``` ``` Summary of Aerobic Respiration Does it require Oxygen? YES Where does it occur? cytoplasm & 3. mitochondria Is it an efficient way to produce energy for the cell? YES ``` Why? 1 glucose can be broken down to produce up to 38 ATP (large amount of energy)!

Question 33

What other molecules besides glucose (a sugar) can be used for cellular respiration?

Answer 33

- Other Carbohydrates: sugars, starch - Proteins - Lipids: fats and oils

Question 34

How can a cell make ATP without O2?

Answer 34

``` Name of process: Anaerobic Respiration (Fermentation) ``` Where does this process occur in the cell? cytoplasm Parts of Fermentation: - glycolysis - fermentation reactions Function: short burst of energy Is Anaerobic Respiration an efficient way to produce energy for the cell? Why? No, breaks down 1 glucose to make 2 ATP (small amount of energy) and lactic acid in human cells

Question 35

enzymes

Answer 35

Type of molecule? proteins What does an enzyme do in the cell? Enzymes are specific to what substrate they work on. They carry out 1 specific type of chemical reaction. Enzymes have active sites where a substrate binds Enzymes are not used up in a reaction but instead are recycled and reused. Enzymes are the workhorses of the cell: they carry out the chemical reactions involved in metabolism

Question 36

Degradation

Answer 36

a substrate is broken down to smaller parts

Question 37

Synthesis

Answer 37

substrates are combined to produce a larger product